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.