5. What are the effects of arsenic on laboratory animals?
Both inorganic and organic forms of arsenic may affect the health of laboratory animals. The effects range from rapid death to effects which only emerge later, such as cancer. The degree of toxicity depends whether the arsenic is inorganic or organic and on its chemical form (valency). Inorganic arsenic is generally more toxic than organic arsenic, and in the case of inorganic arsenic, trivalent forms are more toxic than pentavalent forms, at least at high doses. Many different parts of the body can be affected by arsenic, including the skin, lungs, heart, blood vessels, immune system, kidney, reproductive system, gut and nervous system.
According to IPCS, studies to investigate whether arsenic causes cancer in animals have been inconclusive. However, IARC now considers there is limited evidence for cancer in laboratory animals. For example, female mice of a particular type, given high levels of arsenic in drinking water for 2 years, developed tumors of the lung, liver, gut and skin. (Very recent studies show arsenic causes cancer in several organs and tissues of animals exposed before birth, via their mothers during pregnancy.) Other laboratory studies have investigated how cancer might be caused. Inorganic arsenic does not directly damage DNA, the inherited genetic material in cells. However, arsenic can damage whole chromosomes in cells grown in the laboratory, affect the repair of damaged DNA, cause cells to multiply, and promote the development of tumors induced by other chemicals. One study has indicated that one of the metabolites of arsenic found in the body may cause cancer of the bladder in male rats at high doses. More...