Prenatal greenness, air pollution, and birthweight: Assessing sensitive windows of exposure and sub-populations in a multi-exposure setting.

INTRODUCTION

Studies show that prenatal neighborhood greenness is positively associated with birthweight. However, few go beyond a pregnancy-long greenness average or consider air pollution co-exposures. We used time-varying greenness and air pollution estimates to explore sensitive windows and subpopulations.

METHODS

We examined Michigan (U.S.) birth records between 2007 and 2016 (n = 798,071). We derived the Normalized Difference Vegetation Index (NDVI) from Landsat images (30 m2 resolution) to estimate greenness within 270 m and 1230 m radial buffers around each mother's address, to represent greenness immediately surrounding addresses and within a short walk, respectively, in the three seasons before birth. We joined estimated weekly 1 km2 gridded PM2.5, NO2, and O3 concentrations, and fit distributed lag models to assess trimester-specific greenness, weekly air pollution, and birthweight, adjusting for temperature, seasonality, maternal factors, and gestational age. We examined whether the NDVI-birthweight association varied by socioeconomic status, and whether the air pollution-birthweight association varied by NDVI tertile.

RESULTS

In adjusted models, an IQR (0.2 unit) increase in NDVI within a 270 m buffer was associated with a 12.3 g (95% CI: 9.7 g, 15.0 g) higher birthweight. Positive associations were observed in all trimesters, and across all maternal education and neighborhood median household income levels. PM2.5-birthweight associations (IQR = 5 μg/m3) were largest in the lowest NDVI tertile (PM2.5: -21.3 g, 95% CI: -31.1 g, -11.5 g).

CONCLUSIONS

Birthweight is positively associated with residential greenness in all trimesters after co-adjusting for air pollutants. Addresses surrounded by the least greenness had the strongest inverse PM2.5-birthweight association. Nature-based solutions may attenuate air pollution's negative impacts.