Exposure to coarse particulate matter during gestation and term low birthweight in California: Variation in exposure and risk across region and socioeconomic subgroup.

Despite evidence that particulate matter with an aerodynamic diameter ≤10 μm (PM) or ≤2.5 μm (PM) are associated with several adverse birth outcomes, research on the association between coarse particulate matter (PM) and birth outcomes is scarce, and results have been inconsistent. Furthermore, the literature is unclear whether associations between PM and adverse birth outcomes were driven by PM alone or also by PM exposure. Research on the variation in exposure to and risk from PM across populations is also needed to identify potentially vulnerable subgroups. We used birth certificate and ambient air monitoring data in California from 2002 to 2013 to develop a retrospective cohort study of pregnant women and their infants. Averaged gestational and trimester-specific exposures of PM and PM were calculated for mothers whose residential zip code tabulation areas were within a 20 km radius of monitors. We assessed the relationship between prenatal exposure to PM and term low birthweight (TLBW) using logistic and linear regression, adjusting for maternal and paternal demographic, environmental, temporal, and health-related covariates. We also conducted analyses stratified by socioeconomic characteristics and regions. We found a relationship between PM exposure during pregnancy and TLBW after controlling for PM exposure: odds ratio for second quartile of exposure: 1.00 (95% confidence interval: 0.98, 1.03), third quartile: 1.03 (1.00, 1.06), fourth quartile: 1.04 (1.01, 1.07), compared to the first quartile. Associations were strong among Non-Hispanic Black mothers, mothers living in the Central Valley, and fathers without a college degree. Exposure to and risk from PM were heterogeneous across California indicating environmental justice implications. We also found that paternal characteristics were associated with the risk of TLBW even after controlling for maternal characteristics. In addition to PM total mass, further research is needed on the components of PM which may be driving these associations.