Small, rural communities face higher risk
July 8, 2025
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EWG study shows tackling several tap water contaminants at once offers far greater health benefits than treating pollutants individually.
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Arsenic and chromium-6 frequently occur together and can be reduced using the same technologies.
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Small and rural communities face the highest risks and costs, underscoring a call for updated federal regulations.
A new study suggests that changing how America treats contaminated drinking water could save tens of thousands of lives. Instead of tackling one pollutant at a time, water systems should adopt multi-contaminant treatment strategies that can significantly reduce cancer risks nationwide, according to research published by the Environmental Working Group (EWG) in the journal Environmental Research.
The peer-reviewed study analyzed more than a decades worth of data from over 17,000 community water systems. EWG scientists found that simultaneously targeting dangerous chemicals like arsenic and hexavalent chromium, also known as chromium-6, could prevent more than 50,000 lifetime cancer cases in the U.S. Chromium-6 alone has been detected in water supplies serving about 251 million Americans.
Drinking water is contaminated mostly in mixtures, but our regulatory system still acts like they appear one at a time, said Tasha Stoiber, Ph.D., EWG senior scientist and lead author of the study. This research shows that treating multiple contaminants together could prevent tens of thousands of cancer cases.
Higher risk where pollution overlaps
Arsenic and chromium-6 frequently co-occur in drinking water systems and can be removed using similar technologies like reverse osmosis and ion exchange. The study found that reducing arsenic levels by as little as 27% to 42% in systems already dealing with chromium-6 contamination could quadruple the number of cancer cases avoided compared to treating chromium-6 alone.
States like California, Arizona, and Texas face the highest burden from arsenic pollution and would benefit most from a multi-contaminant approach. In California alone, nearly eight out of 10 preventable cancer cases linked to drinking water are due to arsenic exposure.
Health risks from these pollutants are particularly severe for children, pregnant people, and residents in small or rural communities, which often rely on groundwater and lack resources to upgrade outdated water systems.
Outdated regulations and cost challenges
Under current regulations, the federal government evaluates each contaminant in isolation, considering costs and benefits pollutant by pollutant. But EWG researchers argue this approach is outdated and leaves millions vulnerable to cumulative health risks from chemical mixtures in drinking water.
The federal nitrate limit was set decades ago to prevent infant deaths, but we now know cancer and birth complications can occur at much lower levels, said Anne Schechinger, EWGs Midwest director.
Nitrate contamination, particularly common in agricultural regions, poses significant health risks including cancer and birth defects. EWG estimates that cutting nitrate levels by just 20% could prevent 130 cancer cases each year and save $35 million in healthcare costs, especially when combined with treatment for arsenic and chromium-6.
Despite proven technologies capable of removing multiple pollutants at once, small water systems face steep costs and limited technical support, leaving many communities exposed to significant health risks.
This is about more than clean waterits about protecting health and advancing equity, said David Andrews, Ph.D., acting chief science officer at EWG. We have the engineering solutions to fix the broken drinking water system in the U.S., but we need state and federal policies to reflect the reality people face when they turn on the tap.
What consumers can do
While policymakers debate reforms, consumers worried about tap water contaminants can take steps to protect themselves. EWG recommends reverse osmosis filters for removing arsenic, chromium-6, and nitrate, though filters must be replaced on schedule to stay effective.
Consumers can also search EWGs Tap Water Database to learn which contaminants are present in their local water systems.
As concerns grow about drinking water safety across the country, experts say a shift toward multi-contaminant solutions could be key not only to preventing cancer cases but also to promoting health equity and saving millions in healthcare costs.