Seasonal dynamics, source apportionment and human health risks of PCDD/Fs in fish from a freshwater ecosystem

In this study, the concentrations, bioaccumulation/biomagnification dynamics, and potential health risks of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) were determined in Cyprinus carpio and Esox lucius fish species in Lake Uluabat, one of Türkiye's significant wetlands. All PCDD/F determinations were performed on muscle tissue, representing the primary edible portion and the matrix most relevant to human dietary exposure. The mean total PCDD/F concentration in Cyprinus carpio was determined to be 6.97 ± 0.50 pg/g ww, while in Esox lucius it was 10.41 ± 0.59 pg/g ww. The higher concentrations in Esox lucius were attributed to its predatory nature and position at higher trophic levels in the food chain. Concentrations increased from summer to winter, likely associated with increased surface runoff, seasonal changes in fish physiology, and elevated atmospheric pollution in winter. The bioaccumulation factor (BAF) and bioconcentration factor (BCF) values calculated using the EPI Suite showed a significant negative correlation with logKow. The dissolved-phase water concentration estimated from fish data was 0.25-0.28 pg/L with BAF and 54.04-61.18 pg/L with BCF. It has been suggested that BCF may overestimate water concentrations because it does not account for dietary uptake. The calculated tolerable weekly intake (TWI) values were below the European Food Safety Authority's threshold of 2 pg TEQ/kg body weight for adults but approached this threshold for children, indicating a concerning risk from regular consumption. This study highlights the need for source control of pollution, ongoing monitoring programs, and the adoption of locally based risk assessment approaches for consumption to protect public health in critical wetlands such as Lake Uluabat.