School exposure to air pollution from industrial swine operations in eastern North Carolina

Concentrated animal feeding operations (CAFOs) in North Carolina are disproportionately located in low-income communities and communities of color; several counties claim the highest swine and turkey CAFO densities nationally. Previous studies have associated school proximity to CAFOs with prevalence of asthma-related illness in children. The Rural Air Pollutants and Children’s Health study measured hydrogen sulfide (H₂S) for 28-69 days near the playgrounds at three middle schools surrounded by low, medium, and high CAFO density. We obtained hourly meteorological data, identified CAFO locations within 3 miles of each school using satellite data and geographic information systems imaging, and abstracted total swine weight from North Carolina Department of Water Quality permits. We compared hourly pollutant concentrations at schools with upwind animal weight, using circular plots of mean concentration by wind direction and linear regression. Hourly H₂S concentrations exceeded 1 ppb on 21%, 7%, and 32% of days respectively for low, medium, and highly exposed schools. Total swine weight ranged from 0 to 1651.6 tons within wind direction categories. Upwind swine weight was associated with mean H₂S; at the high CAFO density school, hourly H₂S concentrations increased by 0.0002 ppb for every ton of livestock located upwind within 3 miles (β=2.2E-4, Standard Error=3.6E-0.5).  We conclude that upwind CAFOs are temporally and spatially associated with concentrations of H₂S, a marker of the complex mixture of gases and particles emitted from swine CAFOs near these schools. Future research should evaluate co-pollutants, such as bioaerosols, ammonia, and volatile organic compounds, to better understand potential impacts on children’s health.