Exposure to trihalomethanes (THM) in drinking water is not associated with an increased risk of breast cancer. This is the main conclusion of a new study of the Institute of Global Health of Barcelona (ISGlobal).
Long-term exposure to THM, compounds that are generated after disinfecting water with chemicals, has been associated with an increased risk of bladder cancer, but so far the evidence in other cancers, including breast cancer, is very limited .
The research, published in the journal Environmental International, aimed to examine whether long-term exposure to trihalomethanes could be associated with an increased risk of breast cancer. The study was based on 2,000 women –half of them with breast cancer– from different parts of Spain (Asturias, Barcelona, Cantabria, Guipúzcoa, León, Madrid, Navarra and Valencia), within the framework of the MCC-Spain project.
The study authors conducted interviews with the participants to determine factors such as residence, the type of water consumed, the frequency and duration of showers or baths, and the main known risk factors for breast cancer. Subsequently, they estimated the average residential levels of chloroform, brominated trihalomethanes, and the sum of both during the adult life of the participants.
Tap water vs bottled water
The conclusions of the work indicate that “the type of water consumed at home is not related to breast cancer,” explains Cristina Villanueva, study coordinator and ISGlobal researcher. Approximately 75% of the people studied used to drink tap water, while 21% drank bottled water.
On the other hand, Laia Font-Ribera, first author of the research, highlights that “at common levels in Europe, long-term residential exposure to total THM is not related to breast cancer.” The research does suggest “a moderate association [of breast cancer] with chloroform in the case of high exposure, although more analysis are needed to understand this relationship,” says Font-Ribera.
“This is an epidemiological study that overcomes methodological limitations of previous studies, but more research is needed to confirm the results,” adds Villanueva.