In a study led by ISGlobal researchers and published in Environmental Health Perspectives, no association was observed between exposure to trihalomethanes (THM) in drinking water and colorectal cancer. In an analysis of data from 2,047 cases and 3,717[AK1] controls in Spain and Italy, researchers found no clear evidence of an association between colorectal cancer and exposure to these disinfection by-products (DBP), which form when chlorine is used to disinfect drinking water for human consumption.
THM, which are highly volatile and skin permeable, are the most prevalent DBP. The four THM regulated in the United States of America, the European Union and other countries include chloroform, bromodichloromethane, dibromochloromethane, and bromoform. Earlier animal studies suggest a possible association between DBP exposure and colorectal cancer, a disease that accounts for 10% of the global cancer incidence.
The participants were interviewed to collect information on a range of factors, including the type of water consumed, frequency and duration of showering/bathing and major recognized risk factors for colorectal cancer. The authors then estimated the odds for colorectal cancer in association with estimated mean THM concentrations in each participant’s residential water supply (from age 18 to 2 years before the interview) and the estimated average THM ingestion from residential tap water during their adult life.
“The only positive association with colorectal cancer we found was in the highest category of exposure to concentrations of brominated THM among men”, explains the lead autor on the study, Cristina Villanueva. “By contrast, we found an inverse association between chloroform concentrations and colorectal cancer, a finding that suggests that chloroform could have a protective effect.” However the ISGlobal researcher also made the point that these results should be confirmed by additional studies.
Cristina M. Villanueva, Esther Gracia-Lavedan, Cristina Bosetti, Elena Righi, Antonio José Molina, Vicente Martín, Elena Boldo, Nuria Aragonés, Beatriz Perez-Gomez, Marina Pollan, Ines Gomez Acebo, Jone M. Altzibar, Ana Jiménez Zabala, Eva Ardanaz, Rosana Peiró, Adonina Tardón, Mª Dolores Chirlaque, Alessandra Tavani, Jerry Polesel,Diego Serraino, Federica Pisa, Gemma Castaño-Vinyals, Ana Espinosa, Nadia Espejo-Herrera, Margarita Palau, Victor Moreno, Carlo La Vecchia, Gabriella Aggazzotti, Mark J. Nieuwenhuijsen, and Manolis Kogevinas. Colorectal Cancer and Long-Term Exposure to Trihalomethanes in Drinking Water: A Multicenter Case-Control Study in Spain and Italy. Environ Health Perspect; DOI:10.1289/EHP155.