There is sufficient evidence that cadmium metal and a number of cadmium compounds, such as cadmium chloride, oxide, sulfate, and sulfide, are carcinogenic in animals. Increased rates of testicular, prostate, and lung cancer in animals have been described (Sahmoun et al., 2005; ATSDR,1999).
Current classification of cadmium's carcinogenicity by health agencies.
- EPA has classified cadmium as a Group B1 or “probable” human carcinogen.
- American Conference of Governmental Industrial Hygienists (ACGIH) considers cadmium a suspected human carcinogen.
- The World Health Organization's (WHO) International Agency for Research on Cancer (IRAC) classifies cadmium as a known human carcinogen.
- The National Toxicology Program (NTP) has characterized cadmium as known to be a human carcinogen (NTP 2004).
Occupational cohort studies have suggested possible associations between chronic exposure to cadmium, particularly cadmium oxide, and cancers of the lung, prostate, and genitourinary system such as renal carcinoma. The strongest evidence for a linkage between occupational exposure to cadmium and cancer is that of lung cancer. This linkage is the reason cited by the IARC in 1993 for designating cadmium as a known human carcinogen and by the NTP for its characterization of cadmium as a known human carcinogen in 2000.
The most positive evidence for the IARC's decision came from a series of studies of the “globe cohort” that showed a positive association between occupational cadmium exposure and lung cancer. However, there have been updated studies of that cohort and other evidence (Sorhan and Esmen 2004) since then as reviewed by Verougstraete et al. in 2003. These studies conclude that, to date the epidemiological evidence shows “a small increase in the relative risk of lung cancer in workers exposed to cadmium and cadmium compounds” (Verougstraete et al. 2003).
There is also a consensus that there is not enough evidence to definitely establish a link between cadmium exposure and renal and prostate cancer (Waalkes 2003; NTP 2004). There is no clinical or experimental evidence that background environmental exposures to cadmium causes cancer (Verougstraete et al. 2003).