EPA regulation on arsenic in US public water systems likely prevented over 200 cancer cases per year

Exposure to arsenic in drinking water was significantly reduced among Americans using public water systems following the Environmental Protection Agency (EPA) regulation on maximum levels of arsenic, according to a new study in The Lancet Public Health journal. Compliance with the regulation led to a decline of 17% in levels of urinary arsenic and an estimated reduction of over 200 cases of lung and bladder cancer every year.

In contrast, levels of urinary arsenic in private well users did not change.. The study highlights the crucial role of federal drinking water regulations in reducing toxic exposures and protecting human health.

Anne Nigra, Columbia Mailman School of Public Health, New York, USA, and lead author of the study says: "EPA regulation was associated with a significant decrease in urinary arsenic concentrations among Americans who use public water systems. Levels of arsenic in private wells, estimated to provide water to roughly 45.5 million Americans, vary significantly throughout the USA. 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 across the USA. 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. 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. Private wells are not subject to EPA regulation.

In this study, researchers tested 14127 participants across the USA between 2003 and 2014 for dimethylarsinate (DMA), the main metabolite of inorganic arsenic in human beings. They adjusted for other sources of arsenic such as diet and smoking. Approximately 70% of participants used public water systems.

Among public water users, the concentration of DMA was reduced by 17% between 2003-2004 and 2013-2014 (from 3.01 µg/L to 2.49 µg/L), representing a substantial reduction in exposure when applied at a population level.

The decrease was only observed after 2009-2010, consistent with the regulatory compliance process under the Safe Drinking Water Act, which required time for testing, and time to address the problem by changing the source or installing water treatment.

The authors estimate that the reduction in exposure to arsenic is equivalent to a reduction of 200 cases of lung and bladder cancer per year, but could be as many as 900 cases.

No change was recorded in private well water users. The authors note that because of the relatively small number of private well water users in the study, the findings for private well users have greater uncertainty. Before the new regulation took full effect, DMA concentrations were higher among public water users compared to private well users (3.01µg/L compared to 2.38 µg/L). By the end of the study period in 2013-2014, DMA concentrations were lower in public water users compared to well users (2.49µg/L compared to 2.59 µg/L). The authors note that there is a wide variation in the level of contamination and frequency of testing for private wells.

"Estimates suggest that 1.7 million Americans are at risk of exposure to arsenic concentrations in household well water higher than the EPA maximum regulatory limit of 10 µg/L and 3.8 million Americans are exposed to concentrations higher than 5 µg/L. Continuing efforts are needed to protect public water systems, and additional state and federal initiatives are needed to help families sample, test, and address arsenic exposure from unregulated private wells," adds co-author Dr Ana Navas-Acien, Columbia University Mailman School of Public Health.

The authors say that efforts to address arsenic levels in private wells vary between states. For example, in New Jersey, all wells in northern counties need to be tested as part any real estate transaction, but only one quarter of wells in the northern parts of New Jersey have been tested. Although affected families can receive a no-interest loan to purchase and install water treatment systems in New Jersey, no state government requires homeowners to install treatment systems to reduce arsenic if levels are above the EPA maximum.

Writing in a linked Comment, Professor Philip Landrigan, Icahn School of Medicine at Mount Sinai, New York, USA, says: "2017 has not been a good year for environmental protection in the USA. President Trump's administration is attempting to roll back more than 400 rules and regulations that protect the environment and human health. In addition to announcing their intention to withdraw from the Paris Climate Accord, the administration is undoing the Clean Power Plan, the Clean Water Rule, new source performance standards for oil and gas drilling, and a proposal to ban the neurotoxic organophosphate insecticide, chlorpyrifos... The findings (of this study) are consistent with data from previous studies of the health benefits of reducing arsenic concentrations in drinking water. They are also concordant with analyses of the benefits of interventions against air pollution, which have been shown produced major gains both for human health and the economy."