Exposure to trihalomethanes found in tap water increases the risk of bladder cancer and may be responsible for one in 20 bladder cancer cases in the European Union (EU), according to a study published in Environmental Health Perspectives.
Trihalomethanes are one of the most common disinfection byproducts found in drinking water after chlorination, and previous studies have linked these chemicals to bladder cancer.
In this study, researchers collected recent annual mean trihalomethanes levels in municipal drinking water in 28 European countries from routine monitoring records and assessed outcomes for individuals aged 20 years and older from 2005 through 2018.
The EU has set the maximum level of exposure to trihalomethanes at 100 µg/L. The researchers found that the average exposure was far below the maximum permissible limit at 11.7 µg/L, although the maximum limit was exceeded in nine countries: Cyprus, Estonia, Hungary, Ireland, Italy, Poland, Portugal, Spain, and the United Kingdom.
Chemicals causing 5% of bladder cancer cases
The estimated overall bladder cancer population-attributable fraction was 4.9% (95% CI, 2.5-7.1), accounting for 6,561 bladder cancer cases per year. Denmark and the Netherlands had the lowest population-attributable fraction at 0% each, while Cyprus (23.2%), Malta (17.9%), and Ireland (17.2%) had the highest link among the countries studied.
In the scenario where no country would exceed the current EU mean, 2,868 annual attributable bladder cancer cases—or 43.7% of cases—could potentially be avoided. “Current levels [of trihalomethanes] in certain countries still could lead to a considerable burden of bladder cancer that could potentially be avoided by optimizing water treatment, disinfection, and distribution practices, among other possible measures,” the authors concluded.