Tungsten carbide (cemented)

Synonyms

Cemented tungsten carbide; Cemented WC; Hard metal; [NIOSH] Hard metals containing Cobalt [7440-48-4] and Tungsten carbide [12070-12-1], as Co; [ACGIH]

Category

Metals, Inorganic Compounds

Description

A mixture of tungsten carbide, cobalt, and sometimes other metals & metal oxides or carbides; [NIOSH]

Sources/Uses

Used to manufacture hard metal tools; [LaDou, p. 377] Occupational asthma reported in a metal grinder; [Malo] Used in construction, metalworking, mining, and oil/gas drilling industries; Workers exposed during tool grinding and saw blade sharpening/retipping; Exposure may occur during detonation gun welding; [ACGIH]

Comments

The tungsten carbide (WC) content is generally 85-95% and the cobalt content is generally 5-15%. [NIOSH] Hard metal lung disease is caused by the composite material, a mixture of cobalt and tungsten carbide; It is thought that inhaled cemented tungsten carbide injures the lung by releasing toxic oxygen species; Also may occur after exposure to cobalt metal powder mixed with iron and diamond dust in diamond polishers; There is no evidence that cobalt metal alone or other cobalt compounds can cause hard metal disease; [Nordberg, p. 753] "Sprince and colleagues (1984) reported that interstitial and obstructive lung disease was found in 11 of 290 subjects who worked at two tungsten carbide production plants.' [ACGIH] Skin sensitization to cobalt can occur in the hard metal industries. [Marks, p. 79] See "Tungsten." See "Cobalt." This TLV is listed by ACGIH under "Hard metals containing Cobalt and Tungsten carbide."

Biomedical References

Cobalt in urine = nonquantitative; sample at end of shift at end of workweek;

Yes

0.005 mg/m3, as Co, thoracic particulate matter

Explanatory Notes

NIOSH REL = 0.05 mg/m3 (containing >2% Co) & 0.015 mg/m3 (containing >0.3% Ni); "This TLV does not apply to either tungsten carbide or cobalt exposures alone in the absence of the other material." [ACGIH] See TLVs for "Tungsten and compounds."

Yes

Yes

Yes

Probable (2a)

Anticipated human carcinogen

Suspected Human

Diseases

Occupational diseases associated with exposure to this agent:

• Asthma, occupational
• Contact dermatitis, allergic
• Hard metal disease

Processes

Industrial Processes with risk of exposure:

• Metal Machining
• Mining
• Petroleum Production and Refining