A long-running study suggests that chemicals formed during drinking water disinfection may play a role in uterine cancer risk.
Scientists tracked more than 53,000 California teachers and school administrators for nearly two decades and found that women exposed to higher levels of certain water treatment byproducts were more likely to develop uterine cancer.
The findings were published in JAMA Network Open.
Public drinking water in the United States is closely monitored under the Safe Drinking Water Act. Water companies disinfect water with chlorine to prevent outbreaks of dangerous infections.
While this process saves countless lives, it can also produce small amounts of chemicals called trihalomethanes and haloacetic acids when chlorine reacts with natural material already present in water.
To investigate whether these chemicals might affect women’s health, researchers examined participants who had remained in the same home for many years. They combined residential addresses with public water quality reports collected over 30 years to estimate long-term exposure instead of relying on short-term testing.
Over the course of the study, more than one thousand women developed uterine cancer. The strongest association involved trihalomethanes, especially chloroform.
Women with the greatest long-term exposure had a noticeably higher chance of developing the most common type of uterine cancer, while higher haloacetic acid exposure was linked to a much greater risk of uncommon but aggressive cancers.
The researchers found no meaningful association between uterine cancer and several other drinking water contaminants, including nitrate, arsenic, and uranium. This suggests that not every contaminant carries the same level of concern.
The results are particularly important because the increased risks appeared even when water systems met existing legal standards. Current limits balance health protection with what is technically achievable, but these findings suggest there may still be room for improvement.
Scientists also pointed out that uterine cancer does not affect all populations equally. Black women are more likely to develop advanced disease and have higher death rates, while different parts of the United States experience different patterns of the disease.
Environmental exposures such as drinking water may partly contribute to these differences, although many other factors are also involved.
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Source: University of Maine.
