Traffic-related air pollution and adverse pregnancy outcomes in a multi-ethnic society. Results from the Born in Bradford cohort study.

Abstract

Background:Traffic related air pollution has been linked to several adverse pregnancy outcomes. In Bradford UK there are concerns about adverse birth outcomes and higher than average rates of childhood morbidity and mortality. Aim: We investigated the impact of exposure to traffic-related air pollution (NOx, NO2, PM10, PM2.5-10, PM2.5, and PM2.5 absorbance) on pregnancy outcomes (birth weight, head circumference, and gestational age) with particular emphasis on the possible effect modification by the ethnicity. Method:Mother-child pair data from the Born in Bradford (BiB) cohort study were recruited between March 2007 and November 2010. We used a spatiotemporal exposure assessment framework based on land use regression models that were developed in the ESCAPE project to predict pollutant levels at the geocoded address of each study participant’s residence during each week of her pregnancy. Linear and logistic regression models were used to quantify the associations between air pollution exposure and outcomes. Stratification analyses were conducted by ethnic group. Results: In the analyses we included 10848 mothers - child pairs, with main ethnic groups being White British origin (40%), and of Pakistani origin (45%). We found increased risk of preterm birth, adjusted OR 1.23, (95% CI: 1.02-1.48), reduced birth weight of 35 gr (95% CI: -53gr to -18gr) and reduced head circumference of 2 mm (95% CI: -3mm to -1.5mm) for each 5 ?g/m3 increase in the third trimester exposure to PM2.5. The magnitude of these effects differed by ethnicity: mothers of Pakistani origin tended to have higher risk of preterm birth, no risk for lower birth weight and smaller reduction in the head circumference compared to mothers of White British origin. Conclusions: We found an association between air pollution and adverse birth outcomes, with differential effects between those of White British population origin and those of Pakistani origin.