Exposure to ambient sulfur dioxide during gestation and risk of preterm birth among people in North Carolina, 2003-2014

Abstract

BACKGROUND/AIM: Coal-fired power plants are major contributors of ambient sulfur dioxide (SO2) air pollution. Epidemiological literature suggests an adverse association between SO2 exposure during gestation and preterm birth (PTB; <37 weeks completed gestation). PTB is strongly associated with infant mortality and increased risk for later life morbidities. We investigated associations between SO2 and PTB in North Carolina and evaluated whether the associations were modified by race/ethnicity. METHODS: We assembled a retrospective, administrative cohort of singleton births in North Carolina from 2003-2014. We used USEPA CMAQ data to assign SO2 gestational exposures to eligible births for the entire pregnancy and trimesters. We used multivariable generalized linear regression to estimate risk differences (RD (95%CI)) per 1-ppb increase in SO2, adjusted for gestational parent education, marital status, and season of conception. Multi-pollutant models were additionally adjusted for criteria air co-pollutants (CO, O3, PM2.5, NO2). RESULTS: The median SO2 across exposure windows was ~3.5 (IQR: 4) ppb. The overall baseline risk for PTB was 8800 per 100,000 live births. When stratified by race/ethnicity, the baseline risk for PTB was 12200, 7900, and 7100 per 100,000 live births among non-Hispanic Black, non-Hispanic white, and Hispanic births, respectively. Regardless of exposure window, SO2 was adversely associated with PTB with the strongest associations observed for the entire pregnancy period. RDs per 1-ppb increase in SO2 averaged across the entire pregnancy were 133.5 (95%CI: 117.0, 149.9) and 195.7 (171.6, 219.7) per 100,000 live births for single- and multi-pollutant models, respectively. For multi-pollutant models, we observed similar RDs for non-Hispanic Blacks (239.4 (200.7, 278.2)) and non-Hispanic whites (211.5 (182.4, 240.7)) with smaller RDs for Hispanics (119.8 (80.7, 158.9)). CONCLUSIONS: Across exposure windows, the results for our adjusted single- and multi-pollutant models showed adverse associations between SO2 and PTB, with some evidence of effect measure modification by race/ethnicity. KEYWORD: PTB