Windows of susceptibility to fine particulate matter components for fetal birth weight: a birth cohort study

The effects of prenatal exposure to fine particulate matter (PM2.5) on fetal birth weight (FBW) results have been inconsistent, and the crucial components of PM2.5 may be responsible for these harmful effects. We aimed to explore the effects of prenatal exposure to PM2.5 components on FBW and determine the pregnancy susceptible exposure windows for PM2.5 components. We analyzed data from a birth cohort of 10,164 mother-infant pairs in Hefei, China. The study included singleton live births delivered between 2017 and 2021, with complete exposure and covariate data. We assessed pregnancy exposure to PM2.5 and its components (NH4+: ammonium; NO3−: nitrate; SO42−: sulfate; OM: organic matter; BC: black carbon) with spatial datasets matched to participants’ residential addresses, and assessed green space using the Normalized Difference Vegetation Index (NDVI). Generalized linear regression assessed the crucial components of PM2.5 affecting FBW Z-scores, and to further explore the susceptibility windows. Stratified analyses were conducted to explore potential moderating effects of green space. Our study found that pregnancy exposure to PM2.5 and its components was associated with reduced FBW Z-scores, with black carbon (BC) having a stronger negative effect. Each 1 µg/m3 increase in BC was associated with an expected FBW Z-score decrease of β&95%CI: -0.1176 (-0.1791, -0.0560). The most crucial periods for the effect of PM2.5 components on FBW Z-scores were the second and third trimesters. Finally, we observed that higher levels of green space exposure showed a protective effect on FBW Z-scores. Our research highlights that certain PM2.5 components like BC impact FBW negatively, particularly in the second and third trimesters, and that green space can mitigate this negative effect. This study provides scientific evidence for PM2.5 emission source control and maternal and child health protection.