A new study by researchers at the Columbia University Mailman School of Public Health shows that levels of arsenic in water are associated with higher levels of arsenic in urine among the US population for users of private wells and public water systems. The findings are published in the journal Environmental Investigation.
Long-term exposure to arsenic, even at low and moderate levels, can increase the risk of cancer and other types of chronic diseases. Although drinking water along with the diet is a significant source of arsenic for the general population, the contribution of arsenic in drinking water to total arsenic exposure has not been clear in US populations, especially in lower than high levels in public water supplies.
The researchers evaluated the association between arsenic in private wells and public water supplies using urine arsenic biomarkers within US populations. “To date, no nationwide study has evaluated the link between arsenic from drinking water with urine arsenic biomarkers to assess how drinking water contributes to arsenic exposure for both regulated community water systems (CWS) and unregulated private wells,” said Maya Spaur, PhD. candidate in environmental health sciences at the Columbia Mailman School of Public Health.
The US Department of Health and Human Services Agency for Toxic Substances and Disease Registry lists arsenic as a potent carcinogen and toxicant associated with numerous adverse health outcomes, ranking it number one on its list of priority substances . The US Environmental Protection Agency (EPA) regulates arsenic in public drinking water supplies and sets maximum contaminant levels (MCLs) allowed in public water systems. However, differences in CWS arsenic concentrations persist in the US.
In 2006, the EPA lowered the maximum allowable levels of contaminants from 50 µg/L to 10 µg/L. However, based solely on the health risk, the EPA has set an MCL goal (MCLG) of 0 µg/L. In addition to community water systems, arsenic exposure from drinking water is also a major concern for the approximately 40 million US residents who depend on private well water. However, private wells are not subject to the EPA MCL or other federal regulations.
For the study, the researchers evaluated 11,088 participants from the 2003-2014 National Health and Nutrition Examination Survey (NHANES). For each participant, the researchers assigned arsenic levels in private wells and CWS according to county of residence using estimates previously derived by the US Environmental Protection Agency and the US Geological Survey. Participants also completed an in-person interview, a dietary reminder, and a physical exam.
Mean recalibrated urinary dimethyl arsinate (rDMA), the major metabolite of arsenic excreted in urine, was 2.52 µg/L among private well users and 2.64 µg/L among CWS users. Urinary rDMA was highest among Western and Southern participants, and among Mexican Americans, other Hispanics, and other non-Hispanic participants. Urinary rDMA levels were 25% and 20% higher compared to the highest and lowest third of the CWS population distribution and arsenic from private wells, respectively.
“We found that higher levels of arsenic in public water and from private wells were linked to higher levels of urinary arsenic among NHANES participants,” Spaur noted. “In addition, we observed very similar relationships between arsenic in water and arsenic in urine for both regulated public water supplies and unregulated private wells, but we did see differences by region with the strongest associations in the South and the West, and among Mexican-American participants. Our findings show that Arsenic in water, including public water, is a significant contributor to total arsenic measured in urine. Additional efforts are needed to target regions and communities that continue to experience increased exposure.”
“Assessing the link between arsenic in drinking water and arsenic levels within US populations is critical to inform future drinking water regulatory policies and to identify communities in need of financial, technical and and additional regulatory to reduce the exposure of its residents,” said Anne E. Nigra, assistant professor of environmental health sciences at the Columbia Mailman School of Public Health, and lead author.
Co-authors are Melissa Lombard and Joseph Ayotte, US Geological Survey, New England Water Science Center; Benjamin Bostick and Steven Chillrud, Columbia University Lamont-Doherty Earth Observatory; and Ana Navas-Acienand Anne Nigra, Columbia Public Health.
The study was supported by NIEHS grants P42ES010349 and P30ES009089 and F31ES034284, and NIH/National Institute of Dental and Craniofacial Research grant DP5OD031849.