Retirements of Coal and Oil Power Plants in California: Association With Reduced Preterm Birth Among Populations Nearby

Abstract

Coal and oil power plant retirements reduce air pollution nearby, but few studies have leveraged these natural experiments for public health research. We used California Department of Public Health birth records and US Energy Information Administration data from 2001-2011 to evaluate the relationship between the retirements of 8 coal and oil power plants and nearby preterm (gestational age of <37 weeks) birth. We conducted a difference-in-differences analysis using adjusted linear mixed models that included 57,005 births-6.3% of which were preterm-to compare the probability of preterm birth before and after power plant retirement among mothers residing within 0-5 km and 5-10 km of the 8 power plants. We found that power plant retirements were associated with a decrease in the proportion of preterm birth within 5 km (-0.019, 95% CI: -0.031, -0.008) and 5-10 km (-0.015, 95% CI: -0.024, -0.007), controlling for secular trends with mothers living 10-20 km away. For the 0-5-km area, this corresponds to a reduction in preterm birth from 7.0% to 5.1%. Subgroup analyses indicated a potentially larger association among non-Hispanic black and Asian mothers than among non-Hispanic white and Hispanic mothers and no differences in educational attainment. Future coal and oil power plant retirements may reduce preterm birth among nearby populations.

Figure 1.

Map illustrating locations of 2 coal and 6 oil power plants that retired during 2001–2011 in California, serving as a basis for an analysis of preterm birth before versus after coal and oil power plant retirement . Solid black borders indicate county boundaries. Concentric circles represent the area bins used in the study. The innermost light grey circle is the 0–5-km bin, the next darker grey area is the 5–10-km bin, and the darkest grey area is the 10–20-km bin.

Figure 2.

Mean difference (after retirement minus before retirement) in proportion preterm birth (gestational age of <37 weeks) according to distance in kilometers from power plant (n = 57,005 total births; 3,616 preterm births), California, 2001–2011.

Figure 3.

Average difference in proportions of preterm birth before versus after coal and oil power plant retirement according to distance bin, California, 2001–2011. A) Overall; B) according to gestational age; C) according to race/ethnicity. Results from difference-in-differences linear mixed models with random intercept for power plant; adjusted for maternal age, race/ethnicity, educational attainment, number of prenatal visits, month of birth, neonate sex, and neighborhood-level educational attainment and poverty. Black circles and lines represent the difference-in-differences coefficient and 95% confidence interval for births within 5 km of retiring power plants (compared with births 10–20 km away) and black triangles and lines represent the difference-in-differences coefficient and 95% confidence interval for births 5–10 km away (compared with births 10–20 km away).