Effect of Prenatal Exposure to Wildfire-generated PM2.5 on Birth Weight

Abstract

O-29C4-3 Background/Aims: Prenatal exposure to air pollution is associated with adverse birth outcomes such as low birth weight. We sought to investigate whether prenatal exposure to high levels of particulate matter (PM2.5) from large wildfires were also negatively associated with birth outcomes, independent of background air pollution levels. Methods: In 2003, several large wildfires occurred across 6 counties in Southern California, burning more than 750,000 acres over several days. We investigated the effect of wildfire-generated PM2.5 on birth outcomes, using California vital statistics records for 2003–2004 and exposure estimates created at the zip-code level for the week of the wildfires in 8 counties in southern California, including 2 counties with no wildfire exposure. Exposure estimates were derived in a GIS framework using a combination of existing data from an extensive monitoring network, light extinction data, meteorological conditions, and smoke information extracted from MODIS satellite images. Exact addresses from records were geocoded and assigned an exposure estimate for wildfire PM2.5 and for background ambient PM2.5. Logistic and linear regression models were used to determine whether an association existed between wildfire PM2.5 exposure and birth weight, small-for-gestational age, and preterm birth, after adjustment for background ambient PM2.5 and other covariates. Results: Overall, pregnant women living in 1 of the 6 counties at the time the wildfires occurred delivered babies who weighed on average 18 g less (P = 0.01) than the babies of mothers living in 2 counties with no wildfires. Significant effects were observed by trimester, with a stronger association in the third trimester. When level of wildfire PM2.5 exposure was categorized into low, medium, or high, no strong dose-response was observed. However, the effects were also strongest in the third trimester. No effects were observed for small-for-gestational age or preterm birth. Conclusion: Exposure to wildfire-generated pollution may have an adverse effect on birthweight independent of background pollution.