Treating drinking water for multiple contaminants, especially arsenic and chromium-6, could prevent more than 50,000 cancer cases in the United States, according to the results of a study by the Environmental Working Group that was published in Environmental Research.
Study findings highlighted that co-removal of co-occurring contaminants significantly increased health benefits, which goes against state and federal policies for regulating one tap water contaminant at a time.
The study authors believe the results of their research support the future establishment of new frameworks for water treatment to protect public health from pollution.
“Drinking water is contaminated mostly in mixtures, but our regulatory system still acts like they appear one at a time,” stated lead study author Tasha Stoiber, PhD, Senior Scientist at the Environmental Working Group in Washington, DC. “This research shows that treating multiple contaminants together could prevent tens of thousands of cancer cases.”
“Addressing co-occurring contaminants is scientifically the most sound approach, as well as an efficient way to protect public health,” Dr. Stoiber added.
Background
Hexavalent chromium, or chromium-6, and arsenic are cancer-causing chemicals commonly found in drinking water in the United States. Nitrate is another contaminant found in tap water that can lead to health risks. These three toxic chemicals greatly affect children, pregnant women, and smaller communities reliant on groundwater alone.
“Ensuring clean drinking water for all communities is about fairness and equity,” stated co-author Sydney Evans, MPH, Senior Science Analyst for the Environmental Working Group. “Communities in the US that rely on groundwater are often affected by these contaminants. New water treatment technologies offer a chance to improve water quality overall. This strengthens the case for action and investment.”
Chromium-6 is associated with increased rates of stomach and intestinal tumors. Although levels of total chromium are limited in drinking water, levels of chromium-6 specifically are not regulated.
Arsenic exposure, which can also be attained through contaminated foods, is associated with bladder, lung, and skin cancers as well as cardiovascular and developmental diseases. Arizona, California, and Texas have the highest levels of arsenic pollution and could gain the most from potential multi-contaminant water treatment efforts.
Nitrate is one of the most common tap water contaminants and is associated with colorectal and ovarian cancers as well as preterm birth, low birth weight, and neural tube defects. The standards for nitrate levels in the water have not been updated in more than 30 years to reflect newer research on harmful levels of nitrate.
“Nitrate pollution is a public health crisis, particularly in the Midwest but also across the country,” stated Anne Schechinger, the Midwest Director of the Environmental Working Group. “The federal nitrate limit was set decades ago to prevent infant deaths, but we now know see cancer and birth complications at levels of nitrate far below that outdated standard.”
“Even lowering nitrate slightly could prevent hundreds of cancer cases and save tens of millions of dollars in health-care costs, especially when paired with treatment for other contaminants, such as chromium-6 and arsenic,” she said. “There’s a real cost to inaction—our health and our wallets can’t afford to wait for better treatment.”
Study Methods and Key Findings
The Environmental Working Group researchers analyzed contaminant occurrence data from 6,831 community water systems from between 2011 and 2023. They also extrapolated data for 10,893 additional groundwater systems where chromium testing data were available. They created a case study evaluation for improvement scenarios for these water systems based on the finding that chromium-6 and arsenic contaminants frequently co-occur in drinking water.
Results of the case study showed that an estimated 7,410 lifetime cancer cases due to chromium-6 exposure and 43,418 cases from arsenic exposure in the United States could be prevented in drinking water concentrations were reduced to safe levels.
At hypothetical levels of 10 μg/L chromium-6, estimated avoidable lifetime cancer cases in the United States amounted to 575, which increased to 1,320 at levels of 5 μg/L. For arsenic at a hypothetical level of 10 μg/L, this would reduce the amount of arsenic in the water by 42%, and by a further 28% at 5 μg/L, which would quadruple the number of lifetime cancer cases avoided from exposure to these contaminants.
Reducing nitrate levels by 20% could prevent 130 cancer cases per year. The study authors noted that this could also result in saving about $35 million in health-care costs.
Suggested Next Steps
The Environmental Working Group suggested that ion exchange and reverse osmosis technologies could help to remove all three of these studied contaminants. Additionally, they noted that individuals could install home water filter systems to reduce their exposure, as long as water filters are changed in a timely fashion.
“This is about more than clean water—it’s about protecting health and advancing equity,” stated David Andrews, PhD, Acting Chief Science Officer of the Environmental Working Group. “We have the engineering solutions to fix the broken drinking water system in the United States, but we need state and federal policies to reflect the reality people face when they turn on the tap.”
Disclosure: For full disclosures of the study authors, visit sciencedirect.com.
