A new study has identified a significant association between higher levels of disinfection byproducts in drinking water and an increased risk of uterine cancer, particularly endometrioid tumors, among California women. The research, led by Rena R. Jones, PhD, MS, and colleagues at the National Cancer Institute, utilized a prospective cohort of 53,100 female educators from California, tracking cancer outcomes through December 2020. Participants with at least 10 years of residential exposure to community water supplies were analyzed, revealing a statistically significant increase in uterine cancer risk (HR 1.18, 95% CI 1.02-1.38) and endometrioid tumors (HR 1.23, 95% CI 1.05-1.46) in individuals with elevated total trihalomethane (THM) levels in their water. Chloroform, a common THM, emerged as the strongest correlate, with hazard ratios of 1.18 for overall uterine cancer and 1.27 for endometrioid tumors.
The study further linked five prevalent haloacetic acids (HAAs) in drinking water to nonendometrioid tumors (HR 1.86, 95% CI 1.06-3.25), consistent with findings from the Iowa Women’s Health Study, which similarly connected disinfection byproducts to endometrial cancer in postmenopausal women. Notably, no associations were observed between uterine cancer and arsenic, nitrate, or uranium levels in water. The researchers emphasized that exposure to these carcinogenic compounds is potentially modifiable, underscoring the urgency for public health interventions.
Biologically plausible mechanisms explain these findings, as experimental studies indicate that certain THMs and HAAs can bind to estrogen receptors, disrupting hormonal balance and potentially driving tumor development. “Exposure to drinking water contaminants is a modifiable risk factor, necessitating renewed attention to regulatory standards,” noted the authors.
Dr. Shady Abohashem, MD, MPH, of Massachusetts General Hospital, highlighted the need to reassess decades-old regulatory thresholds for THMs and HAAs, which were primarily set based on bladder cancer data. He advocated for source-water protection, optimized filtration processes before disinfection, and infrastructure investments in underserved communities. Clinicians are urged to consider environmental exposures when counseling patients with environmental cancers, as these risks often go unrecognized.
The study’s limitations include insufficient historical water quality data prior to 1990, restricting assessments of early-life exposures. Nonetheless, the findings add critical evidence to the body of research on disinfection byproducts and cancer, emphasizing the balance between water safety and long-term health implications.
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