Changes in socioeconomic and demographic disparities for traffic-related air pollution exposure during pregnancy over a 20-year period in Texas

Background and Aim: Environmental justice issues surround population exposure to ambient air pollution; however, few studies have specifically examined traffic air pollution (a pollutant with localized concentration patterns) and pregnancy exposures (maternal-infant dyads may be particularly susceptible to air pollution effects). How socioeconomic and demographic disparities may change over time is also unclear but could have important policy implications. Methods: We identified ~ 6.9 million pregnant mothers in Texas from 1996 to 2016 using individual-level vital statistics records. We estimated traffic air pollution exposures using full residential addresses and calculated the total vehicle miles travelled (VMT) within 300 m, assigned nitrogen dioxide (NO2) concentrations from a spatial-temporal land use regression model (an indicator of vehicle tailpipe emissions), and linked the National Air Toxic Agency cancer risk index from vehicles emissions to maternal addresses. From census tract data, we examined median household income. We quantified annual absolute and relative mean percent differences in traffic air pollution across socio-demographic indicators of maternal race and ethnicity, educational attainment, and maternal birthplace. Results: We observed marked differences in traffic air pollution exposures by all socio-demographic variables examined. Overall, the strongest disparities were seen among non-White and foreign-born pregnancies. While the absolute level of disparity shrank from 1996 to 2016 (e.g., in 1996 Black individuals were exposed to NO2 levels 1.8 ppb higher than white individuals, while in 2016 NO2 levels were 1.5 ppb higher among Black compared to white individuals), the relative level of disparity continued to increase. Within census tracts (i.e., neighborhoods), we also observed sizeable disparities among socioeconomic and demographic groups. Conclusion: Despite considerable reductions in traffic-related air pollution, the magnitude of disparity has increased when we compared groups with lower socioeconomic positioning to their higher socioeconomic positioned counterparts. Keywords: traffic-related air pollution, pregnancy, environmental justice