News Release

New Study of Disinfection Byproducts Offers No Evidence of Development Effects

ARLINGTON, VA (June 12, 2008) – A new study claiming a relationship between certain birth defects and maternal exposure to disinfection byproducts (DPBs) in chlorinated drinking water is fundamentally flawed. Unfortunately, these overstated findings only serve to misinform the public.

Chlorination of drinking water supplies is widely acknowledged as one of the major public health advances of the last century.  Where adopted, drinking water chlorination has helped to virtually eliminate deadly waterborne diseases such as cholera and typhoid fever.  The WHO stresses that water disinfection should not be compromised in order to prevent the formation of DBPs because the benefits of disinfection far outweigh possible risks. 

The new study, by Hwang et al., suggests that prenatal exposure to THMs, a class of DBPs, increases the risk of heart and brain defects and cleft palate in children.  However, there are weaknesses in the study design that, combined with an unorthodox statistical analysis, fail to support the authors’ conclusions about a link between these conditions and THMs.

Scientists have found that all disinfectants can react with naturally occurring organic material in water to form disinfection byproducts.  Chlorination byproducts, in particular, have been studied extensively. A comprehensive “weight of evidence” review of available studies (Tardiff et. al., 2006) indicates no biologically relevant association between THMs and a wide array of birth defects, including those investigated by Hwang et al. 

Reassuringly, international and domestic government agencies have established science-based regulatory standards and guidelines for drinking water. U.S. Environmental Protection Agency standards for THMs and other DBPs have been endorsed by a broad range of public health agencies, environmental groups and drinking water utilities. Internationally, the World Health Organization (WHO) has evaluated scientific research on THMs, and to date, has concluded that existing data are not sufficient to show that these byproducts are harmful to human health.

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