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Zebrafish Toxicity Thresholds for PFOS and Implications for the Protection of Aquatic Life
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Multiple environmental agencies have promulgated perfluorooctane sulfonate (PFOS) criteria for the protection of aquatic life.

In prior work, we have noted that a single threshold value (0.6 µg/L) for zebrafish (Dario rerio) exerts a strong influence on freshwater species protection levels developed by the Environmental Protection Authority of Victoria, Australia.  The study from which the 0.6 µg/L value was derived was limited in scope, featuring only 3 PFOS dose levels and only 2 replicates per dose.  The value was also more than 10X less than the next-lowest toxicity value in the criteria-derivation dataset and led to a 99% protection level of 0.00023 µg/L, more than 1000X lower than screening values put forth by other regulatory agencies.  Given the potential influence of this study result on PFOS aquatic life criteria, the US Army Corps of Engineers Environmental Research & Development Center and the Sediment Management Work Group partnered (with oversight by the US Environmental Protection Agency) to repeat the evaluation of the effects of PFOS to multiple generations of zebrafish with a more robust experimental design.  Based on results with the parent generation (lethality, length, and body mass data measured 60, 90, and 180 days post fertilization (dpf) and the total number of viable eggs produced over the last 8 weeks of exposure), the strongest evidence of dose-dependent, potential ecologically significant effects was noted for the 100 µg/L level (highest dose level evaluated).  This level indicated minor, but not statistically significant, 14% lethality (relative to controls) at 180 dpf and a statistically significant 21% effect on body mass at 60 dpf (but not 90 or 180 dpf).  Minor (3-4%) statistically significant effects on length in male fish (but not female fish) were noted for the 20 and 100 µg/L dose levels, although this level of response does not reflect ecologically significant effects.  Importantly, reproduction was unaffected at all exposure levels.  While the study is on-going, preliminary results indicate the threshold for ecologically significant effects on zebrafish survival, growth, and reproduction is 100 µg/L or higher, and not 0.6 µg/L.  The 99% species protection level calculated using this potential threshold value of 100 µg/L would result in a protection value of 1.3 µg/L, as opposed to the current protection value of 0.00023 µg/L.  Additional results from the study will be forthcoming.

Publication Summary

  • Geosyntec Authors: Jennifer Arblaster, Jason Conder
  • All Authors: Jennifer Arblaster, Jason Conder
  • Title: RPIC 2021
  • Event or Publication: Event
  • Practice Areas: Contaminated Site Assessment and Cleanup
  • Citation: Geosyntec, Savron (a Geosyntec company), and SiREM (a Geosyntec company practitioners will present virtually at the Workshop from November 15-18, 2021.
  • Date: November 15-18, 2021
  • Location: Online
  • Publication Type: Platform Presentation