Exposure to drinking water chlorination by-products and fetal growth and prematurity: A nation wide register-based prospective study

Abstract

BACKGROUND: Chlorination isgloballyusedtoproduceofsafedrinkingwater.Chlorinationby-productsareeasilyformed,andthereareindications that theseareassociatedwithadversereproductiveoutcomes. OBJECTIVES: We conductedanationwideregister-basedprospectivestudytoassesswhethergestationalexposuretothefourmostcommonchlorina- tion by-products[totaltrihalomethanes(TTHMs)]viatapwaterwasassociatedwithriskofsmallforgestationalage(SGA),pretermdelivery,and very pretermdelivery.Todate,thisisoneofthelargeststudiesassessingdrinkingwaterTTHM-associatedadversereproductiveoutcomes. METHODS: We includedallsingletonbirths2005–2015 (liveandstillbirths)ofmothersresidinginSwedishlocalitieshaving>10,000inhabitants, ≤2 operating waterworks,adequateinformationonchlorinationtreatment,andasufficient numberofroutineTTHMmeasurementsintapwater. Individual maternalsecondandthirdtrimesterexposurewasobtainedbylinkingTTHMmeasurementstoresidentialhistory,categorizedintono chlorination, <5,5–15, and>15 lg TTHM/L.OutcomesandcovariateswereobtainedviathelinkagetoSwedishhealthandadministrativeregisters. Odds ratios(ORs)and95%confidence intervals(CIs)wereestimatedbylogisticregressionusinginverseprobabilityweighting.Westratified the analyses bychlorinationtreatment(chloramine,hypochlorite). RESULTS: Based onapproximately500,000births,weobservedaTTHMdose-dependentassociationwithincreasedriskofSGA,confined totreat- ment withhypochlorite,correspondingtoamultivariable-adjustedOR=1.20(95%CI:1.08,1.33)comparingdrinkingwaterTTHM>15 lg tothe unexposed. Similarresultswereobtainedwhen,insteadofunexposed,thelowestexposurecategory(<5 lg=L TTHM)wasusedasreference.No clear associationswereobservedforpretermdeliveryandverypretermdelivery. DISCUSSION: Chlorination by-productsexposureviadrinkingwaterwasassociatedwithincreasedriskofSGAinareaswithhypochloritetreatment. https://doi.org/10.1289/EHP6012.