Arsenic contamination is a matter of global concern, especially in developing nations where reliable water sources are already scarce. According to the World Health Organization, long-term exposure to arsenic through drinking water causes cancers of the skin, lungs, bladder and kidneys. Groundwater may be contaminated by arsenic as a result of either natural or human activities.
- Arsenic is naturally abundant in the Earth's crust---more than 200 minerals contain arsenic, and natural sources account for one-third of the arsenic found in the atmosphere. Volcanic activity, erosion of rocks and minerals and forest fires are the largest contributors of the arsenic into the atmosphere, along with arsenic-containing vapor that is generated from various forms of arsenic salts.
- In developing countries like India and Bangladesh, arsenic poses a major threat through drinking water because of geological contamination. A large section of the population depends on deep drilled wells or tube wells for drinking water. Often, the water from such sources, which is consumed untreated, contains high levels of arsenic that has leached out of contaminated soil.
- Industrial activities like mining and smelting release arsenic into the water and air. High-temperature industrial processes such as coal-fired power generation release arsenic into the atmosphere, some of which, of course, eventually ends up in water supplies. An arsenic compound is also used by the forestry industry to treat timber and its by-products can enter groundwater.
- Arsenic can enter groundwater as a by-product of chemical pesticides used in farming.
- When microbes in soil and other sediments process materials containing arsenic, they release arsine gas, which can then, after mixing with oxygen, resettle on the soil and become a contaminant that affects groundwater.
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