Soil and Water Contamination by Perfluoroalkyl Acids (PFAAs) at Fire Outbreak Sites in Ghana: Distribution and Screening-level Risk Assessment

Abstract Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants of concern because of their mobility, persistence, bioaccumulation potential, and possible adverse health effects. In this study, only two legacy perfluoroalkyl acids (PFAAs) that include perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were quantified. Fire-outbreak locations are potential points of release because firefighting foams, thermally affected PFAS-containing materials, industrial activities, wastewater, landfill leachate, and atmospheric deposition can contribute target PFAAs to surrounding soil and water. To our knowledge, this study provides the first field investigation of PFOA and PFOS at documented fire-outbreak sites in Africa. Across 18 fire-affected soil sites, PFOA and PFOS ranged from non-detectable to 5.72 ng/g dw and non-detectable to 10.80 ng/g dw, respectively; lower-bound site means (non-detects assigned zero) were 1.12 and 1.03 ng/g dw. Among seven surface-water sites, PFOA was detected at 5/7 sites and PFOS at 4/7 sites, with ranges of non-detectable–0.793 ng/L and non-detectable–13.50 ng/L and lower-bound means of 0.357 and 2.17 ng/L, respectively. One shallow hand-dug well (WR 3W), interpreted separately from surface water, contained 5.14 ng/L PFOA and non-detectable PFOS. Using updated U.S. EPA 2024 oral reference doses in a deterministic screening model, Hazard Index (HI) exceeded 1 at one surface-water site (GR 6W, driven by PFOS) and at WR 3W (driven by PFOA), while other surface-water HIs were below 1. These Hazard Quotient (HQ)/HI values are screening indicators rather than predictions of disease and depend strongly on intake, body weight, exposure duration, treatment, and benchmark selection. Comparison with the U.S. EPA 4.0 ng/L drinking-water Maximum Contaminant Levels (MCLs) is contextual rather than a compliance determination because most samples were untreated environmental waters. The EU 0.10 µg/L 'Sum of PFAS' parametric value cannot be fully assessed because only two of the 20 listed PFAS were measured, and WHO has not finalized PFOA/PFOS guideline values. The findings therefore provide preliminary baseline evidence of spatially heterogeneous PFOA/PFOS occurrence and support expanded analyte suites, seasonal and groundwater monitoring, source apportionment, biomonitoring, and Ghana-specific exposure assessment.