An evaluation of the role of epidemiology in assessing current and future disinfection technologies for drinking water.

Six members of the International Society for Environmental Epidemiology provide a discussion of the presentations of the authors of six studies dealing with the potential chronic disease side effects of water disinfection. This symposium, which was jointly sponsored by the Society and the United States Environmental Protection Agency (EPA) also involved state epidemiologists and engineers from state drinking water programs. This article summarizes the results of the studies and the comments about them. There was a general consensus that the recent EPA sponsored studies of cancer endpoints have strengthened the evidence linking bladder cancer with long term exposure to chlorinated drinking water. The evidence for links with colon cancer is not convincing and that for serum lipid changes is quite weak. Any risks, if real, are low when compared to the risk of infection from not disinfecting water. This is particularly true for small water systems where chlorination may be the only practical option.