Selected chemical and physical properties of cobalt and cobalt compounds covered in this monograph are presented in Table 2. Metallic cobalt...

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COBALT AND COBALT COMPOUNDS The agents considered herein include (a) metalIc cobalt, (b) cobalt alloys (including cobalt-containing medical implants) and (c) cobalt compounds. Organic

cobalt-containing agents (e.g., vitamin B12) are not covered comprehensively in this monograph. 1. Chemical and Physical Data 1.1 Synonyms, trade narnes and molecular rormulae

Synonyms, trade names and molecular formulae for cobalt, cobalt alloys and cobalt compounds are presented in Table 1. The cobalt alloys and compounds given

in Table 1 are not an exhaustive list, nor are they necessarily the most commercially important cobalt-containing substances; the list indicates the range of cobalt alloys and compounds available.

Table 1. Synonyms (Chemical Abstracts Service names are given in bold type),

trade names and atomic or molecular rormulae or cobalt and cobalt compounds Chemical name

Chem. Abstr. Synonyms and trade names


Servces Reg. No.


Metale cobal



c.I. 77320; cobalt element; Co cobalt-59

Cobalt alloys

Cobalt-chromium alloyb

11114-92-4 (91700-55-9)

Cobalt alloy (nonbase), Co, Co.Cr Cr; chromium alloy (nonbas),

Cr Nickel alloy (base), Ni 47-59, CAI-Co'Cr-Fe.MoNi' Co,

Nickel-based cobalt alloyb



Co 17-20, Cr 13-17, Mo Ti


4.5-5.7, AI


0-1, C 0-0.1 (AISI 687)

3.7-4.7, Ti 3-4, Fe

1262482-7; 12630-37-4;

12636-2-1; 12672-01-4; 12774-12-8;

37323-85-l; 64941-39-5)

APK 1; Astroloy; Cabot 700; NiCo18Cr15MoAlTi; Nimonic AP 1; NK17CADT; PM-ATS 380; PWA 1013; R 77; Rene

77; U 700; U 700m; U700PM; Udimet 700




Table i (contd)

Chemical name

Chem. Abstr.

Synonyms and trade names


CCo:CrFe'MnNi'Si. W

Servces Reg.

No.a MetaUc cobal (contd)



nickel-tungsten alloy



Cobalt alloy (base), Co 48-58, Cr 2426, Ni 9.5-12, W 7-8, Fe 2, Mn 0-1, Si 0-1, C


0.4-.6 (ASTM AS67-2)



AFOR K-CNW; AMS 5382; Co X-4; G-X 55; CoCrNiW 55 25; Haynes Stellite 31; HS 31; 31H114; K-

C2; MA 5382; PN

31H114; S-31; Stellte 31; Stellite 31 X 40; Stellte X4O; 45VF; X 40

Cobalt-chromiummolylxenum alloyb


Cobalt alloy (base), Co 56-,



Cr 25-29, Mo 5-6, Ni 1.8-3.8, Fe 0-3, Mn 0-1, Si 0-1, C


12618-69-8; 55345-18-1;

0.2-0.3 (AST A567-1)



Akrt CoMo35; AMS 5385D;

83272-15-5; 85131-98-2; 94076-26-3; 11520 1-6)

Celsit 290; F 75; Haynes Stellite 21; HS 21; Protasul-2; Stellite 21; Vinertia; Vitallum; X2CoCrM062 28 5; Zimaloy


Acetic acid, cobalt(2 + ) salt;


bise acetato )cbalt; cobalt ace-


tate; cobalt(2 + ) acetate; cobalt


diacetate; cobaltous acetate; cobaltous diacetate


Bis(acetato )tetraquacobalt



Acetic acid, cobalt(3 + ) salt;


Cobal compounds Cobalt(Il) acetate

Coba1t(II) acetate


tetrahydrate Cobalt(III) acetate

cobalt(3 + ) acetate; cobaltic

acetate; cobalt triacetate

Cobalt(Il) carbonate


Carbonic acid, cobalt(2+) salt (1:1); C.I. 77353; cobalt carbonate (1:1); cobalt(2+)

carbonate; cobalt monocrbo nate; cobaltous carbonate




Table i (contd)

Chemical name

Chem. Abstr.

Synonyms and trade names


Basic cobalt cabonate; carbonic acid, cobalt complex; c0 balt cabonate hydroxide; c0 balt, (cabonato )dihydroxydi-;


Servce Reg.


Cob compounds (contd) Cobalt(lI) carbonate


hydroxide (1:1)

cobalt, (.mu.-(carbonato(2- )-0:0' )Jdihydroxydi-

Cobalt(lI) cabonate


Cobalt, bis( carbonato(2-))-

hexahydroxynta-; cobalt,

hydroxide (2:3)


bis( cabonato )hexahydroxypenta-; cobalt carbonate hy-

droxide; cobalt hydroxide car-

bonate Cobalt(lI) cabonate


Basic cobalt carbonate; car-


hydroxide (2:3) mono-

bonic acid, cobalt(2 + ) salt,



basic; cobalt, bis( carbonato-

(2- ))hexahydroxyntamonohydrate; cobaltous cabonate, basic Cobalt(lI) chio


76479-9 (1332-82-7)

Cobalt chloride (CoCli); co balt dichloride; cobaltous chIoride


Cobalt(lI) chloride hexahydrate


Cobalt chIo ride, hexahydrate; cobalt dichloride hexahydrate; cobaltous chIo ride hexahydrate


Cobalt(lI) hydroxide

21041-93-0 (1307-85-3)

Cobalt dihydroxide; cobalt hydroxide (Co(OH)i); cobalt(2+ ) hydroxide; cobaltous hydroxide


Cobalt(lII) hydroxide


Cobalt hydroxide (Co(OH)i);


cobaltic hydroxide; cobalt trihydroxide

Cobalt(ll) naphthenate


Cobalt naphthenates; naftolite; naphthenic acid, cobalt salt; naphthenic acids, cobalt salts

U nspecified

Cobalt Nap-All; Naphthex Co; 8SN-Co

Cobalt(I) nitrate

10141-05-(14216-74-1; 19154-72-4)

Cobalt bis(nitrate); cobalt(2+) nitrate; cobaltous nitrate; ni. tre acid, cobalt(2 + ) salt



366 Table i (contd)

Chemical name

Chem. Abstr.

Synonyms and trade names



Cobalt dinitrate hexahydrate; cobalt nitrate hexahydrate; co



Servces Reg. No.


Cob compounds (contd) Cobalt(II) nitrate hexahydrate

balt(2 + ) nitrate hexahydrate; cobalt(II) nitrate hydrate; co bal tous nitrate hexahydrate; nitric acid, cohalt(2 + ) salt, hexahydrate Cobalt(II) molybdenum(VI) oxide

13762- 14(1225-99- 1; 145663- 1;


Cobalt molybdate; cobalt molybdate(I); cobalt(2 + )


molybdate; cobalt molybdenum oxide (CoMo04);

cobaltous molybdate; cobalt monomolybdate; molybdenum

cobaltate; molybdenum cobalt oxide; molybdic acid (HiMOÛ4), cobalt(2+) salt (1:1) Cobalt(II) oxide


CI. 77322; CI. Pigment Black


13; cobalt black; cobalt monoxide; cobalt monooxide; cobaltous oxide; cobalt oxide (COO);

cobalt(2+) oxide; monocbalt oxide

Zaffre Cobalt(II,III) oxide

1308-01 (12314-25-9; 25729-03-7)

Cobaltic-cbaltous oxide; cobalto-baltic oxide;


cobalto-baltic tetroxide; cobaltosic oxide; cobalt oxide (Coi04); cobalt tetraoxide; tricobalt tetraoxide; tricobalt tetroxide

Cobalt(III) oxide

1308-09 (12314-25-9; 25729-03-7)

CI. 77323; cobaltic oxide; co-


hait oxide (Co20i); cobalt(3 + ) oxide; cobalt peroxide; cobalt

seuioxide; cobalt trioxide;dicobalt oxide; dicobalt trioxide

Cobalt(III) oxide monohydrate

120 16-80-7

Cobalt hydroxide oxide


(Co(OH)O); cobalt(III) hydroxide oxide; cobalt oxide hydroxide; cobalt oxyhydroxide

Co(OH)O or CoiOi.HiO



Table i (contd)

Chemical name


Chem. Abstr. Synonyms and trade names Servces Reg.


Cob compounds (contd)

Cobalt(II) sulfate 101243-3 (10393-49-4)

Cobalt monosulfate; cobaltous


sulfate; cobalt sulfate (1:1); co balt(2 + ) sulfate; cobalt sul-


phate; sulfuric acid, co-

balt(2+) salt (1:1) Cobalt(II) sulfide



Cobalt monosulfide; cobaltous

sulfide; cobalt(2+ ) sulfide Dicobalt octacarbonyl




carbonyldi-; cobalt tetracaroo-

14525-269; 1998-88-0;

(Co(CO)4Ji or


nyl dimer


903-99-5) Tetracobalt dodecacabonyl





19212-11-4; 19478-05-8; 19495-98-8;

(Co(CO)3J4 or



28963-39-5) ~eplaced CAS Registry Numbers are given in parentheses. b Approximately 500 alloys of cobalt with other met

aIs are listed by the Chemical Abstracts Registry Servce, of which cobalt is the bas metal for approximately 20. Chromium is contained in approximately 140 of these alloys and nickel in approximately 1500. An example of each is lIsted here.

1.2 Chemical and physical properties or the pure substances Selected chemical and physical properties of cobalt and cobalt compounds covered in this monograph are presented in Table 2. Metallic cobalt

Cobalt metal was isolated by the Swedish scientist G. Brandt in 1735; in 1780, 'IO. Bergman established cobalt as an element (Donaids~m, 1986).

Cobalt exists in two allotropie forms. The hexagonal close-packed form is more stable at temperatures below 417°C, and the face-centred cubic form at

w O"

Table 2. Physical properties or cobalt and cobalt compoundsa Chemical name


Atomic/ molecular weight

Melting-point ("C)

Typical physical description



1495 (bilng-

Silver-grey, hard, magnetie, ductile, somewhat malleable metal

Practically insoluble in water

MetaUic cobalt


point, 2870)

Cobalt compounds Cobalt(II) acetate




Cobalt(III) acetate

Cobalt(II) carbonate




Light-pink crystals

Readily soluble in dilute nitric acid Readily soluble in hydrofluoric acid and readily in sulfuric and hydrochloric acidsb

Los four HiO

Red-violet monoclinie,

Readily soluble in water Soluble in water, dilute acids, pentyl acetate

at 140


and alcohols


Soluble in water, acetic acid, ethanol, n-butanol


Dark-green, very hygroscopic powder or green


Aqueous solutions hydrolyse slowly at room temperature, rapidly at 6070" C


Red, trigonal

Practically insoluble in water, ammonium hy-

droxide, ethanol or methyl acetate Soluble in acids Cobalt(II) cabonate



hydroxide (2:3)

Pale-red powder, usually

Practically insoluble in water

containing sorne HiO

Soluble in dilute acids and ammonium carbonate solution Insoluble in cold water Decompos in hot water Soluble in acid and ammonium carbonate solution




Cobalt(II) chloride


724 (in HCI gas) Pale-blue, hygroscopic

Violet-red crytals

decomposes at

leafets; colourless in very

40 on long

thin layers; turns pink on expsure to moist air

heating in air

Soluble in water (450 gtl at rc; 1050 gtl at

96°C1 ethanol (544 gt11 acetone (86 gtl1 methanol (385 gtl1 glycerol and pyrdine Slightly soluble in diethyl ether

~ s:

0 Z 0 0 ~ :i C/

â E s: tr LI


Table 2 (contd) Chemical name


Atomic/ molecular weight

Melting-point CC)

Typical physical description



86; loss four H20 at 52-56,

Pink to red, slightly

Soluble in ethanol and in water (767 g/l at O.C;

deliquescnt, monoclinic,

1907 g/l at 100.C), acetone, diethyl ether (29

prismatic; tums blue

g/l) and glycerol

an addition


H20 by 100 and when heated or when another H20 at hydrochloric or sulfuric Cobalt(II) hydroxide

Cobalt(III) hydroxide (trihydrate)



Cobalt(II) molybdenum 218.87


acid is added; slight


odoure Blue-green or rose-red



powder or microscpie

Very slightly soluble in water (0.0032 g/l) Soluble in acid and ammonium salts Insoluble in aqueous hydroxide solutions

Black-brown powder

Practically insoluble in water and ethanol

loss H20 at

Soluble in nitric acid~ sulfuric acid and hydro-


chloric acid


Grey-green powder



Cobalt naphthenate Cobalt(II) nitrate

-g 18296

14t 100105 (decom-

pos) (hexahydrate)

291. 03

55-56; loses

(j 0t:

~ ~ 0


0t: ~ (j

0 s: "'


c: Brown, amorphous powder or bluish-red solidd

Practically insoluble in water Soluble in ethanol, diethyl ether and oils

Pale-red powder

Soluble in water

Red, monoclinic; liquid

Soluble in water (1338 g/l at O.C; 2170 g/l at sooC), ethanol (100 g/l at 125°C), acetone and most organic solvents

three H20 at 55 becomes green and decomposes to the oxide above 74°C




Slightly soluble in ammonium hydroxide VJ

0\ \0



Table 2 (contd) Chemical name

Coba1t(II) oxide

Atomic/ molecular weight




Mel ting-poin t

Typical physical description


Powder or crytals; colour varies from olive-green to

Practically insoluble in water, ethanol and ammonium hydroxide

red, depending on

Soluble in acids (hydrochloric, sulfuric, nitrid)

paricle size, but the


commercial material is

Coba1t(II,III) oxide


895i; transition-

usually dark-grey Black or grey crystals

point to CoO is


Cobalt(III) oxide



Black-grey crystals


Cobalt(II) sulfate



Dark-bluish crystals



Cobalt(II) sulfide

281. 10


;: 1116

96.8; loss HiO

Pink-to-red monoclinic,

at 41.5, six HiO at 71 and seven HiO at 420



Practically insoluble in water, aqua regia, hydrochloric or nitric acid Soluble in sulfuric acid and fused sodium hydroxided Insoluble in water and ethanol Soluble in acids Soluble in water (362 g/l at 2O.C; 830 g/l at 100.C) and methanol (10.4 g/l at 18.C)

0 Z 0 0 ~ ::



Insoluble in ammonium hydroxide


Soluble in water (60 g/l at 3.C; 670 g/l at 70.C~ ethanol (25 g/l at 3.C) and methanol (545 g/l at 18.C)


Exsts-in tw forms:

ß-CoS-reddish, sIlverwhite crystals or grey powder;

Practically insoluble in water (0.0038 g/l at 18.C) and soluble in acids

a-CoS-black amor-

Soluble in hydrochloric acid

phous powder





Table 2 (contd) Chemical name

Dicobalt octacabonyl

Atomicl molecular weight

Melting-point CC)


Decmpos above 52

Tetracobalt dodeca-



Typical physical




ot: Orange crytals or darkbrown microcrystals

Practically insoluble in water Slightly soluble in ethanol Soluble in cabon disulfide and diethyl ether


Black crytals

Slightly soluble in cold water


Soluble in benzene

aprom Weast (1988); Budava (1989), unless otherwse specified bfrom Considine (1974)

.. 'From CP Chemicals (1989a) dfrom Sax & Lewis (1987)

eprom Hall Chemical Co. (undated a) 1From Brauer (1%5) 8'e molecular weight of cobalt naphthenate varies, depending on the source of naphthenate and the method of preparation, rang-

ing betwen 239-4 (6-10.5% cobalt) (US Environmental Protection Agency, 1983l



ot: q


o ~ '1

o C




Iirom Bennett (1974)

Prom Aldrich Chemical Co. (undated a)


UJ -.



higher temperatures (from 417° C to the melting-point; Considine, 1974). The free energy change is low, however, so that transformation from the face-centred cubic

back to the hexagonal close-packed form is slow and may be inhibited by physical form (e.g., grain size or presence of other metals) (Donaldson, 1986).

The main oxidation states of cobalt are Co(2 + ) and Co(3 +). Cobalt is stable to atmospheric oxygen, but when it is heated it is oxidized to the mIxed oxide, Co(II,III) oxide (C0304); at temperatures above 90°C, Co(II) oxide (CoO) is the end-product. Cobalt metal does not combine directlywith hydrogen or nitrogen but

combines with sulfur, phosphorus and carbon when heated. Cobalt forms a protective lay~r of sulfide scale when reacted with sulfur at temperatures below 877° Cor in an atmosphere of hydrogen sulfide. It forms a mIxed oxide-sulfide scale

in air containing sulfur dioxide (Donaldson et al., 1986a). Cobalt also has magnetic properties. Hexagonal cobalt is ferromagnetic. The

cubic form is magnetically anisotropic up to about 100°C and becomes paramagnetic at 1121°C. Single crystals show marked magnetic anisotropy up to about

250°C (Donaldson, 1986).

Cobalt compounds With the exception of the mixed oxide (C03Ü4), the major commercial cobalt

chemicals are aIl compounds of cobalt in its stable + 2 oxidation state. A few simple salts of cobalt in its + 3 oxidation state have been used commercially (e.g., C0203),

and many Co(III) complexes with ligands such as NH3, CN-, N02-, ethylenediaminetetraacetic acid, phthalocyanines and azo dyes have been studied extensively. These electron-donor ligands strongly stabilize C03 + in solution, usually forming octahedral complexes, many of which can be isolated as stable salts. ln acid solution, in the absence of such complexing ligands, C02+ is the stable form table that it is reduced rapidly and spontaneously to C02 + , and C03 + is so uns

oxidizing water to molecular oxygen. ln contras

t, in an alkaline solution containing

ammonium hydroxide or cyanide, C02+ is readily oxidized by air or hydrogen peroxide to the more stable C03+ complex. The C02+ f: C03+ interconversion is important in many applications of cobalt compounds, including their use as catalysts and as paint driers and in the reactions ofvitamin B12(National Research Council, 1977; Donaldson, 1986; Donaldson et aL., 1986a,b). i.3 Technical products and irnpurities (a) Cobalt metal and cobalt alloys

trial use as 'broken' or 'cut' cathodes or electrolytic coarse powder. The cathodes measure 10-25 mm and weigh 20-50 g, Cobalt metal is avaIlable for indus



with a purity greater than 99.5%. The 'fine', 'extrafine' and 'superfine' cobalt powders manufactured from the cathodes have a submicrometre mean particle size tain both allotropic crystal forms in varying proportions for different and con

applications. Electrolytic coarse powder has a mean particle size of 4-10 iim (Cobalt Development lnstitute, 1989). Cobalt iS,also avaIlable as briquets, granules

(99.5% cobalt), rondelles, powder (99.995% cobalt or 99.8% cobalt, ~ 2 iim), ductile strips (95% cobalt, 5% iron), high purity strips (99% cobalt), foIl (99.95 or 99.99% cobalt, 0.1- 1 mm), rads (99.998% cobalt, 5.0 mm) and wire (~ 99.9% cobalt,

0.25-2 mm) (Sax & Lewis, 1987; American Chemical Society, 1988; Aldrich Chemical Co., 199). Cobalt alloys can be categorized into six broad types: superalloys

(high-temperature alloys), magnetic alloys, hard-metal alloys, high-strength steels, electrodePOsited alloys and alloys with special properties (Donaldson, 1986).

Elements used in cobalt alloys are classified in terms of their effect on the transition from the cubic to the hexagonal form. Enlarged-field components, which lower the transition temperature, include aluminium, boron, carbon, copper, iron,

manganese, niobium, nickel, tin, titanium and zirconium. Restricted-field rature, include antimony, arsenic, chromium, germanium, iridium, molybdenum, osmium, platinum, rhenium, rhodium, ruthenium, silicon, tantalum and tungsten (Donaldson, 1986). Cobalt superalloys, a term generally applied to immensely strong, hard, wearand corrosion-resistant alloys, were first introduced in the 1930s. They were components, which raise the transition tempe

developed for use at high temperatures where relatively severe mechanical stressing

or strength at high temperatures arises froID a close-packed face-centred cubic, austentitic lattice system, which can maintain better tensile, rupture and creep properties at

is encountered and where high surface stabilty is required. Their su


elevated temperatures than a body-centred cubic system (Donaldson & Clark, 1985; Donaldson, 1986). Superalloys are usually either cobalt- or nickel-based. Cobalt-based

superalloys typically consist of a cobalt-chromium face-centred cubic solid solution

matrIx with the following ranges of composition: chromium, 15-29.5%; nickel, -i 28%; tungsten, -i 15%; tantalum, -i 9%; molybdenum, -i 5.5%; aluminium, -i 4.3%; titanium, -i 4%; zirconium, -i 2.25%; carbon, 0.04-1%; and boron, -i 0.11%. Small quantities of niobium, yttrium, lanthanum, iron, manganese,

silcon and rhenium are present; and the balance is cobalt. Chromium is added to improve resistance to hot corrosion and oxidation. Nickel is added to stabilze the face-centred cubic structure by offsetting the tendency of the.refractory metals to initiate transformation to the hexagonal close-packed structure (Donaldson & Clark, 1985).



Nickel-based superalloys were developed from the nickel-chromium alloys that had been used for over 50 years for electrical resistance, which often contain cobalt. They consist of a face-centred cubic, solid solution matrIx with the following ranges of composition: chromium, 1.6-28.5%; cobalt, 1.1-22%; tungsten, 0-12.5%; molybdenum, 0-10%; aluminium, 0-6%; titanium, 0-5%; boron, 0-0.62%; carbon, 0.04-0.35%; zirconium, 0-0.13%; small amounts of tantalum, hafnium, iron,

manganese, silicon, vanadium, niobium, magnesium and rhenium; and the balance as nickel (Donaldson & Clark, 1985).

Vitallum (CAS No. 12629-02-6), a cobalt-chromium alloy containing 56-68%

cobalt with additions of chromium (25-29%), molybdenum (5-6%) and nickel (1.8-3.8%) was developed in 1936 (ASTM A567- 1; Planinsek & Newkirk, 1979;

Donaldson et al., 1986b; Johnston, 1988; Roskill Information Services, 1989).

Sorne representative analyses of cobalt-containing alloys are given in Table 3. Magnetic a//oys. Cobalt is the only element capable of increasing the saturation

magnetization of iron and is an important constituent of permanent magnets, commercial magnet steel (35% cobalt) and soft-magnet alloys. Representative analyses of some Alnico magnetic alloys (cobalt added to alloys of aluminium, nickel and iron) are given in Table 4. Magnets combining cobalt with rare-earth

mineraIs were developed in 1967. Rare-earth cobalt alloys contain 60-65% cobalt and have the composition RC05, where R represents a rare-earth metal (Donaldson, 1986). A samarium-cobalt magnet was commercially available in the early 1970s, and a series of magnets with the composition RiC017 was marketed in 1980. ln 'hard-metal a//oys (cemented carbides), cobalt powder is used as a matrix or

bonding agent. The most commonly used cemented carbide, tungsten carbide, al and 5- 10% cobalt, although up to 30% cobalt may be used for certain purposes. The properties of cemented tungsten contains 80-90% by weight of hard met

carbides are sometimes enhanced by addition of the carbides of niobium, tantalum or titanium (Donaldson, 1986).

eobalt-containing high-strength steels. Although cobalt is not a common alloying element in steel, it can be an important component when high strength is

required (Donaldson, 1986). Maraging steels, used in the fabrication of tools and other applications requiring high strength-to-weight ratios, typically con

tain 8- 18%

cobalt alloyed with iron, nickel (8-19%), molybdenum (1-14%) and small amounts of aluminium and titanium (Roskill Information Services, 1989).

Cobalt-containing martensitic stainless maraging steels, especially designed for corrosion resistance and high tensile strength, typically contain 5-20% cobalt,

10~ 15.5% chromium, 0-8.2% nickel, 2-5.5% molybdenum and small amounts of carbon and titanium (Roskill Information Services, 1989).

