Drinking water comes from various sources including reservoirs, lakes and rivers. To protect consumers from microbial contaminants like viruses, bacteria and protozoa, as well as residual dirt, leaf and organic matter, drinking water is carefully treated and disinfected. So water flows through various processes involving chemical purification and filtration before it hits your sink. The most common treatment entails the addition of chlorine and other disinfectants. This process balances one’s risk of illness and infection with the possible byproducts of the disinfection process itself.
Scientists have conducted studies for years on the effects of byproducts on health. Some studies have found links to cancer, while others have not. It is true, however, that water chlorination can produce trihalomethanes, a carcinogenic chemical byproduct. But different levels of trihalomethanes treat the body, and your health, differently.
Studies linking chlorine to cancer, states a recent New York Times article ‘The Claim: Chlorine in Drinking Water Can Increase the Risk of Cancer’, have shown that long-term consumption particularly in men does increase bladder cancer rates by small percentages. But the World Health Organization, the United Nations’ public health arm responsible for monitoring disease outbreaks and assessing the performance of health systems around the globe, believes this evidence is weak. According to the WHO, the chlorine byproduct risk is miniscule when compared to that of nonchlorinated water.
The Environmental Protection Agency, or EPA, has capped the maximum allotted level of trihalomethanes to 80 micrograms per liter in tap water. This level is considered safe for the general population, including vulnerable groups like children. On their website, the EPA states: “The United States has one of the safest water supplies in the world. However, national statistics don't tell you specifically about the quality and safety of the water coming out of your tap. That's because drinking water quality varies from place to place, depending on the condition of the source water from which it is drawn and the treatment it receives.” Their advice to those experiencing a potential acute or chronic health effect as a result of compounds in their drinking water: contact the supplier for additional information specific to your area.