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Fact Sheet - Naturally Occurring Arsenic in Groundwater and Arsenic Pollution

Estimated Population at Risk at Identified Sites: 750,000 People*
Estimated Global Impact: 30 to 80 Million People*

How Does Naturally Occurring Arsenic Contaminate Groundwater?

Arsenic is a semi-metallic element that occurs naturally in the earth’s crust and has no discernible taste or odor. Traces of arsenic can be found in air, soil, water, and food. Though naturally occurring arsenic in the soil is usually only found in very low concentrations, some regions of the world contain arsenic-heavy deposits, which increase arsenic levels in the groundwater. The amount of arsenic that leaches from the earth’s crust into groundwater systems can be increased by human activity. Over-pumping of water for agriculture has been blamed for pulling higher concentrations of natural arsenic into groundwater systems, increasing human exposure.1

What Is the Global Scale of this Pollution Problem?

Many parts of the world rely entirely on groundwater for their water needs, and in some locations, this water is highly contaminated with arsenic. The areas throughout the world that have the worst documented contamination of groundwater by arsenic are in South Asia, and the toxin poses a frequent problems in Nepal, India, and Bangladesh. According to a report by the WHO, “Bangladesh is grappling with the largest mass poisoning of a population in history” due to arsenic contamination in groundwater, with an estimated 35 to 77 million people at risk. 2

What Are the Health Risks Associated with Arsenic?

Arsenic is known to be a dangerous toxin that can lead to death when large amounts are ingested. Small amounts of arsenic exposure over long periods of time can also lead to numerous health problems, including abnormal heart beat, damage to blood vessels and a decrease of red and white blood cells, nausea and vomiting, and clearly visible irritations of the skin. A common effect of arsenicosis, or arsenic poisoning, is dark patches of skin, corns, or warts. 3 Arsenic is also a documented human carcinogen.

*Population estimates are preliminary and based on WHO estimates and an ongoing global assessment of polluted sites.



[1]: Arsenic Poisoning in India and Bangladesh.” SOS – Last updated August 25, 2011. Available at

[2]: Smith, Allan H., et al. “Contamination of drinking-water by arsenic in Bangladesh: a public health emergency.” Bulletin of the World Health Organization, 2000, 78 (9).
Available at

 [3]: ToxFAQs For Arsenic.” Department for Health and Human Services: Agency for Toxic Substances and Disease Registry. August 2007.
Available at