Arsenic is a natural element found widely in the earth's crust. Particles are released during mining, and spread throughout the environment. Arsenic from weathered rocks and soils dissolves in groundwater. Arsenic concentrations in groundwater are particularly high in areas with geothermal activity. Arsenic may be found in some drinking water supplies, including wells. Exposure to high levels of arsenic can cause serious health effects.
There are trace amounts of arsenic in all living matter. For most North Americans, the primary source of exposure to arsenic is food, followed by drinking water, soil and air. Drinking water would only be the major source of exposure for those people living near a source of arsenic.
Arsenic may enter lakes, rivers or underground water naturally, when mineral deposits or rocks containing arsenic dissolve. Arsenic may also get into water through the discharge of industrial wastes and by the deposit of arsenic particles in dust, or dissolved in rain or snow. These arsenic particles can enter the environment through:
- the burning of fossil fuels (especially coal);
- metal production (such as gold and base metal mining);
- agricultural use (in pesticides and feed additives); or
- waste burning.