680: Adverse effects of benzene, toluene, ethylbenzene, and xylene air toxics on preterm birth

Abstract

Air toxics include volatile organic compounds emitted from gasoline and industrial sites, known commonly as BTEX (benzene, toluene, ethylbenzene, and xylene). The effect of these air toxics on the risk of preterm birth (PTB) has not been studied. We sought to determine if rates of PTB differ by census-level variations in BTEX ambient exposures in Philadelphia and whether associations differed between medically-indicated (mPTB) compared to spontaneous PTB (sPTB). We analyzed data from a retrospective cohort (GeoBirth, n= 10,040). We analyzed associations of BTEX compounds exposure by census tract using EPA National Air Toxics Assessment data from 2014 with PTB. Manual chart review was performed to adjudicate each preterm birth (PTB) as either sPTB or mPTB. Each woman’s address was geocoded. We used mixed effects logistic regression models to estimate adjusted odds of PTB, sPTB and mPTB (vs. term births) adjusting for maternal age, race, parity, marital status, and insurance status. There were 10,040 live births, of which 11.1% were PTB, 6.6% were sPTB, and 4.5% were mPTB. Only mean benzene exposure was higher among women with all PTBs (0.696 mg/m3) versus term (0.693 mg/m3) (p = 0.0476). After adjustment for confounding variables, the odds ratio (OR) for PTB vs. term birth for benzene was 1.07 (95% CI 1.02-1.12); for toluene, OR 1.04 (95% CI 0.98-1.11); for ethylbenzenes, OR 1.07 (95% CI 1.00-1.14); and for xylenes, OR 1.06 (95% CI 0.99-1.14). We only found associations of BTEX compounds with sPTB (not mPTB); aORs: 1.16 (95% CI 1.07-1.26) for benzene, 1.16 (95% CI 1.05-1.29) for toluene, 1.20 (95% CI 1.08-1.32) for ethylbenzene, and 1.20 (95% CI 1.08-1.33) for xylene. This study found associations between BTEX air toxics and adverse pregnancy outcomes, specifically sPTB. The methods utilized highlight the importance of careful phenotyping of sPTB and mPTB. Notably, associations of environmental hazards with specific PTB phenotypes may be missed if all PTBs are considered as a single entity. Reducing exposures to air toxics may help to improve birth outcomes.View Large Image Figure ViewerDownload Hi-res image Download (PPT)