A recent study from Sweden has found that chemical by-products produced during the disinfection of tap water in the United States may increase the risk of developing bladder cancer by 33% and colon cancer by 15%, raising concerns about the safety of drinking water.
The study highlights that the main carcinogenic substance is Trihalomethanes (THMs), which are present in almost all public water systems in the United States and the European Union.
“This study’s findings are worrisome, and we need more advanced studies to confirm,” Emilie Helte, the lead researcher of the study from the Karolinska Institute in Sweden, stated in an interview with The Guardian.
The history of water disinfection in the United States can be traced back to 1908 when Jersey City, NJ, first used chlorine to disinfect water sources, successfully eradicating waterborne diseases like cholera and typhoid before it was rapidly adopted nationwide. However, in the 1970s, scientists discovered that chlorine disinfection could produce potentially harmful by-products such as THMs and Haloacetic acids (HAAs), posing threats to human health.
The nonprofit organization Environmental Working Group (EWG) has long warned about the potential risks of THMs and HAAs in relation to cancer and reproductive health issues.
The study indicates that when THM concentrations reach 40 parts per billion (ppb), the risk of cancer significantly increases, with the risk of cancer in males potentially higher than in females.
According to data from EWG between 2013 and 2019, the concentration of THMs in New York City tap water was measured at 38.1 ppb, nearing the risk threshold. The Environmental Protection Agency (EPA) sets the upper limit for THMs in drinking water at 80 ppb, while EWG recommends it not exceed 0.15 ppb, indicating that current regulatory standards may still pose safety hazards.
Researcher Helte pointed out that there is no simple solution to this issue. “Using too little disinfectant may lead to water pollution and impact public health, but removing harmful by-products requires expensive filtration equipment, which can be a heavy burden for the government,” she said.
Helte recommended that the public continue to drink tap water but consider using granular activated carbon water filters to remove harmful substances and lower health risks.