Arsenic is a metalloid element that forms a number of poisonous compounds. It is widely distributed throughout the Earth’s crust, and can be released into the atmosphere and water through natural and human activities.

Soluble inorganic arsenic is highly acutely toxic. Intake of inorganic arsenic over a long period can lead to chronic arsenic poisoning (arsenicosis). Effects – which can take years to develop depending on the exposure level – include skin lesions, peripheral neuropathy, gastrointestinal symptoms, diabetes, cardiovascular diseases, developmental toxicity, and cancer of the skin and internal organs.

Organic arsenic compounds, which are abundant in seafood, are less harmful to health and are rapidly eliminated by the body.
Human exposure to elevated levels of inorganic arsenic occurs mainly through the consumption of groundwater containing naturally high levels of inorganic arsenic (as found in a number of countries), food prepared with this water, and food crops irrigated with high-arsenic water sources. In one estimate, nearly 43 000 deaths annually in Bangladesh alone were attributed to chronic arsenic exposure.

Reduction in human exposure to arsenic can be achieved by screening drinking-water supplies and clearly identifying those delivering water that exceed the WHO provisional guideline of 10 micrograms arsenic per litre or national permissible limits, in conjunction with awareness-raising campaigns. Mitigation options include use of alternative groundwater sources, use of microbiologically safe sources such as rainwater and treated surface water, use of arsenic removal technologies, or dilution of high-arsenic-content source water with lower-arsenic-content source water that is microbiologically safe.