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Environmental Factor

Environmental Factor

Your Online Source for NIEHS News

November 2017

Arsenic declines in public drinking water

Exposure to arsenic in public drinking water significantly declined after the U.S. Environmental Protection Agency lowered levels in 2006.

Anne Nigra Nigra is a graduate student in the Mailman School’s Department of Environmental Health Sciences. (Photo courtesy of Anne Nigra)

NIEHS-funded researchers reported that exposure to arsenic in drinking water was significantly reduced among Americans using public water systems after the Environmental Protection Agency (EPA) lowered maximum levels of arsenic in 2006.

The new findings, reported Oct. 22 in the journal Lancet Public Health, confirmed that federal drinking water regulations helped decrease toxic exposure and protect human health.

Compliance with the regulation led to a 17 percent decline in urinary arsenic levels, equivalent to an estimated reduction of more than 200 cases of lung and bladder disease every year. The authors estimated that the reduction could be as many as 900 cases per year.

Notably, the researchers found no improvements in arsenic exposure rates among users of private wells, which are not federally regulated. “Levels of arsenic in private wells, estimated to provide water to roughly 45.5 million Americans, vary significantly throughout the U.S.,” said lead author Anne Nigra, from Columbia University Mailman School of Public Health. She added that the cost of testing and treating contaminated water means that residents of lower socioeconomic status are especially vulnerable.

NIEHS grantee Philip Landrigan, M.D., from Mt. Sinai School of Medicine, published a commentary that accompanied the paper in Lancet Public Health. “This is a model analysis of the health benefits that can result from a carefully designed, evidence-based environmental intervention,” he wrote.

Significant decrease for public water users

Arsenic is an established carcinogen and naturally occurs in drinking water across the U.S. In 2006, public water systems began complying with a new EPA regulatory limit of 10 micrograms of arsenic per liter of drinking water, down from 50 micrograms per liter. In the Southwest, many cities' public water supplies come from water sources with naturally high levels of arsenic, including Los Angeles, Albuquerque, Scottsdale, and Tucson.

The researchers compared data from 14,127 participants in the National Health and Nutrition Examination Survey between 2003 and 2014. The team looked at levels of dimethylarsinate, which is the main metabolite of inorganic arsenic in humans. They adjusted for other sources of arsenic, such as diet and smoking.

"The 17 percent reduction in water arsenic exposure for public water users represents a significant exposure reduction when applied at the population level," said senior author Ana Navas-Acien, M.D., Ph.D., also from Columbia University. "The decline was strongest among Mexican-Americans, and supports the recent infrastructure investments in many cities in the Southwest that focused on ensuring water arsenic below 10 micrograms per liter."

Private well water may pose risk

Noting the unchanged levels among users of private well water, the authors estimated that 1.7 million Americans are at risk of exposure to arsenic above the maximum contaminant level of 10 micrograms per liter and 3.8 million to arsenic above 5 micrograms per liter.

"To date, no state government requires homeowners to install treatment systems to reduce arsenic if test results exceed these contaminant levels," said Navas-Acien. She added that state and federal initiatives are critical to help families sample, test, and address arsenic exposure from unregulated private wells.

“Evidence of the health impacts of arsenic continue to mount,” said Claudia Thompson, Ph.D., head of the NIEHS Population Health Branch, which provided much of the funding for the study. “The good news is that public policies are making a real difference in certain exposures. But exposures for Americans not served by public water systems remain a concern.”

On Oct. 18, scientists with the United States Geological Survey (USGS) and the U.S. Centers for Disease Control and Prevention published results of a study on the probability of private wells having more than the EPA limit of arsenic. Their estimate of the number of individuals drinking such water was even higher — 2.1 million people, or 4.8 percent of domestic well users.

“These results can be used directly in future public health activities, including targeting specific areas for additional testing and national-scale ecological studies of potential human-health outcomes, as has been done in regional studies,” wrote the authors.

Nigra AE, Sanchez TR, Nachman KE, Harvey DE, Chilled SN, Graziano JH, Navas-Acien A. 2017. The effect of the Environmental Protection Agency maximum contaminant level on arsenic exposure in the USA from 2003 to 2014: an analysis of the National Health and Nutrition Examination Survey (NHANES). Lancet Public Health; doi:http://dx.doi.org/10.1016/S2468-2667(17)30195-0 [Online 22 Oct. 2017].

Landrigan PJ. 2017. The power of environmental protection: arsenic in drinking water. Lancet Public Health; doi:https://doi.org/10.1016/S2468-2667(17)30197-4 [Online 22 Oct. 2017].

Ayotte JD, Medalie L, Qi SL, Backer LC, Nolan BT. 2017. Estimating the high-arsenic domestic-well population in the conterminous United States. Environ Sci Technol; doi: 10.1021/acs.est.7b02881 [Online 18 Oct. 2017].

(This story is based on a press release from Columbia Mailman School of Public Health by Stephanie Berger.)

Probability of arsenic in the United States

Colors indicate varying probabilities of (a) arsenic greater than 10 micrograms per liter; (b) 95 percent confidence lower bound; and (c) 95 percent confidence upper bound. (Photo courtesy of USGS)

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