A new study published in the journal Environmental Health Perspectives suggests that long-term exposure to arsenic in drinking water, even at low levels, can increase the risk of heart disease. Even those exposed to arsenic levels below the federal limits of 10 micrograms per liter were found to have an increased risk of ischemic heart disease, according to the researchers.
“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 Danielle Medgyesi, a doctoral Fellow in the Department of Environmental Health Sciences at Columbia Mailman School.
“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,” added Medgyesi.
Investigating exposure to arsenic in water
For this study, researchers compared various lengths of exposure to arsenic in water and cardiovascular disease using statewide healthcare and mortality records collected from the California Teachers Study cohort identifying fatal and nonfatal cases of ischemic heart disease and cardiovascular disease. Water arsenic data for 30 years was collected from the California Office of Environmental Health Hazard Assessment.
The study involved 98,250 participants under the age of 85 years old without a history of cardiovascular disease, with 6,119 ischemic heart disease cases and 9,936 cardiovascular disease cases. The analysis revealed that the previous 10 years of exposure to water contaminated with arsenic up to the time of a cardiovascular disease event contributed the greatest risk.
These findings are consistent with a study in Chile that found peak mortality of acute myocardial infarction was at around ten years after a period of very high arsenic exposure. This provides new insights into relevant exposure windows that are critical to the development of ischemic heart disease.
Even at low “safe” levels
48% of the participants were exposed to an average arsenic concentration below California’s non-cancer public health goal of <1 µg/L. In comparison to this low-exposure group, those exposed to 1 to <5 µg/L had a modestly higher risk of ischemic heart disease, with increases of 5 to 6 percent. The risk increased to 20% among those in the exposure ranges of 5 to <10 µg/L (or one-half to below the current regulatory limit), and more than doubled to 42% for those exposed to levels at and above the current EPA limit ≥10µg/L.
The relationship was consistently stronger for ischemic heart disease compared to cardiovascular disease, and no evidence of risk for stroke was found, largely consistent with previous research and the conclusions of the current EPA risk assessment.
This study draws needed attention to the serious health consequences not only when community water systems do not meet the current EPA standard but also at levels below the current standard. Findings highlight a substantial 20% risk at arsenic exposures ranging from 5 to <10 µg/L which affected about 3.2 percent of participants, suggesting that stronger regulations would provide significant benefits to the population.
The study also found higher arsenic concentrations, including concentrations above the current standard, disproportionally affect Hispanic and Latina populations and residents of lower socioeconomic status neighborhoods.
“Our results are novel and encourage a renewed discussion of current policy and regulatory standards,” said Columbia Mailman’s Tiffany Sanchez, senior author. “However, this also implies that much more research is needed to understand the risks associated with arsenic levels that CWS users currently experience. We believe that the data and methods developed in this study can be used to bolster and inform future studies and can be extended to evaluate other drinking water exposures and health outcomes.”
Substantial evidence that arsenic exposure increases risk
The American Heart Association and other leading health agencies suggest that there is substantial evidence that arsenic exposure increases the risk of cardiovascular disease. This includes evidence of risk at high arsenic levels (>100µg/L) in drinking water. The U.S. Environmental Protection Agency reduced the maximum contaminant level (MCL) for arsenic in community water supplies (CWS) from 50µg/L to 10µg/L beginning in 2006. Even with the reduction, drinking water still remains an important source of arsenic exposure among community water supply users. The natural occurrence of arsenic in groundwater is commonly observed in regions of New England, the upper Midwest, and the West, including California.
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