Exposure To Chlorination Disinfection By-products And Their Associations With Low Birth Weight And Small For Gestational Age During Pregnancy

ObjectivesThe potential reproductive health effects of the chlorination disinfection byproducts (CDBPs) in drinking water have received considerable public concerns,which prompted lots of toxicological and epidemiological studies to investigatethe possible reproductive effect. However, evidence for association betweenexposure to CDBPs during pregnancy and adverse reproductive outcomes suchas low birth weight (LBW) and small for gestational age (SGA) is stillinconsistent and inconclusive. In the present study, we conducted a populationbased study to investigate the trimester-specific exposure levels of CDBPs duringpregnancy and their associations with LBW and SGA as well as the windowperiod of exposure to CDBPs, and finally to provide scientific proofs for furtherstudy.MethodsWe collected the relevant information of3903parturient that had givenbirth to a singleton from April2010to July2012and whose drinking water wassupplied by one single water plant. During the period of study, we monthlycollected the tap water samples from three sites with different distances of distribution network from the plant, which take both temporal and spatialvariability of CDBPs into account. Four regulated halomathanes (includingchloroform, chlorodibromomethane, bromodicloromethane and bromoform) andtwo chlorohaloacetic acids (including dichloroacetic acid and trichloracetic acid),were used as exposure assessment indicators and measured bygas-chromatography with electron capture. Maternal exposure to each CDBPswas evaluated for each trimester and the entire pregnancy. The CDBPsconcentrations were divided into tertiles, the lowest concentration was used asreference. Non-conditional logistic regression analysis was used to estimate theassociations of trimester-specific exposure to CDBPs during pregnancy withLBW and SGA in newborns.Results(1) Among all the84(100%) tap water samples, chloroform,chlorodibromoethane, dichloroacetic acid and trichloracetic acid were detectable;Bromodicloromethane and bromoform were detectable in67(79.76%) and19(22.62%) samples, respectively. All the concentration of CDBPs detected metthe national standards for drinking water quality. The concentration ranges ofthe CDBPs were:1.54-53.76μg/L for chloroform,0.34-16.40μg/L forchlorodibromoethane, LOD (limit of detection)-5.66μg/L forbromodicloromethane, LOD-13.29μg/L for bromoform,1.92-48.23μg/L fordichloroacetic acid,2.55-38.56μg/L for trichloracetic acid. The CDBPs levelswere not associated with the difference of distance in sampling sites, but therewas a statistical difference in the CDBPs levels while the seasons changed.(2) Exposure to high-level of chloroform during the first trimester (OR=2.57,95%CI:0.98~6.70) and high-level of bromo-THMs during the last trimester(OR=2.26,95%CI:1.02~5.02) may lead to increased risk of LBW, respectively. Adose-response relationship was found between exposure to bromo-THMs duringthe last trimester and LBW (p value for trend=0.02). Exposure to high-level ofdichloroacetic acid during the first two trimesters (OR=2.91,95%CI:1.01~8.40; OR=5.26,95%CI:1.88~14.67) and exposure to high-level of trichloracetic acidduring the first trimester (OR=4.48,95%CI:1.51~13.27) may result in increasedrisk of LBW, respectively. A dose-response relationship was found betweenexposure to dichloroacetic acid during the second trimesters and to trichloraceticacid during the first trimester and LBW (all the p values for trend <0.05).(3) Exposure to high-level of trichloracetic acid during the first trimester(OR=1.80,95%CI:1.01-3.22), and high-level of chloroform as well asdichloroacetic acid during the last trimester (OR=1.78,95%CI:1.09~2.91;OR=1.71,95%CI:1.04~2.82) may be a risk factor of SGA, respectively. Exposureto high-level of chloroform, total THMs, dichloroacetic acid and trichloraceticacid during the entire pregnancy may contribute to increased incidence of SGA,the OR (95%CI) were1.87(1.01~3.49),2.30(1.22~4.35),1.93(1.05~3.52) and2.16(1.19~3.91), respectively. A dose-response relationship was found betweenexposure to chloroform and total THMs during the entire pregnancy and SGA(both the p value for trend<0.05).ConclusionExposed to high levels of CDBPs in drinking water during pregnancy couldbe a risk factor both for LBW and SGA in newborns. Exposure to chloroform,dichloroacetic acid and trichloracetic acid during the first trimester,dichloroacetic acid during the second trimester and bromo-THMs during the lasttrimester may result in increasing incidence of LBW. Exposure to trichloraceticacid during the first trimester, chloroform, dichloroacetic acid and trichloraceticacid during the last and the entire trimesters may be the risk factor of SGA. Ourresults suggested that the first and the last trimester of pregnancy may play aswindow period to fetal growth when exposed to some CDBPs (chloroform,dichloroacetic acid and trichloracetic acid). However, the association of exposureto CDBPs during pregnancy with LBW and SGA still warrant further studies inhumans.