Rappazzo Kristen M, Daniels Julie L, Messer Lynne C, Poole Charles, Lobdell Danelle T
Department of Epidemiology, UNC Gillings School of Global Public Health, Chapel Hill, North Carolina, USA.
Environ Health Perspect. 2015 Oct;123(10):1059-65. doi: 10.1289/ehp.1408953. Epub 2015 Apr 24.
Particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5) has been consistently associated with preterm birth (PTB) to varying degrees, but roles of PM2.5 species have been less studied.
We estimated risk differences (RD) of PTB (reported per 106 pregnancies) associated with change in ambient concentrations of elemental carbon (EC), organic carbon (OC), nitrates (NO3), and sulfates (SO4).
From live birth certificates from three states, we constructed a cohort of singleton pregnancies at or beyond 20 weeks of gestation from 2000 through 2005 (n = 1,771,225; 8% PTB). We estimated mean species exposures for each week of gestation from monitor-corrected Community Multi-Scale Air Quality modeling data. RDs and 95% confidence intervals (CIs) for four PTB categories were estimated for each exposure using linear regression, adjusted for maternal race/ethnicity, marital status, education, age, smoking, maximum temperature, ozone, and season of conception. We also adjusted for other species in multi-species models.
RDs varied by exposure window and outcome period. EC was positively associated with PTB after 27 and before 35 weeks of gestation. For example, for a 0.25-μg/m(3) increase in EC exposure during gestational week 9, RD = 96 (95% CI: -20, 213) and RD = 145 (95% CI: -50, 341) for PTB during weeks 28-31 and 32-34, respectively. Associations with OCs were null or negative. RDs for NO3 were elevated with exposure in early weeks of gestation, and null in later weeks. RDs for SO4 exposure were positively associated with PTB, though magnitude varied across gestational weeks. We observed effect measure modification for associations between EC and PTB by race/ethnicity and smoking status.
EC and SO4 may contribute to associations between PM2.5 and PTB. Associations varied according to the timing of exposure and the timing of PTB.
空气动力学直径≤2.5μm的颗粒物（PM2.5）一直与早产（PTB）在不同程度上存在关联，但对PM2.5各成分的作用研究较少。
我们估计了与元素碳（EC）、有机碳（OC）、硝酸盐（NO3）和硫酸盐（SO4）环境浓度变化相关的早产风险差异（RD，每106例妊娠报告）。
根据三个州的出生证明，我们构建了一个队列，纳入2000年至2005年妊娠20周及以上的单胎妊娠（n = 1,771,225；8%为早产）。我们利用经监测校正的社区多尺度空气质量模型数据估计妊娠各周的平均成分暴露量。使用线性回归估计每种暴露下四个早产类别对应的RD和95%置信区间（CI），并对产妇种族/民族、婚姻状况、教育程度、年龄、吸烟情况、最高温度、臭氧和受孕季节进行校正。我们还在多成分模型中对其他成分进行了校正。
RD因暴露窗口和结局时期而异。妊娠27周后至35周前，EC与早产呈正相关。例如，妊娠第9周时EC暴露每增加0.25μg/m³，妊娠28 - 31周和32 - 34周早产的RD分别为96（95%CI：-20，213）和145（95%CI：-50，341）。与OC的关联为无或负相关。NO3的RD在妊娠早期暴露时升高，后期为无关联。SO4暴露的RD与早产呈正相关，尽管在妊娠各周的程度有所不同。我们观察到EC与早产之间的关联因种族/民族和吸烟状况而存在效应测量修正。
EC和SO4可能导致PM2.5与早产之间的关联。关联因暴露时间和早产时间而异。
