To Chlorinate or not to Chlorinate?: That Is the Watery Question

Abstract

ISEE-0470 Background: Water disinfection using chlorine compounds or disinfection byproducts (DBPs) has been a commonly used method for purification in the U.S. and other developed nations for the past 8 decades. The toxicology of chlorine and trihalomethanes DBPs is well studied, and chlorine is an effective disinfectant. We wanted to contrast chlorine and other disinfection methods for efficiacy and infection prevention capacity. Methods: A review of the Medline and Toxline literature published after 1995 returned numerous epidemiologic studies demonstrating weak associations between DBPs and some cancers, and more recently evidence of modest associations with birth defects and spontaneous abortions. Little risk information was detected for alternative disinfection methods. Synthesis: Alternative methods of disinfection such as UV radiation, chloramines, ozone and paracetic acid are as effective as chlorine DBPs at disinfecting the water at the point of purification. However, the non-specific biocidal activity of chlorine products demands the meticulous control of the concentration levels. In contrast with chlorine products, these alternative methods do not continue to disinfect water downstream from the site of purification. Because municipal water distribution systems are not watertight, especially in older cities (of the U.S.), this presents a risk-risk tradeoff, contrasting acute versus chronic illnesses. Summary: Currently, the risk of not using a method that will disinfect the water all the way through the system to the point of consumption outweighs the low risk of adverse chronic health defects from exposure to chlorine DBPs. Alternatives to chlorine compounds must demonstrate equivalent efficaciousness before widespread adoption. Although chlorine compounds have known toxicity, their use has demonstrated biocidal properties throughout urban water supplies. Adoption of nonchlorine methods can lead to higher possible infectious disease risks.