Drinking Water Contamination With Trihalomethanes Associated With Uterine Cancer Risk: JAMA
USA: Researchers have found in a cohort study of female California educators that exposure to trihalomethanes in drinking water was associated with uterine cancer overall and specifically with endometrioid tumors. The findings were consistent with the only previous study from the Midwestern United States, highlighting the need for further research into drinking-water contaminants as potentially modifiable risk factors for this common gynecologic cancer.
The findings, published in JAMA Network Open, come from a study led by Maya Spaur of the Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Maryland, and colleagues. The researchers investigated whether long-term exposure to regulated contaminants in public drinking water, including disinfection byproducts and inorganic chemicals, was associated with uterine cancer risk.
The prospective study analyzed data from 53,100 female California educators enrolled in the California Teachers Study. Women who were free of cancer and had not undergone hysterectomy at enrollment between 1995 and 1996 were followed through December 31, 2020. To estimate long-term exposure, researchers calculated average concentrations of drinking-water contaminants from 1990 to 2005, including trihalomethanes (THMs), haloacetic acids (HAAs), nitrate, arsenic, and uranium. Cancer outcomes were assessed using adjusted statistical models accounting for age, body mass index, and smoking status.
Key findings included:
- Higher exposure to total trihalomethanes (THMs) was associated with an increased risk of uterine cancer (HR 1.18) and endometrioid tumors (HR 1.23).
- Among individual THMs, chloroform showed a positive association with uterine cancer risk.
- Higher levels of the combined haloacetic acids (HAAs) were associated with an increased risk of nonendometrioid uterine tumors (HR 1.86), with similar findings for monochloroacetic acid.
- No significant associations were observed between uterine cancer risk and exposure to nitrate, arsenic, or uranium.
- Mixture analyses suggested that chloroform and dibromochloromethane contributed most to the observed associations between drinking-water contaminants and uterine cancer.
The researchers acknowledged several limitations, including the lack of water quality data before 1990, exposure estimates based on residential address rather than individual water consumption, and the absence of water intake data. The cohort primarily comprised highly educated teachers, which may limit generalizability; women using private wells were excluded because contaminant data were unavailable.
Despite these limitations, the findings add to growing evidence linking drinking-water disinfection byproducts with uterine cancer. The researchers noted that uterine cancer is the sixth most common cancer among women worldwide, with incidence continuing to rise.
The authors concluded that long-term exposure to trihalomethanes may increase the risk of uterine cancer, particularly endometrioid tumors, while haloacetic acids may be associated with nonendometrioid tumors. They called for further studies to confirm these findings and guide public health strategies targeting modifiable environmental risk factors.
Reference:
Spaur M, Marcus Post L, Beane Freeman LE, et al. Drinking Water Contaminant Exposures and Risk of Uterine Cancer. JAMA Netw Open. 2026;9(7):e2624391. doi:10.1001/jamanetworkopen.2026.24391
Next Story