Adverse reproductive health effects of exposure to chlorination disinfection by-products

Abstract

Chlorination disinfection by-products (DBPs) are formed when water is chlorinated and the organic matter in the water reacts with chlorine to form these by-products. There have been concerns about the potential health effects of these by-products, including cancer and reproductive effects. Here we have reviewed the literature on reproductive health effects. Epidemiological studies on neural tube defects, urinary tract defects and small for gestation age/intra growth retardation have shown the most consistent statistically significant associations with an index of DBPs, but generally the risk estimates are small. The interpretation of the studies is not straight forward because they may not be directly comparable because of differences in DBP mixtures, exposure categories and actually uptake of DBPs due to differences in e.g. ingestion rates, showering, bathing, and swimming. Only few specific DBPs have been studied and THMs have often been used as a marker for other DBPs, since they are often routinely available. Sample sizes, and therefore power, have at times been low, particularly when the population was split into exposure categories. Although most studies considered some confounders, (residual) confounding by other water contaminants or other factors related to water intake, cannot always be excluded. Case ascertainment, for outcomes such as spontaneous abortion and certain congenital anomalies is far from straight forward, and for the latter at times anomalies are lumped together with different aetiology, which may be inappropriate. Furthermore, as with many reproductive epidemiological, if the putative agent affects both early pregnancy loss and later birth outcomes such as congenital anomalies, interpretation of later birth outcomes may be more difficult.