Effect modification by socioeconomic status on the associations between early placental protein damage and exposure to ambient air PM2.5 chemical components.

BACKGROUND Ambient fine particulate matter (PM2.5) exposure is associated with systemic protein damage in pregnant women. However, its effect on protein damage in human placentas is unclear. OBJECTIVES We estimated the associations of PM2.5 and chemical component exposures with advanced oxidation protein products (AOPP) in placental villi tissues before 13 weeks of gestation. METHODS We enrolled 165 women with unintended normal early pregnancy (NEP) who requested induced abortion during the first trimester and 165 women with early pregnancy loss (EPL) who also requested induced abortion (2017-2022). Maternal daily PM2.5, black carbon (BC), organic matter (OM), sulfate, nitrate, and ammonium exposures from the 12th week before ovulation to villi collection were estimated using data accessed from the Tracking Air Pollution in China platform. Associations of pollutant exposures during the 30 days before villi collection, during the post-conception period (from ovulation to villi collection), and during the periovulatory period (from the 12th week before to 3rd week after ovulation) with villi AOPP were estimated and compared between the NEP and EPL groups. Additionally, effect modifications by socioeconomic status expressed in family monthly income per capita were estimated using stratified distributed lag non-linear models. RESULTS Thirty-day cumulative and average post-conception exposures to higher concentrations of PM2.5, BC, and OM were associated with higher villi AOPP in all subjects and both groups. Thirty-day cumulative effects of per interquartile range increase in the residuals of BC and OM were robust in EPL (βs [95% CI] of villi AOPP were 111.22% [17.96%, 278.24%] and 93.87% [20.63%, 211.56%]), but were not robust in NEP. The associations of per interquartile range increase in the concentrations of BC and OM at some lag days with higher villi AOPP were stronger in low-income stratification (with the ranges of βs of villi AOPP were 10.51-11.99% and 8.08-12.50%) than those in medium-income stratification (3.19-3.80% and 1.95-3.73%) and high-income stratification (2.57-2.78% and 2.51-2.72%). Periovulatory OM exposure was positively associated with villi AOPP in EPL but not in NEP, and the susceptible periods to PM2.5 and other four components were 1-4 weeks earlier in EPL than in NEP. DISCUSSION Maternal PM2.5, BC, and OM exposures were positively associated with oxidative protein damage in early placenta. The associations were stronger in women with EPL or low-income. https://doi.org/10.1289/EHP15170.