IARC Monographs evaluation of the carcinogenicity of cobalt, antimony compounds, and weapons-grade tungsten alloy

The results of the recent IARC Monographs evaluation of the carcinogenicity of nine agents, including cobalt metal (without tungsten carbide or other metal alloys), soluble cobalt(II) salts, cobalt(II) oxide, cobalt(II,III) oxide, cobalt(II) sulfide, other cobalt(II) compounds, trivalent antimony, pentavalent antimony, and weapons-grade tungsten (with nickel and cobalt) alloy, have now been published in The Lancet Oncology. This summary article presents the conclusions of IARC Monographs Meeting 131.

Two of these agents – pentavalent antimony and weapons-grade tungsten (with nickel and cobalt) alloy – were evaluated by the Working Group for the first time.

Antimony is used in flame retardants, lead–acid batteries, lead alloys, plastics, brake pads, clutch discs, glass and ceramics, and as an ammunition primer in explosives. Some pentavalent antimony compounds are used in the treatment of leishmaniasis. Cobalt is used in the manufacture of cutting and grinding tools, in pigments and paints, coloured glass, medical implants, electroplating, and increasingly in lithium-ion battery production. Weapons-grade tungsten alloys (tungsten, 91–93%; nickel, 3–5%; and cobalt, 2–4%) are used in armour-penetrating munitions. Military personnel and civilians can be exposed to metal aerosols generated during firing or impact, or after injury with retained embedded munitions fragments.

For all agents, exposures are expected to be higher in occupational situations than in the general population.

The Working Group classified trivalent antimony as probably carcinogenic to humans (Group 2A) on the basis of limited evidence of carcinogenicity in humans, sufficient evidence of carcinogenicity in experimental animals, and strong mechanistic evidence in human primary cells and in experimental systems. Cobalt metal and soluble cobalt(II) salts were classified as probably carcinogenic to humans (Group 2A) on the basis of sufficient evidence in experimental animals and strong mechanistic evidence in human primary cells. Cobalt(II) oxide and weapons-grade tungsten alloy were classified as possibly carcinogenic to humans (Group 2B) on the basis of sufficient evidence in experimental animals. Cobalt(II,III) oxide, cobalt(II) sulfide, other cobalt(II) compounds, and pentavalent antimony were each evaluated as not classifiable as to its carcinogenicity to humans (Group 3). 

The full scientific assessment will be published as Volume 131 of the IARC Monographs.

Karagas MR, Wang A, Dorman DC, Hall AL, Pi J, Sergi CM, et al.
Carcinogenicity of cobalt, antimony compounds, and weapons-grade tungsten alloy
Lancet Oncol, Published online 7 April 2022;
https://doi.org/10.1016/S1470-2045(22)00219-4

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