Occupational exposure is the main exposure path for humans, particularly for workers in the hard metal industry. Workers are exposed to tungsten carbide-cobalt (WC-Co) dusts when powders are handled or tools are polished, and particles may be inhaled or absorbed via the skin.

 

To minimise exposure, suitable protective clothes like gloves and masks should be worn. For the users of tools made of WC-Co an exposure to the particles is unlikely, since the sintered tools are extraordinary hard and wear-resistant. Hence, new release of particles during usage of drillers or others tolls is not relevant.

 

A mixture of WC and cobalt, WC-Co particles, exhibit a higher toxicity than cobalt alone. Cobalt is a compound of known human toxicity [1] and a daily dose of 20 mg and above may induce severe health problems. Hence, the International Agency for Research on Cancer (IARC) classified cobalt alone as "possibly carcinogenic" to humans and the combination of tungsten carbide and cobalt, WC-Co, as "probably carcinogenic" to humans [2]. An mechanism called "contact-corrosion" between cobalt and WC is assumed as a reason for this enhanced toxicity, inducing the formation of free radicals in the presence of oxygen, which in turn may damage cells of the body (mostly lung cells) [3]. Alternative or additionally, particles may act as a "trojan horse" and increase the availability of cobalt in the cells.

In the small town of Fallon (Nevada, USA) human exposure by airborne WC and Co particles has been reported. A hard metal facility located in the town or a close by military base (WC-Co is also used for ammunition) have been discussed as potential sources for WC-Co release [4]. Modern hard metal facilities are equipped with filter systems which prevent particle release.

 

Literature arrow down

  1. ATSDR TOX FAQs (Apr 2004): Cobalt. Agency for Toxic Substances and Disease Registry, U.S. Public Health Service (ATSDR).
  2. IARC (2006), IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, No. 86: Cobalt in Hard-metals and Cobalt Sulfate, Gallium Arsenide, Indium Phosphide and Vanadium Pentoxide.
  3. Gries, B et al. (2007), Euro PM 2007, Powder Metallurgy World Congress & Exhibition, 2007 Oct 15-17; Toulouse (France) Vol. 1, 189-196.
  4. Sheppard, PR et al. (2007), Environ Health Perspect, 115(5): 715-719.

 

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