A Nested Case-control Study On Association Of Organophosphate Esters Exposure During The First Trimester Of Pregnancy With Spontaneous Abortion

ObjectivesBased on the Ma’anshan-Anhui Birth Cohort(MABC),this study was conducted to describe the levels of organophosphate esters(OPEs)exposure during the first trimester of pregnancy in Ma’anshan,Anhui Province,to evaluate the cumulative health risk assessment of exposure to OPEs,and to explore the relationship between OPEs exposure alone and mixed exposure during the first trimester of pregnancy and spontaneous abortion(SA).MethodsThe study was a nested case-control study was conducted in which all 99 pregnant women in the cohort with SA and adequate urine samples in the first trimester of pregnancy were included in the case group,and the control group was matched(1:3)according to age ± 2 years,for sum of 396 pregnant women.Demographic information and pregnancy status of pregnant women were recorded by questionnaire and clinical information during pregnancy follow-up,and morning urine was collected from pregnant women in each trimester,and the levels of 6 OPEs metabolites,namely dibutyl phosphate(DBP),diphenyl phosphate(DPHP),dibenzyl phosphate(DBZP),di-o-tolylphosphate(Do CP),bis(2-ethylhexyl)phosphate(BEHP)and bis(2-butoxyethyl)phosphate(BCIPP)were detected by liquid chromatography-triple quadrupole tandem mass spectrometry(LC-MS)in the laboratory at a later stage,and the detection rates and exposure levels of OPEs metabolites were calculated.Urinary creatinine values were measured by the picric acid method,and the corrected exposure levels were calculated by creatinine correction of the raw concentrations;the cumulative risk of OPEs exposure in early pregnancy was assessed by calculating the estimated daily intake(EDI),hazard quotient/hazard index(HQ/HI);the correlation between various OPEs exposures was elaborated by Spearman correlation analysis.After Ln transformation of OPEs metabolite concentrations,t-tests were used to elucidate the differences in OPEs exposure between case and control groups.Generalized linear mixed models(GLMs)were used to analyze the association between OPEs metabolite concentrations and demographic characteristics and to identify influential factors associated with maternal OPEs exposure levels.Logistic regression was used to analyze the association between tertiles of OPEs metabolite concentration(both raw and creatinine-corrected concentrations)and SA,and SA was stratified according to gestational weeks of miscarriage.Bayesian regression models(BKMR)were used to analyze the association between mixed OPEs exposure and SA.ResultsIn 396 first trimester pregnancy urine samples,the detection rate of all six OPEs metabolites exceeded 50%,with DPHP having the highest detection rate and BCIPP having the lowest detection rate.The concentration of BCIPP was the highest,followed by that of DPHP and the lowest concentration of Do CP,and there was a low association between the different OPEs metabolites in pregnant women(r = 0.12-0.40,P < 0.01).The EDI of all six OPEs in this study were well below their respective reference intakes(Rf D),and HI < 1.The result of t-test revealed that the raw and creatinine corrected urinary concentrations of DBP,DBZP,Do CP,and BCIPP were significantly different between the case and control groups(P < 0.05),and the concentrations were higher in the case group.Univariate logistic regression results showed that based on the original concentrations of OPEs metabolites,compared to lower concentrations of OPEs metabolites,high concentrations of DBP(OR = 1.98,95% CI: 1.16-3.40),DBZP(OR= 2.37,95% CI: 1.43-3.92),Do CP(OR = 2.10,95% CI: 1.23-3.57),and BCIPP(OR =2.63,95% CI: 1.60-4.32)were associated with an increased risk of SA.After creatinine correction for urinary OPEs metabolite concentrations,in addition to the above associations,which remained statistically significant,moderate concentrations of DBZP(OR = 1.89,95% CI: 1.02-3.50),BCIPP(OR = 2.14.95% CI: 1.16-3.93)were also associated with an increased risk of SA,but moderate concentrations of Do CP(OR =0.43,95% CI: 0.22-0.83)was associated with a decreased risk of SA.After adjusting for gestation and primiparity,the above associations were still found to be statistically significant(P < 0.05).Stratified by gestational week of SA,the results of univariate logistic regression showed that based on the results of the raw concentration analysis,high concentrations of DBP(OR = 2.39,95% CI: 1.21-4.76),DBZP(OR = 3.49,95%CI: 1.82-6.68),Do CP(OR = 2.21,95% CI : 1.16-4.20,BEHP(OR = 2.31,95% CI:1.10-4.82)were associated with an increased risk of EL;high concentrations of BCIPP(OR = 3.48,95% CI: 1.72-7.06)were associated with an increased risk of FL.Based on the results of the urinary creatinine corrected concentration analysis,it was found that in addition to the above associations,which remained statistically significant,moderate concentrations of DPHP(OR = 2.41,95% CI: 1.18-4.93),DBZP(OR = 3.59,95% CI: 1.47-8.77),and BEHP(OR = 2.26,95% CI: 1.05-4.89)were associated with an increased risk of EL,and high concentrations of BCIPP(OR = 2.18,95% CI: 1.05-4.55)were also associated with an increased risk of EL.However,moderate concentrations of Do CP(OR = 0.36,95% CI: 0.15-0.87)was associated with a decreased risk of EL.After adjusting for gestational age and primiparity,the results revealed that the associations remained statistically significant,except for high concentrations of Do CP,which was not statistically associated with EL.Results of the mixed exposure analysis using creatinine-corrected metabolite concentrations revealed that the posterior probability(PIP)of DBP and DBZP in the BKMR model was 1,and there was a positive correlation between the concentrations of DBP,DBZP and Do CP and the risk of SA.ConclusionsThe widespread exposure of pregnant women in Ma’anshan city of China to OPEs,with the highest detection rate of DPHP in urine,but no potential health risk to humans was found from the HI evaluation.The results also indicated that some OPEs were independent risk factors for SA,and that EL and FL were affected to different degrees.The results of the mixed exposure analysis found that tributyl phosphate(TNBP),tribenzyl phosphate(TBZP)and tricresyl phosphate(TCP)exposure increased the risk of SA,and TNBP and TBZP may play the most important role in this.