Table 3. Examples or superalloys cODtaining cobalt (values iD weight %)Q Trade name

Nimoct alloy



























263 Udimet 500

Hastelloy alloy

19.0 1.5
















0.00 0.04







0.007 0.05











Inconel alloy 617
















Haynes alloy 1002
















WI-52 Haynes alloy










Haynes alloy 556






















q 0











max 3.0


max 20.0






Ü en

aprom Nickel Development Institute (1987)

w -. VI



Table 4. Composition and magnetic properties or A1nico alloysQ Compoition (%) Co






21-28 16-20 18-21


2-4 3-6 2-4 2-4

0-1 0-1 4-8

12-14 17-20 23-25 32-36

2425 32-36

12-15 14-16 13-15 14-16

9-11 8-10 7.8-8.5 7-8 7.8-8.5 7-8


2-4 4

Method of manufacture

Coercive force

Cast Cast Cast Field treated Field treated

3656 4050 6072 4652

Columnar Columnar





0-1 0-1


110-140 110-140

aprom Donaldson (1986)

The uses and composition of electrodeposited alloys and alloys with special

properties are described below. Typical specifications for one class of special purpose alloys, those used in surgical implants, are given in Table 5. Table 5. Composition or sorne cobalt-containing allOys used ror surgical implants (%)Q







Cobalt Chromium Molybdenum Nickel Iron Carbon

Balance 27.0-30.0 5.0-7.0 1.0 max


Balance 26.0-30.0 5.0-7.0


1.0 max 1.0 max

Balance 19.0-21.0 9.0-10.5 33.0-37.0 1.0 max 0.025 max 0.15 max

Manganese Nitrogen Phosphorus Sulfur Titanium Tungsten

0.75 max 0.35 max


0.15 max

NA 0.015 max 0.010 max 1.0 max NA


3.0-.0 15.0-25.0

4.0-.0 0.05 max 0.50 max 1.0 max

NA NA 0.010 max 0.50-3.50


1.0 max 0.75 max 0.35 max 1.0 max 1.0 max 0.25 max NA NA NA NA

aprom American Society for Testing and Materials (1984, 1987a,b, 1988)

NA, not applicable



(b) Cobalt compounds

Cobalt(ll) acetate is sold byone company as a reddish-pink solution containing 6-9% cobalt and 2% acetic acid (Hall Chemical Co., undated b).

Cobalt(ll) acetate tetrahydrate is avaIlable at purities up to 100% from several companies as pink to red-violet crystals (BDH Ltd, 1989a; CP Chemicals, 1989b;

J.1: Baker, 1989a; Mallnckrodt, 1989a; Hall Chemical Co., undated c). Technical-grade cobalt(II) acetate tetrahydrate, offered by one US company as red crystals, contains a minimum of 23.5% cobalt and small amounts of impurities (iron, 0.005% max; copper, 0.005% max; chlorine, 0.01% max; sulfate ion, 0.05% 1989a). Cobalt carbonate is offered by one US company as a reddish-purple powder

max; insolubles in acetic acid, 0.03% max; Shepherd Chemical Co., 1987a,

containing a minimum of 45.5% cobalt and small amounts of impurities (iron, 0.005% max; copper, 0.005% max; lead, 0.005% max; chlorine, 0.01% max; sodium, 0.6% max; insolubles in dilute hydrochloric acid, 0.05% max; cadmium, 0.005%

max; sulfate ion, 0.2% max; Shepherd Chemical Co., 1987b, 1989b). Several companies offer cobalt carbonate as a pink powder or red crystals at 90-100%

purity (CP Chemicals, 1989c; J.1: Baker, 1989b; Hall Chemical Co., undated d). Basic cobalt carbonate, the primary commercial product, typically contains 45-47% cobalt (Donaldson et al., 1986a). Cobalt chlonde is sold commercially mainly as the hexahydrate or other hydrated form. Cobalt chloride hexahydrate is available from several companies as red crystals in purities up to approximately 100% (BDH Ltd, 1989b; CP Chemicals, 1989c; Mallnckrodt, 1989b; Aldrich Chemical Co., undated b,c; Hall Chemical Co.,

undated a). Technical-grade cobalt chloride hexahydrate, available from one US

company as red crystals, contains a minimum of 24% cobalt and small amounts of impurities (iron, 0.02% max; copper, 0.02% max; sulfate ion, 0.1% max; water insolubles, 0.05% max; Shepherd Chemical Co., 1987c, 1989c). The hexahydrate is alsoavaIlable as a pink-to-red powder at 98-100% purity(J.I Baker, 1989c)

and as a

clear reddish aqueous solution containing 14.5% cobalt (Hall Chemical Co., undated e). Cobalt chloride is also available commercially as a c1ear, purple

aqueous solution containing approximately 6% cobalt chloride (Mallnckrodt, 1989c) and as essentially pure (99.99%) hydrated red-violet powder and chunks (Aldrich Chemical Co., undated d). Anhydrous cobalt chloride is available from two companies as a blue powder at purities up to 97% (BDH Ltd, 1989c; Aldrich Chemical Co., undated e) and from another at a purity of 100% (Hall Chemical Co., undated f).



eobalt(ll) hydroxide is avaIlable commercially as a solid containing 62% cobalt and an antioxidant (Donaldson et al., 1986a), as a blue-green, moist press cake (E

grade) containing 68% cobalt hydroxide and less than 500 ppm ammonia (Hall Chemical Co., undated g), as a technical grade (95% cobalt hydroxide; Aldrich Chemical Co., 199) and as a pink powder containing a minimum of 61 % cobalt and

small amounts of impurities (chlorine, 0.02% max; acetic acid insolubles, 0.2% max; copper, 0.01% max; iron, 0.01% max; manganese, 0.03% max; nickel, 0.3% max; sulfate ion, 0.3% max; Shepherd Chemical Co., 1988a, 1989d). Cobalt molybdenum oxide is produced by one company in the USA (Chemical

Information Servces Ltd, 1988). Commercial grade cobalt naphthenate is available as a solution of 65% cobalt naphthenate (6% cobalt) in white spirits (Nuodex, 1986; Hall Chemical Co., undated h). One US company offers 6 and 8% liquid grades; another offers liquid, flake and solid forms (American Chemical Soiety, 1988). One Canadian company and one US company offer 6% cobalt naphthenate in solution with white spirits and 10.5% flaked cobalt naphthenate (Dussek Campbell Ltd, 1989a,b; Shepherd

Chemical Co., 198ge,f). One US company offers cobalt nitrate hexhydrate as a red-brown crystallne

powder at 99.99% purity or as red chips in reagent grade or at 99% purity. The reagent grade is 98% pure and contains small amounts of impurities (insolubles, ~ 0.01%; chloride ion, ~ 0.002%; copper, ~ 0.002%; iron, ~ 0.001%; ammonium, ~ 0.2%; nickel, ~ 0.15%; and sulfate ion, ~ 0.005%) (Aldrich Chemical Co., 199, undated f,g,h). The hexahydrate is available as pink-to-red crystals at 90-100%

purity from three US companies and from one company in the UK (BDH Ltd, 1989d; J.1: Baker, 1989d; MalInckrodt, 1989d; Hall Chemical Co., undated i). Technical-grade cobalt nitrate hexahydrate is available from one US company as

small, red flakes with a slight odour of nitric acid and contains a minimum of 19.8% cobalt, with small amounts of impurities (iron, 0.002% max; copper, 0.005% max; lead, 0.005% max; zinc, 0.05% max; chlorine 0.005% max; sulfate ion, 0.01% max;

water insolubles, 0.02% max; Shepherd Chemical Co., 1986a, 1989g). Aqueous cobalt nitrate (Co(N03)i°xHiO) is available froID one US company as a dark-red solution containing approximately 14% cobalt (Hall Chemical Co., undated D.

Cobalt nitrate is also available in 1-2% aqueous nitric acid solution as a laboratory standard containing 100 ppm cobalt (0.1% w Iv; J.1: Baker, 198ge;

Aldrich Chemical Co., 199). eobalt(ll) oxide is available as a laboratory reagent from one US company as a green, red, greyor black powder at 90-100% purity (70-74% as cobalt), with small

amounts of impurities (chloride, 0.02% max; nitrogen compounds as nitrogen, 0.02% max; sulfur compounds as sulfate ion, 0.1% max; iron, 0.1% max; nickel~

0.2% max; insolubles in hydrochloric acid, 0.05%; J.1: Baker, 1989f,g). One



company in the UK offers cobalt oxide as a fine, black pOVlder (BDH Ltd, 198ge).

Cobalt(II) oxide is also available in ceramic grade (70-71% cobalt), metallurgical grade (76% cobalt) and high-purity powder grade (99.5%; may contain 10 ppm

metallc impurities; American Chemical Soiety, 1988). Cobalt(II) oxide is produced by only a few companies (Chemical Information Services Ltd, 1988) and is not of major commercial importance. eobalt(ll,/ll) oxide is available as a black powder at 99.995% purity (Aldrich Chemical Co., undated a), as a black powder with a cobalt content of 72-73% (Aldrich Chemical Co., 199, undated i) and as a black-grey powder with 71-72%

cobalt as cobalt oxide and less than 1% nickel as nickel monoxide (Hall Chemical Co., undated k). Another mixed oxide, containing a ratio of 3:1 cobalt(III) oxide:cobalt(II) oxide, is available at 99.99% purity (Chemical Dynamics Corp., 1989). It is produced by many companies throughout the world.

eobalt(lll) oxie is available in small quantities for laboratory use from one US company as a powder at 99.99% purity (72.3% as cobalt) with small amounts of impurities (chloride, 80 J.g/g; nitrate, 35 J.g/g; silicon, 2 J.g/g; aluminium, ~ 1 J.g/g; copper, ~ 0.5 J.g/g; iron, 1 J.g/g; magnesium, 0.7 J.g/g; nickel, 2 J.g/g; J.1: Baker, 1989g).

Cobalt sulfide (form unspecified) is sold by one company in the USA (Chemical Information Services Ltd, 1988).

Cobalt sulfate heptahydrate is available from several companies as pink-to-dark-red crystals in purities of

90- 100% (BDH Ltd, 1989f; 1.1: Baker, 1989h;

Mallnckrodt, 198ge; Aldrich Chemical Co., undated j,k; Hall Chemical Co.,

undated 1). Technical-grade cobalt sulfate heptahydrate avaIlable from one US

company as red-pink crystals contains a minimum of 20.8% cobalt and small amounts of impurities (iron, 0.005% max; copper, 0.002% max; water insolubles, 0.05% max; Shepherd Chemical Co., 1986b, 1989h). The monohydrate is avaIlable as pink-to-red crystals with a minimum of 33% cobalt and with small amounts of impurities (iron, 0.007% max; copper, 0.003% max; water insolubles, 0.1% max; Shepherd Chemical Co., 1987d, 1988b), and with a purity of 100% (Hall Chemical Co., undated m).

Cobalt sulfate is also available commercially as a rose-to-dark-red aqueous solution containing approximately 8% cobalt (CP Chemicals, 1989d; Hall Chemical Co., undated n).



2. Production, Use, Occurrence and Analysis 2.1 Production (a) Cobalt and cobalt alloys

Cobalt, a major constituent of about 70 naturally occurring oxide, sulfide, arsenide and sulfoarsenide mineraIs, is produced primarily as a by-product of the mining and processing of copper and nickel ores and, to a lesser extent, of silver,

zinc, iron, lead and gold ores. Commercial cobalt production began in Canada in 1905. ln 1924, a company in Zaire (then the Belgian Congo) started recovering cobalt during the mining of copper ores, and that country has been the worlds largest producer since 1926

(Roskill Information Services, 1989). World mine production of cobalt peaked in the mid- 1980s, but the production of refined cobalt metal has been decreasing since

the early 1980s because beneficiation and extractive metallurgy are not designed for maximizing the recovery of cobalt (Roskill Information Services, 1989). World mine and metal production of cobalt iD 1970-88 is presented in Table 6.

Table 6. World mine and metal production or cobalt, 1970-88 (tonnes)a Year

1970 1971 1972 1973 1974 1975 1976 1977 1978 1979

Mine production

Metal production


28 985 26 405

25 90

1980 1981 1982 1983 1984 1985 1986 1987 1988 1989

30 177

35 746 39 453 37 479 26 024 26 303

27 203 24 645 28 113


30 745 25 275 22 827 25 227 24 780

36 148


Mine production



37 873 37 363 24 567 37 875

36 720 31 325

41075 48 30

23 627

48 903 46 382 43 90b

30 673 26 939 25 28c,d

38 700b,c


19 292

18 08

26 90

"From Roskill Infonnation Servce (1989), unless otherwse specified bprom Shedd (199)

~timate dprom Shedd (1988)

NA, Not available



Between 1983 and 1987, cobalt was mined in amounts gre~ter than 100 tonnes in 16 countries and was refined in 12. The cobalt-producing countries or regions in

those years were Albania, Australia, Botswana, Brazil, Canada, China, Cuba, Finland, MOf()Cco, New Caledonia, the Philippines, South Africa, the USSR, Zaire, Zambia and Zimbabwe. The countries that refined cobalt during this period were Belgium, Canada, China, Finland, France, Japan, Norway, South Africa, the USSR,

Zaire, Zambia and Zimbabwe (Johnston, 1988; Shedd, 1988). (i) Cobalt mining, refining and/or production by country Autralia: Cobalt is mined but not refined in Australia (Shed

d, 1988). ln 1986,

one company ceased supplying nickel-cobalt sulfides to Japanese refineries and began to supply aIl of their by-products to a refinery in Finland (Kirk, 1986). Belgium: Sm

aIl quantities of partly processed materials containing cobalt have

been imported, but information is inadequate to estimate the recovery of cobalt (Kirk, 1986). About one-third of the cobalt exported by Zaire is processed in Belgium, and about half of this production is exported to the USA (Kirk, 1985). Botswana: One company in Botswana began mining for cobalt in 1973 (Kirk, 1985). The cobalt-containing nickel-copper matte is sent to Norway (74%) and

Zimbabwe (26%) for refining (Shedd, 1988); previously, it was refined in the USA (Kirk, 1985).

Brazil: One company began production of electrolytic cobalt in late 1989 at a nickel plant with an initial production capacity of 300 tonnes. It produced a cobalt concentrate which was sent to a Norwegian refinery for processing. Previously, Brazil depended on imports from Canada, Norway, Zaire and Zambia (Kirk, 1987; Shedd, 1988, 1989).

Bulgaria: Bulgaria is known to produce ores that contain cobalt, but information is inadequate to estimate output (Kirk, 1985).

Canada: Cobalt production in Canada began in 1905 (RoskiIl Inforffation Services, 1989). Three companies currently mine cobalt, and one of these refines it

(Shedd, 1988). The intermediate metaIlurgical product cobalt oxide has been shipped to the UK for further processing, and a nickel-copper cobalt matte has been shipped to Norway (Kirk, 1986, 1987).

China: A primary cobalt deposit mine was equipped in 1986 and has a reported annual output of 45 thousand tonnes of ore (Kirk, 1986). Cobalt mine production in 1987was estimated to be 270 tonnes (Johnston, 1988). A large deposit of nickel-copper-cobalt was discovered in China in 1988 (Shedd, 1988).

ezechoslovakia: Czechoslovakia is believed to recover cobalt froff Cuhan nickel-cobalt oxide and oxide sinter (Kirk, 1985; Shedd, 1988).

Finland: ln 1986, a company in Finland began processing nickel-cobalt sulfide froff Australian nickel oxide production into cobalt and nickel salts (Kirk, 1986). ln



1987, a mining and metallurgical cobalt and nickel producing company in Finland suspended production of standard-grade cobalt powder and briquets to focus on producing extra-fine powder and cobalt chemicals. ln 1988, the copper-cobalt mine d,

was closed and cobalt concentrates were no longer produced (Kirk, 1987; Shed


Germny. Ores that contain cobalt are produced in Germany, but information is inadequate to estimate output (Kirk, 1985).

Greece: Ores that contain cobalt are produced in Greece, but information is inadequate to estimate output (Roskill Information Servces, 1989).

lndia: A plant projected to open in 199 can recver approximately 27 tonnes of cobalt per year from a lead-zinc ore mine in India. ln addition, recovery of cobalt

from lateritic overburden in chromite mines is being studied (Shedd, 1988). lndonesia: One company in Indonesia produces ores that contain cobalt, but information is inadequate to estimate output (Shed

d, 1988).

Japan: Mining of cobalt in Japan ceased in 1986. Two Japanese refiners have received nickel-matte from a Canadian facilty in Indonesia and feedstock from Australia and the Philppines (Shedd, 1988).

Morocco: Mining of cobalt was begun in Morocco in the late 1930s (Roskill Information Services, 1989); mining of cobalt as a primary product ceased in 1982, but mining from cobalt-iron-nickel arsenides was resumed in 1988. Beginning in 1988, Morocco agreed to provide China with cobalt concentrate (Shed

d, 1988).

New ea/edonia: Ores and intermediate metallurgical products have been exported to France, J apan and the USA (Kirk, 1987; Shedd, 1988).

Norway. One company in Norway refines cobalt mostly from nickel-cobalt-copper matte imported from Canada (60%) and Botswana (30%) (Shedd, 1988).

Philippines: Cobalt was recovered as a by-product of nickel mining by a state-owned company in the Philppines until 1986, when the mine was closed. Production of cobalt from the mine peaked at about 1360 tonnes in 1979 (Kirk, 1987; Shedd, 1988).

Po/and: Ores that contain cobalt are produced in Poland, but information is inadequate to estimate output (Kirk, 1985).

South Afrca: Cobalt is mined and refined in South Africa (Shedd, 1988), and a

foreign-owned company produced cobalt as a by-product of platinum mining operations (Kirk, 1987).

Spain: Ores that contain cobalt are produced in Spain, but information is inadequate to estimate output (Kirk, 1985).

Uganda: Construction-of a cobalt refinery is planned in conjunction with the rehabiltation of copper mines, which ceased operation in 1979 (Shedd, 1988).



UK: Products of Canadian origin are processed in the UK (Kirk, 1986, 1987). USA: The USA began mining cobalt in the late 1930s but ceased domestic mine production at the end of 1971. Refining of imported nickel-cobalt matte by the sole US cobalt refinerywas discontinued in late 1985. ln 1985-88, the USAimported

31% of its cobalt from Zaire, 21% from Zambia, 21% from Canada, 10% from Norway (originating in Canada and Botswana) and 17% from other countries

(Shedd, 199), which include Belgium, Finland, France, Germany, Japan, the Netherlands, South Africa and the UK (Kirk, 1987).

Two companies in the USA produce extra-fine cobalt powder: one is a foreign-owned company that uses imported primary metal; the other is a

domestically controlled company that uses cobalt recovered from recycled materials. Seven companies produce cobalt compounds (Shedd, 1990). SR (Shedd, 1988); in addition, nickel-cobalt sulfide concentrate from Cuba is refined (Kirk, 1985). Zaire: Cobalt recovery from the mining of copper ores began in 1924, and since 1926 Zaire has been the worlds largest producer of cobalt (Roskill Information USSR: Cobalt is mined and refined in the US

Services, 1989). Sulfide and oxide concentrates are processed to cobalt metal in the form of cathodes and granules. About one-third of their exports go to Belgium for further processing (Kirk, 1985).

Zambia: Mining of cobalt began in Zambia in the late 1930s (Roskill Information Services, 1989). Cobalt is also mined and refined as a by-product of copper mining (Kirk, 1985; Shedd, 1988). Zimbabwe: Cobalt is mined and refined in Zimbabwe and is also recovered from nickel-copper matte imported from Botswana (Shedd, 1988).

Mine and metal production of cobalt by country or region with reported outputs for 1984 to 1988 are presented in Tables 7 and 8.

(ii) Metallurgy

Cobalt-containing ores vary widely in composition but usually contain less than 1% cobalt. Although each type of ore (arsenide, sulfide or oxide) is processed differently, six general metallurgical processes can be distinguished; depending on the ore's composition, recovery of cobalt may require one or a combination ofthese

techniques. It is important to note that in nearly aIl cases cobalt is a by-product of aIs (Roskill Information Services, 1989), especially copper

the refining of other met

and nickeL. Refinery methods therefore are generally not designed to maximize cobalt recovery (Anon., 1990a).

. The main sources of cobalt (in decreasing ease of recovery) are ores of copper-cobalt oxides (Zaire) and sulfides (Zaire and Zambia), copper-nickel sulfides (Canada), cobalt-iron-nickel arsenides (Mof()Cco and China) and



Table 7. World mine production of cobalt by country or region, 1984-88Q


Albania Australia Botswana

Mine output, metal content (tonnes) 1984





590 938 259





1 136

1 218

1 20

1 100


182 150

292c 150

2 no



162 150

2330 1 40




1 491

1 500

1 590


1 094







New Caledoniab





Philppines South Afcab

64 682

913 682

700 92 682





2 815



25 997

29 226

33 403

29 056b

25 425


5 812b

5 770b

5 950b

6 675






46 838


45 80

43 950

Bral Canada Cubad Finland



Zare Zambia Zimbabweb Total

41 014.


200 182 253


aprom Shedd (1988), unless otherwse speified

b&timates ~eported figure

~timates from reported nickel-cbalt content of granular and powder oxide, oxide sinter and sulfide production

NA, not available

nickel-cobalt oxides (Iateritic nickel ore from most other sources) (Planinsek & Newkirk, 1979; Donaldson et al., 1986a; Shedd, 1988). After crushing and grinding, the first stage of cobalt recovery from ore involves

the physical separation of cobalt-containing minerais from other nickel ores and gauge, usually by gravity (arsenide ores) or froth flotation (sulfoarsenide and sulfide ores). Flotation is also used for separating cobalt in oxide and mIxed oxide-sulfide

ores. Flotation is frequently aided by the addition of xanthates, oils or cyanide to depress cobalt flotation (Donaldson, 1986; Donaldson et aL., 1986a); the amount of cobalt in the concentrate is usually enhanced four to eight fold by these operations (Roskill Information Services, 1989).

Cobalt is extracted from ore and concentrated by pyrometallurgical, hydrometallurgical and electrolytic processes alone or in combination. Arsenicfree cobalt concentrates can be mixed with lime and coal and smelted in a reducing



Table 8. World metal production or cobalt by country, 1984-88 (tonnes)a







Canada Finland France

2218 1456

2027 2235

1994 1350

2 205D






l09D 124

220 50

J apan

Noiwy South AfcaD USSRD

Zaire Zambia Zimbabwe Total





1340 1583






4725 9083 3475





10 690


11 911

10 150










23 751

27 766


26 881

25 298




'Prom Shedd (1988)


environment to give copper-cobalt alloys. The alloy is further processed to separate copper and cobalt. The most commonly used hydrometallurgical processes involve roasting and leaching of ore concentrates (with acid or alkali solutions), fraction

al aIs in the leachate (by differential sulfide or hydroxide precipitation) and reduction of the cobalt ions to metal (by chemIcal or electrochemical means) (Donaldson, 1986; Donaldson et al., 1986a; Roskill separation of cobalt from other met

Information Services, 1989). The three main processes for leaching cobalt from ores and concentrates are described below.

Acid sulfate leaching can be done byone of four methods: (a) treating oxide ore

concentrates with sulfuric acid and reducing agents (S02); this is the priffary process used in Zaire; (b) water extraction of cobalt sulfate from ores following an oxidizing roast; (c) cobalt sulfate extraction of sulfide ore concentrate following a

sulfatizing roast; this method is used in Zaire, Zambia and Finland; or ( d) pressure leaching with sulfuric acid, which has recently been introduced in Canada and is

useful for arsenic-containing ores. The cobalt is separated from copper, iron, nickel

al dissolution with sulfide. Cobalt is precipitated as the hydroxide, redissolved and refined by electrolysis or hydrogen reduction to cobalt metal cathode or powder, respectively (Roskill Information Services, 1989). and zinc (when present) by alkalinization and fraction

Acid chlonde leaching of ore mattes and recyclable materials is used as an

alternative to acid sulfate leaching on oxides, sulfides, arsenides and alloys. This



method is usually followed by solvent extraction or ion exchange purification. The soluble chloride complexes are often formed by reaction with chlorine or hydrogen chloride gas or a metal chloride. This method is used in Japan. Ammoniacal solution leaching gives rise to the hexammine cobalt complex 2 (Co(NH3)6)

+ . This method has been used to treat alloy scrap and laterite or

arsenide ores. It is used in Canada for procssing lateritic nickel ores. The soluble extract is treated with hydrogen sulfide to produce mixed nickel-cobalt sulfides,

which are redissolved in sulfuric acid. Cobalt powder is recovered after the introduction of ammonia and hydrogen under high pressure.

Metallc -cobalt can also be recovered directly from purified leachate by electrolysis (electrowinning) after nickel has been removed as the carbonyL. Sorne cobalt salts can be formed by dissolution of the metal in the corresponding acid.

