Arsenic ingestion and internal cancers: a review.

Inorganic arsenic is known to cause skin cancer by ingestion and lung cancer by inhalation. However, whether arsenic ingestion causes internal cancers is still a matter of debate. This paper has reviewed the epidemiologic literature that bears on this question. Published studies of populations who have ingested arsenic in medicines, wine substitutes, or water supplies, as well as workers exposed to arsenic by inhalation, were considered in terms of whether the observed associations might be explained by the presence of biases, the consistency of the evidence, and the biologic plausibility of the associations. Many studies were found to be uninformative because of low statistical power or potential biases. The most informative studies, which were from Taiwan and Japan, involved exposure to arsenic in drinking water. These studies strongly suggest that ingested inorganic arsenic does cause cancers of the bladder, kidney, lung, and liver, and possibly other sites. However, confirmatory studies are needed.