Maternal exposure to disinfection by-products in drinking water and risk of adverse birth outcomes in Taiwan
Date Issued
2011
Date
2011
Author(s)
Lee, Yi-Tien
Abstract
Water chlorination has been the major disinfection process of drinking water in Taiwan. Disinfection by-products could be produced during the disinfection process, such as trihalomethanes (THMs) and haloacetic acids (HAAs). Concerns about the potential health effects from exposures to the disinfection by-products have been raised. Many toxicological and epidemiological studies have been conducted to investigate the possible associations between the maternal exposure to disinfection by-products and the adverse health effects such as cancers and adverse birth outcomes, but the results were inconsistent. The objective of this study was to examine the effects of maternal exposure to total THMs (TTHMs) in drinking water during the first and the third trimesters on the risks of adverse birth outcomes in Taiwan. The adverse birth outcomes investigated in this study included all congenital malformations, congenital heart disease, nervous system defects, orofacial cleft, stillbirth, term low birth weight, and small for gestational age.
We used the birth registration data to conduct a registry-based study between 2001 and 2009 in Taiwan. There were 1,126,714 live births and 10,337 stillbirths, and 1,148,308 live births included in the analysis of the first and the third trimesters, respectively. We obtained the TTHMs data routinely collected in distribution systems by Taiwan EPA from 2001 to 2005 and 2007 to 2009 as our exposure data, and used multiple regression models to estimated unavailable monthly average TTHMs concentrations. Adjusted ORs (95% CIs) were calculated by logistic regression, for the association between TTHMs exposure of the mothers averaged over the first and the third trimesters, and various adverse birth outcomes under two ways of classifying TTHMs exposure groups. Although we improved the previous exposure assessments and overcame the study limitation of low-level TTHMs in Taiwan, we still found no statistically significant positive associations between the TTHMs and the adverse birth outcomes, except stillbirth in the two classifying ways of the high exposure group of TTHMs, as well as treating complete exposure data as continuous (OR=1.077, 95%CI=1.01-1.49; OR=1.148, 95%CI=1.056-1.248; and OR=1.003, 95%CI=1.001-1.006, respectively). Weak evidence of a dose-response trend was found between TTHM exposure groups and TLBW and stillbirth.
We temporarily concluded that with low levels of average TTHMs concentrations (9.86 ± 10.05 µg/L) in Taiwan, we do not need to worry about the effects of TTHMs on adverse birth outcomes. If we strictly revise the MCL of TTHMs to 40µg/L in the future, the health of the people will be sufficiently protected. Further studies with individual water use and other exposure routes were needed to find the range above which TTHMs concentration would have an effect on adverse birth outcomes in order to set up stricter regulation to control the TTHMs to be within the safe range. Further studies of examining the relationship between other more toxic DBPs and adverse birth outcomes are also required.
Subjects
Taiwan
Disinfection by-products
total THMs (TTHMs)
Drinking water
adverse birth outcomes
Type
thesis
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