Accessible, safe, and affordable water in every household is essential for protecting public health and promoting equality across communities. Decades of investigations have proved that impure drinking water significantly increases the risk of cancer, cardiovascular disease, and even prenatal developmental issues in unborn children. However, in the U.S., the drinking water regulations have been primarily focused on single pollutants, without considering the possibility of compounded risks posed by mixtures of contaminants.
A recent study highlights the potential public health benefits of targeting multiple pollutants simultaneously. It shows how the suppression of several contaminants could help prevent thousands of cancer cases and supply cleaner water to millions of Americans.
The study used national contaminant data from the Unregulated Contaminant Monitoring Rule 3 (UCMR3) and other state records collected between 2011 and 2023. They targeted hexavalent chromium [Cr (VI)], arsenic, and nitrate: these anionic pollutants are frequently found in combination and can be mitigated by shared treatment technologies such as ion exchange. By estimating average contaminant levels across more than 4,000 water systems in the country, and determining theoretical lifetime cancer risks using established health benchmarks. In cases where Cr (VI) data were not available, total chromium was used as a substitute to estimate potential risks.
There was also California-specific monitoring, where Cr (VI) averages were recalculated using the assumption that non-detects could still indicate low-level contamination. These adjusted figures were compared with state-specific estimates to determine how feasible it would be to establish stronger limits to cut down these risks of cancer.
The results are alarming. An estimated 100 million people in the U.S. get their water supply from water systems where the levels of Cr(VI), arsenic, and nitrate exceed health-based thresholds. Approximately 82% of the population served by community water systems can be subjected to water containing at least one of these contaminants at unsafe levels. The states of California, Arizona, and Texas seem to show the greatest burden, with many preventable cancer cases linked particularly to arsenic exposure.
The study estimates that implementing a federal Cr(VI) limit of 5 ÎĽg/L could prevent around 1,320 lifetime cancer cases. If combined with a 28% reduction in arsenic levels, the number of cancer cases avoided could more than double to approximately 2,647 nationwide.
In contrast to the one-by-one contaminant problem of the Safe Drinking Water Act today, mixture consideration would change cost-benefit analyses and protection of the population. Technologies like ion exchange and reverse osmosis can remove multiple pollutants at once, maximizing the return on investment for communities. Nevertheless, many small and medium-sized systems, serving millions of people frequently, cannot afford the installation of high-tech systems by themselves. This gap can be filled by providing support to these communities in the form of regional alliances, financing, and introducing infrastructural improvements by policymakers and regulatory agencies.
The research also emphasizes that cleaner water is not only about reducing healthcare costs, but also about healthy families, securing the lives of future generations, and improving the well-being of communities at large.
This study demonstrates that simultaneous examination of co-occurring contaminants may nearly increase the health benefits of drinking water regulations, saving both money and lives. Although challenges remain in oversight and funding, the path forward is clear: Â reconsideration of how to address numerous threats to on-demand water quality has an opportunity to improve the U.S. situation, along with safer, healthier, and more equitable access to drinking water for everyone.
References: Stoiber T, Evans S, Campbell C, et al. Short communication: Simultaneous removal of co-occurring contaminants reduces drinking water-attributed cancer risk: A United States case study. Environ Res. 2025;284:122125. doi:10.1016/j.envres.2025.122125