Sorne refineries utilze cobalt hydroxide to form the oxide and other cobalt compounds directly (Donaldson, 1986; Donaldson et al., 1986a; Roskill Information Services, 1989; Anon., 199a). (iii) Production processes

Refined cobalt is available to the industrial market primarily as broken or cut cathodes (92%) and to a lesser extent as electrolytic coarse powder (3%) and in other forms. The cathode form is further processed to alloys, chemicals and oxide or used in the manufacture of special cobalt powders for cemented carbide by chemIcal and pyrometallurgical processes. About 20 tonnes of cobalt cathode are converted to a distinct allotropic mixure, called 'fine powder' or 'extrafine

powder', by specialist producers for cemented carbide and diamond polishing. The

process involved is a chemical reaction that results in a submicrometre powder wi th a high proportion of face-centred cubic crystal retained in the mixure. This special

material differs from electrolytic coarse powder and from cobalt powders generated during industrial attritive operations, which are predorninantly hexagonal crystals (Cobalt Development Institute, 1989). Cobalt alloys are usually manufactured from broken or cut cathodes byelectric

arc or by induction melting techniques, although vacuum induction melting is required for sorne alloys containing metals such as aluminium, titanium, zirconium, boron, yttrium and lanthanum. The resultant mas

ter alloy is then rernelted and cast

into moulds (Donaldson & Clark, 1985; Donaldson, 1986). An important use of cobalt is in the production of cernented tungsten carbide, also called 'hard metal'. Hard metals are used to tip the edges of drills and cutting tools and for dies, tye studs and stamping machines (Kipling, 1980). Hard metal is made bya process in which precise weights of tungsten carbide (80-90% by weight)

and cobalt metal powder (5-10%) and, in sorne grades, srnall amounts of other carbides (titaniurn, tantalum, niobium and molybdenum) are added and thoroughly



mixed in mils. The cobalt thus acts as a matrix; nickel is also used with cobalt as a matrix in some grades. Organic solvents, such as acetone and n-hexane, are added for mixng; the mixure is dried, and the organic solvents are evaporated off. The powder is put into frames made of steel or rubber and then pressed into the desired

shapes; the pieces are placed on graphite plates and embedded in nitrous aluminium powder; and the pressed material is presintered in hydrogen furnaces at 500-80°C. After presintering, the material has the consistency of chalk, and it is

cut, ground, driled or shaped into the configurations required. The shaped material is finally sintered at temperatures of 1550°C. After sintering, the product

approaches the hardness of diamond. Hard-metal products are sand blasted or shot blasted, brazed into holders made of iron using f1uoride-based f1uxes and then

ground with diamond or carborundum wheels. These processes are iIustrated in Figure 1 (Kusaka et al., 1986).

The manufacture of sorne alloys containing cobalt and their further fabrication into engineering parts can be assumed to take place to sorne extent in almost aIl industrialized countries. Manufacture specificaIly of superalloys for aircraft engines is concentrated in the USA, the UK, France, Germany and Japan, but sm


volumes of manufacture and specialist manufacture occur in several other regions.

Use of cobalt in magnetic applications occurs mainly in Japan, but the USA and

European countries (particularly Germany, France and the UK) also have large production capacities (Johnston, 1988).

(b) Cobalt compounds

Europe produces 50% of the global amount of cobalt chemicals and 70% of fine cobalt powders (Johnston, 1988). Most cobalt chemIcals (75-80%) are

produced by six companies in Belgium, Germany, Finland and the USA. A further 6-8% is made by three Japanese companies; minor quantities are made directly from concentrates in France and South Africa; and the balance is shared by a or specializing in perhaps one group of cobalt products, such as naphthenates for the paint (Sisco et al., 1982) and number of small manufacturers serving local markets

ink industries. Most countries - industrialized or not - have a ceramics industry of some kind or size, many of them very ancient, and in each there is sorne use of cobalt oxide or

sorne manufacture of cobalt pigment. The major world suppliers of cobalt pigments are, however, located in Germany, the USA, the Netherlands and the UK.



Fig. 1. Steps in the rnanuracture or hard-rnetal tooisa

Mlxed ..

1 Carbon 1

l Heated ln hydrogen

at 140-1500C

~ ~ ~l~' M¡e: 1 l

Paraffln 1

Organlc solvents 1


. Pressed

l Preslntered: heated ln hydrogen or vacuum at 50-800 ° C



l Sintered: heated ln hydrogen or vacuum at 150 ° C

Sand blasted

Shot blasted

l Brazed Into holders w1h f1uxes

l Ground wlth dlamond or carbrundum wheels

l 1 Flnlshed hard-metal tools 1

Ilrom Kusake et aL. (1986)



eobalt(II) acetate is prepared commercially (a) by concentrating solutions of

cobalt powder in acetic acid in the presence of oxygen or (b) from cobaltous hydroxide or carbonate and an excess of dilute acetic acid. Preparation of the tetrahydrate involves treatment of cobalt powder in acetic acid solution with hydrogen peroxide (Donaldson et al., 1986a; Budavari, 1989).

eobalt(lll) acetate can be prepared by electrolytic oxidation of cobalt(II)

acetate tetrahydrate in glacial acetic acid containing 2% (v/v) water. Another method is oxidation of solutions of cobaltous salts by alkalIne persulfates in the presence of acetic acid (Budavari, 1989).

eobalt(ll) chlonde can be produced by several processes: (a) from cobalt powder and chlorine, (b) from the acetate and acetyl chloride, (c) by dehydration of the hexahydrate with thionyl chloride and (d) by dissolving cobalt metal, oxide, hydroxide or carbonate in hydrochloric acid (Considine, 1974; Donaldson et al., 1986a; Budavari, 1989). The hexahydrate is prepared by treating an aqueous

solution of a cobaltous salt with hydrochloric acid (Budavari, 1989). Solutions of high-purity cobalt chloride and its hexahydrate can be manufactured by dissolving high-purity cobalt metal electrolytically using a dilute hydrochloric acid electrolyte

at about 60°C (Donaldson et al., 1986a). eobalt(ll) carbonate is prepared by heating cobalt sulfate with a solution of sodium bicarbonate. Basic cobalt carbonate (cobalt(II) carbonate hydroxide (2:3)

monohydrate) is prepared by adding sodium carbonate to a solution of cobaltous acetate followed by filtration and drying (Sax & Lewis, 1987). eobalt(ll) hydroxide is prepared commercially as a pink soIid by precipitation

from a cobalt(II) salt solution with sodium hydroxide. Precipitation at higher temperatures (55-70°C) causes partial oxidation of cobalt(II) to cobalt(III) and yields the pink form, whereas precipitation at lower temperatures yields the blue

form. Cobalt(II) hydroxide is prepared in situ during the manufacture of secondary

batteries: typicaIly, a spongy nickel foam plate is impregnated with an acidic solution of cobalt chloride, nitrate or sulfate, and cobalt(II) hydroxide is

precipitated by alkaIi treatment (Donaldson et al., 1986a). eobalt(lll) hydroxide can be produced by several methods, e.g., addition of sodium hydroxide to a solution of cobaltic salt, action of chlorine on a suspension of cobaltous hydroxide, or action of sodium hypochlorite ion on a cobaltous salt

(Brauer, 1%5; Sax & Lewis, 1987). eobalt(ll) molybdenum(V) oxide is obtained by raising the pH to 6.4 to

coprecipitate the hydroxides of cobalt and molybdenum from mIxed solutions of

cobalt nitrate and ammonium molybdate. The product is dried at 120°C and calcined at 400°C to give the mIxed metal oxide (Donaldson et al., 1986a). This is invariably also mIxed with aluminium oxide in commercial manufacture and use.



eobalt(ll) naphthenate is prepared by treating cobalt hydroxide or cobalt acetate with naphthenic acid (Sax & Lewis, 1987), which is recovered as a by-product of petroleum refining. Commercial naphthenic acids used in the production of cobalt naphthenate differ widely in properties and impurities, depending upon the crude oIl source and refining procsses. AlI contain 5-25 wt % hydrocarbons, the composition of which corresponds to the petroleum fraction

from which the naphthenic acids are derived; and ail contain impurities (e.g., phenols, mercaptans and thiophenols) in small quantities (Sisco et al., 1982).

eobalt(ll) nitrate hexydrate is produced by dissolving cobalt metal, the oxide,

hydroxide or carbonate in dilute nitric acid and concentrating the solution (Considine, 1974; Donaldson et al., 1986a).

eobalt(ll) oxie (CoQ) containing 78.7% cobalt is usually manufactured by controlled oxidation of the metal at above 90 ° C, followed by colIng in a protective

atmosphere to prevent partial oxidation to cobalt(II,III) oxide (Donaldson et al., 1986a ).

Cobalt(II) oxide can also be prepared by additional processing of the white alloy formed during the processing of arsenic-free cobalt-copper ores to remove copper and iron as sulfates and calcining cobalt as the carbonate (Morral, 1979) or by calcination of cobalt carbonate or its oxides at high temperatures in a neutral or

slightly reducing atmosphere (Sax & Lewis, 1987). Another method for preparing cobalt(II) oxide is dissolution of a cobalt salt that is unstable at high temperatures (e.g., cobalt sulfate) in molten sodium sulfate

or potassium fluoride. The cobalt salt decomposes, leaving the cobalt(II) oxide,

which crystallzes out at high temperatures. The water-soluble salts are then dissolved, leaving cobalt(II) oxide crystals (Wilke, 1964).

Cobalt(II,lII) oxie (C0304) containing 73.44% cobalt can prepared by the controlled oxidation of cobalt metal or cobalt(II) oxide or by thermal decomposition of cobalt(II) salts at temperatures below 90°C. It ab

sorbs oxygen

at room temperature but is not transformed to cobalt(III) oxide (COi03) (Donaldson et al., 1986a). Pyrohydrolysis of cobalt chloride has also been used to manufacture cobalt(II,III) oxide. The reaction ìs performed in a spray roaster by heating a fine

spray of aqueous solution of cobalt(II) chloride in a countercurrent heating gas stream. The hydrogen chloride gas produced is removed with the exhaust gases, and the cobalt(II,III) oxide falls to the bottom of the furnace (Donaldson et al., 1986a ).

Cobalt(lll) oxie (CÜZ03) is derived by heating cobalt compounds (e.g., hydroxides) at low temperature with an excess of air (Sax & Lewis, 1987).



eobalt(ll) sulfate heptahydrate is prepared commercially by dissolving cobalt metal in sulfuric acid (Donald

son et al., 1986a).

ex-eobalt(ll) sulfide can be precipitated from cobalt nitrate hexahydrate by reaction with hydrogen sulfide and dried for 90 h, the temperature being raised slowly from 100 to 540°C (Brauer, 1965). ß-eobalt(ll) sulfie can be synthesized by

heating fine cobalt powder mIxed with fine sulfur powder at 650°C for two to three days. It can also be derived by treating a solution of cobalt chloride with acetic acid, precipitating with hydrogen sulfide and drying for 90 h, the temperature being raised slowly from 100 to 540°C (Brauer, 1%5). Cobalt sulfides are normally

produced in situ as needed, as mIxed metal catalysts with molybdenum (Roskil Information Services, 1989). Dicobalt octacarbonyl is prepared commercially by heating cobalt metal with

carbon monoxide at high pressure (20-300 atm) £20.2-30.3 X 1() kPa) or byheating a mixure of cobalt(II) acetate with cyclohexane at about 160 ° C and 300 atm (30.3 X

1() kPa) in the presence of a 1:1 mixure of carbon monoxide:hydrogen (Donaldson et al., 1986a). Dicobalt octacarbonyl is frequently prepared in situ as needed. 2.2 Use

Cobalt compounds have been used as blue colouring agents in ceramic and glass for thousands ofyears, although most of the blue colour of ancient glasses and glazes has been found to be due to copper. Cobalt has been found in Egyptian pottery dated at about 26 BC, in Persian glass beads dating from 2250 Be, in

Greek vases and in pottery of Persia and Syria from the Christian era, in Chinese pottery from the Tang (60-90 AD) and Ming (1350-1650 AD) dynasties and in Venetian glass from the early fifteenth century. Leonardo Da Vinci was one of the first artists to use cobalt as a brillant blue pigment in oH paints. The pigment was probably produced by fusing an ore containing cobalt oxide with potash and silica to produce a glass-like material (a smalt), which was then reduced to the powdered pigment. ln the sixeenth century, a blue pigment called zaffre was produced from silver-cobalt-bismuth-nickel-arsenate ores in Saxony (Young, 1960; Donaldson, 1986).

It was not untIl the twentieth century, however, that cobalt was used for industrial purposes. ln 1907, a US scientist, E. Haynes, patented a series of cobalt-chromium alloys known as stelltes that were very resistant to corrosion and

wear at high temperatures (Kirk, 1985). Cobalt was added to tungsten carbide in 1923 to produce cemented carbides (Anon., 1989) and to permanent magnet alloys known as AlnIcos (cobalt added to alloys of aluminium, nickel and iron) in 1933 (Johnston, 1988).


392 (i) Cobalt

Cobalt has many important uses in industry today, and in some major applications there is no suitable replacement. The most important use of metallic cobalt is as an alloying element in superalloys, magnetic and hard-metal alloys, such

as stellte and cemented carbides, cobalt-containing high-strength steels, electrodeposited alloys and alloys with special properties. Cobalt salts and oxides

are used as pigments in the glass and ceramics industries, as catalysts in the oH and chemical industries, as paint and printing ink driers and as trace metal additives for agricultural and medical uses (Donaldson, 1986).

Most cobalt is used industrially in the form of cobalt metal as an alloying

component and in the preparation of cobalt salts. Estimated consumption as primary raw materials, such as cobalt metal, cobalt oxide and cobalt salts, in selected countries in 1979-87, is presented in Table 9. These countries represented

approximately 59% of total consumption in the western worId in 1979, 71.5% in 1980, 65% in 1981, 65.5% in 1982, 59.4% in 1983, 53% in 1984, 53.6% in 1985 and

62.5% in 1986. Consumption of cobalt in the western world represented approximately 85% of total worId consumption from 1983 to 1988 (Roskill Information Servces, 1989).

Table 9. Consumption or cobalt in selected countries, 1979-87 (thousand tonnes)Q Country











7.9 2.2 2.5 0.95 0.23 0.29 0.12








2.00 0.75 0.19 0.21 0.10

1.5 1.2


2.3 1.0 0.23 0.39 0.11

1.4 1.1 1.5

6.1 1.7



1.7 1.6

1.8 1.33

0.74 0.57 0.36




J apan

UK France Italy

Sween Canada

0.23 0.21 0.09

0.51 0.30 0.17 0.10

0.91 0.62 0.38 0.31 0.11

0.% 0.48 0.36 0.36 0.16

0.56 0.26

aprom Roskill Infonnation Servces (1989)

/leliminar c:timated Industrial consumption of cobalt in the western worId averaged 40 tonnes ¡n 1936-46, 700 in 1947-52, 10 00 in 1953-62, 16 80 in 1963-72, 19 500 in 1973-78,

2100 in 1979-81 and 17500 in 1982-84. Recently, less cobalt has been used in alloys

and more in chemical applications. Table 10 presents overall estimates of cobalt consumption in western economies by end use.



Table i o. Evolution or cobalt consumption in selected cou


ries (thousand tonnes)a

End product


Hard metals Magnets Ceramics Chemicals Total






2.85 0.30 2.10 0.90

5.95 0.73 3.77 1.60 2.46 14.50

6.98 0.78 3.41





4.56 19.01

6.83 2.02 2.15 2.04 6.77 19.81






tlrom Johnston (1988)

(ii) Cobalt alloys

Superalloys are used primarily in the manufacture of components for gas turbine and jet engines. Their combined properties of resistance to hot corrosion and high strength at elevated tempe

ratures contribute to their great commercial

and strategic importance. They are used in turbine components that operate at temperatures above 540°C, including ducts, cases and liners, as weIl as the major turbine blade, vane, disc and combustion-can components. Nickel-based

superalloys are usually used for gas turbine components such as discs because they

an cobalt-based superalloys; the latter have excellent resistance to thermal shock and hot corrosion and are used for combustor tubes, are more workable th

stator vanes and diaphragms. Superalloys designed to operate for long periods at

temperatures above 90°C sacrifice some of their resistance to oxidation and hot corrosion for increased strength. The nickel-based superalloys are more resistant

to oxidation than the cobalt-based superalloys because they have a higher aluminium content and form a better aluminium oxide coating on the alloy. The cobalt-based superalloys primarily form a chromium oxide coating which is not as stable, and when they are used in components subject to extremely high operating temperatures, such as turbine blades and nozzle guide vanes, oxidation-resistant

protective coatings are required. Two types of coating can be used: intermetallc and overlay coatings. Intermetallc coatings are applied by heat treatment of the

surface of the alloy with cement powders containing aluminides or, less often, silcides. Overlay coatings, which are applied by hot vapour deposition methods, are alloys containing aluminium, chromium and yttrium togetherwith nickel, cobalt or iron. Other applications of the superalloys include airframes, chemical reactors,

natural gas transmission pipelines, marine equipment and hazardous waste incineration equipment (Donaldson & Clark, 1985; Donaldson, 1986; Kirk, 1987; Cobalt Development Institute, 1989).



Magnetic alloys. Cobalt is used in a wide variety of magnetic applications,

including telecommunication systems, magnetic couplings, electromagnets, meters, loudspeakers, permanent magnet motors and repulsion devices. AlnIco magnets, invented in the mid- 1930, are used for heavy-duty applications such as automobile anti-skid braking systems. Consumption of Alnicos declined through the 196s and

1970s due to the introduction in the 196s of the less powerful but cheaper and aller ferrite-ceramic combinations of barium and strontium with iron (Kirk,


1985; Donaldson, 1986; Cobalt Development Institute, 1989; Anon., 199b). Magnets combining cobalt with rare-earth mineraIs were developed in 1967 1988). The first such magnets were samarium-cobalt alloys, but Iimited


supplies of samarium led to the development of competitive neodymium-

iron-boron magnets, which became available commercially in 1983. Rare-earth

cobalt magnets have remained important because of their power/size advantages in certain applications. ln the 1980s, they contributed to the miniaturization of

electrical and electronic equipment. They are used as focusing magnets in travellng wave tubes, as magnetic bearings in ultra-high-speed centrifugaI separators and inertia wheels, and in actuators, motors, and generators of various sizes, froID

watches to 100-hp (74.6-kw) motors (Kirk, 1985; Donaldson, 1986; Anon., 199b). Magnetic alloys are also used in medicine to provide an external attractive force. For instance, Alnicos have been used to operate a reed switch in implanted heart pacemakers; samarium-cobalt magnets have been used to hold dental plates in mouth reconstruction, to correct funnel chest and to remove magnetic fragments from the posterior portion of the eye. Magnetic cobalt alloys attached to flexible

tubes have also been used to remove iron-containing material from the intestinal and bronchial tubes. Platinum-cobalt and samarium-cobalt magnetic alloys are also used as prostheses, to provide a mechanical closing device in situations where

muscle function is impaired. They have been used in the treatment of urinary incontinence in women, to close eyelids in patients with facial paralysis and as

colostomy closure devices. ln addition, rare-earth-cobalt magnets are used in hearing aids (Donaldson et al., 1986b).

Use of cobalt in magnetic aUoys in western countries declined from 28% in 1950,26% in 196, 22% in 1970 and 13% in 1981 to 10.8% in 1987 (Johnston, 1988).

Hard-metal alloys (cemented carbides) have essential applications in wear-related engineering because of their high strength, corrosion resistance and ability to retain hardness at elevated temperature. 'Fine', 'extrafine' and 'superfine'

special cobalt powders are used as the metal matrIx or bonding agent in cemented

carbides used in cutting, grinding and driling tools destined for use on hard materials, such as met

aIs and rocks, and in diamond polishing. Annual industrial

consumption of these special powders is approximately 20 tonnes. Applications

of cemented carbides include grinding wheels, moulds, seal rings, dies, valves,



nozzles, pump liners, wear parts subject to severe shock, hot miI roUs, extrusion and

can tooling, cutters and slitters, mining, drillng and tunnellng (Kirk, 1985; Donaldson, 1986; Anon., 1989; Cobalt Development Institute, 1989). Consumption of cobalt for hard-metal aUoys in the western world rose from

4% in 1950 to 10.2% in 1987. The tungsten carbide industry accounted for the majority of use in 1987 and diamond polishing for the rest (Johns

ton, 1988).

eobalt-containing high-strength steels (maraging steels) are used in the aerospace industry for the manufacture of helicopter drive shafts, aircraft landing

gear components and hinges for swing-wing aircraft. Machine component uses include timing mechanisms in fuel injection pumps, index plates for machine tools, bolts and fasteners, barrels for rapid-firing guns and components for cryogenic applications. They also find use in marine equipment, such as deep-submergence vehicles and foil assemblies on hydrofoil ships. ln addition, they are used in the

manufacture of tools, espeially hot forging and stamping dies, close tolerance plastic moulds and die holders (Roskil Information Services, 1989). Cobalt-containing martensitic stainless maraging steels have been developed for a variety of applications, including in machine construction, the aerospace industry, the chemical industry and naval engineering (Roskill Information Services, 1989).

Electrodeposited nickel-cobalt aUoys have good corrosion resistance in many

environments and have been used as protective coatings in the production of mirrors and decorative coatings and for electroforming. Electrodeposited

cobalt-tungsten alloys retain their hardness at high temperature and are used to improve the wear resistance of hot forging dies. Electrodeposited cobalt aUoys

containing iron, nickel, platinum or phosphorus have magnetic properties suitable for use in recording systems and computer applications (Donaldson, 1986).

Æloys with special properties. Some cobalt-containing alloys have special applications as dental material, surgi

cal implants, low expansion alloys and springs.

Properties that are suitable for dentistry include ease of casting, resistance to tarnish, compatibilty with mouth tissues, high strength and stiffness, and low density. Vitallum, a cobalt-chromium alloy, was used for cast denture bases, complex partial dentures and sorne types of bridgework. A modified aUoy is used to fuse porcelain coatings to crowns via a metal bridge. Cobalt-chromium surgical implant alloys were first used in the 1940 for femoral head cups because of their resistance to corrosion by body fluids; they were subsequently developed for use in bone replacement and bane repair (Donaldson,

1986). The use of metallc implants has played an increasingly important role in orthopaedy: about 500 00 knee, hip and other joint replacements were

manufactured in the 1970s (Donaldson et al., 1986b). Total joint arthroplasty using artificial prostheses has become a corn

mon surgical technique in the treatment of



severely injured or diseased hip joints; other applications include plates, screws and

nails. The implantation of each metallc device is associated with the release of metal, either by corrosion, dissolution or wear or sorne combination of these

processes. Although different materials have ben used in the fabrication of prostheses, the preferred material for clinically accptable knee or hip prostheses is the cobalt-chromium-molybdenum alloy (Donaldson et al., 1986b; Cobalt

Development Institute, 1989).

A range of iron-nickel-cbalt alloys is used by the electronics industry for sealing metals in glas

ses (Donaldson, 1986).

A new chemical use of cobalt is in the manufacture of video tapes. Cobalt is used to coat the basic ferrc oxide particles to increase coercivity and reconcIle

opposing properties of erasabilty and control of stray magnetic effects. Manufacturers of high-quality audio tapes have also applied this development. Thin films containing cobalt phosphate and cobalt-nickel alloy particles are the most important metallc recording materials. The introduction of cobaltchromium film for perpendicular recording is a potentially very important use of cobalt. Normally, magnetic particles are orientated horizontally on the tape surface; but by getting them to orientate verticaIly, much closer packing of information is allowed. Magnetic optical recording (using gadolinium-cobalt and terbium-cobalt alloys) and, to a much smaller extent, bubble memory applications also involve cobalt. Another use of cobalt is as an additive in dry electric cells (Donaldson et al., 1988). (ii) Cobalt compound

Table 11 summarizes the uses of a number of compounds of cobalt. The commercially significant compounds are the oxides, hydroxide, chloride, sulfate,

nitrate, phosphate, carbonate, acetate, oxalate and other carboxylic acid derivatives (Donaldson, 1986). The compounds of cobalt have a variety of end uses. Cobalt oxides and organic

compounds are used in paints, ceramics and alled products as decolorizers, dyes, tes the adherence of enamel to steel. ln the rubber industry, organic cobalt compounds are used to promote the adherence of metal to rubber in steel-belted radial tyres. Cobalt is also used in chemical procsses. It is used in the petroleum industry dryers, pigments and oxidizers. Cobalt oxide, used as a ground-coat frit, promo

principally as a catalyst for hydrodesulfurization, oxidation, reduction and

synthesis of hydrocarbons. The artificial isotope cobalt-60 provides a controllable source of gamma-radiation and is used in physical, chemical and biological research, the treatment of cancer, and in industrial radiography for the

investigation of physical strains and imperfections in metals (Kirk, 1985).



