A new U.S. Geological Survey study published on March 18 highlights the importance of homeowners testing their water well systems to ensure it is safe for consumption, particularly in drought-prone areas.
The first-of-its-kind national-scale study of private well water, conducted in collaboration with the Centers for Disease Control and Prevention, showed drought may lead to elevated levels of naturally occurring arsenic and that the longer a drought lasts, the higher the probability of arsenic concentrations exceeding the U.S. Environmental Protection Agency’s standard for drinking water.
Researchers estimate that during drought conditions, 4.1 million people in the continental United States who use private domestic wells are potentially exposed to unsafe levels of arsenic. This is an increase of 54 percent from the estimated 2.7 million people exposed to unhealthy arsenic levels in private wells during normal, nondrought conditions.
Arsenic is a metal that can occur naturally in bedrock and sediments around the world and is commonly reported in drinking-water supply wells. However, chronic exposure to arsenic from drinking water is associated with an increased risk of several types of cancers, including bladder, lung, prostate, and skin cancers. Other adverse effects include developmental impairments, cardiovascular disease, adverse birth outcomes, and impacts on the immune and endocrine systems.
“The population potentially exposed to arsenic levels exceeding the EPA standard during simulated drought conditions amounts to roughly one-tenth of the estimated 37.2 to 43.2 million people in the conterminous United States who use domestic wells for household water supply,” said Melissa Lombard, a USGS hydrologist and lead author of this study.
This is the first national-scale study to assess the potential impact of drought on arsenic levels in private domestic wells.
The states with the largest populations facing elevated arsenic levels in private domestic well water during the simulated drought conditions were Ohio (approximately 374,000 people), Michigan (320,000 people), Indiana (267,000 people), Texas (200,000 people), and California (196,000 people).
“While the results suggest that drought will have a negative impact, the study cannot predict what might happen at an individual well, further highlighting the importance of testing,” Lombard said.
NGWA encourages homeowners with well systems to get their well tested annually. Go to NGWA’s site for well owners, WellOwner.org, which contains resources about private well systems and groundwater.
NGWA also has a best suggested practice, Reducing Problematic Concentrations of Arsenic in Residential Water Well Systems, that is free to members. There is a fee for nonmembers. Click here to learn more.