A 25-year study of more than 53,000 California women found that greater exposure to common drinking-water disinfection byproducts was associated with increased rates of uterine cancer, including both endometrioid and more aggressive nonendometrioid tumors.
By yourNEWS Media Newsroom
Long-term exposure to chemicals formed during the chlorination of drinking water may be associated with a higher risk of uterine cancer, according to a large study that followed more than 53,000 California women for approximately 25 years.
Published July 22 in JAMA Network Open, the National Cancer Institute-led research examined exposure to trihalomethanes and haloacetic acids, two major classes of disinfection byproducts created when chlorine reacts with naturally occurring organic material in water. Women with the greatest estimated exposure to several of those compounds experienced higher rates of certain uterine tumors than those with lower exposure.
The findings do not establish that chlorinated water directly causes uterine cancer, but they add to concerns about the possible long-term health effects of disinfection byproducts routinely found in public water systems. Researchers identified particularly strong associations involving chloroform and five commonly measured haloacetic acids.
Women with the highest long-term exposure to total trihalomethanes had an 18% greater risk of uterine cancer overall and a 23% higher risk of endometrioid tumors, the most common form of the disease. Chloroform, one of the principal trihalomethanes found in treated water, was associated with a 27% increase in endometrioid tumor risk.
The strongest result involved haloacetic acids. Higher exposure to five commonly detected compounds was associated with an 86% greater risk of nonendometrioid uterine tumors, which are generally less common but can be more aggressive and difficult to treat.
The study was led by Dr. Rena R. Jones of the National Cancer Institute and drew from a long-running group of California educators. By tracking participants over decades and estimating their exposure through local water-quality information, the researchers were able to examine whether cumulative contact with disinfection byproducts corresponded with later cancer diagnoses.
Chlorine remains widely used because it kills bacteria, viruses and other organisms that can spread serious waterborne disease. The potential concern arises after treatment, when chlorine reacts with organic matter and produces secondary compounds that remain in the water supply.
Trihalomethanes include chloroform and related chemicals, while haloacetic acids comprise another group of compounds formed through similar reactions. Both are regulated in public drinking water, but the new findings raise questions about whether current limits adequately address long-term exposure and cancer risks beyond those emphasized when the standards were developed.
The federal maximum contaminant level for total trihalomethanes is 80 parts per billion. That standard was established during the 1990s, when regulatory attention centered heavily on bladder cancer evidence and the practical limits of treatment technology.
Chloroform had already been classified decades earlier as a probable human carcinogen, yet millions of Americans have continued to encounter small amounts of it and other disinfection byproducts through municipal water. The latest results suggest that uterine cancer may need to be considered when regulators reassess the health effects of those exposures.
The California findings also align with earlier research involving women in Iowa, strengthening concern that the association may not be confined to a single population or water system. Researchers pointed to the endocrine-disrupting properties of some disinfection byproducts as one possible biological explanation.
Uterine cancer, particularly endometrial cancer, is strongly influenced by hormones. Chemicals capable of interacting with estrogen receptors or disrupting hormonal signaling could theoretically affect the cells lining the uterus and contribute to abnormal growth over time.
The study did not determine precisely how trihalomethanes or haloacetic acids might influence tumor development. However, the observed associations and the ability of some of these compounds to interfere with endocrine activity provide a plausible pathway for further investigation.
Exposure can also occur through more than drinking water. Some trihalomethanes are volatile, meaning they can enter the air during showering, bathing or other household activities involving hot water. People may inhale the chemicals or absorb them through the skin, adding to the amount consumed directly.
That broader exposure makes individual risk difficult to calculate solely from the number of glasses of tap water a person drinks. Water temperature, ventilation, bathing habits, local contaminant levels and the amount of time spent in contact with treated water may all influence cumulative exposure.
The findings do not mean communities should abandon water disinfection, which remains essential for controlling infectious disease. Instead, they strengthen the case for examining treatment methods that can reduce harmful byproducts while maintaining protection against dangerous microorganisms.
Alternatives and supplemental technologies include ultraviolet treatment, ozonation, activated carbon filtration and changes in how utilities remove organic matter before applying disinfectants. Each method has different costs, operating requirements and limitations, and some can create byproducts of their own.
For households concerned about exposure, certain properly certified filtration systems may reduce trihalomethanes and other contaminants, although performance varies considerably. Consumers should confirm that a device is specifically certified for the compounds they want to remove rather than assuming any countertop pitcher or basic filter will provide sufficient protection.
The research also does not show that every woman exposed to chlorinated water faces a high likelihood of developing uterine cancer. The reported percentages represent relative differences between exposure groups, not the absolute probability that an individual will become ill.
Age, genetics, obesity, hormone exposure, reproductive history and other established risk factors remain important in uterine cancer development. The study adds drinking-water contaminants as a possible environmental factor requiring further investigation rather than replacing those known influences.
Researchers are now calling for additional work in other populations, more detailed measurement of individual exposure and closer examination of how specific compounds may affect different uterine tumor types. Future studies could also determine whether risks appear below current legal limits and whether reducing exposure changes cancer outcomes.
The results place renewed pressure on public health agencies to revisit standards that have remained largely unchanged while evidence concerning disinfection byproducts has continued to develop. With chlorinated water used by millions of households every day, even a modest increase in risk could have significant public health implications when applied across the population.
The challenge for regulators and water providers will be to preserve the lifesaving benefits of disinfection while reducing long-term exposure to chemicals formed during the treatment process. The new findings suggest that uterine cancer should now be part of that discussion.
Source: Natural News
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