Table i 1. Industrial uses of cobalt compoundsa Compound



Acetate(III) Acetate(II)


Catalyst Driers for lacquers and vamishes, sympathetic inks, catalysts, pigment for oil-cloth,


mineraI supplement, anodizer, stabi1izer

Acetylacetonate Aluminate Ammonium sulfate

Co(C5H702h CoAl204 CoS04(N4)2S04"6H2O



for malt beverages Vapour plating of cobalt Pigment, catalysts, grain refining Catalysts, plating solutions Pigment for paint, glass and porcelain


CoBr 2

Catalyst, hydrometers



Carbonate (basic)


Pigment, ceramics, feed supplements, catalyst Chemicals






Catalyst Chemicals, sympathetic inIe, hydrometers, plating baths, metal refining, pigment,


Chromate Citrate Dicobalt manganese tetroxide Dicobalt nickel tetroxide Dilanthanum tetroxide 2-Ethylhexanoate



C03(C6H507 )2"2H2O

Therapeutic agents, vitamin preparations



NiC0204 La2Co04

Catalyst, anode Catalyst, anode Paint and vamish drier Catalyst, pigment Fluorinating agent Fluorinating agent Catalyst Ceramics Catalyst Paints, chemicals, catalysts, printing inIe Moisture indicator Electrode Paint and vamish drier




Fluoride(II) Fluoride(III) . Fluoride Fluorosilicate Formate Hydroxide Iodide

CoF2 CoF3

CoF2"4H20 CoSiF6"6H20


Co(OH)2 COI2

Lanthanum trioxide




Lithium oxide


LiCo02 CoMn204


Battery electrode

Catalyst; electroctalyst



Table 11 (contd) Compound



Naphthenate Nitrate


Catalyst, paint and varish drier


Pigments, chemicals, ceramics, feed supplements, catalyst



Paint and vaish drier

()alate ()de(II) ()de(II,III)



Catalysts, cobalt powders Chemicals, catalysts, pigments

CÛ3() 4

Enamels, semiconductors

Mixed metal COlP()4h-8l12()



()des Phosphate

Olazs, enamels, pigments, steel pretreatment

Potasium nitrite Resinate


Sodium oxide


Pigment Paint and vamish drier,catalyst Battery electrode



~aint and vamish drier, tye cord adhe-

Succinate Sulfamate Sulfate Sulfide



Co(2S()3)'3l12() CoS()4il2()

Therapeutic agents, vitamin preparations Plating baths Chemicals, ceramics, pigments

Tricobalt tetralanthanum decaoxide


Catalysts Catalyst



Drier for paints and vaishes


Ilrom Donaldson (1986); Donaldson et al. (1986a)

Cobalt is an effective catalyst for many organic reactions. Its major use in this

way is in hydrotreating catalysts, the active components of which are molybdenum

and cobalt sulfides. This type of catalyst is used in the synthesis of fuels (Fischer-Tropsch process). The reactions catalysed by cobalt also include the oxo synthesis, in which olefins and carbon monoxide are combined to form aldehydes.

The basic catalyst is cobalt carbonyl (COi(CO)8), although other cobalt carbonyls can be used. ln both the Fischer-Tropsch and the oxo process, the catalysts are normally generated in situ in the reactor. Cobalt catalysts are also used in

hydrogenation reactions, such as the hydrogenation of nitriles to amines. Cobalt able oxidation catalysts, e.g., for the production of terephthalic acid by

salts are valu

the oxidation of para-xylene, and the manufacture of phenol by the oxidation of toluene. Cobalt-containing catalysts have also been used for polymerization



reactions, e.g., polyethylene production by the Amoco proce~s (Morral, 1979; Donaldson, 1986; Donaldson et al., 1986a; Johnston, 1988; Schrauzer, 1989). Combinations of the oxides of cobalt and those of aluminium, magnesium, zinc and silcon are constituents of blue and green ceramic glazes and pigments

(Donaldson, 1986). Cobalt zinc silcate is used in a blue underglaze paint for

porcelain articles; the pigment is specially developed to withstand intense heat (Raffn et al., 1988). Cobalt is also used in the glass industry to impart blue colours and to mask the greenish tinge in glass or porcelain caused by iron impurities (Donald

son, 1986).

Spinels are mIxed metal oxides with a special crystal structure, based on

magnesium and aluminium oxides (MgAi04). These two metals may be partially replaced in the crystal structures by other metals, such as cobalt(II) and chromium(III). Spinels occur naturally and are also produced syntheticaIly. Sorne cobalt spinels, such as the cobalt-magnesium-aluminium and cobalt-aluminium oxide spinels, are used as pigments (Donaldson et al., 1986a; Sax & Lewis, 1987).

An important use of cobalt is as a drying agent for paints, varnishes, lacquers and printing inks. ln these processes, cobalt oleate, resinate and linoleate have been used, but cobalt naphthenate is the more common ingredient (Buono & Feldman, 1979). Cobalt naphthenate is also added to polyester and silcone resins to promote hardening (Bedello et al., 1984). Consumption in ceramics was relatively stable from 1950 to 1987, ranging from a low of 9.5% to a high of 12% of the total annual cobalt consumption. Use of cobalt

in chemicals in 1987 was almost equal to the amount used in alloys. Consumption in chemicals was 17-18% during 1950-70, 24% in 1981 and 34.2% in 1987; use in chemIcals during 1987 represented 42.6% of consumption in Europe and 34.4% in

the USA. ln 1987, applications were: chemicals, catalysts, paint, ink and rubber additives, 24.9%; unspecified, 3.7%; electronics and magnetic tape, 2.8%; medical

and veterinary, 1.5%; and plating and anodizing, 1.3% of total cobalt consumption (see Table 10; Johnston, 1988).

eobalt(lll) acetate has been used as a catalyst in cumene hydroperoxide decomposition (Budavari, 1989). eobalt(ll) acetate is used much more commonly, in the manufacture of drying agents for inks and varnishes, as dressings for fabrics,

as catalysts and pigments, and in anodizing and agricultural applications. Mixed metal acetates such as cobalt-tin acetate can also be prepared (Donaldson, 1986;

Donaldson et al., 1986a; Budavari, 1989). During the 196s, cobalt(II) acetate, cobalt chloride and cobalt sulfate (see below) were used as foam stabilizers in malt beverages in Canada, Belgium and the USA. ln 196-66, US breweries reportedly added up to 1.5 i.g/ml of cobalt in 20-25% of ail beer sold (Morral, 1979; Budavari,

1989; Cobalt Development Institute, 1989).



eobalt(ll) carbonate is used in ceramics, as a trace element added to soils and animal feed, as a temperature indicator, as a catalyst and in pigments (Morral, 1979; Sax & Lewis, 1987). Basic cobalt carbonate is often used as a starting material in the

manufacture of other chemicals, such as cobalt oxide, cobalt pigments and cobalt salts. It is also used in ceramics and in agriculture (Donaldson, 1986; Donaldson et al., 1986a; Budavari, 1989).

The main use of cobalt(ll) chlonde hexahydrate is as an intermediate in the manufacture of other cobalt salts. It has been used in invisible inks because, when it is heated, the crystal water is liberated and the almost invisible colour changes to

dark blue (Suvorov & Cekunova, 1983). Because of its hygroscopic nature, anhydrous cobalt chloride has been used in barometers and as a humidity indicator in hygrometers; the anhydrous form turns from blue to pink when hydrated. Other

uses include the absorption of military poison gas and ammonia, as electroplating flux for magnesium refining, as a solid lubricant and dye mordant, in the

preparation of catalysts, for painting on glass and porcelain, as a temperature indicator in grinding, as a fertilizer additive, as a trace mineraI supplement in animal feed and in magnetic recording materials (Morral, 1979; Donaldson et aL., 1986a; Budavari, 1989). The hexahydrate is used to prepare a standard solution of

cobalt for analytical purposes (National Library of Medicine, 1989).

armaceuticals for the manufacture ofvitamin Bii and as catalysts for the oxidation in air Cobalt chloride is also used in the ceramic and glass industries, in ph

of toxic waste solutions containing sulfites and antioxidants (Considine, 1974). It

was used as a foam stabilizer in malt beverages in the 1960s (see under cobalt acetate above). Cobalt chloride has been used as an adjunct to iron therapy (if cobalt deficiency is suspected) in patients with refractory anaemia to improve haematocrit, haemoglobin and eryhrocyte values. Although cobalt stimulates eryhropoietin production, it also blocks certain enzymes involved in iron transport and may stimulate eryhrocyte production by causing intracellular hypoxia.

Therapeutic doses of 20-300 mg per day orally have been used (Goodman & Gilman, 1975; Goodman-Gilman et al., 1985; Berkow, 1987). According to Reynolds (1989), its general therapeutic use is unjustified.

eobalt(ll) hydroxide is used in the manufacture of other cobalt compounds, as

a starting material to make driers for paints and printing inks, as a catalyst or starting material for catalysts and in solutions for impregnating electrodes in storage batteries (Morral, 1979; Donaldson et al., 1986a; Budavari, 1989). eobalt(lll) hydroxide is used as an oxidation catalyst (Sax & Lewis, 1987; Budavari, 1989).



Cobalt molybdenum oxie is used with aluminium oxide as a desulfurization

and reforming catalyst in oil refining (Considine, 1974; Donaldson, 1986; Sax & Lewis, 1987).

eobalt(II) naphthenate is used primarily as a drying agent in paints, inks and varnishes. Additionally, it is used to enhance the adhesion of sulfur-vulcanized rubber to steel and other metals (i.e., in tyres), as a dressing for fabrics, as a catalyst and as an antistatic adhesive (Buono & Feldman, 1979; Donaldson et al., 1986a; Sax & Lewis, 1987).

eobalt(ll) nitrate hexydrate is used mostly in the preparation of catalysts, in pigments, chemicals, ceramics, feed supplements, battery materials, invisible inks, hair dyes and vitamin Bii preparations. It serves as an important source of

high-purity cobalt for use in the electronics industry (Considine, 1974; Morral, 1979; Donaldson, 1986; Donaldson et al., 1986a; Budavari, 1989).

eobalt(ll) oxide (COO) is used as a starting material for the manufacture of other chemicals and catalysts, in pigments such as colour reagents and in ceramics, gas sensors and thermistors (Donaldson et al., 1986a).

eobalt(ll,lll) oxide (C0304) is used in ceramics and enamels as a colorizer and decolorizer, in semiconductors, as a catalyst, in solar collectors, in grinding wheel coolants and as an implant into the oesophagus of cobalt-deficient ruminants (Morral, 1979; Donaldson, 1986; Donaldson et al., 1986a; Sax & Lewis, 1987). Lilac pigments containing 22-33 wt % cobalt(lll) oxide (COi03) and bluegreen pigments containing 8-20 wt % cobalt(III) oxide are used in ceramics. A prime enamel has been prepared that contains 0.8 wt % cobalt(III) oxide (Donaldson et al., 1986a). Cobalt(III) oxide monohydrate is used as an oxidation catalyst (Budavari, 1989).

eobalt(ll) sulfate is the preferred source of water-soluble cobalt salts used in the manufacture of other cobalt chemicals p.nd in electroplating, because it has less tendency to deliquesce or dehydrate than the chloride or nitrate. The monohydrate

and heptahydrate are used in plating, feed supplements, to make catalysts, magnetic recording materials, anodizing agents and corrosion protection agents (Morral, 1979; Donaldson et al., 1986a; Budavari, 1989). Cobalt sulfate is also used in the manufacture ofvitamin Bii during the biological fermentation of molasses by Pseudoneras denitrificans (Cobalt Development Institute, 1989). Treating cobaltdeficient soil with 100-150 glacre (247-371 g/ha) of cobalt sulfate prevents cobalt

deficiency in ruminant animaIs (Jones et al., 1977); injection of cobalt sulfate solution through rumenal fistulas and subcutaneous implantation of slow-release cobalt glasses have been used as alternative methods of supplying cobalt son et al., 1986b). ln the 196s, cobalt sulfate was used in various countries (Donald

as a foam stabilizer in beer (see under cobalt acetate above).



Both ~- and ß-cobalt sulfies are used as catalysts for hydrodesulfurization of organic compounds in petroleum refining. The sulfide is generated as needed by passing hydrogen sulfide over mIxed cobalt-molybdenum-aluminium oxides in refinery reactors to form catalytic cobalt sulfide in situ (Brauer, 1965; Donaldson et aL., 1986a; Budavari, 1989). 2.3 Occurrence (a) Geologicaloccurrence

Cobalt is widely distributed throughout the environment. It is thirty-third in t, accounting for 0.001-0.002%. The largest concentrations of cobalt are round in mafic (igneous rocks rich in magnesium and iron and comparatively low in silca) and ultramafic rocks; the abundance among the elements in the earth's crus

average cobalt content in ultramafic rocks is 270 mg/kg, with a nickel:cobalt ratio of 7. Sedimentary rocks contain varying amounts of cobalt; average values are 4 mg/kg for sandstone, 6 mg/kg for carbonate rocks and 40 mg/kg for clays or shales. Levels

of cobalt in metamorphic rock depend on the amount of the element in the original igneous or sedimentary source. Cobalt has also been found in meteorites

(Donaldson, 1986; Donaldson et al., 1986b; Weast, 1988; Budavari, 1989).

Cobalt mineraIs occur in nature as a silall percentage of other metal deposits (particularly copper), generally as sulfides, oxides or arsenides, which are the largest mineraI sources. Smaltite (CoAsi) has a cobalt content of 25% and is the

most important arsenide found in the USA, Canada and Morocco; other arsenides

include safflorite (CoFe)Asi, skutterudite ((Co,Fe)As3) and the arsenosulfide (CoAsS; cobaltite), which contains up to 35% cobalt and is found in Cobalt City, Australia, and in Burma. CarroIIte ((Co,Ni)iCUS4) and linnaeite (C03S4) are

sulfides which contain 40-50% cobalt and are found in the African copper belt; siegenite ((CO,Ni)3S4), which contains 25% cobalt, is found in the mines of

Missouri, USA. The supplies of oxides that have the greatest economic importance are heterogenite (CoO(OH)) and sphaerocobaltite (containing 50% cobalt) from

Katanga, Zaire, and asbolite (obtained from manganese copper) from New Caledonia (Kipling, 1980; Merian, 1985; Donaldson, 1986; Budavari, 1989; Schrauzer, 1989).

(b) Occupational exsure The main route of absorption during occupational exposure to cobalt is via the

respiratory tract, due to inhalation of dusts, fumes or mists containing cobalt or inhalation of gaseous cobalt carbonyL. Occupational exposures occur du

ring the

production of cobalt powder, in hard-metal production, processing and use, and in the use of cobalt-containing pigments and driers. Workers who regenerate spent catalysts may also be exposed to cobalt sulfides.



Occupational exposure to cobalt can be measured by analysis of ambient air levels and by biological monitoring, Le., analyses of cobalt concentrations in blood

or urine (for reviews see Ferioli et al., 1987; Alessio & DellOrto, 1988; Angerer, 1989; Angerer et al., 1989). (See also Table 19 and p. 419).

Data on exposure to cobalt measured by air and biological monitoring in

various industries and occupations are summarized in Table 12. Where possible, the correlations between the concentrations of cobalt in air and biological body f1uids are given. Information available to date on blood and urinary concentrations se tests are suitable for assessing exposure on a group basis. The determination of urinary levels of cobalt seems to offer more advantages of cobalt indicates that the

than that of blood levels. The biological indicator levels are influenced by the

chemical and physical properties of the cobalt compound studied and by the time of

pound, the timing of collection of biological samples (normally at the end of a shift) and the analytical methods differ among the studies. sampling. It should be noted that the type of corn

Using biological indicators, the concentration of cobalt in air was related to

that in biological f1uids; an exposure to 50 J.g/m3 cobalt in air was found to be equivalent to a level of 2.5 J.g/I cobalt in blood and 30 J.g/I cobalt in urine (Angerer, 1989).

Lehmann et al. (1985) took stationary and personal air samples at workplaces

during dry grinding (with exhaust facilties) in the mechanical processing of cobalt alloys containing 5-67% cobalt. They found the following airborne concentrations: stationary sampling-total dust, 0.1-0.85 mg/m3 (median, 0.55 mg/m3; 13 samples);

cobalt in total dust, 0.06-23.3 J.g/m3 (median, 0.4 J.g/m3; 13 samples); personal sampling-total dust, 0.42-2.05 mg/m3 (median, 0.55 mg/m3; six samples); cobalt in

total dust, 0.2-69.1 J.g/m3 (median, 3.2 J.g/m3; seven samples).

ln dental laboratories, concentrations of cobalt were measured during the preparation and polishing of cobalt-chromium alloys and ranged from 30 to 190 J.g/m3 (Kempf & Pfeiffer, 1987). Kusaka et al. (1986) carried out extensive personal air monitoring at different stages of hard-metal (cemented carbide) manufacturing and processing; the results)

by group of workers, are given in Table 13. A similar study was performed by Lehmann et al. (1985), who took stationary and personal air samples during various grinding operations involving hard metal (Table 14). The airbome concentrations

of cobalt were mainly below 100 J.g/m3; higher concentrations were observed mainly during dry and wet grinding operations without ventilation or exhaust facilties. Exposure to cobalt during wet grinding presumably originates not only in the workplace but also from cobalt dissolved in coolants. After one week of use,


Table 12. Occupational exposures to cobalt in various industries and activitiesa Industiy/activity

Hard-metal production (two subgroups)

No. of samples 10



Concentration of cobalt in ambient air a. b.

Mean, 0.09 mg/m3 Mean, 0.01 mg/m3

(personal samples)

Concentration of cobalt in bloo



Significant correlations:


and urine




b. Mean, 0.7 ¡.gll a. Mean, (l06) ¡.gll

Mean, 10.5 ¡.gll

air:urine (r = 0.79); air:bloo (r = 0.87);

bloo:urine (r = 0.82)

b. Mean, (,. 3) ¡.gll

Hard-metal tool

production (11 subgroups)


170 5



Significant correlation: serum (x)/urine (y)

Up to 61 ¡.g/m3

Median values for all subgroups:

(stationaiy samples)

serum, 2.1 ¡.gll; urine, 18 ¡.gll


Bloo: mean, 3.3-18.7 ¡.gll;

Significant correlations

urine, 10-235 ¡.gll

(based on mean values):

Sampling on Wednesday or Thursay at end of shift

y = 0.67x + 0.9;


¡.g/m3 (persnal


Alexanderson (1988)

Sampling on Friday pm Hard-metal grinding (seven subgroups)

& Lidums (1979);

y = 2.69x + 14.68

air (x)/urine (y):

Hartung & Schaller (1985) Ichikawa et al. (1985)

urine (x)/bloo (y): y = 0.0065x +0.23



Serum: mean, 2.0-18.3 ¡.gll; urine, 6.4-64.3 ¡.g/g creatinine

serum/urine, r = 0.93

Posma & Dijstelberger (1985)

Range, approx.

Urine: Monday at end of shift

Significant correlations:

Scansetti et al.

0.002-0.1 mg/m3;

(a) up to 36 ¡.gll ; Friday at end

air (x)/urine (y):


0.3-15 mg/m3with

(six subgroups)

Hard-metal production

Breathable dust range, 4-17% cobalt



median, approx. 0.01 mg/m3 (personal sam

Cobalt powder production Presintered tungsten

6 15

carbide production Hard-metal use







(a) y = 0.29x +0.83; (b) y = 0.70x +0.80


Times of sampling: Monday am for basic expoure level; Friday evening for cumulative exp




mean, 35.1 ¡.gll

b. mean, 9.6 ¡.gll 0.120-0.284



of shift (b) up to 63 ¡.gll


mg/m3 b.

Significant correlation:


c. mean, 11.7 ¡.gll Sampling on Sunday (24 h)

sure level

~ ~

0 Z 0 0 ~ :: en

air (x)/bloo (y): y = 0.OO4x + 0.23;

Hard-metal production


Pellet et al. (1984)

â 5 ~



Table 12 (contd) Industry /activity

No. of sam

Cobalt powder and cobalt salt production (seven subgroups) Cobalt oxide processing







and cobalt salt manufacture

Concentration of cobalt in ambient air Mean, 46-1046

Concentration of cobalt in bloo


Significant correlations:

Angerer et al. (1985)


n 0t:

jJglm3 (stationary

mean, 19-438 jJg/l

air/urine; airlbloo; bloo


Post-shift sampling

(x)/urine (y): y = 7.5x

Median, 0.52 mg/m3;

Urine: mean, 0.34 mg/l; range,

Poor correlation air:urine

range, 0.1-3.0 mg/m3

0.1-0.9 mg/l

Morgan (1983)

Mean, 2.16 jJg/l;

Significant correlation:

Christensen &

b. Mean, 0.63 jJg/l;

bloo/urine (r = 0.88)

Mikkelsen (1986)


(persnal sam

Painting porcelain with


soluble cobalt salts Painting porcelain with slightly soluble cobalt salts






Range, 0.07-8.61 mg/m3 Range, 0.05-0.25 mg/m3

(persnal sam



Bloo: Urine:



Mean, 8.35 jJg/

mmol creatinine;



Mean, 0.13 jJg/

mmol creatinine

Ilrom Angerer & Heinrich (1988)


and urine

Bloo: mean, 5-48 jJgll; urine:

n 0t: q 0

q n 0 ~ ~

0 c:


Û ~

~ Ut



Table 13. Airborne concentrations of cobalt at various stages in the manuracture and processing or bard metalsa Activity





Concentration of cobalt




Mean :: SD Powder Press




68 :: 1075



473 :: 654


25 21 47

27 38

85 :: 95


28 :: 26


126 :: 191

2-145 6-1155

205 2

53 :: 106


Electron discharging



4 :: 1




3 :: 1


Rubber Machine Sintering Shaping Grinding Wet Dry


1292 :: 179

11-1247 1113-1471

1-5 1-4

'Trom Kusaka et al. (1986)

Table i 4.

ring hard-metal

Concentrations of cobalt iD total dust du

grindinga Typ of grnding! ty of sam


No. of

No. of



Sampling time (h)

Concentration of cobalt (llglm3) Median


2 2

3.1 12.3

0.1-203.5 0.5-223.8

2 2





2 2

6.9 13.7

1.1-11.8 1.3-29.9

Dry grinding with

exhaust facilties Stationary Personal Wet grinding without





9 14


exhaust facilities

Stationary Personal


Wet grnding with

exhaust facilities Stationary Personal

8 7

'Trom Lehmann et al. (1985)

1 1



levels of up to 118 mg/kg were found in the coolant; after four weeks, up to 182 mg/kg

were observed (Lehmann et al., 1985). This finding was confirmed by Hartung (1986). Einarsson et al. (1979) studied the dissolution of cobalt in nine commercial cutting fluids one to five days after use in the grinding of hard-metal alloys. Mter one day, most of the cobalt liberated by grinding was found in solution; this percentage decreased when grinding was continued using the same coolant fluid. Only a small fraction of the cobalt was found as partic1es in the circulating fluid. th

The au

ors conc1uded that the bulk probably remains in the sediment in the

storage tank.

The concentration of cobalt dust was measured in the air of a Danish porcelain factory in 1981. ln personal air sam

pIes taken for 19 female plate painters, the levels

were 0.07-8.61 mg/m3. The cobalt levels in blood and urine were measured in 1982 in 46 female plate underglaze painters exposed to soluble cobalt silcate and in 51 female plate overglaze painters with no exposure to cobalt. The mean levels in the blood of exposed persons (longer than four weeks) were 2.16 Jlg/l (range, 0.2-24; troIs (range, 0.05-0.6; median, 0.2). median, 1.0) compared with 0.24 Jlg/l in the con

Mean levels in urine were: 77 Jlg/l (median, 26; range, 2.2-848) in exposed workers and 0.94 J.g/I (median, 0.3; range, 0.05- 13.8) in unexposed workers (Mikkelsen et al., 1984; Christensen & Mikkelsen, 1986). ln 1984, after conditions in the workplace had been improved, the concentration of cobalt in air had decreased to about 0.05

mg/m3. The mean urinary level of cobalt in 38 of the 46 workers investigated originally who were selected for urine analysis was 2.6 J.g/mmol creatinine (range,

0.16-16.1) compared to 4.2 J.g/mmol creatinine (range, 0.24-29.1) in 1982. A significant correlation was observed between blood cobalt and creatinine-corrected

urinary cobalt levels (p ~ 0.(01). ln 1982, in a factory using a slightly soluble cobalt silcate, the mean cobalt levels in blood and urine from 15 female plate painters were

0.63 J.g/I (median, 0.60; range, 0.37-1.58) and 0.13 J.g/mmol creatinine (median, 0.11; range 0.02-0.37), respectively (Christensen & Mikkelsen, 1986; see also Table 12). (c) Air

Levels of cobalt in the ambient air are a function of the extent to which partic1es of soil are dispersed by the wind. They are higher near factories in which cobalt is used, and atmospheric concentrations of cobalt in remote areas are very an 1 ng/m3 in the Antarctic. ln other areas, ambient air concentrat,ions are usually around 1 ng/m3. Levels exceeding 10 ng/m3 have been reported in heavily industrialIzed cities (ElInder & Friberg, 1986). Combustion of organic low: less th

materials containing cobalt is reported to be an additional source of emission (Lange, 1983; Angerer & Heinrich, 1988). Coal contains up to 40 mg/kg (average, 1 mg/kg) cobalt (Angerer & Heinrich, 1988), and hard co

al contains about 8 mg/kg



(Schrauzer, 1989). Merian (1985) estimated a global an


al generation of about

500 tonnes of cobalt from the burning of coaL.

