A good deal of evidence points to the fact that exposure to arsenic increases cardiovascular disease risk.

Community water supplies are, unfortunately, a significant source of arsenic exposure, particularly in parts of New England, the upper Midwest and the Southwest, including California. That is why, starting in 2006, the U.S. Environmental Protection Agency reduced the maximum level of arsenic in community water supplies from 50 µg/L to 10 µg/L.

Even this reduction may not be enough. A team led by researchers at the Columbia University Mailman School of Public Health recently found the relative risk of cardiovascular disease, particularly ischemic heart disease, was still increased at arsenic levels below the federal 10 µg/L limit.

Most of the pitchers sold for filtering tap water are ineffective at removing arsenic.

Study participants exposed to 10-year average arsenic concentrations between five µg/L and less than 10 µg/L, who represented about 3.2 percent of the study population, had a 20 percent increased risk of ischemic heart disease compare to those exposed to lower concentrations.

The findings are evidence of the serious health outcomes that can occur even when arsenic levels in community water supplies are below the EPA standard. They also point to a window of time during which arsenic exposure increases the risk of heart disease, the number one cause of death in the U.S. and worldwide, Danielle Medgyesi, corresponding author on the study, told TheDoctor.

Health and mortality records from more than 98,000 participants in the California Teachers Study were analyzed for the current study. More than 6,100 cases of ischemic heart disease and over 9,900 cases of cardiovascular disease were identified between 1995 and 2018 from this group.

People exposed to concentrations between 1 µg/L and less than 5 µg/L for 10 years had an increase in their risk of ischemic heart disease of five to six percent. The risk went up to 42 percent for those exposed to concentrations at or above the 10 µg/L limit.

More than 90 percent of participants lived in areas served by community water supplies rather than private wells. The researchers worked with the California Office of Environmental Health Hazard Assessment to gather data about the arsenic levels in these water supplies between 1990 and 2020.

Short-term (three years) arsenic exposure was compared to long-term (10 years) exposure. Almost half (48 percent) of the participants were exposed to arsenic concentrations below California's public health goal of less than one µg/L. But the duration of exposure made a difference. Those exposed to 10-year average concentrations between one µg/L and less than five µg/L had an increase in their risk of ischemic heart disease of five to six percent. The risk increased to 42 percent for those exposed to concentrations at or above the 10 µg/L limit.

For every doubling of arsenic exposure, the risk of ischemic heart disease increased by four percent and the risk of cardiovascular disease increased by two percent. The association between disease risk and arsenic exposure levels was consistently stronger for ischemic heart disease than for cardiovascular disease. No evidence of an association between arsenic exposure and stroke risk was found.

The findings underscore the need for further risk assessment by the FDA. The women in the California Teachers Study were mostly white and well-educated and likely healthier than other, less affluent, populations. Higher arsenic levels, including levels that exceed the current standard, have been disproportionately noted in communities of color and lower socioeconomic status.

Those concerned about the arsenic concentration in their drinking water should contact their local public health department, said Medgyesi, a doctoral fellow at Columbia Mailman. They may be able to provide arsenic testing free of charge, particularly to private well users. EPA-certified water testing kits are also available online. Unfortunately, most of the pitchers designed to filter tap water are ineffective at removing arsenic.

To get a fuller picture of the generalizability of the results and the degree of exposure disparities among different populations in California, the researchers point out that the data and methods of this study can be applied to more diverse populations. In addition, future studies could determine the heart risk associated with arsenic levels in water among private well users.

The study and a related editorial are published in Environmental Health Perspectives.