June 5, 2008 — Drinking water disinfected by
chlorine while pregnant may increase the risk of having children with
heart problems, cleft palate or major brain defects, according to a
study published in BioMed Central’s open access journal Environmental
This finding, based on an analysis of nearly 400,000 infants in
Taiwan, is the first that links by-products of water chlorination to
three specific birth defects.
Water chlorination is a widely used and efficient method to
disinfect drinking water and reduce the occurrence of waterborne
diseases. However, numerous studies have revealed the presence of many
chlorination by-products in the water. Recent research suggests that
prenatal exposure to these by-products may increase the risk of birth
A research team led by Jouni Jaakkola from the Institute of
Occupational and Environmental Medicine, University of Birmingham, UK,
gathered data on almost 400,000 infants born in Taiwan. The researchers
used statistical analyses to see if drinking tap water containing high,
medium or low levels of chlorination by-products increased the risk of
11 common birth defects.
Although the researchers found no direct link between the prevalence
of any birth defect and the level of exposure, their calculations
revealed that exposure to high levels of by-products substantially
increased the risk of three common defects: ventricular septal defects
(holes in the heart), cleft palate, and anencephalus (where neural
development fails, resulting in the absence of a major portion of the
brain, skull, and scalp).
Exposure to total trihalomethanes above 20 ìg/L was associated with
an increased risk of 50 to 100% compared with levels below 5 ìg/L.
These results were corroborated by additional analyses, using pooled
data from a number of similar studies.
"The biological mechanism for how these disinfection by-products may
cause defects are still unknown," says Jaakkola. "However, our findings
don’t just add to the evidence that water chlorination may cause birth
defects, but suggest that exposure to chlorination by-products may be
responsible some specific and common defects. Whilst the benefits of
water chlorination are quite evident, more research needs to be carried
out to determine these side-effects."
Source : BioMed Central/Environmental Health