The Relationship Between Exposure To Chlorinated Drinking Water During Pregnancy And Oxidative Stress Levels

Chlorination is an important method to guarantee the safety of drinking water. However, chlorination disinfection by-products (CDBPs) can be produced during water treatment when chlorine disinfectant reacts with organic pollutant in the source water. Recently, some researches reported the association between exposure to DBPs and adverse pregnancy outcome. Oxidative stress may be one of the mechanisms through which CDBPs cause adverse pregnancy outcome. CDBPs have been proved to induce oxidative stress in animal studies and in vitro studies. But related studies on population are limited. In this study, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and malondialdehyde (MDA) were used as biomarker of oxidative stress to investigat a possible relationship between exposure to chlorinated drinking water and oxidative stress levels in pregnant women.The study included two parts. In the first part, urinary trichloracetic acid (TCAA levels) was measured as internal exposure biomarker of non-volatile CDBPs, such as the haloacetic acids (HAAs), to estimate the effect of exposure to chlorinated drinking water through ingestion on oxidative stress levels in pregnant women. In the second part, showering and hand-washing were used as external exposure biomarker of volatile CDBPs, such as the trihalomethanes (THMs), to estimate the effect of exposure to chlorinated drinking water through inhalation and dermal absorption on oxidative stress levels in pregnant women. Part One: The relationship between exposure to non-volatile CDBPs during pregnancy and oxidative stress levelsMethod: A total of 207 healthy pregnant women who were waiting for delivery during November 1^st, 2008 and May 15^th, 2009 in a hospital were selected as the study objects. Each of them completed a face-to-face questionnaire. Urinary TCAA was measured using HPLC. GSH-Px, SOD and MDA in serum were measured with commercial kit. General linear regressions were employed to analyze the effects of exposure to non-volatile CDBPs on oxidative stress levels of pregnant women.Results: The concentrations of urinary TCAA ranged from below limit of detection (LOD) to 43.5μg/ml (1.7⁴2.5μg/g Cr). The activities of GSH-Px and SOD were 28.9³81.8U/ml and 34.0⁸0.5U/ml, and the the levels of MDA were 0.3⁵.8nmol/ml. General linear regression showed that activities of GSH-Px and SOD were positively correlated with the levels of urinary TCAA (β=0.22, P<0.01 andβ=0.26, P<0.01, respectively). There was no significant association between levels of MDA and urinary TCAA.Part Two: The relationship between exposure to volatile CDBPs during pregnancy and oxidative stress levelsMethod: A total of 117 healthy pregnant women who lived in a same water supply district in Wuhan and waiting for delivery during November 1^st, 2008 and May 15^th, 2009 in a hospital were selected as the study objects. Each of them completed a face-to-face questionnaire. The data of showering and hand-washing were analyzed. GSH-Px, SOD and MDA were measured with commercial kit. General linear regression was employed to analyze the effects of multi-routinely exposure to chlorinated drinking water on oxidative stress levels of pregnant women.Results: The concentrations of urinary TCAA ranged from below LOD to 16.5μg/ml (1.7⁴2.5μg/g Cr). The activities of GSH-Px and SOD were 82.8³21.0 U/ml and 42.2⁸0.5U/ml, and the levels of MDA were 0.3⁵.8nmol/ml.General linear regression shows that activities of GSH-Px in pregnant women were positively related with the time spent in the showering (β=0.25, 95%CI: 5.74⁴3.70, P=0.01). Activities of SOD in pregnant women were not related with the time spent in the showering. Futhermore, both of them were not related with hand-washing during pregnancy.ConclusionExposure to chlorinated drinking water during pregnancy failed to induce significant oxidative damage but induced changes in the status of oxidative/anti oxidative in pregnant women. The results of the present study need to be conformed in further investigations with larger sample size and better study design.