Environmental risk limits (ERLs) for individual congeners of polychlorinated biphenyls (PCB 77, 105, 118, 126, 153, 156, 157, and 169) are derived. After lipid normalization, toxicity data for birds, mammals, and aquatic organisms were converted to equivalent concentrations in soil or sediment organic carbon (OC). Accumulation in the food chain was taken into account. Field-derived data on the environmental fate of PCBs, e.g., biomagnification factors and biota-to-sediment accumulation factors, were used in the calculations. The variability in these data was incorporated by using probabilistic techniques. Parameters that are difficult to measure for these hydrophobic compounds, such as the bioconcentration factor or the sediment/water partition coefficient, were avoided where possible. Probability distributions for various species were combined per congener when statistically appropriate; ERLs were based on the fifth percentile of these combined distributions. Congener patterns occurring in various sediments and invertebrates in The Netherlands were used for determining a mixture ERL for non- and mono-ortho PCBs. The PCB 118 was selected as a guiding congener. If the concentration of PCB 118 is less than 5 μg/kg OC, Dutch ecosystems are assumed to be protected for effects of the whole mixture of non- and mono-ortho-substituted PCBs. Concentrations associated with adverse effects in field studies were comparable to concentrations that would result if all congeners would be present at the ERL level.
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