Drinking from the tap? This new study might make you think twice

We open the tap, fill a glass and drink without thinking twice. However, a new study published earlier this week in JAMA raises a troubling question about certain substances created during the drinking water disinfection process and their possible link to uterine cancer.

The study followed 53,100 women in California for an average of more than 19 years. During this period, about 1,000 cases of uterine cancer were diagnosed, and researchers examined whether there is a link between the disease and long-term exposure to various contaminants in household drinking water.

The notable finding concerned trihalomethanes, substances created as a byproduct in the water disinfection process. Women who were exposed to higher levels of these substances for more than 15 years were found to be at a higher risk for uterine cancer, particularly for endometrioid-type tumors.

Another group of disinfection byproducts, known as haloacetic acids, was also linked to other types of uterine tumors. In contrast, other substances tested in the water, including nitrate, arsenic, and uranium, were not found to be associated with an increased risk.

Why might this happen? Previous experimental studies have shown that some of these byproducts can bind to estrogen receptors and affect the hormonal system. The researchers estimate that this may be one of the explanations for the link found, but emphasize that the mechanism is still not clear.

And yet, there is no proof here that tap water causes cancer. This is an observational study that points to a statistical link, not cause and effect. The researchers note that it is now necessary to examine in depth whether reducing exposure to these byproducts can also reduce the risk of the disease.