Chronic effects and thresholds for estuarine and marine benthic organism exposure to perfluorooctane sulfonic acid (PFOS)-contaminated sediments: Influence of organic carbon and exposure routes

Guideline values for perfluorooctane sulfonic acid (PFOS) in estuarine/marine sediments have been derived based on determinations of water quality guideline values, using data for toxicity to benthic biota, and a consideration of partitioning between sediments and overlying waters. Measured and literature chronic toxicity data for PFOS to 11 benthic estuarine/marine species were used in a species sensitivity distribution yielding 99% and 95% species protection concentrations of 6 and 25 μg PFOS/L respectively. The lowest dissolved PFOS concentrations causing toxicity were 0.28 mg/L (LOEC) to 28-day bivalve growth, 0.49 mg/L to survival and growth of juvenile amphipods, and 1.2 and 0.9 (0.7–1.6) mg/L as a LOEC and EC10 values for 10-day amphipod reproduction, respectively. A strong relationship (Kd) existed for PFOS-partitioning between sediment and overlying water concentrations and organic carbon (0.1 to 5.6% OC), with a Kd range of 16 to 150 L/kg. A conservative Kd value of 10 was used to derive a benthic sediment PC99 screening value of 60 μg/kg PFOS (for 1% OC) representing a low risk to benthic organisms in estuarine/marine environments from direct toxicity and secondary poisoning. No toxicity from PFOS occurred to benthic algae, copepod, or crab species in exposures with 170–180 mg/kg in spiked-sediments and 0.8–2 mg/L in the overlying waters. Toxicity of PFOS to amphipod survival and reproduction occurred and was attributed to dissolved rather than dietary exposure. The derived sediment quality screening value was used to assess a range field-collected sediments. These sediments were dominated by PFOS, with 4–15 μg/kg (1% OC) at estuarine/marine sites, being below the screening value. None of the sediments caused chronic toxicity to benthic algae, amphipod, and copepod tests, where the most highly PFAS-contaminated field-collected sediment had 0.18 mg/kg PFOS and resulted in 0.0014 mg/L PFOS in the overlying waters during tests.