Background. Prenatal exposure to air pollution has been associated with increased risk of adverse birth outcomes, and traffic exhaust is the most important contributor to air pollution in Los Angeles (LA) County, California.
Methods. Our studies focused on preterm birth (<37 weeks completed gestation), very preterm birth (<32 weeks completed gestation) and term low birth weight (LBW) (≥37 weeks completed gestation, and <2500g at birth) as the pregnancy outcomes of interest.
Summary of findings. The LA County populations in our studies are predominantly Hispanic, multiparous, and of a lower-SES profile. Unseasonalized LUR estimates of ambient NO, NO2, and NOx exposures were associated with increased odds of term LBW, preterm birth, and very preterm birth. For term LBW, the strongest associations for seasonalized LUR-estimated and air toxics exposures were seen for the third trimester, the entire pregnancy, and the last pregnancy month averages. Third trimester benzene, toluene, ethyl benzene, and xylene exposures were associated with term LBW when stratified by closest monitoring station. Exposure to PAHs (benzo(a)pyrene and benzo(g,h,i)perylene) were associated with increased term LBW odds in the last pregnancy month. Vanadium exposures were not associated with increased term LBW risk. These results are consistent with previous studies of term LBW using criteria pollutant data, which also observed associations with entire pregnancy and late pregnancy exposures to air pollution.
For preterm birth, we observed increased risk with seasonalized LUR-estimated exposures in the first trimester, last pregnancy month, and entire pregnancy averages, as well as entire pregnancy average exposure for benzene, toluene, ethyl benzene, and xylene (BTEX).
Odds of very preterm birth increased with higher exposures to seasonalized and unseasonalized LUR-estimated NO, NO2, and NOx, and BTEX pollutants for 1st trimester, 2nd trimester, entire pregnancy, and last month of pregnancy averages. PAH exposure also increased odds of very preterm birth, for last pregnancy month exposures. Vanadium was not associated with preterm birth or very preterm birth.
Poor indoor air quality was also associated with increased odds of term LBW and preterm birth. Most notably, mothers who reported living with one or more smokers had increased odds of both adverse birth outcomes, although the risk was attenuated for those women who also reported keeping their windows open at least half the day. Additionally, women who reported using 1 or more of the surveyed personal and household products (nail polish, hairspray, and insect spray) regularly or frequently had increased odds of term LBW and preterm birth, but only if they also reported having low/no window ventilation. Mothers who worked at home exclusively during pregnancy had stronger associations with the ETS and personal/household product exposure measures, compared to women who reported working outside the home for at least some part of their pregnancy. Measures of home air quality are most likely better measures of exposure for at-home mothers compared to mothers who work outside the home due to the presumed length of time spent indoors at home. (Abstract shortened by UMI.)