孕前及孕期细颗粒物PM2.5对早产效应的因素分析

Single factor analysis of association between fine particulates PM2.5 exposure before and during pregnancy and preterm birth

目的分析细颗粒物PM2.5暴露与早产的相关性。方法以河源市全市范围内2014年12月1日至2015年11月30日分娩的单胎活产儿和2013年12月1日至2015年11月30日河源市的细颗粒物PM2.5逐日浓度为研究对象。考虑到孕期的空气污染暴露是一个慢性的、累积的过程,并且每个产妇的孕程不同,首先以新生儿出生时的孕周为起点向后计算,将暴露时间分为4个阶段:孕前3个月,孕早期(1~13周末)、孕中期(14~27周末)和分娩前4周,分别计算PM2.5早产效应的组间差异。以某日为起点向后求和12个月的逐日暴露量作为该日分娩孕妇过去1年的PM2.5暴露总量,建立该日过去1年PM2.5累积暴露量在当日及滞后1~10d内早产例数的回归模型,并计算相对危险度。结果河源市单胎活产儿的早产发生率为4.25%。逐日PM2.5浓度波动区间为7~108μg/m3,均值37.88μg·(m3)-1·d-1。研究对象孕前3个月、孕早期、孕中期的PM2.5合计暴露水平区间为12 470~14 960μg/m3,平均值为13 700μg/m3。孕前3个月、孕早期、孕中期的PM2.5暴露水平在早产组与足月组间的差异无统计学意义(t值分别为2.199、2.343、0.947,均P>0.05),早产组与足月组间的PM2.5暴露水平在孕晚期的差异有统计学意义(t=4.818,P<0.05)。以PM2.5累积暴露量下四分位数及其早产例数为参照(即RR=1),暴露于PM2.5累积量中位数,在滞后的10日内有意义的效应表现在滞后的第8、9、10日,RR值分别为1.49(1.01~2.21)、1.63(1.01~2.63)、1.06(1.01~1.11);暴露于PM2.5累积量中位数在滞后的10日内有意义的效应表现在滞后的第8、9、10日,RR值分别为2.05(1.02~4.15)、2.41(1.02~5.70)、1.11(1.03~1.21),累积暴露量的变化幅度与其对早产的效应呈正比,累积暴露量升高越大,在滞后期内对早产的影响也越大。结论河源市孕期PM2.5暴露与早产有关,PM2.5暴露对早产存在非线性的滞后影响。

Objective To analyze the association between fine particulates PM2. 5 exposure and preterm birth. Methods Study was conducted on single live births from December 1,2014 to November 30,2015 and daily fine particulates PM2. 5 concentration from December 1,2013 to November 30,2015 in Heyuan. Considering that air pollution exposure during pregnancy was a chronic and cumulative process and individual woman had different pregnancy process,exposure time was calculated taking gestational age when neonate was born as starting point. Exposure time was divided into four stages,3 months before pregnancy,early pregnancy（ 1stweek to end of 13thweek）,second trimester（ 14 thweek to end of 27thweek） and 4 weeks before delivery. Difference in effect of PM2. 5 on premature delivery between groups was calculated respectively. Sum of daily exposure dose for 12 months starting from a certain day was taken as total PM2. 5 exposure dose of the past year of a pregnant woman. Regression model of accumulation of PM2. 5 exposure of one year starting from the certain day in premature delivery cases on that day and 1-10 days afterwards was built and relative risk was calculated.Results Premature delivery rate of single live births in Heyuan City was 4. 25%. Daily PM2. 5 concentration ranged from 7 to 108μg/m3,and the average value was 37. 88μg/m3 per day. The total PM2. 5 exposure of study objects in three months before pregnancy,early pregnancy and mid pregnancy ranged from 12 470 to 14 960μg/m3 with the mean value of 13 700μg/m3. The difference in PM2. 5exposure in three months before pregnancy,early pregnancy and mid pregnancy between preterm group and full term group had no statistical significance（ t value was 2. 199,2. 343 and 0. 947 respectively,all P 〉0. 05）. Difference in PM2. 5 exposure in late pregnancy between preterm group and full term group was statistically significant（ F = 4. 818,P〈 0. 05）. Lower quartile of cumulative PM2. 5 exposure and number of preterm cases were taken as reference（ RR = 1）. Cases were exposed in mean value of cumulative PM2. 5,and the effects in lag10 days showed in 8,9,10 day with RR value of 1. 49（ 1. 01-2. 21）,1. 63（ 1. 01-2. 63）,and 1. 06（ 1. 01-1. 11）. Cases were exposed in mean value of cumulative PM2. 5,and the effects in lag 10 days showed in 8,9,10 day with RR value of 2. 05（ 1. 02-4. 15）,2. 41（ 1. 02-5. 70） and 1. 11（ 1. 03-1. 21）. Cumulative exposure change range was proportional to its effect on preterm birth.The more cumulative expose,the more effect on preterm birth in lag period. Conclusion PM2. 5 exposure during pregnancy is associated with preterm birth in Heyuan City. PM2. 5 exposure has nonlinear lagged effect on preterm birth.