Chlorinating drinking water at common levels in the U.S. and E.U. may raise the risk of bladder and colorectal cancer due to toxic byproducts, according to a new global analysis.
Tom Perkins reports for The Guardian.
In short:
- Disinfecting water with chlorine creates trihalomethanes (THMs), which are found in nearly all public water systems in the U.S. and E.U.
- A new meta-analysis of 30 studies and 90,000 participants found a 33% increased risk of bladder cancer and a 15% increased risk of colorectal cancer.
- Researchers say water treatment alternatives exist but may be costly, and they stress that people should continue drinking municipal water while considering home filtration.
Key quote:
“What we see is alarming and we need some more high quality studies.”
— Emilie Helte, study lead author, Karolinska Institutet
Why this matters:
For more than a century, chlorination has been a cornerstone of public health, virtually eliminating deadly waterborne diseases like cholera and typhoid. But as science advances, concerns over the long-term health effects of chlorine byproducts — specifically trihalomethanes — are becoming harder to ignore. A new study suggests that even at levels well below current regulatory limits, these byproducts may increase cancer risks, raising questions about the adequacy of existing water safety standards. Given that millions rely on chlorinated water, the findings could have broad implications for public health.
Related: There are concerning carcinogens in Western Pennsylvania water
