Modeling and Analysis of Air Pollution and Environmental Justice: The Case for North Carolina’s Hog Concentrated Animal Feeding Operations

Abstract

BACKGROUND: Concentrated animal feeding operations (CAFOs) emit pollutants that can cause negative impacts on human health. The concentration of hog production in North Carolina raises concerns regarding the disproportionate exposure of vulnerable communities to air pollution from CAFOs. OBJECTIVES: We investigated whether exposure to gaseous ammonia (NH3 ) and hydrogen sulfide (H2 S) (in 2019) differs between subpopulations by examining demographics, including race/ethnicity, age, educational attainment, language proficiency, and socioeconomic status. METHODS: We used an Air Monitoring Station (AMS)/Environmental Protection Agency (EPA) Regulatory Model (AERMOD)–based Human Exposure Model (version 3) to estimate ambient concentrations of NH3 and H2 S from hog farms in Duplin County and its surrounding counties in North Carolina and estimate subsequent exposures of communities within 50 km of Duplin County, North Carolina, or the Duplin County Region. We combined estimated exposures with 2016 American Community Summary Census data, at the block group level, using spatial analysis to investi-gate whether exposures to these pollutants differ by race and ethnicity, age, income, education, and language proficiency. Based on these estimations, we assessed associated exposure risks to the impacted communities and used multivariable regression modeling to evaluate the relationship between average ammonia exposures from Duplin regional hog farms and the presence of vulnerable populations. RESULTS: The average [ ± standard deviation ðSD)] annual estimated concentration of NH3 and H2 S in the Duplin County Region is 1:75 ± 2:81 μg/m3 and 0:0087 ± 0:014 μg/m3, respectively. The maximum average annual ambient concentrations are estimated at 54:27 ± 4:12 μg/m3 and 0:54 ± 0:041 μg/m3 for NH3 and H2 S, respectively. Our descriptive analysis reveals that people of low income, people of color, people with low educational attainment, and the linguistically isolated in the Duplin Region are disproportionately exposed to higher levels of pollutants than the average exposure for resi-dents. Alternatively, our statistical results suggests that after adjusting for covariates, communities of color are associated with 1.70% (95% CI: −3:79, 0.44) lower NH3 concentrations per 1-SD increase. One-standard deviation increases in the adults with low educational attainment and children <19 years of age is associated with 1.26% (95% CI: −0:77, 3.33) and 1.20% (95% CI: −0:62, 3.05) higher NH3 exposure per 1-SD increase, respectively. DISCUSSION: Exposures to NH3 and H2 S differed by race and ethnicity, educational attainment, language proficiency, and socioeconomic status. The observed associations between exposure to CAFO-generated pollutants and sociodemographic indicators differed among demographics. The disproportionate distribution of hog facilities and resulting pollutant exposures among communities may have adverse environmental and human health impacts, raising environmental justice concerns.