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Droughts can increase the amount of naturally occurring arsenic in private domestic wells

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A new study by the US Geological Survey ( shows the importance of regular monitoring of private wells. This monitoring is particularly important in drought areas, as the study data shows an increase in arsenic concentration, especially during long periods of drought. It can even cause the U.S. Environmental Protection Agency's drinking water limit for arsenic to be exceeded.

Approximately 4.1 million people in the United States are exposed to potentially harmful levels of arsenic from the periods of drought. That is over 50 % more than those that are already at risk from high arsenic concentrations in their private wells.

The semi-metal arsenic occurs worldwide in certain rock and sediment layers. Through natural processes, arsenic compounds can leach into groundwater and thus end up in drinking water used by humans. In addition to its acute toxicity, long-term exposure to arsenic increases the risk of developing cancer, including bladder, lung, prostate and skin cancers. Other adverse effects include developmental disorders, cardiovascular disease, adverse birth outcomes, and effects on the immune and endocrine systems.

The results of the study can help to develop and apply targeted measures for affected areas. In particular, knowing the probability of which wells are affected by arsenic contamination helps to improve monitoring. The public water supply is regulated by the respective municipal water supplier. However, private well owners are responsible for their own water quality. However, working with government agencies can help test their water and choose an effective method for arsenic removal.

The highest populations to expect elevated arsenic concentrations under drought conditions are found in the following states: Ohio (approximately 374,000 people), Michigan (320,000 people), Indiana (267,000 people), Texas (200,000 people), and California (196,000 people).

The advancing climate change is fueling this problem. Rising temperatures and falling precipitation increase the likelihood of drought events. This means that more people will likely be at risk from arsenic contamination in drinking water in the future.

Information on effective ways to remove arsenic can be found here.