Persistent chemicals in particulate matter (PM) near a hazardous waste thermal treatment facility

Colfax, an overburdened community in central Louisiana, hosts the last commercially-operated open-burn/open-detonation (OB/OD) hazardous waste thermal treatment facility in the United States. Until December 2023 when their permit disallowed OB/OD, the facility processed military waste, fireworks, propellants, soils excavated from Superfund sites, and other hazardous materials. This community-engaged study measured ambient fine particulate matter (PM_2.5), environmentally persistent free radicals (EPFRs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and metals using two high-volume PM_2.5 samplers deployed 1.2 mi and 9.0 mi from the facility from April, 2022 through February, 2023. Elevated PM_2.5 concentrations were recorded at both sites during spring and summer 2022. EPFR concentrations increased during fall and winter, coinciding with increases in PCDD/F but in contrast to PM_2.5. Similarities between the 1.2 mi and 9.0 mi sites for both PM_2.5 and EPFRs suggest a common emission source influencing concentrations at both sites. Regularized linear regression analyses indicated that EPFRs were significant predictors of PM_2.5 at both sites, with a markedly stronger effect at the 9.0 mi site than at 1.2 mi. Among the metals, Zn was consistently the strongest and most significant predictor of EPFRs and PM_2.5 across both sites and seasons, supported by both moderately high Pearson correlations and Elastic Net coefficients. Through this study, we aim to provide crucial information on exposure risks from an OB/OD facility with the goal of empowering exposed community members for mitigating their risks.