Polycyclic aromatic hydrocarbons in 30 river ecosystems, Taiwan: Sources, and ecological and human health risks

Polycyclic aromatic hydrocarbons (PAHs) are diverse contaminants of global concern because of their ubiquity, toxicity, and carcinogenicity to many organisms, including humans. This study determines the distribution and sources of PAHs in sediments and fish from 30 major rivers in Taiwan, and the risks these PAHs pose to river ecosystems and human health. The total concentrations of 26 PAHs in sediments and fish were 0.016-7.44 mg/kg dw and 0.096-5.51 mg/kg ww, respectively. The PAH composition in sediments differed from that in fish, indicating that sediments may not be the major contributor of PAHs to fish. The accumulation of different PAH compounds in fish was species-specific, depending on the lipid content, living pattern, and trophic level of each fish species, and on the level of environmental contamination. The diagnostic ratios revealed that PAHs in the sediment primarily originated from pyrogenic sources, with some contribution from petrogenic sources. The contribution of each source varied with the sampling site and season. Several water and air quality variables were found to significantly correlate with PAH concentration in sediments and fish, suggesting that PAHs were mainly derived from wastewater discharge and combustion emissions. The 95th percentile risk quotient values suggested that PAHs in sediment from six rivers pose high ecotoxicological risks. The toxic equivalents of benzo[a]pyrene for 16 PAHs in fish were 12-108 μg/kg dw. A human risk assessment using the 95th percentile values of hazard quotient, hazard index, and margin of exposure revealed that the consumption of contaminated fish muscle poses no remarkable risk to human health. However, the 95th percentile carcinogenic risk values indicated that benzo[a]pyrene concentrations in some fish muscles may pose a carcinogenic risk. Benzo[a]pyrene risk management measures are, therefore, necessary.