Inorganic arsenic (In-As) occurs naturally in ground water, and to a lesser extent surface water, in many regions of the world. From the standpoint of human health, In-As can be considered unique for several reasons: a) most of the evidence linking In-As to health effects is based on epidemiologic studies, and risk estimates can be derived from environmentally relevant exposures; b) there are no definitive animal models for most of the effects observed in human population studies; c) In-As is associated with a large range of different adverse health consequences, and as more studies are conducted, more such effects are found. To date, we know that In-As from drinking water can cause severe skin diseases including skin cancer; lung, bladder, and kidney cancers, and perhaps other internal tumors; peripheral vascular disease; hypertension; and diabetes. More recently, several reproductive outcomes have also been found associated with In-As exposure, including infant mortality, reduced birth weight and premature birth; d) In-As is clearly a global problem, and newly found, exposed populations continue to be uncovered. In addition, the toxicological mechanisms by which In-As causes such a myriad of health effects are still not completely understood, but it is clear that a number of factors can affect both individual and population-level susceptibility to the toxic effects of In-As, such as smoking, diet, and possibly the concurrent exposure to other substances.

We will present a basic overview of the health impact of In-As, reviewing some basic metabolism and toxicology, and a synthesis of epidemiologic research and findings to date. We will describe the geographic distribution of exposure and observed health effects, and some potential factors that may account for variability across and within populations. We will also focus on some of the more recent findings regarding reproductive outcomes.