Long-term exposure to even low levels of arsenic in drinking water can raise a person’s risk of heart disease, a new study warns.

Even folks exposed to arsenic levels below the federal limit of 10 micrograms per liter (ug/L) had an increased risk of heart disease, researchers reported Oct. 23 in the journal Environmental Health Perspectives.

“Our results are novel and encourage a renewed discussion of current policy and regulatory standards,” said senior researcher Tiffany Sanchez, an adjunct assistant professor of environmental health sciences with Columbia University’s Mailman School of Public Health in New York City.

“However, this also implies that much more research is needed to understand the risks associated with arsenic levels” in community drinking water, Sanchez added in a university news release.

The American Heart Association and leading health agencies agree there is substantial evidence that arsenic exposure increases the risk of heart problems.

The U.S. Environmental Protection Agency reduced the maximum contaminant level for arsenic in drinking water from 50 ug/L to 10 ug/L in 2006, but concerns remain that any level of exposure is unhealthy, researchers explained.

Arsenic naturally occurs in groundwater, and it's most commonly observed in regions of New England, the upper Midwest and the West, including California, researchers noted.

For this study, researchers tracked health data from a long-term study of more than 98,000 California teachers, comparing cases of heart disease with exposure to arsenic in drinking water.

Nearly half (48%) of the participants were exposed to an average arsenic concentration below California’s public health goal of less than 1 ug/L, researchers said.

Those exposed to an average 1 to 5 ug/L of arsenic in drinking water had a 5% to 6% increased risk of heart disease.

Heart disease risk jumped to 20% among those in the exposure range of 5 to 10 ug/L, which is below the current federal limit, researchers said.

The risk then doubled to 42% for those exposed to levels at or above the current EPA limit of 10 ug/L, results show.

“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 EPA. 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,” said researcher Danielle Medgyesi, a doctoral fellow of environmental health sciences at Columbia. “This study offers resounding proof of the need for regulatory standards in protecting health and provides evidence in support of reducing the current limit to further eliminate significant risk.”