A survey of atmospheric trace elements in the UK in 1977 showed ambient concentrations of cobalt in the range of 0.04-6.5 ng/kg at seven stations sampled. Around 57% of the cobalt content was in a soluble form (Cawse, 1978). (d) Tobacco smoke

The content of cobalt in cigarettes has been studied by means of neutron activation; different brands of tobacco were found to contain c: 0.01-2.3 mg/kg dry

weight (Wytenbach et al., 1976; Iskander, 1986; Iskander et al., 1986). When cigarettes were smoked in a standard smoking machine, 0.5% of the cobalt content

of the cigarette was transferred into smoke condensate (Nadkarmi & Ehmann, 1970). (e) Water and sediments


Uncontaminated samples of fresh water generally contain low concentrations 0.1-5 llg/l

cobalt, rangingfromO.1 to 10 J.g/I(Schrauzer, 1989). Concentrations


have been found in drinking-water (Elinder & Friberg, 1986). Approximately 20 00 tonnes of cobalt are transported annually by rivers to oceans, where they are precipitated (Merian, 1985). A cobalt content of 74 mg/kg

has been measured in sediments (Schrauzer, 1989). Natural transport is not significantly affected by mining activities or industrial use. The concentration of

cobalt in seawater is normally quite low, at 0.002-0.007 llg/l, the level decreasing with increased depth (Knauer et al., 1982). æ Foods and b~erog~

Human dietary intake of cobalt is highly variable; Table 15 summarizes estimated total intake of cobalt from food in various countries. Most of the cobalt

ingested is inorganic: vitamin B12, which occurs almost entirely in food of animal origin, accunts for only a very small fraction. Vegetables contaiß inorganIc cobalt

but little or no vitamin B12 (Friedrich, 1984; Donaldson et al., 1986b). Values for the cobalt content of foods vary widely between reports, even among

analyses of the same foods, probably owing as much to differences in environmental cobalt levels as to analytical difficulties or inadequate analytical techniques. Green

leafy vegetables and fresh cereals are the richest and most variable sources of cobalt aIs and sugar contain the

(0.2-0~6 J.g1g dry mass), while dairy products, refined cere

least cobalt (0.01-0.03 J.g/ g dry mass; Donaldson et aL., 1986b). Plant products have

been estimated to contribute up to 88% of the total cobalt in the Japanese diet (Yamagata et al., 1963). Normal cows' milk contains very little cobalt (average,



Table 15. Total daily intake or cobalt rrom foo peT caput Country

Daily intake per caput (Jlg)


Canada Finland Germany


Kirkpatrick & Coffin (1974)


Varo & Koivistoinen (1980)

17 15

Pfannhauser (1988) Pfannhauser (1988)

5-10 (vitamin B12 only)

Schormûller (1974)



Lindner-Szotyori & Gergely



(1980) Pfannhauser (1988)

J apan


Yamagata et al. (1963)

Netherlands Spain


Pfannhauser (1988)


Barberá & Farré (1986)


Spring et al. (1979)


Harp & Scoular (1952)

1.7 31

Nodiya (1972)

UK (vitamin B12 only) USA USSR

Reshetkina (1965)

about 0.5 J1g/I); shelled eggs have been reported to contain 0.03 J1glg (Donaldson et al., 1986b). Varo and Koivistoinen (1980) found concentrations of 30-50 J1glkg dry

weight in fish and vegetables; that in meat and dairy products was 10 J1glkg. The daily diet of the 70-kg 'reference man' contains cobalt at 0.01-0.02 mg/kg fresh weight (based on 20-40 J1g/day intake) (Donald

son et al., 1986b).

ln 15 commercial beers analysed in 1965 using a colorimetric method, the levels of cobalt were weIl below 0.1 mgll. When cobalt salts had been added during processing, values of up to 1.1 mgll were recorded (Elin

der & Friberg, 1986).

The cobalt content offive brewed teas averaged 0.2 l.g/g (range, 0.16-0.34) and that of seven brewed coffees, 0.75 l.glg (range, 0.42-2.0 l.g/g; Horwitz & Van der Linden, 1974).

(g) Soils and plants

ln one study, the cobalt content of soils ranged from 1 to 40 mg/kg (Merian, 1985) with an average of 8 mg/kg (Schrauzer, 1989). ln general, cobalt tends to be deficient in areas where there is granite, sand or lImestone and in volcanic and peaty

soils. Good drainage may reduce cobalt content (Kipling, 1980). The solubilties of cobalt compounds are pH-dependent, and cobalt is more mobile in acid soIls th

in alkaline soIls (Schrauzer, 1989).




ln industrIalized areas, up to 75 mglg cobalt have been found in the soil around factories using cobalt powders, and higher concentrations may occur in waste-metal dumps (Kipling, 1980). The uptake of cobalt by plants is species-dependent: cobalt is hardly

detectable in green beans and the level is exceedingly low in radishes (Schrauzer, 1989). Leafy plants, such as lettuce, cabbage and spinach, have a relatively high

cobalt content, whereas the content is low in grasses and cereals (Kipling, 1980). It is as yet unknown whether cobalt is essential for plants. ln sorne cases, small amounts se are dose-dependent and may be indirect (Schrauzer, 1989). It has been suggested that the element is necessary for of cobalt produce positive growth effects, but the

the fixation of nitrogen in vegetables that are relatively rich in cobalt. Cobalt concentrations in pastures vary according to season and the presence of fertilzers (Kipling, 1980).

(h) Human tissues and body jluids Over the years, there has been a progressive downward adjustment in the

reported normal levels of cobalt in human tissues and body fluids as a result of improvements in analytical methodology. Concentrations of cobalt observed in the blood and urine of the general population are summarized in Table 16. The

concentrations in body fluids are weIl below the microgram per litre level; mean concentrations reported in serum range from 0.1 to 0.3 l1g/L. Alexandersson (1988) found that smokers with no occupation

al exposure had a

significantly higher mean cobalt concentration in urine (0.6 l1g/l; sn, 0.6) than nonsmokers (0.3 l1g/l; SD, 0.1). There was no difference between smokers and nonsmokers in the cobalt levels in blood. Patients in various stages of renal failure showed a significantly higher serum

concentration of cobalt than a control group, but there was no correlation to the degree of renal insufficiency. Haemodialysis did not influence the levels, whereas kidney transplantation reduced them (Lins & Pehrsson, 1984). Values for whole blood were a little higher than serum concentrations but were not well documented

(Iyengar & Woittiez, 1988). ln urine samples obtained from normal adults, the concentrations of cobalt were reported to be approximately 0.1-2 l1g/1 (see Table 16). Greatly increased urinary levels have been reported for persons taking multivitamin pils containing cobalt (Reynolds, 1989).

Considerable differences have been found in the levels of cobalt in hair, ranging from 0.4 to 500 l1g/kg (Iyengar & Woittiez, 1988).

ln autopsy studies, the liver has been shown to contain the highest concentration of cobalt, with individual values ranging froID 6 to 151 l1g/kg (median, 30 l1g/kg) in seven studies. This may be attributed, at least in part, to differences in



Table 16. Concentrations or cobalt in urine, serum and whole bloo or persons

not exposed occupationally to cobalt Urine

Serum (or plasma)




Whole bloo



Versieck et al. (1978)

0.108 :l 0.06 0.5 :l 0.1

Alexandersson & Swenssn (1979)

0.4 p.g/l


0.5 0.195 :l 0.015


Alexanderson & Lidums (1979) Kasperek et al. (1981)

(plasma) Kennedy et al. (1981)

0.18 p.g/creatinine

0.38 p.gI

0.1-0.75 J.g/I

Schumacher- Wittkopf

& Angerer (1981)

Hartng et al. (1982)

1.3 J.g/l


Masiak et al. (1982) 0.09 :l 0.02

0.94 p.g/l

0.15 :l 0.07

Andersn & Høgetveit



0.05-13.8 p.g/l

4.6 J.g/g creatinine

Ostapczuk et al. (1983)

Mikkelsen et al. (1984)


Posma & Dijstelberger (1985)

0.41 p.g/l or 0.28

Scansetti et al. (1985)

p.g/g creatinine 2.0 p.g/l

1.9:l 1.1


0.09 p.g/mmol


0.001.21 p.g/ mmol creatinine

Ichikawa et al. (1985) Lewis et al. (1985)

0.24 (0.050.6)

Christensen & Mikkel-

sen (1986)


Hartung (1986)

0.73:l 0.10

Collecchi et al. (1986)

(plasma) 0.4 J.g/l

0.1-2.2 p.g/l

0.01 p.g/l

~ange, or mean:l standard deviation -, not given

0.5 (0.1-1.2)

Alexanderson (1988)


Angerer et al. (1989)



food intake, since this organ stores vitamin Bu (lyengar & Woittiez, 1988). ln New Zealand, 96 human liver samples showed a mean concentration of 120 iiglkg wet weight cobalt, with no significant difference between sex, age or regional district (Pickston et aL., 1983). Levels of cobalt were lower in liver carcinoma tissue than in

normal hepatocytes from the same liver samples (Kostic et al., 1982). The total cobalt content of a 70-kg, unexposed man was estimated to be about 1.5 mg. The total amount of vitamin B 12 in the body of an adult is about 5 mg, corresponding to

0.25 mg cobalt, of which 50-90% is localized in the liver (Schrauzer, 1989). Cobalt concentrations in the hearts of patients dying from myocardiopathy associated with the consumption of beer containing cobaltous salts were found to be 10 times higher than in normal cardiac muscle (Sullvan et al., 1968).

(i) lt;trogenic exsure Cobalt is the major constituent (approximately 62%) of POrous-coated

cobalt-chromium alloys used in surgical implants; therefore, body levels of cobalt (urine, serum) have been used as an index of the wear rate of the prostheses. Table

17 summarizes the results of several investigations on trace metal concentrations in the body fluids of patients with total knee and hip arthroplasty with metal prostheses. Cobalt-containing particles have also been identified by microscopic examination of tissues adjacent to prostheses (Hildebrand et al;, 1988; Sunderman et aL., 1989).

Certain authors observed significant increases in mean concentrations of cobalt in the serum or urine from patients with various metal implants (especially those with metal-to-metal contact), while others found that the concentrations of this metal were only sporadically elevated. These discordant results may retlect greater rates of release of metals from implantswith metal-to-metal versus

metal-to-polyethylene articular surfaces, as weIl as differences among the cobalt-containing alloys used (e.g., porous-coated versus non-porous surfaces and cemented versus cementless implants). Analytical limitations may also play a major role, since the concentrations of cobalt in the serum and urine specimens from control subjects far exceeded the currently accepted ranges. Analytical inaccuracIes in previous studies probably resulted from metal contamination during specimen

collection, inattention to quality assurance techniques and/or inadequate instrumental sensitivity and specificity (Sunderman et al., 1989). Raithel et al. (1989) investigated the cobalt content in tissues surrounding hip arthroplasties and in distant muscle samples. From 10 patients with loosening of

prostheses, tissue samples were taken from the implanted cup (polyethylene surface to avoid metal-to-metal friction), from the implanted shaft and from the musculus vastus lateralis, and the patients received new hip prostheses. The old cobaltchromium-molybdenum types (ASTM F 75-74) were replaced after 5-15.5 years

Table 17. Cobalt concentrations in boy ßuids or patients with total hip or knee arthroplasty" Study


No. of patients


et al.

Period of observation

3 weeks to 32 months

(1973) Jones et al.


Not given



1Y of implant


Concentrations of cobalt



Synovial fluid

Hip, cobalt-molybdenum-chro-

Increased cobalt and chromium

mium alloy, cemented, nonpo rous, with or without polyethylene component (C cast alloy)

15-73 ¡.gll

4.5-16 ¡.gll

in bloo and urine, only with

after 1 year

after 1 year

22- 55 ¡.gll







Hip, cobalt-chromium-molybdenum alloy, cemented, nonporous, with metal-to-metal contact (C

metal-to-metal contact (no poly-

(j 0i:


Increased cobalt in urine and (in one case) in syovial fluid and liver, bone and brain tissues

250 ¡.gll 0.5-3 mglkg

cast alloy)



et al.

6 months

Knee, cobalt-chromium alloy,

to 10 years

cemented, nonporous, with or

(1981) J orgensen

without polyethylene compone


Increased cobalt and chromium in syovial fluid and serum, espent

Hip, cobalt-chromium-molybde-

cially with metal-to-metal contact

et al.

num alloy, porous-coated or

Increased cobalt in urine, especially in patients with porous-

Porous: mean,


nonporous, cementless

coated implants


Not given


Bartolozzi & Black (1985)










1 day to 6

Hip, cobalt-chromium-nickel


Increase in serum chromium

alloy, cemented, nonporous,

(peak at 15 days), serum nickel

polyethylene cup (cobalt-chro-



(peak at 6 months); nonnal serum cobalt


Hip, cobalt-chromium alloy, cemented, nonporous, poly-

Increase in chromium (serum

1 to :: 30 days

Peak, 26.2 ng/

Peak, 39.9

pg/mg protein

peak at 10 days, urine peak at 15 days)

mg creatinine

7-15 years

Hip, cobalt-chromium-molybdenum alloy, cemented, nonporous, with or without polyethylene cup

Increased cobalt and chromium in urine and chromium in plasma

0.9-1. 05 ¡.gll

1 week to

Hip, cobalt-chromium alloy, ce-

1 year

mentless, porous-coated, poly-

Increased urinary nickel in 2 of 14 patients at 6 months; increased urinary nickel and cobalt in 3 of 4 measured at 1 year

ethylene cup (PCA~)



ethylene cup

et al.

(1986) Jones & Hungerford (1987)



(j 0i:


14.2 ¡.gll;

mean, 8.4 ¡.gll

Black et al. (1983)

~ ~



~ f-


~ ~ ~ Table i 7 (contd) Study

Braun et al. (1986)

No. of patients


Period of observation

5 months to 3 years

1Y of implant

Hip, cobalt-chromium-molybdenum alloy, cementless, porous-


Increased urinary chromium

Concentrations of cobalt Urine


Synovial fluid





~ ~

Increased serum cobalt


1. 8 ).gll

0 Z 0 0

Lo hip, cobalt-chromium-

Increased urinary chromium,



nickel molybdenum alloy, cem-

3.8 ).gll

nickel and cobalt, increased se-

( mean,

ented, nonporous with polyethyl-

rum nickel


ene cup; old hip replaced

1 day to 2.5 years

Knee or hip, cobalt-chromium

Slight increase in serum and uri-

alloy (ASTM F-75-82), porous-

nary cobalt in knee prostheses. 2

coated, 10 cemented, 18 cement-

patients, substantially elevated

less with polyethylene

levels (7 weeks and 22 months

coated, polyethylene cup, fixd

Raithel et


2 years

Fixed hip, cobalt-chromium-

nickel-molydenum alloy, cem-

al. (1989)

ented, nonporous with polyethylene cup 10

Sundennan et al.



5-15.5 years

aultrahigh molecular weight polyethylene (total hip replacements)



â 1 ).g/g crea


nine (6-120 weeks)

7.7 ).g/g creapost-arthroplasty, with looning tinine and 5.6 of prostheses); serum and urinary chromium levels also elevated in ).gll in the 2 patients one patient

O. 15 ).gll


(6-120 weeks)


I and 1.15


).gll in the 2 patients





(median, 12.5 years). The concentrations of cobalt in the tissues surrounding the shaft ranged from 367 to 6510 l1glkg (median, 868 l1g/kg), and those in tissues surrounding the cup, from 98 to 16293 l1g1kg (median, 1080 l1g/kg). Muscle tissue

contained 24-151 l1g1kg (median, 124 l1g1kg) cobalt.

Hildebrand et al. (1988) also found extremely high concentrations of cobalt, up to three orders of magnitude (140 l1g1g dry weight) above the normal values, in

connective tissue taken on a Vitallum plate. (¡) Others

The total concentration of cement made in Asia ranged from 8.1 to 14.2 l1g/g. The metal existed mainly as insoluble salts; the concentration ofwatersoluble cobalt was 0.39-0.65 l1g1g (Goh et al., 1986). The cobalt content in 42 US cement samples was ~ 0.5 l1g/g (Perone et al., 1974). The cobalt content of 30 household cleaning products sold in Spain in 1985

ranged from 0.1 to 14 mg/l; the highest levels were found in two bleaches, containing 1. 1 and 1.4 mg/l (Vilaplana et al., 1987). 2.4 Regulatory status and guidelines

Occupational exposure limits and guidelines established in different parts of the world are given in Table 18.

Table 18. Occupational exposure lirnit values ror cobalt


Country or region


Concentration (mg/m3)


Australia Belgium


0.1 cobalt, metal fumes and dust


0.05 cobalt, metal dust and fumes (as Co)



0.5 cobalt and compounds (as Co); cobalt, metal dust and fumes (as Co)




0.1 cobalt as metal dust and fume



0.05 cobalt and compounds (as Co)

0.1 cobalt and compounds (as Co)





0.1 cobalt cabonyl (as Co); cobalt hydro-

cabonyl (as Co) 0.05 cobalt in the form of powder, dust and fumes and inorganic compounds (as Co) 0.05 cobalt and inorganic compounds (as Co)





Table 18 (contd) Country or region


Concentration (mg/m3)




Indonesia Italy


0.1 cobalt and compounds (as Co) 0.2 cobalt and compounds (as Co) 0.1 cobalt and compounds (as Co)


0.1 cobalt, metal dust and fumes (as Co)



0.1 cobalt, metal dust and fumes (as Co)



0.1 cobalt, metal dust and fume (as Co)



0.05 cobalt and compounds (as Co)



0.5 cobalt and compounds (as Co);



cobalt, metal dust and fumes (as Co) 0.2 cobalt and cobalt oxide and cobalt, metal TWA



dust and fumes (as Co)

0.5 cobalt and cobalt oxide and cobalt, metal max dust and fumes (as Co)



0.05 cobalt and inorganic compounds (as Co)


Switzerland Taiwan


0.1 cobalt dust and compounds (as Co)


0.1 cobalt, metal dust and fumes (as Co)


0.1 cobalt and compounds (as Co)



0.05 cobalt (as Co) metal dust and fumes


0.1 cobalt carbonyl (as Co);




cobalt hydrocrbonyl (as Co) 0.1 cobalt (as Co) metal dust and fume 0.5 cobalt and compounds (as Co); cobalt, metal dust and fumes (as Co)

TWA Guidelines TWA max

0.01 cobalt hydrocbonyl and decmpoition products (as Co) Venezuela


0.1 cobalt, metal dust and fumes (as Co)



0.1 cobalt and compounds (as Co); cobalt, metal dust and fumes (as Co)


'Trom Direktoratet for Arbeidstilsynet (1981); Arbeidsinspectie (1986); Cook (1987); Health al Health (1987); Arbejd-

and Safety Exective (1987); National Sweish Board of Occpation

stilsynet (1988); National Institute for Occpational Safety and Health (1988); American Conference of Govemmental Industrial Hygienists (ACGIH) (1989); US Occpational Safety and

Health Administration (OSHA) (1989); United Nations Environment Programme (199). Guidelines and standards are generally prepared by scientific boies and sometimes become

offciaI standards, or they are recognized and applied in practice on a voluntary basis as a guide for monitoring the working environment or for technical prevention. lrWA, 8-h time-weighted average; STEL, 1Q-15-min short-term expure limit



2.5 Analysis

Typical methods for the analysis of cobalt in air, water, various working materials, food and biological materials are summarized in Table 19.

Table 19. Methods ror the analysis or cobalt pIe prepartion




Digestion with nitric/sulfuric


Asay procdurea

Limit of detection



0.1 ¡.g/l

Lidums (1979)


0.1 ¡.g/l

Schumaeher- Wittkopf

acid; ion-exchange separation

Chelatization, extraction

& Angerer (1981)

Dilution with nitrie acid Dilution with nitric acid Digestion with sulfurie, nitric,


Not given

Hartng et al. (1983)

2 ¡.g/l

Pellet et aI. (1984)

1 ¡.g/l

Ichikawa et al. (1985)


6 ¡.g/l

Bournan et al. (1986)

1 ¡.g/l

Bournan et al. (1986)

perchlorie acid; chelation, extraction Direct analysis

N ,N-Hexamethyleneammo-


(0.2 ¡.g/l for

carbamic acid/xylene extrae-


tion Magnesium nitrate modifier


2.6 ¡.g/l

Dilution with nitric acid


0.1 ¡.g/l

Protein precipitation; dilution with nitric aeid Digestion with nitric, sulfuric


0.1 ¡.g/l



6 ml urine)

Kim berley et al. (1987) Christensen et al. (1983)

Christensen & Mikkelsen (1986)


0.1 ¡.g/l

Lidums (1979)


0.2 ¡.g/l

Delves et aI. (1983)

0.8 ¡.g/l

Ichikawa et al. (1985)

acid Dilution and matri modifica-


tion Freeze-dried, low-temperature GF-AA (Z) ashing; resolved in nitrie aeid Digestion with nitrie, sulfuric, LCP


perehlorie aeid

10 ¡.g!g

National lnstitute for


Occpational Safety

0.2 ¡.g!g

and Health (1985)



Wet digestion with nitrie, sul-


furie, perchloric aeid; che


tion, extraction Dry ashing at 4500C


0.1 ¡.g/l

Barfoot & Prtchard (1980)



Not given

Versieek et al. (1978)



Table 19 (contd) Sample

Sample prepartion


Plasma, un



Limit of detection

Palladium matri modification

GF-AAS (Z) 0.15 i.gli

Wet digestion with nitric, sulfuric acid



Sampsn (1988)




1 ngl in the

Ostapck et al.

analyte solu-




Digestion with nitric acid Digestion with nitric, perchlotic acid


Not given

Harng et al. (1983)


1 i.glsample

National Institute for Occpation

al Safety

and Health (1984a)

Digestion with aqua regia



National Institute for


Ocpational Safety and Health (1984b)

Digestion with hydrochloric, nitric acid Digestion with nitric acid


1 i.glm3

Ichikawa et al. (1985)


20 nglm3 (sample vol-


ume 1.5 m3)

Kettrup & Angerer


Direct analysis


6 pmol (0.4 ng)



Chelation with ammonium


.. 1 i.gll

Bemdt et al. (1985)

Adsorption voltammetry GC

Not given

Meyer & Neeb (1985)

50 ngl sample

Meyer & Neeb (1985)

Donat & Bruland


preconcentration on activated


charcoal Dry digestion; triethanolamine electrolyte

Dry digestion; chelation with soium di(trifluoroethyl)di-



Digestion with nitric acid; extraction with cupferron, chIoroform


1.4 nglml

Barberá et al. (1986)

Ashing in muffe fumace


Not given

Gunshin et al. (1985)

aAbbreviations: GF-AA, graphite fumace-atomIc absorption spectrometry; F-AA, flame atomic absorption spetrometry; Z, background correction for Zeeman effect; ICp, inductively coupled

plasma emission spectrometry; NAA, neutron activation analysis; ADP~ adsorption differential pulse voltammetry; DPCSV, differential pulse cathodic stripping voltammetry; GC, gas chroma-




Methods for quantitative analysis include graphite furnace-atomic absorption spectrometry (GF-AAS), inductively coupled plasma emission spectrometry (ICP),

neutron activation analysis and electrochemical methods such as differential pulse anodic stripping voltammetry (DPASV). ICP and X-ray fluorescence appear to be too insensitive for the determination of cobalt in environmental and biological matrices; this is also true of the older photometric methods, which also showed lack of specificity.

WIth NAA, cobalt can be determined at the nanogram per kilogram level. This

method offers the advantage that it requires littIe sample preparation, but its application is restricted to a few highly specialized laboratories. Voltammetry and,

in particular, GF-AAS are much more common and permit determination of cobalt at the nanogram per kilogram level. GF-AAS, in comparison to voltammetry, does not usually require complete digestion of the sam

pIe, which makes the technique

more practicable.

Air samples are collected on cellulose ester membrane fiters, wet-digested

with nitric and perchloric acids or aqua regia and analysed by AAS or ICP (National Institute for Occupational Safety and Health, 1984a,b; Kettrup & Angerer, 1988). The routine procedures do not permit identification of individual cobalt compounds. Analysis of cobalt in soil, food, industrial samples and human tissues also requires complete digestion of the matrices. The US Environmental Protection

Agency (1983) established standard methods using ICP and GF-AAS for the chemical analysis of water and wastes. An extremely low detection limit of 1.2 ngl

natural water was obtained using cation-exchange liquid chromatography with luminol chemiluminescence (Boyle et al., 1987). A similarly high sensitivity, 0.64 ng/kg, is obtained by photoacoustic spectroscopy after extraction with 2-nitroso1-naphthol/meta-xylene (Kitamori et al., 1986). Determination of cobalt in whole blood, plasma, serum and urine is used as a biological indicator of exposure to cobalt (Ichikawa et al., 1985; Ferioli et al., 1987; Angerer et al., 1989). Choice of specimen, sampling strategies, specimen collection,

transport, storage and contamination control, as weIl as quality control and quality assurance procedures (Schaller et al., 1987), are of fundamental importance for an adequate monitoring programme. GF-AAS and DPASV are practical and reliable

techniques that furnish the requisite sensitivity for measuring cobalt concentrations in biological samples. The detection limits for cobalt determination by GF-AAS analysis with Zeeman background collection are below 0.6 ).gll of body fIuids, depending on the type of sam

pIe preparation.



