Optimizing the physiological pharmacokinetic model to rank the risks of persistent organic pollutants towards fish on the Tibetan Plateau

Persistent organic pollutants (POPs) could pose adverse risks towards fish in aquatic environments. However, related risk assessments in remote regions are lacking. In this study we investigated three kinds of POPs in four common fish species (n = 62) from high-altitude rivers and lakes on the Tibetan Plateau. The results showed that the lipid weight concentrations of organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and perfluoroalkyl sub-stances (PFAS) in fish muscle followed the order & sigma;13PAHs (24.5-3354 ng/g) > & sigma;11PFAS (2.48-164 ng/g) > & sigma;7OCPs (1.61-82.2 ng/g), which is comparable to that found in other remote regions. The physiologically based pharmacokinetic (PBPK) model was optimized using physiological parameters specific to the sampled Tibetan fish to generate accurate ef-fective concentration (EC) thresholds. Based on these measured concentrations and newly simulated EC thresholds, the ecological risk ratios for selected toxic POPs (dichlorodiphenyltrichloroethane (DDT), pyrene (Pyr), and perfluorooctane sulfonate (PFOS)) ranged from 8.53 x 10-8 to 2.03 x 10-5. Racoma tibetanus and Schizothorax macropogon were the most vulnerable Tibetan fish species. All the risk ratios were far below 1, indicating that there was no risk of POPs to-wards Tibetan fish. However, the risk ratios for emerging POPs (i.e., PFOS) were 2-3 orders of magnitude higher than for legacy POPs (i.e., DDT and Pyr), suggesting that monitoring of emerging POPs should be reinforced. Our study sheds light on the risk assessment of wildlife exposed to POPs in remote regions with limited toxicity data.