Sulfur dioxide reduction at coal-fired power plants in North Carolina and associations with preterm birth among surrounding residents.

Coal-fired power plants (CFPP) are major contributors of air pollution, including the majority of anthropogenic sulfur dioxide (SO₂) emissions, which have been associated with preterm birth (PTB). To address a 2002 North Carolina (NC) policy, 14 of the largest NC CFPPs either installed desulfurization equipment (scrubbers) or retired coal units, resulting in substantial reductions of SO₂ air emissions. We investigated whether SO₂ air emission reduction strategies at CFPPs in NC were associated with changes in prevalence of PTB in nearby communities.

Methods: We used US EPA Air Markets Program Data to track SO₂ emissions and determine the implementation dates of intervention at CFPPs and geocoded 2003-2015 NC singleton live births. We conducted a difference-in-difference analysis to estimate change in PTB associated with change in SO₂ reduction strategies for populations living 0-<4 and 4-<10 miles from CFPPs pre- and postintervention, with a comparison of those living 10-<15 miles from CFPPs.

Results: With the spatial-temporal exposure restrictions applied, 42,231 and 41,218 births were within 15 miles of CFPP-scrubbers and CFPP-retired groups, respectively. For residents within 4-<10 miles from a CFPP, we estimated that the absolute prevalence of PTB decreased by -1.5% [95% confidence interval (CI): -2.6, -0.4] associated with scrubber installation and -0.5% (95% CI: -1.6, 0.6) associated with the retirement of coal units at CFPPs. Our findings were imprecise and generally null-to-positive among those living within 0-<4 miles regardless of the intervention type.

Conclusions: Results suggest a reduction of PTB among residents 4-<10 miles of the CFPPs that installed scrubbers.