Disinfection By-Products

Background

Safe drinking water is one of the greatest triumphs in public health over the past 100 years. It is something that we all take for granted. Whether it’s drinking water from a tap, taking a slurp from the drinking fountain in the hall, or purchasing a bottle of “pure spring water” most of us indulge without a second thought. This has not always been the case, however. Before water was routinely treated with disinfectants, diseases such as typhoid fever, cholera, hepatitis and polio were easily spread through the consumption of contaminated water. These diseases are no longer a water-borne threat to the majority of the public in this country due to the disinfectant treatment of drinking water. Water treatment is a great success, but isn’t perfect. Within the past 10 years, 400,000 people became ill in Milwaukee after the municipal water supply in that City was contaminated with Cryptospordium. At least 4000 were hospitalized and 50 deaths were linked to the outbreak. (http://www.epa.gov/OGWDW/mdbp/mdbp.html). Outbreaks of disease associated with Giardia, Salmonella and Shigella also still occur in communities with ineffective water distribution systems or that have been affected by natural disasters.

As with all advances in science and technology there are trade-offs. Increasingly, science has found a link between the chlorine, ozone, chloramines, or chlorine dioxide that is used to disinfect our water supply and the development “disinfection by-products” or DBPs. These chemical disinfectants react with naturally occurring organic material (NOM) such as dissolved leaves, other vegetation, and fecal material to create a series of compounds that have been identified as potential carcinogens and the cause of reproductive and development defects in laboratory animals. What is at issue is that 200 million people across the United States currently receive their water from some type of central treatment and distribution system. Even if the exposure to these chemicals is limited, due to the large number of individuals exposed the out effects could be significant. Stopping the disinfection of water supplies would be more catastrophic, however, as the risk of bacterial contamination is substantially higher than the possible cancer risk posed by these compounds.