Arsenic

Abstract

Arsenic is a naturally occurring element, found in soil, some groundwaters, and food. Throughout the world, including Taiwan, India, Mongolia, and Bangladesh, human populations are exposed to high levels of arsenic in drinking water. Short‐term exposures to large doses of arsenic can cause health effects such as encephalopathy, peripheral neuropathy, and death. Long‐term human exposure to high levels of arsenic causes a variety of noncancer health effects (including pigmentation changes, hyperkeratosis, and vascular effects) and also cancer (including skin, bladder, and lung cancer). However, consistent health effects have been observed only in populations outside the United States exposed to relatively high concentrations of arsenic in drinking water, often in populations suffering from nutritional deficiencies that may increase susceptibility. To standardize quantitative risk assessments for arsenic, US regulatory agencies have developed arsenic‐specific toxicity factors (reference doses for noncancer effects, and cancer slope factors for cancer), based primarily on Taiwanese populations exposed to high levels of arsenic in drinking water. These analyses contain conservative elements; what is particularly important is that there is convincing human and mechanistic data to support a nonlinear dose–response relationship for arsenic. Overall, the arsenic cancer slope factor is likely to overestimate cancer risk at low levels of exposure.