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 today in BioMed Central's open
access journal Environmental Health.
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 defects.
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.