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

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Pages :
128 - 144

Nieuwenhuijsen M.J.
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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.

Chlorination by products, trihalomethane, reproductive health effects, cancer