REPRODUCTIVE AND DEVELOPMENTAL EFFECTS OF DISINFECTION BY-PRODUCTS INDRINKING-WATER

Recent epidemiologic studies have reported associations between the co nsumption of chlorinated drinking water and reproductive and developme nt effects. Here we review the available epidemiologic data, assess th e hazard potential posed by exposure to disinfection by-products, iden tify critical data gaps, and offer recommendations for further researc h. The epidemiologic evidence supporting associations between exposure to water disinfection by-products (DBPs) and adverse pregnancy outcom es is sparse, and positive findings should be interpreted cautiously. The methods used during the early stages of research in this area have been diverse. Variability in exposure assessment and endpoints makes it difficult to synthesize or combine the available data. Exposure mis classification and unmeasured confounding may have lead to bias in ris k estimation. Future studies of reproductive outcome and exposure to c hlorinated water should use improved methods for exposure assessment t o 1) assure selection of appropriate exposure markets, 2) assess seaso nal and annual fluctuations in DBPs, 3) assess variability within the distribution system, and 4) assess exposure through multiple routes su ch as bathing and showering, as well as consumption. Population-based studies should be conducted to evaluate male and female fertility, con ception delay, growth retardation, and specific birth defects. The rep roductive and development effects of exposure to DBPs could be efficie ntly explored in ongoing investigations by incorporating valid exposur e markers and relevant questionnaire information. Future studies shoul d make use of naturally occurring variability in the concentrations of DBPs and may incorporate biomarkers of exposure and effect in their d esign. Epidemiologic investigations should be conducted in parallel wi th laboratory-based and animal studies in a coordinated, multidiscipli nary approach.