Greater sensitivity in DPASV analysis can be achieved by using a dimethylglyoxime-sensitized mercury electrode, which provides detection lImits

down to 1 ngl for cobalt in biological media (Ostapczuk et al., 1983, 1984). Koponen et al. (1982) analysed cobalt-containing airborne dusts from hard-metal ffanufacturing and grinding processes by AAS and instrumental NAA. The structure of the dusts was studied by scanning electron microscopy with an energy dispersive X-ray. Cobalt was found to exist as separate particles in the dust

from the mixng of raw material powders only. ln the dusts from the pressing, forming and grinding of hard metal, cobalt appeared mainly in contact with

tungsten carbide particles. . 3. Biological Data Relevant to the Evaluation of

Carcinogenic Risk to Humans 3.1 Carcinogenicity studies in anirnals

(a) Inhalation exsure1 Hamster. As part of a larger study, groups of 51 male Syrian golden hamsters (ENG:ELA strain), two months of age, were exposed by inhalation to 0 or 10 mg/m3 cobalt/Il) oxide dust (with a mass median diameter of 0.45 l.m) for 7 h per day on five days per week for life. Median survival was 16.6 months in treated hamsters compared to 15.3 months in controls. No difference in the incidence of any tumour was observed between the cobalt oxide-treated and untreated hamsters (Wehner et al., 1977). (The Working Group noted the poor survival of the treated and control animaIs. ) (b) lntratracheal instillation

Rat: Groups of 50 male and 50 female Sprague-Dawley rats, ten weeks of age, received intratracheal instilations of 2 or 10 mg/kg bw cobalt/Il) oxide powder (derived from thermal decomposition of cobalt(II) nitrate; approximately 80% of particles 5-40 l.m (purity unspecifiedD or 10 mg/kg bw of a cobalt-aluminiumchromium spinel (a blue powder (purity unspecified), with the empirical formula Co

(II) 0.66, Al 0.7, Cr

(III) 0.3, 0 3.66, made of a mixure of CoQ, AI(OH)) and

Cri03 ignited at 12500 C; 80% of particles cC 1.5 l.m) in saline every two weeks (then

IThe Working Group wa awae that an inhalation study of cobalt sulfate heptahydrate wa planned

in mice and rats (lC, 199)



every four weeks from the nineteenth to the thirtieth treatment) for two years (total doses, 78 and 390 mg/kg bw cobalt oxide and 390 mg/kg bw cobalt spinel). Control

groups of 50 males and 50 females received instilations of saline only or remained untreated. AnimaIs were allowed to live until natural death or were sacrificed when

moribund. No appreciable difference in body weights or survival times was observed between the treated and control groups (exact survival data not given). Bronchoalveolar proliferation was observed in 0/100 untreated controls, 0/100 saline controls, 51/100 low-dose cobalt oxide-treated rats and 70/100 high-dose

cobalt oxide-treated rats, and in 61/100 rats treated with the spineI. (The Working Group noted that the nature of the bronchoalveolar proliferation or possible association with inflammation was not described.) No pulmonary tumour was observed in 100 untreated or 100 saline controls. ln the groups treated with the low dose of cobalt oxide, one male and one_ female developed benign lung tumours; in the groups treated with the high dose of cobalt oxide, one bronchoalveolar

carcinoma occurred in a female and three adenocarcInomas and two

bronchoalveolar adenomas were observed in males; in the groups receiving the spinel, one squamous-cell carcinoma was observed in males and two squamous-cell carcinomas were observed in females (Steinhoff & Mohr, 1991). ln a smaller experiment by the same authors, groups of 20 female

Sprague-Dawley rats, 10 weeks of age, received weekly intratracheal instilations of 10 mg/kg bw cobalt/Il) aride for seven weeks and 20 mg/kg bw once every two weeks for 20 treatments (total dose, 470 mg/kg bw), and 20 mg/kg bw benzo(a)pyrene following the same dose regimen (total dose, 20 mg/kg bw), with a four-day interval 20 females received treatment with benzo(a)pyrene alone. AnimaIs were allowed to live their natural lifespan or were between the two treatments. A further group of

sacrificed when moribund (exact survival not stated). Eight rats treated with cobalt

oxide and benzo(alpyrene had squamous-cell carcInomas and one had an adenocarcinoma of the lung. One animal given benzo(a lpyrene had a squamouscell carcinoma of the lung (Steinhoff & Mohr, 1991). Hamster. ln a large experiment to study the effects of particulates on N-nitrosodiethylamine (NDEA)-induced respiratory tract carcInogenesis, groups of 25 male and 25 female hamsters (strain unspecifiedl, seven weeks old, were given subcutaneous injections of 0.5 mg ND EA in saline or saline alone once a week for 12

weeks. One week later and once a week thereafter for 30 weeks, 4 mg cobaltlII,III) oxide powder (particle size, 0.5-1.0 llm (purity unspecifiedJ) suspended in a gelatin

and saline vehicle were administered by intratracheal instilation. Groups of 25 male and 25 female hamsters receiving subcutaneous injections ofNDEA or saline troIs. At the end of treatment (42 weeks), 39, 43, 33 and 43 animaIs were stil alive in the four

and intratracheal instilations of the gelatin-saline vehicle served as con

groups, respectively. AnimaIs were observed for an additional 43-68 weeks



following the last intratracheal instillation. Two of 50 hamsters receiving injections

of saline and cobalt oxide by intratracheal instilation developed pulmonary alveolar tumours; 1/50 hamsters receiving injections of saline and gelatin-saline intratracheally developed a tracheal tumour. The incidences of tumours at varIous

sites in hamsters given NDEA with cobalt oxide in gelatin-saline were simIlar to those in animaIs receiving NDEA and gelatin-saline alone (Farrell & Davis, 1974). (c) Subcutaneous injection

Rat: ln a study designed to monitor cobalt-induced hyperlipidaemia, 20 male Wistar rats, about four weeks of age, received two courses, separated by a nine-day interval, of five daily subcutaneous injections of 40 mg/g bw cobalt/Ill chlorie rpurity unspecified) dissolved in saline, and were observed for 12 months. A control group of 20 males received injections of saline alone. At the end of the observation period, 8/11 surviving treated rats had developed subcutaneous fibrosarcomas (four ofwhich were reported to be distant from the injection site), whereas none of the 19 surviving controls developed a tumour ip .c 0.001, Fisher's exact test). Post-mortem examinations were not made on the nine rats that died during the experiment. ln a second experiment, 20 male Wistar rats received the same

treatment but were observed for eight months. No control group was provided. At

the end of this observation period, six of the 16 survivors had subcutaneous fibrosarcomas, including one tumour distant from the site of injection. Four rats that died during the observation period were not autopsied (Shabaan et al., 1977).

Groups of 10 male Sprague- Dawley rats, 10 weeks of age, received subcutaneous injections of saline (two groups) or 2 mg/kg bw cobalt/II 1 oxie rpurity unspecified) suspended in saline, five times a week, or subcutaneous injections of 10 mg/kg bw cobalt

fIl) oxide in saline once a week over a period of two years (total

dose, 100 mg/kg bw). AnimaIs were allowed to live their naturallifespan or were

sacrificed when moribund (survival data not given). Malignant tumours (histiocytomas or sarcomas) developed at the injection site in 0/10, 0/10, 5/10 and 4/10 rats in the four groups, respectively (Steinhoff & Mohr, 1991). (d) Subcutaneous implantation

Rat: Groups of five male and five female Wistar rats, four to six weeks of age, received subcutaneous implants of four pellets (approximately 2 mm in diameter) of either a cobalt-chromium-molybdenum (and lesser amounts of nickel) alloy (Vitallum; see p. 374 of this monograph), nickel metal, copper metal, nickel-gallium alloy (60% nickel, 40% gallium) or one of seven other implant materials not known

to contain nickel, chromium or cobalt. AnimaIs were observed for up to 27 months rsurvival of animais receiving cobalt-chromium-molybdenum alloy not given). Sarcomas (mostly fibrosarcomas and rhabdomyosarcomas) developed around the



implants in 5/10 rats that received nickel pellets and in 9/10 rats that received

nickel-gallum alloy pellets; no sarcoma developed in rats that received the cobalt-chromium-molybdenum pellets or in any of the other groups (Mitchell et al.,

196). (e) 1 ntramuscular injection

Mouse: A group of 50 female Swiss mice, two to three months of age, i:eceived single intramuscular injections of 10 mg/site of unwashed powdered cobalt/Illoxide (particle size, ~ 5 l.m (purity unspecified)) in 10% aqueous penicilin G procaine in each thigh. Within two to six days, 25 mice had died. A further group of 25 females

received simIlar injections of the powdered cobalt oxide that had been washed

repeatedly in distiled water; this washed cobalt oxide did not induce acute the first group and the 25 mice from the second group were combined, and 46 were stil alive 13 weeks after injection. A control group of mortality. The 25 survivors of

51 female mice similarly received intramuscular injections of penicilin G procaine

vehicle (60 00 lU/site) into each thigh; 48 survived 13 weeks after injection. AnimaIs were observed for up to 110 weeks (survival unspecified). No tumour developed at the injection site in any of the cobalt oxide-treated or control mice. Incidences of tumours at other sites were similar in the treated and control groups (Gilman & Ruckerbauer, 1962). A group of 30 mice (sex, strain and age unspecified) received intramuscular injections of 0.2 mg cobalt as cobalt naphthenate (purity, dosage, schedule, vehicle and duration unspecified) into the right hind limb. Tumours of the muscle in the hind leg developed in eight of the mice (Nowak, 196). (The Working Group noted the incomplete reporting.)

Rat: A group of 10 male and 10 female hooded rats, two to three months old,

received a single intramuscular injection of 28 mg cobalt metal powder (spectrographically pure, 40 mesh; 3.5 l.m x 3.5 iim to 17 iim X 12 iim with large the order of 10 l.m x 4 l.m) in 0.4 ml fowl serum into the thigh; a control group of ten males and ten fèmales received fowl serum

numbers oflong narrow particles of

only. Average survival times were 71 weeks in treated males and 61 weeks Ìn treated females; survival of controls was not specified. During the observation period of up to 122 weeks, 4/10 male and 5/10 female treated rats developed sarcomas (mostly

rhabdomyosarcomas) at the injection site compared to 0/20 controls. A further group of ten female rats received a single intramuscular injection of 28 mg cobalt metal powder in 0.4 ml fowl serum; others received injections of 28 mg zinc powder

(five rats) or 28 mg tungsten powder (five rats). Average survival time for cobalt-treated rats was 43 weeks. During the observation period of up to 105 weeks, sarcomas (mostly rhabdomyosarcomas) developed In 8/10 cobalt powder-treated rats; none occurred in the zinc powder- or tungsten powder~treated rats. No other



tumour occurred in any of the cobalt-treated or other rats, except for one malignant lymphoma in a zinc-treated rat (Heath, 1954a, 1956). ln a supplementary study, a group of 30 male hooed rats, two to three months

of age, received a single intramuscular injection of 28 mg cobalt metal powder (spectrographicaUy pure (particle size unspecifiedD in 0.4 ml fowl serum into the right thigh; a control group of 15 males received a single injection of fowl serum only. The rats were killed at intervals of one to four weeks after injection or at fortnightly intervals up to 20weeks after injection, when the first tumour appeared. The author

described leukocyte infiltration, muscle fibre necrosis and regeneration and the development of a tumour nodule in one rat (Heath, 196). Groups of 10 male and female Wistar rats (sex ratio unspecified), two to three months old, received a single intramuscular injection of 30 mg/site of POwdered, reagent-grade cobalt/Il) oxie (particles ground to ~ 5 llm and washed repeatedly in distiled water) suspended in 10% aqueous penicilin G procaine or penicilln G one into the thigh muscle and were observed for 74 weeks (number of survivors unspecified). No tumour occurred at the site of injection in

procaine (90 00 lU/site) al

the 10 control rats during the study, whereas rhabdomyosarcomas developed at the

injection site in 5/10 cobalt oxide-treated rats. Metastases were seen in four of the five tumour-bearing rats. No other neoplasm was noted in control or treated rats (Gilman & Ruckerbauer, 1962). A group of 30 male and female Wistar rats (sex ratio unspecified), two to three months of age, received simultaneous intramuscular injections of 20 mg/site of powdered cobalt/Il) sulfde (purity unspecified) (ground to ~ 5 llm diameter and washed repeatedly in water) suspended in penicilln G procaine into each thigh. A

total of 35 sarcomas were observed at the 58 injection sites in the 29 rats that an latency of 28 weeks. Metastases

survived 13 weeks after treatment, with a me

were noted in 16/29 rats with tumours; no other neoplasm was seen. No control was reported (Gilman, 1962).

Groups of male and female Wistar rats (sex ratio unspecified), two to three

months of age, received two simultaneous intramuscular injections (five rats) in each thigh or single injections (19 rats) of cobalt/Il) onde (20 mg/site; particle size ~ 5 llm; washed repeatedly in water) suspended in aqueous procaine G penicillin. No control group was reported. A total of 13 sarcomas (mostly rhabdomyo-

sarcomas ) were noted at the 29 injection sites of the 24 rats that survived 13 weeks of

treatment (mean latency, 25 weeks). Metastases were noted in 3/12 rats with tumours (Gilman, 1962). ln a series of three experiments, a total of 80 female hooded rats, seven to nine weeks of age, received an intramuscular injection of 28 mglrat of wear particles, obtained by working in Ringer's solution in vitro of artificial hip or knee prostheses



made from cobalt-chromium-molybdenum alloy (66.5% cobalt, 26.0% chromium,

6.65% molybdenum, 1.12% manganese; particle diameter, down to O.l).m (mostly 0.1-1 ).mD, in 0.4 ml horse serum and were observed for up to 29 months (survival not specified). No control group was reported. Sarcomas developed at the injection

site in 3/16,4/14 and 16/50 rats in the three series, respectively. Approximately half of the tumours were rhabdomyosarcomas; the remainder were mostly

fibrosarcomas (Heath et al., 1971; Swanson et al., 1973). if 1 ntramuscular implantation

Rat: As a follow-up to the studies by Heath and Swanson (see above), groups of female Wistar and hooded rats, weighing 190310 and 175-220 g, respectively, received intramuscular implants of 28 mg ~f coarse (100-250 ).m diameter; 51

Wistar rats) or fine (0.5-50 ).m diameter, 85% 0.5-5 ).m; 61 Wistar and 53 hooed rats) particles as a dry powder, obtained by grinding a cobalt-chromium-

molybdenum alloy (68% cobalt, 28% chromium, 4% molybdenum), and were

observed for life. A sham-operated control group of 50 female Wistar rats was available. Survival at two years was 11/51 rats receiving the coarse particles, 7/61 Wistar rats receiving the fine particles, 0/53 hooded rats receiving the fine particles

and 5/50 Wistar controls. No tumour was noted at the implantation site of rats treated with either of the alloy particles or in sham-operated control animaIs (Meachim et al., 1982).

Groups of 15 male and 15 female Sprague- Dawley rats, aged 20-30 days, shed rods (1.6 mm diameter, 8 mm length) of one of three alloys (wrought Vitallum: 19-20% chromium, 14-16% tungsten, received intramuscular implants of poli

9-11% nickel, -: 0.15% carbon, -: 2% (manganese), -: 1% silcium, -: 3% iron,

balance cobalt; cast Vitallium: 27-30% chromium, 5-7% molybdenum, -: 2.5% nickel, -: 0.3% carbon, -: 1% (manganese), -: 1% silcium, -: 0.75% iron, balance cobalt; MP3SN alloy: 19-21% chromium, 33-37% nickel, 00 0.025% carbon, -: 1%

iron, -: 0.15% manganese, 9.5-10.5% molybdenum, -: 0.15% silcium, 0.65-1% titanium; balance cobalt) and were observed for up to two years (survival unspecified). Groups of 15 male and 15 female untreated and sham-operated control animaIs were available. No benign or malignant tumour developed at the implant site in any of the groups receiving metal implants or in either control group.

The incidences of malignant tumours at distant sites did not differ significantly among the treated and control groups (Gaechter et al., 1977).

Guinea-pig: A group of 46 female Dunkin-Hartley guinea-pigs, weighing

550-930 g, received intramuscular implants of 28 mg of a powdered cobalt-chromium-molybdenum alloy (68% cobalt, 28% chromium, 4%

molybdenum; particle diameter, 0.5-50 ).m) and were observed for life; 12/46 animaIs were alive at three years. No control group was reported. No tumour was



observed at the implantation site of any guinea-pig; nodular fibroblastic hyperplasia was observed at the implantation site in eight animaIs (Meachim et al., 1982). (g) lntra-osseous implantation

Rat: Groups of 10- 17 male and 8- 15 female Sprague- Dawley rats, 30-43 days of age, received implants of one of seven test materials containing cobalt alloyed with

chromium and nickel, molybdenum, tungsten and/or zirconium, with traces of other

elements (as small rods, 1.6 mm diameter and 4 mm length, powders or porous compacted wire), in the femoral bone and were observed for up to 30 months. Groups of 13 male and 13 female untreated and sham-operated controls were an 22 months. Sarcomas at the implant avaIlable. Average survval was longer th

site were observed in 1/18 rats (males and females given cobalt-based alloy powder containing 41% Co), 3/26 rats (males and females given MP3SN powder containing 33% Co) and 3/32 rats (males and females given porous compacted wire containing 25 rats given rods containing 69 26 rats given rods containing 0.11 or 33% cobalt, in 51 % Co). No tumour was observed in two groups of

or 47% cobalt, in two groups of

two groups of 25 and 26 untreated rats, or in a group of 26 sham-treated control rats

(Memoli et al., 1986). (h) lntraperitoneal injection

Mouse: ln a screening study based on the enhanced induction of lung tumours, groups of 10 male and 10 female strain A mice, six to eight weeks of age, received intraperitoneal injections of cobaltfllll acetate (;: 97% pure) in saline three times per week for eight weeks (total doses, 95,237 and 475 mg/kg bw). After 30 weeks, lung tumours were found in 8/20, 8/20 and 10/17 mice in the respective treatment

troIs (not significant) (Stoner et al., 1976). Rat: Groups of 10 male and 10 female Sprague-Dawley rats, 10 weeks of age, received three intraperitoneal injections at two-month intervals of saline or 20 mg/kg bw cobaltflll axide (purity unspecified) or cobalt-aluminium-chroniium spinel powder(see above) in saline (total dose, 60 mg/kg bw). AnimaIs were allowed to live their nattlrallifespan or were sacrificed when moribund (survival not given). Malignant peritoneal tumours occurred in 1/20 controls (histiocytoma), 14/20 cobalt oxide-treated rats (10 histiocytomas, three sarcomas, one mesothelioma) and 2/20 spinel-treated animaIs (one histiocytoma, one sarcoma) (Steinhoff & Mohr, groups, and in 7/19 saline-treated con

1991). (i) lntrarenal administration

Rat: Two groups of 20 and 18 female Sprague- Dawley rats, weighing 120- 140 g,

received a single injection of 5 mg cobaltflll sulfide (reagent grade; purity and



particle size unspecified) or 5 mg metallic cobalt powder (purity unspecified) suspended in 0.05 ml glycerine into each pole of the right kidney. A group of 16 female rats receiving injections of 0.05 ml glycerine into each pole of the kidney served as controls. Mter 12 months, all rats were necropsied; no tumour was observed in the kidneys of treated or control rats (Jasmin & Riopelle, 1976). (The

Working Group noted the short duration and inadequate reporting of the experiment.) 0) Other

Rat: Two groups of 10 female hooded rats, two to three months of age, received intrathoracic injections of 28 mg cobalt metal powder (spectrographically pure; particle size, -: 40 mesh; 3.5 llm x 3.5 llm to 17 llm x 12 llm, with many long narrow particles of the or

der of 10 llm x 4 llm) in serum (species unspecified)

through the right dome of the diaphragm (first group) or through the fourth left intercostal space (second group) and were observed for up to 28 months. Death occurred within three days of the treatment in 6/10 rats injected through the diaphragm and in 2/10 rats injected through the intercostal space. The remaining

rats in the first group (diaphragm) survived 11-28 months and in the second group the 12 rats that survived the injection, four developed intrathoracic sarcomas (three of mIxed origin, including rhabdomyosarcomatous elements, one rhabdomyosarcoma arising in the intercostal muscles) (Heath & Daniel, 1962). Rabbit: Twelve male rabbits (strain unspecified), weighing 2-2.5 kg, were given (intercostal space), 7.5-17.5 months. Of

intramuscular, intravenous, intrapleural or intrahepatic injections of cobalt

naphthenate (purity and dose unspecified). Within two to six months, tumours developed at the site of injection in eight rabbits, including one pleural

mesotheIioma, one haemangioendotheIioma of the Iiver, one osteochondroma of the ear and five skeletal muscle tumours (Nowak, 1961). (The Working Group noted the lack of controls, the small number of animaIs and the incomplete reporting of the experiment.)

A summary of most of these studies is given in Table 20. 3.2 Other relevant data

The metabolism and toxicity of cobalt have been reviewed (Taylor & Marks, 1978; Elinder & Friberg, 1986). Recent interest has centred on the biological monitoring of cobalt, Le., the determination of cobalt in human biological materials

such as blood and urine, and how such data ffay be used to assess absorption, exposure and possible health risks (Alessio & DellOrt?, 1988).

.i ~

Table 20. Summary or animal carcinogenicity studies by rorm or cobalt Reference

Species/ strain


Dos schedule

Exrimental parame










Cobalt metal powdr Heath (1954,





i.m., single inj.,

Dos (mg)

fowl serum


Survval (122 weeks)

Not given

Lol sarcoma



Dos (mg)




Survval (122 weeks)

Not given

Loal sarcoma




Dose (mg)




Heath & Daniel (1962)




intrathoracic in serum

12/20 4/12

Suivival (3 days)

Thoracic tumour Jasmin &

Riopelle (1976)

Rat SpragueDawley



Dos (mg) Suivival (12 months) Kidney tumour





Not given



0/18 28




:: í/

Cobalt alloys Heath et aL.


(1971); Swanson et al. (1973)



Lm., single inj., wear partic1es

Dose (mg)


Survval (29 months)

Not given

from Co/Cr /Mo,

Loal sarcoma

in hors serum Gaechter et al.


Rat Sprague-



Memoli et al. (1986)

Mitchell et al. (1960)

Rat SpragueDawley


Rat Wistar


Lm. impl. Co/Cr/


W /Ni/C/Mn/Si/

Dos (polished rod) Survval (2 years)

Not given

Fe (1.6 x 8 mm)

Lol tumour

intraos iinpl., Co/Cr/Ni/Mo/W /







Dose (powder, wire, rod) Survval (30 months)





Lol sarcoma




S.c. impl. Co/Cri Mo/Ni

Dos (pellets - 2-mm diam) Survval (27 months)

Not given

Rat Wistar and



No significant difference in distant tumours

Not given


Lol tumour

Meachim et al. (1982)

n~ ~ 0 Z 0 0

i.m. impl. Co/Cri Mo fine and

Dos (mg) Survval (2 years)

coars partic1es


Lol tumour



28 11/51 0



7/61 0

0/53 0

m VI


Table 20 (contd) Reference

Speciesl strain


Dos schedule

Experimen tal parameter 1 observation









Cobalt alloys (contd)

Steinhoff & Mohr (1991) Steinhoff & Mohr (1991)

Rat SpragueDawley


Rat Sprague-



3 i.p. inj., Co/Ali Cr spinel powder

Dos (mg/kglbw) Survval (2 years)

Not given

Loal tumour



Intratracheal inst. 1 x 2 weeks

Dos (mg/kg bw) Survval (2 years)



Col AlICr spinel

Squamous-cell tumour of


2 years

Meachim et al. (1982)



Lm. impL. Co/Cri

Mo powder


0 CC

~ ~

Not given


the lung

Dos (mg) Survval (3 years)




12/46 0/46 8/46

Loal tumour

Lol fibroblastic hypr-

0 CC


q 0

Cobalt(lI) oxide

Gilman & Ruckerbauer (1962) Steinhoff & Mohr (1991)


(1 F


Rat SpragueDawley


Lm. inj. in each thigh

Intratracheal inst. 1 x 2 weeks 2 years

Dos (mg/site)



Survval (13 weeks)

Loal sarcoma

48/51 0/48

46/75 0/46

Dose (mg/kg bw)




Survival (2 years) Benign squamous pulmonary

Not given




0/100 0/100

2/50 2/50 1/50

tumour Bronchioalveolar adenoma


Bronchoalveolar adenocarcinoma


0/50 0/50 0/50

Dos (mg/kg bw) Survval Bronchoalveolar adenoma Bronchoalveolar carcinoma




1/50 0/50

0/50 1/50

Pulmonary adenocarcinoma



0 c:


Ü C/

Not given

0/100 0/100

.i ~

.i w 0

Table 20 (contd) Reference

SpecIes/ strain


Dos schedule

Experimental parameter/








Cobalt(II) oxide (contd)

Gilman &

Ruckerbauer (1962) Gilman (1962)

Rat Wistar Rat Wistar



Î.m. inj.

