The epidemiology of chemical contaminants of drinking water

A number of chemical contaminants have been identified in drinking water. T hese contaminants reach drinking water supplies from various sources, inclu ding municipal and industrial discharges, urban and I ural run-off, natural geological formations, drinking water distribution materials and the drink ing water treatment process. Chemical contaminants for which epidemiologic studies have reported associations include the following: aluminium, arseni c, disinfection by-products, fluoride, lead, pesticides and radon. Health e ffects reported have included various cancers, adverse reproductive outcome s, cardiovascular disease and neurological disease. In evaluating epidemiol ogic studies for risk assessment, considering whether the study design was qualitative (hypothesis generating) or quantitative (hypothesis testing) is important and whether sufficient epidemiologic data of a quantitative natu re exists to determine the dose-response curve. Each of the chemical contam inants mentioned are summarized by study designs (qualitative and quantitat ive) and whether a dose-response curve based on epidemiologic data has been proposed. Environmental epidemiology studies are driven by environmental e xposures of interest. For drinking water contaminants, the design of epidem iologic studies and their interpretation should consider the following expo sure issues: the source of the contaminant: other sources of the contaminan t; the route of exposure; the frequency, duration and magnitude of exposure ; the ability to document an actual internal dose; and the ability to docum ent the dose to the target organ. Health effects of concern have other risk factors that must be measured in the conduct of these studies. In evaluati ng epidemiologic studies, potential errors and biases that may occur must b e considered given the very low magnitude of associations (less than 2.0 fo r either odds ratio or risk ratio). Given the issues. the next generation o f drinking water epidemiologic studies should include a multidisciplinary t eam beyond traditional epidemiologists and statisticians. Study teams will require toxicologists, chemists, engineers and exposure assessors. Arsenic is briefly discussed as an example of the importance of susceptible populat ions. Disinfection by-products are discussed as an example of epidemiologic studies of mixtures. Published by Elsevier Science Ltd.