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Cancer

Reducing Multiple Tap Water Contaminants May Prevent Over 50,000 Cancer Cases

Strategic Insights

— 2 min read

The Environmental Working Group's recent study has challenged the conventional approach to regulating tap water contaminants, one at a time. By analyzing data from over 17,000 community water systems, researchers found that pursuing a multi-contaminant approach to treat several pollutants at once could prevent more than 50,000 lifetime cancer cases in the U.S. The study, published in the journal Environmental Research, emphasized that two cancer-causing chemicals, arsenic and hexavalent chromium (chromium-6), often appear together in systems and can be treated using the same technologies.

Key Takeaways:

  • The study found that reducing arsenic levels to a range of 27% to 42% in systems with chromium-6 contamination could avoid up to quadruple the number of cancer cases compared to just lowering chromium-6 levels alone.
  • The Environmental Working Group's research discovered that treating multiple contaminants at once increases the health benefits and that those benefits can expand along with the number of pollutants treated at the same time.
  • The study highlighted that communities in the U.S. that rely on groundwater are often affected by co-occurring contaminants, and new water treatment technologies offer a chance to improve water quality overall.
  • Federal regulations still evaluate the cost and benefit of water treatment on a one-contaminant basis, a model EWG's report calls outdated and inefficient.
  • Small and rural water systems often face the steepest per-person costs to implement new treatment technologies but are among the most exposed to pollutants and associated risks.

Statistics:

  • Over 50,000 lifetime cancer cases in the U.S. could be prevented by pursuing a multi-contaminant approach to treat several pollutants at once.
  • Up to quadruple the number of cancer cases could be avoided by reducing arsenic levels to a range of 27% to 42% in systems with chromium-6 contamination.
  • 251 million Americans have been found to have chromium-6 in their drinking water.
  • California alone has nearly eight out of 10 preventable cancer cases linked to arsenic exposure.
  • Reducing nitrate levels alone by 20% could prevent 130 cancer cases each year and save $35 million in health care costs.
  • Proven technologies like ion exchange and reverse osmosis can remove nitrate, chromium-6, and arsenic at the same time.

Sources:

  • *The Environmental Working Group.* "Reducing Multiple Tap Water Contaminants May Prevent Over 50,000 Cancer Cases." July 2025.
  • *ScienceDirect.* "Multi-contaminant treatment of drinking water: A review."
  • *Environmental Research.* "Multi-contaminant treatment of drinking water: A review."
  • *National Toxicology Program.* "Toxicology and Carcinogenesis Studies of Chromium(III) in F344/N Rats and B6C3F1 Mice (Feed Studies)." 2008.
  • *European Studies.* "Nitrate in Drinking Water." 2023.
  • *Environmental Protection Agency.* "National Primary Drinking Water Regulations."

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