New research conducted at Columbia University’s Mailman School of Public Health finds exposure to arsenic in drinking water was significantly reduced among Americans using public water systems following a 2006 EPA regulation on maximum levels of arsenic. Compliance with the regulation led to a decline of 17 percent in levels of urinary arsenic, equivalent to an estimated reduction of more than 200 cases of lung and bladder disease every year. However, there were no improvements in arsenic exposure rates among users of private wells, which are not federally regulated. The findings, published in The Lancet Public Health, confirm the critical role of federal drinking water regulations in decreasing toxic exposures and protecting human health.
“EPA regulation was associated with a significant decrease in urinary arsenic concentrations among Americans who use public water systems,” said Anne Nigra, ScM, in the Mailman School’s Department of Environmental Health Sciences, and the study’s lead author. “Levels of arsenic in private wells, estimated to provide water to roughly 45.5 million Americans, vary significantly throughout the U.S. Because of the cost of testing and treating contaminated water, private well-water users remain inadequately protected against arsenic exposure in drinking water, especially residents of lower socio-economic status.”
Arsenic is an established carcinogen and naturally occurs in drinking water. In 2006, public water systems were required to meet the new EPA 10 µg/L regulatory limit for the maximum arsenic level in drinking water, down from 50 µg/L. Particularly in the Southwest, public drining water originates from sources containing naturally high levels of arsenic, with affected cities including Albuquerque, Los Angeles, Scottsdale, and Tucson.

Related story: U.S. schoolchildren exposed to arsenic well water have lower IQ scores

The researchers compared data from 14,127 participants in the National Health and Nutrition Examination Survey, 2003-2014, who tested for dimethylarsinate—the main metabolite of inorganic arsenic in humans. Arsenic was also measured in spot urine samples collected from a random subsample of participants 6 years of age or older. Data analysis adjusted for other sources of arsenic such as diet and smoking. The study is the first to evaluate the impact of the 2006 maximum contaminant level regulation on reducing arsenic exposure at the individual level or by using biomarker data.
Among public water users—approximately 70 percent of participants—arsenic levels decreased from 3.01 μg/L in 2003-2004 to 2.49 μg/L in 2013-2014, or 17 percent. The decrease was only observed after 2009-2010, consistent with the EPA regulatory compliance process, which dictates time for testing, and time to address the problem by changing the source or installing water treatment.  

“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 μg/L,” said Ana Navas-Acien, MD, PhD, professor of Environmental Health Sciences at the Mailman School, and co-author. 
However, there was no change recorded among well-water users. An estimated 1.7 million Americans are at risk of exposure to arsenic above the maximum contaminant level, >10 μg/L. The authors note that efforts to address arsenic levels in private wells vary between states.

“To date, no state government requires homeowners to install treatment systems to reduce arsenic if test results for arsenic exceed these contaminant levels,” said Navas-Acien. “Additional state and federal initiatives are critical to help families sample, test, and address arsenic exposure from unregulated private wells,” 
Co-authors of the study are Tiffany R. Sanchez and Joseph Graziano at the Mailman School of Public Health; Keeve E. Nachman, Johns Hopkins Bloomberg School of Public Health; David Harvey, Commissioned Corps Officer of the U.S. Public Health Service; and Steven N. Chillrud,  Lamont-Doherty Earth Observatory, Columbia University. The study is supported by the National Institute of Environmental Health Sciences (grants ES025216, ES021367, ES009089, ES010349, ES007322).

Source: Columbia University Mailman School of Public Health