Î.m. inj.

Dose (mg/site)


Survval (90 days)


30 10/10

Lol sarcoma



Dos (mg/site)

20 24/32 13/29 sites

Survval (13 weeks)

Lol sarcoma

Steinhoff &

Mohr (1991)

Rat SpragueDawley


Dos (mglkg bw) Survval (2 years)


2 mglkg bw 5/week or

Loal malignant tumour


s.c. inj.






~ ~

0 Z 0 0

Not given

10 mglkg bw

l/week for 2


years Steinhoff &

Mohr (1991)

Rat Sprague-


3 Î.p. inj. at

2-month intervals


Wehner et al.


( 1977)



Total dos (mglkg bw) Survval (2 years)


Lol malignant tumour



:: (/



Not given


Dos (mg/m3)



7 h/day,

Survival (18 months)

5 d/week

Reticulum-cell sarcoma CarcInoma

7/51 0/51 0/51 0/51 0/51 1/51

9/51 1/51 1/51 0/51 0/51 0/51

for life

Lymphosrcoma Leukaemia Plasma-celI1umour

No statistical difference

Rat Wistar


Î.m. inj.

Dos (mg/site)

20 29/30 35/58 sites

Survval (13 weeks)

Loal sarcoma

Jasmin &

Riopelle (1976)

Rat SpragueDawley



Dos (mg) Survval (12 months) Kidney tumours



Not given




tr VI IV

Cobalt(II) sulfide

Gilman (1962)



Table 20 (contd) Reference

Species/ strain

Dos schedule


Experimental parame









n 0tI

Cobalt(U) chloride Shabaan et al.


Rat Wistar


s.c. inj. 2 x 5 d, 9-d interval

Dos (mglkg bw) Survvalc Subcutaneous sarcoma


19/20 0/19

40 11/20 8/11

40 16/20 6/16

p c: 0.001 (Fisher exact

Cobalt naphthenate Nowak (1966) Mouse



l.m. 1Oj.


Dos (mg) Survval Thmour of the striated






n 0tI


n 0





Dos unspecified





i. pleural i. hepatic


~ '"


0 C

Cobalt(lll) acetate

Stoner et al.





Nowak (1961)


Mouse Strain A


i.p. inj.

Total dos (mglkg bw)




3/week, 24 doses

Survval (30 weeks)

19/20 7/19


20/20 8/20

Pulmonary tumour


475 17/20 10/17

Not significant




llroup 0, untreated; group 1, sham-treated

UPowder, 1/18 sarcoma; MP3SN, 3/26 sarcomas; compacted wire, 3/32 sarcomas

c12 months for groups 0 and 1; at 8 months for group 2 NS, not specified






(a) Experimental sytems

(i) Absorption, distribution, metabolism and exretion Cobalt compounds The gastrointestinal absorption of radiolabelled cobalt chloride in rats was found to vary between 11 and 34%, depending on the administered dose (0.01-100 iig/rat). The relative absorption decreased with increasing dose (Taylor, 1962). However, less th

an 0.5% of cobalt oxide given at an oral dose of 5 mg was absorbed

by hamsters (Wehner & Craig, 1972). The pulmonary absorption of inhaled cobalt(II) oxide (particle size, 1.0-2.5 iim) by hamsters was both rapid and high: about 25% was recovered in the carcass, lung, liver and kidney 24 h after inhalation of 0.8 mg cobalt oxide; essentially aIl of the cobalt oxide was eliminated by the sixh day afterexposure (Wehner & Craig, 1972). Intratracheally instiled cobalt(II) oxide (1.5 iig) was cleared slowly froID the

rat lung (half-time, 15 days), and only very low concentrations were found in extrapulmonary tissues (Rhoads & Sanders, 1985). Mter inhalation or instilation of cobalt oxides in dogs and rats, the highest concentrations of cobalt were found in

the lungs(Barnes et al., 1976; Rhoads & Sanders, 1985). After rapid initial elimination (half-time, 0.7 days), the half-time of cobalt oxides deposited in the lungs of dogs was 36-86 days (Barnes et aL., 1976).

Kreyling et al. (1986) exposed beagle dogs by inhalation to radioactive cobalt(II,III) oxide particles of different size (0.3-2.7 iim) and found that small particles were c1eared more rapidly from the lungs. Brune et al. (1980) exposed rats by inhalation to chromium-cobalt-containing abrasive dust obtained from dental laboratories. The concentration of cobalt in the lung increased with the length of exposure, indicating slow elimination of deposited metal. Histological examination

revealed macrophages containing metal partic1es. The concentration of cobalt was also elevated in liver and kidney, showing that sorne systemic uptake of cobalt had taken place. AnimaIs given cobalt chloride orally or by injection showed highest

concentrations in the liver, with lower concentrations in kidney, pancreas and spleen (Taylor & Marks, 1978; Stenberg, 1983). Relatively high concentrations were

also found in myocardium (Stenberg, 1983; Clyne et al., 1988) and in cartilage and bone (Söremark et al., 1979).

The major proportion of parenterally administered cobalt is cleared rapidly from the body, mainly via urine: 63% of radioactive cobalt chloride was recovered in

the urine of rats within 24 h (Taylor, 1962). After a single intravenous injection of cobalt chloride to rats, about 70 and 7% were recovered in the urine and faeces, respectively, during the first three days (Onkelinx, 1976). Similarly, 73 and 15% of an intravenous dose of cobalt chloride (0.3 mg/kg bw) to rats was eliminated via urine and faeces, respectively, within four days (Gregus & Klaassen, 1986). Dogs



injected intravenously with 20 ).g/kg bw radioactive cobalt sulfate eliminated 40- 70% of the label in urine and bile (90% in urine) over a period of 7-13 h (Lee & Wolterink, 1955). ln rats, only 2-7% of intravenously injected cobalt chloride was eliminated in the bile (Cilat & Tichy, 1981; Gregus & Klaassen, 1986). Autoradiographic examination of pregnant mice injected intravenously with radioactive cobalt chloride revealed high activity in maternaI liver, kidney, pancreas and cartilage and in the fetal skeleton and other tissues (Flodh, 1968; Söremark et al., 1979).

Metal alloy implants ln an experiment in vitro simulating mechanical stress on four different types of metallc hip prostheses, three ofwhich contained cobalt, more than 1 mg/l cobalt was found in solution, and metal particles with a size down to O.l).m were formed as a result of frictional movement (Swanson et al., 1973). (ii) Toxic effects

Cobalt compounds The oral LDsos for different inorganIc cobalt(II) compounds (cobalt fluoride, oxide, phosphate, bromide, chloride, sulfate, nitrate and acetate) in rats ranged

from 150 to 500 mg/kg bw anhydrous compound (Speijers et aL., 1982). When the

amounts were expressed in moles, the variabilty in toxicity between different compounds ranged from 1.5 to 3 mmol/kg cobalt. Acute effects recorded in the

animaIs included sedation, diarrhoea and decrease in body temperature. AlI hamsters died after 6-h exposures by inhalation to 100 mg/m3 cobalt oxide (Wehner

& Craig, 1972). Pulmonary haemorrhagia and oedema and death were observed in guinea-pigs exposed by inhalation to co~alt chloride (dose unclear) (Höbel et al., 1972).

Life-time exposure of hamsters to cobalt oxide by inhalation (10 mg/m3, 7 h per day, five days a week) resulted in emphysema and in hyperplastic and hypertrophic changes in the alveolar epithelium and distal bronchi (Wehner et al., 1977). Exposure of rabbits by inhalation to concentrations of 0.4 or 2 mg/m3 cobalt

chloride for 6 h per day on five days a week for 14-16 weeks produced nodular aggregation of alveolar type II ceIls, abnormal accumulation of enlarged, vacuolated

alveolar macrophages and interstitial inflammation (Johansson et al., 1987). Daily doses of 2.5- 10 mg/kg bw cobalt(II) salts given orally or parenterally

caused polycythaemia in rats (Orten & Bucciero, 1948; Hopps et al., 1954; Oskarsson et al., 1981); reduced weight gain was seen as an early sign of general

toxicity in sorne of these studies. Parenteral administration of 10-60 mg/kg bw cobalt chloride caused hyperlipidaemia in rabbits (CapIan & Block, 1963),

induction of hepatic haemoxygenase and a decrease in activi ty of 8-aminolaevulinic



synthase and certain cytochrome P450-dependent drug metabolizing enzymes in

rats (Maines & Kappas, 1975; Maines et al., 1976; Numazawa et al., 1989). Myocardial toxicity of cobalt salts has been reported in rats (Grice et al., 1969; Lin & Duffy, 1970; Rona, 1971), guinea-pigs (Mohiuddin et al., 1970; Desselberger & Wegener, 1971), rabbits (Hall & Smith, 1968) and dogs (Sandusky et al., 1981) following long-term dietary (10-100 mg/kg bw) or parenteral (5-30 mg/kg bw) administration. Observed toxic effects included nonintlammatory myocardial

degeneration, alterations in mitochondria and myofibrils and abnormal electrocardiographic traces. Metallie cobalt

Intratracheal instilation of metallc cobalt (50 mg/animal; sterile suspension (particle size not given D caused pulmonary haemorrhage and oedema and death in rats (Harding, 1950).

ln miniature swine exposed to 0.1- 1 mg/m3 metallc cobalt particles (0.4-3.6

j.m) for 6 h per day on five days per week for three months by inhalation, a progressive decrease in lung compliance was observed. ln addition collagenization of alveolar septa in lung biopsies and electrocardiographic changes indicative of cardiomyopathy were observed (Kerfoot et al., 1975). ln contrast to findings with cobalt chloride, exposure of rabbits by inhalation to metallc cobalt dust (0.2- 1.3 mg/m3, 6 h per day, five days per week for four weeks) had no profound effect on alveolar macrophages (Johansson et aL., 1980, 1986).

Cobalt released from cobalt metal, alloys or dissolved salts was cytotoxic to

chick primary cultures and rodent fibroblast cell Hnes, inducing cell death, growth

inhibition and mitotic abnormalities at concentrations greater than 7.5 j.glml (Heath, 1954b; Daniel et al., 1963; Bearden, 1976; Bearden & Cooke, 1980; Takahashi & Koshi, 1981).

(ii) Effects on reproduction and prenatal toxicity Reproductive effects: Ingested cobalt chloride (265 mg/kg di

et for 98 days,

20 mglg bw cobalt) induced degenerative and necrotic changes in the seminiferous tubules of rats. Cyanosis and vascular engorgement of the testes were seen on day 35 of treatment, and necrosis, degenerative and necrotic changes in the germinal epithelium and Sertoli cells by day 70. Damaged tubules were present side by side with normal ones. Multinucleated giant cells containing cellular debris were observed in the damaged tubules. Loss of sperm-tailfilaments and degeneration of sperm mitochondria were also observed (Corrier et al. 1985a; Mollenhauer et al., 1985). The same group of investigators did not find the lesion in sheep treated with 3.0-15.0 mg/kg bw cobalt for 109 days (Corrier et al. 1985b). providing an initial dose of



and 6 days before sacrifice stimulated spermiogenesis and spermatogenesis in the mouse testis Intraperitoneal injection of cobalt chloride (1 mglg bw cobalt) 16

(Niebrój,l967). Intraperitoneal administration of

20 j.mol (47.6 mg)/kg bw cobalt

chloride for three days to male mice resulted in small but significant decreases in fertilty two to three weeks later in an acute study. Similarly, in a chronic study, 100, 20 and 40 mgl cobalt chloride given in drinking-water ad libitum for 7-13 weeks

decreased fertiIty, sperm concentration, sperm mobilty and testicular weight in a time-dose-dependent manner (Pedigo et al., 1988). (The Working Group noted that the apparent differences in the results described above may be due to differences in dose and duration of observation.)

Developmental toxicity Embryonic death was reported following administration to rats of cobalt chloride in the drinking-water either before and during pregnancy (0.05-5 mg/) or during pregnancy only (0.005-0.05 mg/l) (Nadeenko et al.,

1980). ln contrast, no developmental toxicity was observed in the offspring of rats given daily doses of 0, 25, 50 or 100 mg/kg bw cobalt chloride by gavage on days 6- 15 of gestation, except for a nonsignificant increase in the incidence of stunted fetuses in the groups given 50 and 100 mg/kg (Paternain et aL. 1988).

Numbers of litters as weIl as growth and survival of the offspring were reduced

in rats that received 12, 24 and 48 mg/kg bw per day cobalt chloride by gavage from day 14 of gestation through day 21 of lactation (Domingo et al., 1985). Delay in ossification of the skeleton during embryonic and fetal development was observed at gestation day 17 in the offspring of sIx- to eight-week-old female mice (24-26 g) administered cobalt chloride (0.1 ml of a 5 mM solution (4.8 mg/kg bw)) intravenously on day 8; the effect was not seen when the cobalt was administered on day 3 of pregnancy. There was no change in fetal body weight on day 17 of pregnancy, and no increase in the frequency of resorption or implantation sites compared with controls (Wide, 1984). ln CF-1 mi

ce, cobalt chloride was reported to protect against deft lip and

palate induced by cortisone (Kasirsky et al., 1967).

As rePOrted in an abstract, fetal damage was detected on gestation day 15 in

hamsters administered cobalt acetate (40, 60, 80, 100 or 160 mg/kg bw) subcutaneously on day 8 of pregnancy. The resorption rate ranged from 6% at the

low dose to 100% at the high dose. Central nervous system defects were reported at

the median doses. Similarly, resorptions and central neivous system defects were observed after intraperitoneal injections of 40-70 mg/kg (Gale, 1980). (The Working

Group noted that no information on maternaI toxicity was reported.)

Studies on the effects of cobalt salts on chick embryos have produced conflicting results, perhaps due to differences in dose and routes of adminis-

tration. Degeneration of the brain (Ridgway & Karnofsky, 1952), neural tube



malformations (Adhikari, 1967), lethality, eye abnormalIties and structural defects (Kury & Crosby, 1968; Gilani & Alibai, 1985, abstract) have ben reported.

(iv) Genetic and related effects

The results of tests for genetic and related effects of cobalt and cobalt compounds, with references, are given in Table 21. Other studies are described in the text.

The genetic toxicology of cobalt and cobalt compounds has been reviewed (Léonard & Lauwerys, 199). With few exceptions, only soluble cobalt(II) salts have been tested. Only two reports were available on genetic effects of insoluble cobalt

sulfide, and no data have been reported on genetic effects of metallc cobalt. Like other metallc compounds, cobalt compounds are known to be relatively inactive in prokaryotic systems (Rossman, 1981; Swierenga et al., 1987). The precipitation of metal as phosphates in bacterial culture media may contribute to

this inactivity (Rossman, 1981; Arlauskas et al., 1985). However, four of 15 cobalt(III) complexes with aromatic ligands were active in a DNA repair assay and

were mutagenic to Salmonella tyhimurium (Schultz et al., 1982). Several other studies of cobalt salts with positive results have been reported in prokaryotes. Cobalt(II) chloride was inactive in the À prophage induction assay, and it gave conflicting results in the Bacillus subtilis rec + j- growth inhibition assay. ln the study with positive results, a preincubation procedure was used. Cobalt(II) chloride was

inactive in aIl but one bacterial mutagenicity test. One study gave positive results in the absence but not in the presence of an exogenous metabolic system. ln bacteria, cobalt

(II) chloride was reported to reduce the incidence of

spontaneous mutations and to inhibit mutations induced by N-methyl-N'-

nitro-N-nitrosoguanidine and Trp-P- 1 (Kada & Kanematsu, 1978; Inoue et al., 1981;

Mochizuki & Kada, 1982). It was comutagenic with several heteroaromatic compounds (Ogawa et al., 1986, 1987, 1988).

ln Saccharomyces cerevisiae, cobalt(II) chloride induced gene conversion and mitochondrial but not other types of mutation. Cobalt(II) salts induced chlorophyll mutations, chromosomal aberrations and aneuploidy in plant ceIls.

ln cultured mammalian ceIls in vitro, predominantly positive results were obtained, with induction ofDNA-protein cross-linkage, DNA strand breakage and sister chromatid exchange. Chromosomal aberrations were not observed in

cultured human ceIls. (The Working Group noted the low concentrations employed.) Cobalt(II) chloride induced aneuploidy in cultured human lymphocytes. It also induced mutations at the hprt locus in Chinese hamster V79 ceIls, but not, in a single study, at the tk locus in mouse lymphoma L5178Y cells.

Cobalt(II) acetate enhanced viral transformation in Syrian hamster embryo cells, and cobalt sulfide induced morphological transformation in Syrian hamster



embryo cells; the crystallne form of cobalt sulfide was more active than the amorphous form. CobaltfII) chloride administered in vivo to Syrian hamsters by intraperitoneal injection induced aneuploidy in bone marrow and testes. ln an assay for dominant ce, reported as an abstract, significant increases in early lethal mutation in mi embryonic los

ses were observed (Pedigo, 1988).

A mechanism for the genetic effects of soluble Co(II) salts may involve decreased fidelity of DNA polymerase (Sirover & Lob, 1976). Cobalt(II) chloride caused extensive cleavage of isolated DNA in the presence of hydrogen peroxide; this effect was attributed to the generation of reactive oxygen species at those sites of DNA bound to cobalt ions (Yamamoto et al., 1989). (b) Humans

(i) Absorption, distribution, exretion and metabolism The normal concentrations of cobalt in blood and urine from non-

occupationallyexposed persons are about 0.1-2 J.g/l. The levels of cobalt in blood, and particularly in urine, increase in proportion to the level of occupational

exposure and can be used for biological monitoring in order to assess individual exposure (Elinder et al., 1988). Increased levels of cobalt have also been found in blood (serum) from uraemic patients (Curtis et al., 1976; Lins & Pehrsson, 1984). ln a patient who died three months after treatment with cobalt(II) chloride (50 mg per day for three months), the myocardial concentration of cobalt was 1.65 mg/kg wet weight, which was 25-80 times higher than that in control samples

(0.01-0.06 mg/kg) (Curtis et al., 1976). Increased levels of cobalt were also reported

in lung and mediastinal lymph nodes from hard-metal workers with lung disease;

concentrations of cobalt were about 100-100 J.glg in two lung tissue samples compared to 5 J.g/kg wet weight in controls, and 328 J1g/kg in mediastinal lymph nodes compared to :: 2 J.g/kg in controls (Hilerdal & Hartung, 1983). The mean urinary excretion within 24 h of radioactive cobalt chloride given orally at 20 J1M was estimated to be about 18% (Sorbie et al., 1971). When healthy

persons and uraemic patients were given 50 mg cobalt chloride orally, the two the dose via the urinewithin healthyvolunteers eliminated between 5.7 and 8.3% of

one week; elimination was considerably slower in uraemic patients, confirming the

importance of renal clearance (Curtis et al., 1976). High concentrations of

radiolabelled cobalt were found in the lIver shortly after parenteral administration

of cobalt chloride to humans. Afer eight days, 28-56% and 2- 12% of the dose were eliminated via the urine and faeces, respectively. A significant component (9-16% of the administered dose) was cleared very slowly, with a biological half-time of

about two years (Smith et aL., 1972). Similar results, suggesting that a small

.; w

Table 21. Surnrnary or studies on genetic and related etTects or cobalt Test sytem





LED/HID Without exogenous metabolIc

With exogenous metabolIc




Cobalt(II) salts PRB, Prophage induction in Escherichia coli

BSD, Bacillus subtilis rec strains H17/M45, growth inhibition BSD, Bacilus subtilis rec strain H17, growth inhibition BSD, Bacillus subtilis rec strain H17, growth inhibition BSD, Bacillus subtilis rec strain H 17, growth inhibition ???, Bacillus subtilis strain NIG 1125, revers mutation


0 0

+ (+ ) (+ )

0 0 0 0 0 0


SA7, Salmonella typhimurium TA1537, revers mutation


SA7, Salmonella typhimurium TA1537, revers mutation


SAü, Salmonella typhimurium TA100, revers mutation

SAü, Salmnella typhimurium TA100, revers mutation SAü, Salmonella typhimurium TA100, revers mutation

SA2, Salmnella typhimurium TA102, revers mutation SA5, Salmonella typhimurium TA1535, revers mutation

SA5, Salmonella tyhimurium TA1535, revers mutation SA7, Salmonella typhimurium TA1537, revers mutation

SA8, Salmonella typhimurium TA1538, revers mutation SA8, Salmonella typhimurium TA1538, revers mutation

SA9, Salmnella tyhimurium TA98, revers mutation SA9, Salmonella typhimurium TA98, revers mutation

SA9, Salmonella typhimurium TA98, revers mutation SA9, Salmonella typhimurium TA98, revers mutation




'I & Fung (1981)

Arlauskas et al. (1985)


:i tI

Arlauskas et al. (1985)

40. ~~


Wong (1988)

0 0

O. ~~



0 0 0 0 0



O. ~~ 130. ~~ O. ~~ O. ~~


0 Z 0 0



0 0 0 0

EC2, Escherichia coli WP2, revers mutation SCG, Saccharomyces cerevisiae D7, gene conversion

SAS, Salmonella typhimurium TA2637, revers mutation



40. ~~



EC\ Escherichia coli WP2 uvrA, revers mutation


Rosman et al. (1984)

Nishioka (1975) Kanematsu et al. (1980) Kanematsu et al. (1980) Kanematsu et al. (1980) Inoue et al. (1981)

ügawa et al. (1986) Wong (1988)




4. ~~ 325.~~ 325.~~


6500.~~ O. ~~

20. ~~ O. ~~ 20. ~~ O. ~~ O. ~~ O. ~~

6500.~~ O. ~~ 20. ~~ 1300. ~~

Arlauskas et al. (1985) ügawa et al. (1986) Wong (1988)

Mochizuki & Karla (1982) Arlauskas et al. (1985) Mochizuki & Kada (1982) Arlauskas et al. (1985) ügawa et al. (1986) Wong (1988)

ügawa et al. (1986) Arlauskas et al. (1985) Kada & Kanematsu (1978) Fukunaga et al. (1982)


tT V\


Table 21 (contd) lèst sytem



Without exogenous metabolic




With exogenous metabolic system

sytem Cobalt(II salts (contd) SCG, Saccharomyces cereia D7, gene conversion

SCG, Saccharomyces cerevisia D7, gene conversion SCF, Saccharomyces cereviiae, petite mutation SCF, Saccharomyces cerevisia SBT-2B, petite mutation

SeP Saccharomyces cereviae, petite mutation SCF, Saccharomyces cereviiae D7, petite mutation

SCR, Sacchaomyces cereviia SIM 13-D, eryhromycin-resistant mut. SCR, Saccharomyces cereviae D7, ilv gene mutation SCR, Sacchamyces cerevia D7, i/v gene mutation SCR, Saccharomyces cereviae D7, ilv gene mutation PLM, Pium abssinicum, chlorophyll mutation ACC, A//um cepa, chromosmal aberration ?11, A//ium cepa, aneuploidy DIÁ, DNA strand breaks, Chinese hamster CHO cens DIA, DNA cros-links, Novikoff hepatoma cells G9H, Gene mutation, Chinese hamster V79 cells, hprt locus G9H, Gene mutation, Chiòese hamster V79 cells, hprt locus G5T, Gene mutation, mouse lyphoma L5178Y cens, ti locus SIM, Sister chromatid exchange, mouse macrophage P388D 1 cellline TIS, Cell transformation, SA 7 /Syran hamster embryo cells TIS, Cel1 transformation, SA 7 /Syran hamster embryo cel1s DIH, DNA strand breaks, human white bloo cens DIH, DNA strand breaks, human diploid fibroblasts DIH, DNA strand breaks, HeLa cens

