What is Arsenic?
Arsenic is a naturally occurring metalloid (exhibits both metallic and nonmetallic properties) that is found in many minerals in the Earth's crust. It is released into the atmosphere from both natural and anthropogenic sources. The primary natural source is volcanic activity, however, exudates from vegetation and wind-blown dusts also contribute the atmospheric burden. Most anthropogenic emissions to the atmosphere come from industrial processes (such as byproducts of smelting) as well as fertilizer use. Arsenic is widely distributed, generally as arsenic sulfide or as metal arsenates and arsenides. The trivalent and pentavalent forms are the most common oxidation states. Arsenicis listed as one of the 10 major chemicals of public health concern in the World Health Organization Chemical Safety Agenda.
Sources of Exposure
Generally, arsenic is released into the atmosphere by industrial high-temperature processes; upon its entrance into the atmosphere, arsenic is mainly absorbed by smaller particles, which are then dispersed by wind currents and deposited on land and water. Natural activities (such as volcanic activity, dissolution of minerals (into groundwater), and exudates from vegetation and dusts can also release arsenic into the atmosphere. Human activities (like mining, smelting, combustion of fossil fuels, agricultural pesticide production and use, and timber treatment with preservatives) also contribute to the environmental increase of arsenic. Additionally, the remobilization of historic sources (such as mine drainage water) and the drilling of tube wells for the mobilization into drinking-water from geological deposits can also release arsenic particles into water.
Human exposure to arsenic can occur in a variety of manners; major sources of arsenic exposure include (but are not limited to):
- Drinking water — This poses the greatest threat to public health from arsenic; inorganic arsenic is naturally present at high levels in groundwater in a number of countries.
- Industrial processes — In industrial processes, arsenic is mostly used to produce antifungal wood preservatives (which may lead to soil contamination). It is also utilized in the pharmaceutical and glass industries, in the manufacture of alloys, sheep dips, leather preservatives, arsenic-containing pigments, antifouling paints and poison baits, and agrochemicals (to a diminishing extent).
- Food — In areas where arsenic is not naturally present at high levels, food usually contributes most to the daily intake of arsenic (fish, shellfish, meat, poultry, dairy products, and cereals). In areas where arsenic is naturally present at high levels, food prepared with high-arsenic waters and food crops irrigated with contaminated water generally contribute to total daily intake (i.e. rice).
- Smoking — The natural, inorganic arsenic content of tobacco in conjunction with tobacco plants that have been treated with lead arsenate insecticides expose smokers to arsenic.