Exposure to particulate air pollution during early pregnancy is associated with placental DNA methylation.

Maternal exposure to particulate matter with aerodynamic diameter <10μm (PM10) during pregnancy results in adverse birth outcomes. Changes in placental DNA methylation might mediate those adverse effects. In this study, we examined the associations between prenatal PM10 exposure and DNA methylation of LINE1, HSD11B2 and NR3C1 in human placenta. One hundred and eighty-one mother newborn pairs (80 fetal growth restriction newborns, 101 normal newborns) participated in this study. The average PM10 exposure of each trimester and of the whole pregnancy was calculated using daily air pollution concentration data. Placental DNA methylation was measured by quantitative polymerase chain reaction-pyrosequencing. Placental LINE-1 DNA methylation was reversely associated with first trimester PM10 exposure 1.78% (-β=1.78, 95% CI: -3.35, -0.22%), while placental HSD11B2 DNA methylation was associated with both first and second trimester PM10 exposure, and relatively increased by 1.03% (95% CI: 0.07, 1.98%) and 2.33% (95% CI: 0.69, 3.76%) for each 10μg/m3 increase in exposure to PM10. Those associations were much more evident in fetal growth restriction newborns than those in normal newborns. In summary, early pregnancy PM10 exposure was associated with placental DNA methylation of LINE1 and HSD11B2, suggesting that such methylation alterations might mediate PM-induced reproductive and developmental toxicity.