Objective: To understand the levels of exposure to traffic-related air pollutants including nitrogen dioxide (NO(2)), PM(10) and PM(2.5), and the relationship between the exposure to air pollutants during pre-pregnancy or early pregnancy and birth defects. Methods: Data on air pollution and birth defects from 2013 to 2015 was collected. A case-crossover design was employed to analyze the exposure-response relationship between traffic-related air pollutants and birth defects. Results: A total of 4 235 pregnant women were studied. During the study period, the daily average concentrations of ambient NO(2), PM(10) and PM(2.5) appeared as 60.83 μg/m(3), 104.94 μg/m(3) and 103.88 μg/m(3), respectively, with the concentration of PM(2.5) larger than the 2(nd) version of Standard National Ambient Air Quality Standard. In addition, there were strong correlations seen between each of the pollutants (P<0.01). After adjustment for the influence of meteorological factors, it was found that the exposure to high level of NO(2) and PM(10) during pre-pregnancy or early pregnancy increased the risk on birth defects (P<0.05). Conclusion: Levels of exposure to adverse environmental factors during pre- pregnancy or early pregnancy could increase the risk of birth defects, suggesting that in these sensitive periods, women should try to avoid being exposed to high concentration of traffic-related air pollutants as NO(2), PM(10) etc. in order to reduce the risk of birth defects.
目的： 了解2013－2015年西安市交通相关空气污染物（NO(2)、PM(10)、PM(2.5)）浓度与人群暴露水平，定量分析和评价孕前期和孕早期交通相关空气污染物暴露与出生缺陷的关系。 方法： 收集2013－2015年西安市出生缺陷的个案资料，以及对应时期的空气质量数据、气象资料。采用病例交叉设计分析大气污染浓度与出生缺陷的暴露-反应关系。 结果： 共收集4 235名产妇资料，西安市在研究期间大气NO(2)日均浓度为60.83 μg/m(3)，PM(10)日均浓度为104.94 μg/m(3)，PM(2.5)日均浓度为103.88 μg/m(3)，其中PM(2.5)浓度高于GB 3095－2012《环境空气质量标准》国家二级标准限值，且各污染物之间均存在很强的相关性（P<0.01）。在控制气象因素的影响下，孕前期和孕早期NO(2)和PM(10)高浓度暴露可增加出生缺陷发生的风险（P<0.05）。 结论： 西安市产妇孕前期和孕早期暴露于不良环境可能导致胎儿发生出生缺陷。.
Keywords: Air pollutants; Birth defects; Case-crossover study.