Spatial Modeling to Identify Sociodemographic Predictors of Hydraulic Fracturing Wastewater Injection Wells in Ohio Census Block Groups

BACKGROUND: Hydraulically fractured wells produce 2–14 million liters of wastewater, which may contain toxic and radioactive compounds. The wastewater is predominantly disposed of using Class II injection wells. OBJECTIVE: Our objective was to evaluate the relationship between sociodemographic characteristics and injection well locations in Ohio. METHODS: Using state and federal data sources, we classified Ohio census block groups by presence of injection wells, number of hydraulically fractured wells, sociodemographic factors (median household income, % white, population density, % [Formula: see text] education, median age, voter turnout), and geographic information (land area, water area, situated over shale). We modeled the odds of having at least one injection well within a block group with respect to all covariates using three multivariable models incorporating different spatial components to account for similarities in neighboring block groups. RESULTS: In bivariate analyses, block groups with injection wells ([Formula: see text]) compared with those without ([Formula: see text]) had lower population density (71 vs. [Formula: see text] or 27 vs. [Formula: see text]), larger median area (43.5 vs. [Formula: see text]), higher median age (42.8 vs. 40.2 y), and higher % white (98.1% vs. 92.1%). After adjustment using a spatial logistic regression model, the odds of a block group containing an injection well were 16% lower per [Formula: see text] increase in median income [[Formula: see text]; 95% credible interval (CI): 0.719, 0.961] and 97% lower per [Formula: see text] (or per [Formula: see text]) increase ([Formula: see text]; 95% [Formula: see text] , 0.072). Block groups on shale and those containing fewer hydraulically fractured wells were more likely to include an injection well. Percentage white, median age, % [Formula: see text] education, and % voter turnout were not significant predictors of injection well presence. CONCLUSION: In Ohio, injection wells were inversely associated with block groups’ median incomes after adjusting for other sociodemographic and geographic variables. Research is needed to determine whether residents in census blocks with injection wells face increased risk of chemical exposures or adverse health outcomes. https://doi.org/10.1289/EHP2663