Long-term exposure to arsenic in drinking water may significantly increase cardiovascular disease risk, even at levels below current federal limits, new research suggests.
The study is the first to demonstrate exposure-response relationships at concentrations under the current regulatory threshold of 10 micrograms per liter (µg/L).
These findings are particularly troubling, given that 2.1 million Americans are already exposed to arsenic levels above 10 µg/L and that nearly half of U.S. drinking water wells tested by the United States Geological Survey (USGS) show concentrations over 1 µg/L.
The research, published in the journal Environmental Health Perspectives, found that exposure to arsenic during the decade preceding a cardiovascular event posed the greatest risk.
"Our findings shed light on critical time windows of arsenic exposure that contribute to heart disease and inform the ongoing arsenic risk assessment by the [Environmental Protection Agency]," Danielle Medgyesi, the study's lead author, said in a statement.
"It further reinforces the importance of considering non-cancer outcomes, and specifically cardiovascular disease, which is the number one cause of death in the U.S. and globally."
The comprehensive study analyzed data from nearly 100,000 participants in California, tracking health records from 1995 to 2018. Researchers discovered that individuals exposed to arsenic levels between 1 and 5 µg/L showed a 5-6 percent higher risk of coronary heart disease.
More alarmingly, those exposed to levels between 5-10 µg/L—still below current regulations—demonstrated a 20 percent increased risk. The risk more than doubled for those exposed to levels at or above the current EPA limit.
About 1 in 20 adults aged 20 and older have coronary heart disease, according to the Centers for Disease Control and Prevention (CDC). In 2022, it killed 371,506 people nationally.
"Our results are novel and encourage a renewed discussion of current policy and regulatory standards," senior author Tiffany Sanchez of Columbia Mailman School said.
While the EPA reduced the maximum contaminant level from 50 µg/L to 10 µg/L in 2006, these new findings suggest even this lower limit may not adequately protect public health.
Newsweek reached out to the EPA via email and the USGS via its website for comment.
Are You at Risk?
While the new research focused on drinking water in California, arsenic contamination is a pervasive problem nationwide.
A 2017 study found that as many as 2.1 million Americans may be exposed to dangerously high levels of arsenic in drinking water.
The USGS's assessments also paint a worrying picture. In a national study of groundwater quality, the agency found arsenic in nearly half of sampled wells at levels above 1 µg/L, while 7 percent of wells had levels exceeding the EPA's safe limit.
The Southwest is of particular concern, with 16 percent of drinking water wells exceeding the legal levels. Other aquifers raised as problematic by the USGS include several in the northern U.S. and the Mississippi Embayment–Texas Coastal Uplands Aquifer System in the Southeast.
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Reference
Medgyesi, D. N., Bangia, K., Spielfogel, E. S., Fisher, J. A., Madrigal, J. M., Jones, R. R., Ward, M. H., Lacey, J. V., & Sanchez, T. R. (2024). Long-Term Exposure to Arsenic in Community Water Supplies and Risk of Cardiovascular Disease among Women in the California Teachers Study. Environmental Health Perspectives, 132(10), 107006. https://doi.org/10.1289/EHP14410
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