SHL, sister chromatid exchanges, human lyphoces


(+ ) +

0 0

+ + (+ ) +




(+ ) + + + + (+ ) (+ ) +


+ + + + + + +

0 0 0 0 0 0

0 0 0

0.000 1500.~~ 130.~~ 260. ~~ 640. ~~ 750.~~

Singh (1983) Kharab & Singh (1985) Lindegren et al. (1958) Prazmo et al. (1975) Egilsson et al. (1979) Kharab & Singh (1987)

1300. ~~ 1300. ~~ O. ~~ 3000. ~~ O. ~~

Putrament et al. (1977)

3. ~~


O. ~~

0 0

260.~~ 130.~~


26. ~~ O. ~~

0 0 0 0 0

57.~~ 13. ~~

35.~~ 55.~~

Fukunaga et al. (1982) Singh (1983) Kharab & Singh (1985) von Rosn (1964)b Gori & Zucconi (1957) Gori & Zucconi (1957) Hamilton-Koch et al. (1986) Wedrychowski et al. (1986)

Miyaki et al. (1979)

Hartg et al. (1990)

0o: ~ ~ Ü


0o: q 0 ('

~ '"




Ü en

Amacher & Pailet (1980) Andersn (1983) Casto et al. (1979) Casto et al. (1979) McLean et al. (1982) Hamilton-Koch et al. (1986)





0 0

O. ~~

Hartg et al. (1990)

1. 300

Andersn (1983)

~ w



Table 21 (contd) 1èst sytem

LED/IUD Without exogenous metabolic

sytem Cobalt(II) salts (contd) CHF, Chromosmal aberrations, human fibroblasts CHL, Chromosmal aberrations, human lyphoces CIH, Chromosmal aberrations, human leukoces AIH, Aneuploidy, human lyphoces AVA, Aneuploidy, bone marrow and testes of male hamsters






With exogenous metabolic system

~ a:

0 0 0 0


Paton & Allison (1972)


Voroshilin et al. (1978)


Paton & Allison (1972)


Resende de Souz-Nazreth (1976)



+ +

0 0


(+ )



+ +

Farah (1983)C

Cobalt sulfide

DIA, DNA strand breaks, Chinese hamster CHO cells TC, Cell transformation, Syran hamster embryo cells TC, Cell transformation, Syran hamster embryo cells

Cobalt(III) salts BSD, Baeil/us subtilis ,ee strain H17, growth inhibition aAntimutagenic eHeet

bOr as EDTA chelate 'lnjected intraperitoneally over nine days


Robison et al. (1982) Costa et al. (1982) Costa et al. (1982)

0 Z 0 0 ~ :: CI

â E ~ tr VI


(+ )



Kanematsu et al. (1980)

COBALT AND COBALT COMPOUNDS proportion of the cobalt (from either the met


al or the oxide) retained after

inhalation has a biological half-time in the order of years, were obtained by other investigators (Newton & Rundo, 1970; Hedge et al., 1979). pers

Measurements of cobalt, chromium and nickel in blood and urine from ons with metaIIc hip replacements containing a high proportion of these

metals have repeatedly shown elevated levels of one or several of them compared to

controls or prior to surgery (Coleman et al., 1973; Jones et al., 1975; Hildebrand et al., 1985; Braun et aL., 1986; Hildebrand et al., 1988). (The Working Group noted that the analytical accuracy of several of the earlier studies was not confirmed. J

Sunderman et al. (1989) measured the concentrations of chromium, cobalt and nickel in serum and urine samples collected from patients who had undergone bone

surgery and had received metaIIc hip or knee prostheses. Patients were followed for

up to two years. The concentration of chromium in serum and urine remained essentially unchanged, whereas the concentration of nickel was markedly increased in both urine and serum collected shortly after the operation (1 -14 days). The cobalt concentration, however, displayed a relatively smaIl, slow increase in serum and

blood. The highest concentrations were seen after two and 22 months in two patients who had loosening of their prosthesis. (ii) Toxic effects

Pulmonary effects have been regarded as the major occupational problem in relation to cobalt, particularly in the hard-metal industry where cobalt-containing dust is generated. Two types of lung lesions may develop-interstitial fibrosis (so-called 'hard-metal pneumoconiosis') and occupational asthma (Demedts &

Ceuppens, 1989). Hard-metal pneumoconiosis is a severe and progressive tye of pneumoconiosis which may develop after several years of exposure to cobaltcontaining dust at concentrations of 0.1-2 mg/m3 (for reviews, see Elinder & Friberg, 1986; Sprince et al., 1988). As the dust in the hard-metal industry always contains agents in combination with cobalt (tungsten carbide and sometimes other

metals such as titanium and tantalum), it has been questioned whether cobalt is solely responsible for the observed health effects (Brooks, 1981). Diamond polishers exposed to fine dust containing cobalt and diamond had severe lung fibrosis (Demedts et al., 1984). Symptoms and signs of obstructive lung disease can develop as a result of occupational exposure to cobalt-containing dust during the production of hard

metal (Coates & Watson, 1971, 1973; Bech, 1974; Scherrer & Mailard, 1982), but these were also observed in workers in a porcelain factory using cobalt dye (Raffn et al., 1988) and among diamond polishers (Gheysens et al., 1985). This condition, which usually improves after cessation of exposure, is considered to be of allergic origin (Sjögren et al., 1980). Provocation tests with cobalt usually iIiduce a typical



asthmatic reaction (Hartmann et al., 1982). Shirakawa et al. (1989) examined eight Japanese hard-metal plant. The total number ofworkers was about 40. The eight asthmatic workers aIl reacted with a drop in peak expiratory flow rate after an inhalation challenge with cobalt chloride. ln four of them, it was possible to identify specific IgE antibodies towards

workers who developed asthma after havingworked in a

cobalt-conjugated human albumin. This finding supports the hypothesis that cobalt hypersensitivity has a role in hard-metal asthma.

Histopathological findings in lung biopsies from workers with fibrosis (hard-metal pneumoconiosis) and/or obstructive problems (hard-metal asthma) have been published (Coates & Watson, 1971, 1973; Davison et al., 1983; Demedts et

al., 1984; Anttila et al., 1986; Cugell et al., 199). Typical microscopic findings include advanced fibrosis and desquamative interstitial pneumonia of the giant-cell type (Coates & Watson, 1971; Anttila et al., 1986). Cobalt has an eryhropoietic effect and has ben used for the treatment of anaemia (Berk et al., 1949; Duckham & Lee, 1976). Berk et al. (1949) gave patients

about 100 mg cobalt in the form of cobalt chloride three times a day for several

weeks and recorded vomiting and anorexia in sorne patients, but only mild symptoms in the alimentary tract were seen as side-effects of the treatment in others. Duckham and Lee (1976) used a lower dose of cobalt chloride (25-50 mg cobalt per day) and observed fewer side effects. Polycythaemia has also been

reported in heavy drinkers of cobalt-fortified beer (Morin et al., 1971; Alexander, 1972).

Endemic outbreaks of cardiomyopathy with mortality rates of up to 50% were

described among heavy consumers (up to 10 1 per day) of cobalt-fortified beer (Morin & Daniel, 1967; Kesteloot et al., 1968; Morin et aL., 1971; Alexander, 1972). As the daily dose of cobalt ingested by heavy beer drinkers (a few millgrams) was

certainly excessive compared to the normal daily intake of cobalt (around 5-50 j.g1day), but considerably lower th

an the doses prescribed to patients with anaemia,

it was suggested that the cardiomyopathy had a multicausal origin (Morin & Daniel, 1967; Balazs & Herman, 1976). Three cases of cardiomyopathy, two of which were fatal, were described in workers exposed industrially to cobalt (Barborík & Dusek, 1972; Kennedy et al., 1981; Alušík et aL., 1982).

There are sorne indications that workers in hard-metal plants have increased morbidity and mortality from cardiovascular disease. Alexandersson and Atterhög (1980) examined workers exposed to cobalt-containing dusts at concentrations of 0.01-0.06 mglm3. Symptoms of dyspnoea, 'heavy breathing' and 'tightness in chest

were more prevalent in exposed workers than in controls, but no pulmonary dysfunction was found. ln a recent study of 3163 workers exposed to

cobalt-containing dusts at concentrations ranging from 0.001 to up to Il mglm3 for

at least one year, Hogstedt and Alexandersson (199) found an excess of deaths



from ischaemic heart disease (standardized mortality ratio (SMR), 169; 95% confidence interval (CI), 96-275) among workers who had been exposed to 0.02-11 mg/m3 cobalt for at least 10 years (see also p. 445). Cobalt may provoke allergic dermatitis (Camarasa, 1967). Of 853 patch-tested

workers, about 7% showed allergic reactions to 1% cobalt chloride (Fischer & Rystedt, 1983). Cobalt allergy, which is usually found in people who suffer from

other skin allergies and/or eczema (Rystedt & Fischer, 1983), is also seen in other al groups, such as offset printers and construction workers handIing cobalt-containing cement (Goh et al., 1986). occupation

Cobalt and nickel released from orthopaedic or dental prostheses may precipitate allergic reactions, with local effects and inflammation (Jones et al., 1975; Fernandez et al., 1986; Thomas et al., 1987). (iii) Effects on reproduction and prenatal toxicity

The spontaneous abortion rate appeared to be increased in women who either

worked in metal smelting or had spouses working in the metallurgical industry. Exposure to cobalt, arsenic, copper, zinc and sulfur was considered possible in the

work setting (Hemminki et al., 1983). (The Working Group noted that the contribution of cobalt, if any, to the increase in abortion rate was not separately identified.) (iv) Genetic and related effects No data were available to the Working Group.

3.3. Case reports and epidemiological studies or carcinogenicity in humans (a) lmplanted medical devices

The first report of development of a sarcoma at the site of a stainless-steel plate prosthesis for a fracture of the humerus was made in 1956 (McDougall, 1956). There have been 17 further reports of single cases of malignant neoplasia at the site of implants of metal-containing fracture plates or joint prostheses. The metal

material used was unknown in four cases, stainless-steel in three cases and cobalt-containing alloys in 10 cases. The period between implantation and tumour development ranged from one to 30 years. The tumours described were various types of sarcoma in 14 cases (Delgado, 1958; Castleman & McNeely, 1965; Dube & Fisher, 1972; Arden & Bywaters, 1978; Tayton, 1980; Bagó-Granell et al., 1984; Lee et al., 1984; Penman & Ring, 1984; Swann, 1984; Weber, 1986; Hughes et al., 1987; Ryu et al., 1987; Martin et al., 1988; Ward et al., 199), one carcInoma (Mazabraud et al.,

1989) and lymphoma in two cases (McDonald, 1981; Dodion et al., 1983). Incident cancers were recorded for a cohort of 1358 persons who received a total hip replacement in New Zealand in the period 196-73 and were followed up



for six months to 17 years (me

an, 10.5 years) to the end of 1983 (Gilespie et aL., 1988).

Total cancer incidence was simIlar to that expted (164 observed versus 179.4 expected on the basis of general population rates; SMR, 91 (95% CI, 78- 107)). While

the overall cancer risk within 10 years of hip replacement was significantly low (SMR, 74; 95% CI, 61-90, based on 107 observed cases), the risk after 10 or more years was significantly high (SMR, 160; 95% CI, 122-20, based on 57 cases). There

was a significant overall increase in the incidence of tumours of the lymphatic and

haematopoietic system (21 observed versus 12.5 expeted; SMR, 168; 95% CI, 106-26). When the five lymphatic and haematopoietic malignancies diagnosed within two years of hip replacement were excluded, this SMR fell to 151 (16 versus 10.6 expected (95% CI, 86-245)). There were significant deficits of breast cancer (six observed versus 16.6 expected; SMR, 36; 95% CI, 14-82) and of colorectal cancer (21

observed versus 33.8 expected; SMR, 62; 95% CI, 39-96). (No specific information on the composition of the hip prostheses was provided.)

(h) Occupational exsure Schulz (1978) reported a cobalt-containing giant-cell tumour of the buccal membrane in a mineral-oil refinery employee five months after a single accidental

exposure to dust containing cobalt(II) phthalocanine. Saknyn and Shabynina (1970, 1973) examined mortality rates among workers at four nickel plants in the USSR in 1955-67. The workers were exposed to cobalt, but also to various nickel and arsenic compounds. A two- to four-fold increase in the risk for lung cancer was reported. The risks relative to those of inhabitants in the towns in which the plants were located were increased in various parts of the plants, including the cobalt shops (relative risks, 5-13), where there was exposure to cobalt dust but also to nickel sulfates, nickel chlorides and arsenic compounds. A 1.5-3.3-fold increase in stomach cancer risk was also noted. (The observed numbers

of deaths were not given, and no allowance was made for potential confounding factors.) Cuckle et al. (1980) studied mortality in 297 men employed in two departments

opened in 1937 and 1938 at a nickel refinery in the UK. ln one department, a wet treatment plant, nickel sulfate, copper sulfate, 'cobaltic hydrate' and precious metal

concentrates were manufactured; in the other, a chemical production department, a men had aIl been first employed in the refinery in or after 1933 and had worked in one or other of range of compounds of nickel, cobalt and selenium were produced. The

the departments for at least 12 months before 196. They were followed up to 30 June 1980. Overall, there were 105 deaths (SMR, 109 (95% CI, 89- 132)). There were 13 deaths from lung cancer (SMR, 131 (95% CI, 70-224)); six of the men who died

from lung cancer (SMR, 154; 95% CI, 57-336) had been employed in the precious metal concentration section of the wet treatment plant. When the expected number



of lung cancer deaths was estimated from death rates in rural districts of Glamorganshire (where the refinery was located), rather than in the population of England and Wales as a whole, the SMR was (172; 95% CI, 92-295). Excess mortality from lung cancer occurred mainly less than 20 years from first employment in the refinery (SMR, 178 (95% CI, 65-387)) and among men who had been employed for six or more years (SMR, 138 (95% CI, 55-283)). Among the 1173 workers employed in the whole refinery in or after 1930 (International Committee on Nickel Carcinogenesis in Man, 199), those first employed in 1930-39 had a SMR for lung cancer of 154 (95% CI, 97-233), those first employed in 1940-49 a SMR of 130 (95% CI, 71-218) and those first employed after 1950 a SMR of 77 (95% CI,

33-152). Cuckle et al. (1980) did not attribute any increase in risk in this cohort to exposure to cobalt. Mur et al. (1987) followed up 1143 workers with at least one year of employment

betwen 1950 and 1980 in an electrochemical plant producing cobalt and sodium in France. Altogether, 24.9% of the cohort were migrants (mainly North Africans and Italians). Vital status was established for 99.5% of the French-born workers and for 81.3% of the migrants. A total of 213 deaths occurring before 1981 was identified; cause of death was determined for 80% by interview with attending physicians and from hospital records. After adjustment for unknown causes of death (assuming that the distribution by cause of death was similar to that of cases with known cause of death), a SMR of

90 (95% CI, 44-159, based on nine cases) was observed for the

total cohort for cancer of the lung, using mortality rates for France as a reference. For workers employed only in cobalt production, the SMR for lung cancer was 46 (95% CI, 146-106, based on four observed cases). (Te migrants may have had

different rates of lung cancer from French-born workers, but the proportion of migrant workers in the different departments of the plants was not reported.) A case-control analysis was performed of lung cancer cases and controls, matched for

year of birth, year of death and smoking habits. (The quality and manner of collection of information on smoking is unclear.) An odds ratio of 4.0 (95% CI, 1.6-9.9; calculated by the Working Group using an unmatched analysis) was

associated with ever having worked in cobalt production. Workers in cobalt production were also exposed to unknown levels of forms of nickel and arsenic. rIt is

not known whether workers in other areas also had such exposure. No analysis based on latency or duration of exposure was presented.) Hogstedt and Alexandersson (199) reported on 3163 male Swedish workers

with at least one year of exposure to cobalt-containing hard-metal dust at one of three hard-metal manufacturing plants in 1940-82 who were followed up during the

period 1951-82. There were t.2!:rcategories of exposure (with estimated ambient air concentrations prior to 1970): oCcasionaUy present in rooms where hard metal was handled (less than 2 Ilg/m3 Co); continuously present in rooms where hard metal



was handled, but own work not involving hard metal (1-5 )lglm3 Co); manufacturing

hard-metal objects (10-30 )lglm3 Co); and exposed to cobalt in powder form when manufacturing hard-metal objects (60-11 00 )lglm3 Co). No specific information

was given on exposure to other substances in this cohort, but the workeis were exposed to a number of substances that are used in the production of hard metal, such as tungsten carbide. There were 292 deaths among persons under 80 years of age during the study period; the SMRs relative to that of the male Swedish population were 96 (95% CI, 85- 108) for mortality from aIl causes and 105 (95% CI, 82- 132) for aIl lncident tumours (73 cases). There were 17 cases of lung cancer versus 12.7 expected (SMR, 134; 95% CI, 77-213). WIth more than 10 years of exposure

time and more than 20 years since first expsure, there were seven cases of lung cancer versus 2.5 expected (SMR, 278; 95% CI, 111-572); there were three cases of

cancer of the lung versus 1.3 expected in the two lower exposure groups, and four cases of lung cancer versus 1.2 expeted in the two higher exposure groups. A survey carried out at the end of the 1970s among hard-metal workers in Sweden showed

that their smoking habits were not different from those of the male Swedish population (Alexandersson, 1979).

4. Summary of Data Reported and Evaluation 4.1 Exposure data

Cobalt is widely distributed in the environment; it is the thirty-third most abundant element in the earth's crust. Cobalt is obtained primarily as a by-product of the mining and processing of copper and nickel ores and is a consti tuent of about 70 naturally occurring oxide, sulfide, arsenide and sulfoarsenide mineraIs. Cobalt is

extracted from ore and concentrated by pyrometallurgical, hydrometallurgical and electrolytic processes alone or in combination. Refined metallc cobalt is available to the industrial market as cathodes and to a lesser extent as powders; oxides and other compounds are also available.

Cobalt compounds have been used as pigments in glass and ceramics in many countries for thousands of years. Since the beginning of the twentieth century, the

major uses of cobalt have been in the production of metal alloys, such as superalloys

and magnetic alloys, as weIl as high-strength steels and hard-metal cemented carbides. At the end of the 1980, about one-third of the cobalt used was in the production of cobalt chemicals, which are used primarily as catalysts and pigments.

The main route of occupational exposure is via the respiratory tract by inhalation of dusts, fumes and mists containing cobalt. Exsures have been measured in hard-metal production, processing and use and in porcelain painting. Occupational exposure to cobalt is regulated in many countries.



Cobalt occurs in vegetables via uptake from soil, and vegetables account for the major part of human dietary Intake of cobalt. Animal-derived foods, particularly liver, contain cobalt in the form ofvitamin B12. Cobalt is also found in air, water and tobacc smoke. Human tissues and fluids normaIIý contain low levels

of cobalt, which may be increased as a result of ocupational exposures. Cobalt concentrations in tissue, serum and urine can be increased in patients with implants

made of cobalt-containing alloys. Cobalt-containing particles have been detected in tissues immediately adjacent to such prostheses. 4.2 Experimental carcinogenicity data Cobalt metal powder was tested in two expenments in rats by intramuscular

injection and in one experiment by intrathoracic injection, producing sarcomas at

the injection site. A finely powdered cobalt-chromium-molybdenum alloy was testedin rats by intramuscular injection, producing sarcomas at the injection site. ln two other

experiments In rats, coarsely or finely ground cobalt-chromium-molybdenum alloy implanted in muscle or pellets of cobalt-chromium-molybdenum alloy implanted

subcutaneously did not induce sarcomas. Implantation in the rat femur of three different cobalt-containing alloys, in the form of powder, rod or compacted wire, resulted in a few local sarcomas. ln another experiment, intramuscular implan-

tation of polished rods consisting of three different cobalt-containing alloys did not produce local sarcomas. ln an experiment in guinea-pigs, intramuscular implantation of a cobalt-chromium-molybdenum al/oy powder did not produce local

tumours. Intraperitoneal injection of a cobalt-chromium-aluminium spinel in rats produced a few local malignant tumours, and intratracheal instilation of this spinel in rats was associated with the occurrence of a few pulmonary squamous-cell carcinomas. ln two experiments in rats, intramuscular injection of cobalt/Ill oxie powder produced sarcomas at the injection site. ln an èxperiment in mice, intramuscular injection of cobalt oxide powder did not produce local tumours. Intratracheal instilation of cobalt oxide powder in rats was associated with a few benign and malignant pulmonary tumours. ln a study Iimited by por suivival, hamsters admi-

nistered a cobalt oxide dust by inhalation showed no increase in the incidence of pulmonary tumours. ln two experiments in rats by subcutaneous and intraperitoneal injection, cobalt oxide powder produced local malignant tumours.

Cobalt/Ill sulfie powder was tested in one study in rats by intramuscular injection, producing a high incidence of local sarcomas.



eoba/tlllj ch/oride was tested in one study in rats by repeated subcutaneous injection, producing many local and a few distant subcutaneous sarcomas. eoba/tlll,IIlj oxie was tested in one experiment in hamsters to determine the

effects of various particulates on carcinogenesis induced by N-nitrosodiethylamine.

Intratracheal instilation of cobalt(II,III) oxide did not increase the incidence of pulmonary tumours over that in appropriate control groups. Studies in mice and rabbits with cobalt naphthenate could not be evaluated. ln a screening test for lung adenomas by intraperitoneal injection, coba/tlIllj acetate did not increase the incidence of lung tumours in strain A mice. Interpretation of the available evidence for the carcinogenicity of cobalt in experimental animais was difficult bec


se many of the reports failed to include

sufficient details on results of statistical analyses, on survival and on control groups.

Further, statistical analyses could not be penormed by the Working Group in the absence of specific information on survval and on whether the neoplasms were fataL. Nevertheless, weight was given in the evaluation to the consistent occurrence

of tumours at the site of administration and to the histological types of tumours observed.

4.3 Human carcinogenicity data

A number of single cases of malignant tumours, mostly sarcomas, have been reported at the site of orthopaedic implants containing cobalt. ln one cohort study of people with a hip prosthesis, there was a significant increase in the incidence of lymphatic and haematopoietic malignancies, and significant deficits of breast and colorectal cancers. Overall cancer incidence was significantly lower than expected

in the first 10 years after surgery, but significantly higher than expected after 10 or more years. No data were provided on the composition of the prostheses in this study. Four cohort studies on the association between industrial exposure to cobalt and death from cancer were reviewed, two of which provided information for the evaluation. ln a French electrochemical plant, there was a significant increase in the risk for lung cancer among workers in cobalt production, who were also exposed to nickel and arsenic, but not among workers in other departments of the factory. ln a

study in Sweden of hard-metal workers with documented exposure to cobaltcontaining dusts, a significant increase in lung cancer risk was seen in people exposed for more than 10 years whose exposure had begun more th

an 20 years


Interpretation of the available evidence on the possible association between al exposure to cobalt and cancer in humans is made difficult by the fact that in three of the four studies there was concurrent exposure to other potentially




carcinogenic substances, including forms of nickel and arsenic. ln the Swedish study, there was concurrent exposure to other components of hard-metal dust. 4.4 Other relevant data

al exposure to cobalt-cntaining dusts can cause fibrotic changes in the lung and can precipitate asthma. Cardiotoxic effects have been reported in exposed humans; in particular, cardiomyopathy can occur after prolonged oral intake. Cobalt(II) chloride reduced fertilty in male mice. Occupation


(II) compounds had weak or no genetic effect in bacteria; sorne

cobalt(III) complexes with heterocyclic ligands were active. ln single studies with an extensive range of eukaryotes, including animal and human cells in vitro, cobalt(II) compounds induced DNA damage, mutation, sister

chromatid exchange and aneuploidy. Gene conversion and mutation in eukaryotes and DNA damage in human cells were observed in several studies. There was sorne se compounds can also induce aneuploidy in hamsters in vivo. ln

evidence that the

single studies, cobalt(II) sulfide induced DNA damage and transformation in cultured mammalian cells. 4.5 Evaluationl There is inadequate evidence for the carcinogenicity of cobalt and cobalt

compounds in humans. There is suffcìent evidence for the carcinogenicity of cobalt metal powder in experimental animaIs.

There is limited evidence for the carcinogenicity of metal alloys containing cobalt, chromium and molybdenum in experimental animais. There is suffcìent evidence for the carcinogenicity of cobalt(II) oxide in experimental animais.

There is limited evidence for the carcinogenicity of cobalt(II) sulfide in experimental animaIs. There is limited evidence for the carcinogenicity of cobalt(II) chloride in experi-

mental animaIs.

There is inadequate evidence for the carcinogenicity of cobalt-aluminiumchromium spinel, cobalt(II,III) oxide, cobalt naphthenate and cobalt(III) acetate ¡n experimental animaIs.

lFor definition of the italicized terms, see Prearnble, pp. 30-33.



Overall evaluation

Cobalt and cobalt compounds are possibly carcinogenic to humons (Group 2B).

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