The February 2021 issue of Environmental Toxicology and Chemistry included a comprehensive review of the literature on bioconcentration factors (BCFs) and bioaccumulation factors (BAFs) for PFAS (Burkhard 2021). The author, Larry Burkhard, is a senior research scientist with the U.S. Environmental Protection Agency’s (EPA) Environmental Effects Research Laboratory in Duluth, Minnesota. The EPA is developing surface water quality criteria (WQC) for PFAS and Burkhard’s work will likely support their development.¹

Data for 22 taxonomic classes were reviewed and the quality of each study was ranked considering evaluation criteria such as adherence to protocols, number of samples, and spatial/temporal coordination of surface water and organism measurements. Data were sufficient to derive BCFs and BAFs for several organism classes including fish, bivalves, and crustaceans for several carboxylic and sulfonic acids and a limited number of other PFAS. Due to the wide range in values, BCFs and BAFs were reported in log scale. The median BCFs and BAFs reported for PFOA and PFOS in whole body and fillet/muscle tissue are summarized below for fish. The article also presents distributions of the BCFs and BAFs, as well as a supplemental data file.

The Burkhard fillet BAF of 1500 L/kg (antilog of 3.18) for PFOS is lower than many of the BAFs currently used by states to derive human health WQC for protection of water and fish consumption. For example, Michigan used BAFs of 2329 and 5047 L/ kg for trophic level (TL) 3 and 4 fish, respectively, to derive its PFOS WQC of 11 ng/L. Minnesota used a BAF of 7210 L/kg to derive its PFOS WQC of 0.05 ng/L. Florida used BAFs of 937 (TL2), 2959 (TL3), and 6304 (TL4) to derive its PFOS WQC of 10 ng/L.

The wide range in BAFs reflects differences in the selected studies, species mix, and the statistic used to represent the dataset. Burkhard’s PFOS fillet BAF of 1500 L/kg is the median of a dataset comprised of roughly 20%, 60%, and 20% of TL 2, TL 3, and TL 4 fish species, respectively. In contrast, Minnesota’s PFOS fillet BAF of 7210 L/kg is the 90th percentile of 22 from different waterbodies and is weighted toward higher trophic level species. The variation in BAFs underscores the importance of the species mix and data quality.

Burkhard’s compilation helps to fill a data gap in our understanding of PFAS bioaccumulation in aquatic biota. For the species commonly consumed by humans (i.e., fish, bivalves, crustaceans), BCF and BAF measurements are available for many of the carboxylic acids (C6 through C10), several sulfonic acids (PFBS, PFHxS, and PFOS), and FOSA. However, data for other PFAS are limited. Studies of marine species are also limited and the question of whether marine species have BAFs greater than, less than, or the same as freshwater species remains a data gap. Burkhard also noted uncertainty in the water concentration – organism uptake relationship, with some PFAS exhibiting lesser uptake at higher concentrations, indicating active transport mechanisms (e.g., renal clearance) and biotransformation along with diffusional processes may affect elimination (Burkhard 2021). In summary, Burkhard’s work provides an important compilation and springboard for further evaluation of PFAS bioaccumulation.

¹BCFs relate the organism’s uptake of a chemical in water while BAFs relate uptake from all aquatic exposures (diet, sediment, and water). BAFs are preferred for the development of numeric WQC (EPA 2017).

AUTHORS

Betsy Ruffle, Senior Scientist

Christine Archer, Senior Ecological Risk Assessor

Heather Loso, Senior Ecological Risk Assessor

Sagar Thakali, PhD, Senior Risk Assessor

REFERENCES

Burkhard, L.P. 2021. Evaluation of Published Bioconcentration Factor (BCF) and Bioaccumulation Factor (BAF) Data for Per‐ and Polyfluoroalkyl Substances Across Aquatic Species. Environmental Chemistry and Toxicology. https://setac.onlinelibrary. wiley.com/doi/full/10.1002/etc.5010 U.S. EPA. 2017. Water Quality Standards Handbook, Chapter 3: Water Quality Criteria. Office of Water, EPA 823 B 17 001.