Environmental Monitoring of Perfluoro octane Sulfonate and Perfluorooctanoic Acid in Khanpur Stream, Pakistan: Implications for Human and Ecosystem Health

PFAS are widely used synthetic chemicals that persist in aquatic environments and can accumulate in biota, raising concerns regarding freshwater quality and ecosystem health. Information on PFAS contamination in Pakistani freshwater systems remains limited despite increasing industrialization. This study evaluated the occurrence, distribution patterns, ecological risk, and human health implications of PFOS and PFOA in Khanpur Stream, Sheikhupura, Pakistan, a freshwater source used for irrigation, fisheries, and domestic purposes.

Sample from 32 locations along a 15 km reach of the stream during February and March 2026 following APHA standard procedures. At each site, triplets’ surface and subsurface water samples were collected from depths ranging from 1 to 5 m, resulting in 192 samples. Samples were collected in precleaned glass bottles, concentrated by SPE, and analyzed using LC-MS/MS. Ecological risk was assessed using the risk quotient approach, while noncarcinogenic HHR was evaluated through hazard quotient calculations based on adult drinking water exposure.

PFOS and PFOA were detected in all samples. Surface water concentrations ranged from 10.8 to 36.3 ng/L for PFOS and from 7.8 to 15.2 ng/L for PFOA, whereas subsurface concentrations ranged from 1.7 to 20.4 ng/L and 1.4 to 11.1 ng/L, respectively. Elevated concentrations were consistently observed near paper and pulp industrial zones, while the lowest levels occurred in irrigation dominated areas. ERA indicated that PFOS posed the greatest environmental concern, with risk quotient values ranging from 1.61 to 5.42 in surface waters and from 0.25 to 3.04 in subsurface waters. In contrast, PFOA exhibited low to moderate ER, with RQ values ranging from 0.03 to 0.32. HQ values for both compounds remained below 1, indicating negligible noncarcinogenic risk through direct water consumption. The results identify industrial activities as the primary source of PFAS contamination in Khanpur Stream and highlight PFOS as the dominant contributor to ER within the aquatic environment.