Formatted Title:

Per- and Polyfluoroalkyl Substances (PFAS) Whole Sediment Toxicity

Background/Objectives:

Per- and polyfluoroalkyl substances (PFAS) have been detected in sediments and surface waters of Michigan and are a risk to aquatic life. The Michigan Department of Environment, Great Lakes, and Energy (EGLE) currently has surface water values protective of aquatic life and human health for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). However, data are not currently available to estimate PFAS sediment screening values protective of aquatic life. The purpose of this work was to perform field and laboratory studies to produce data that will facilitate the determination of PFAS sediment screening values and potentially sediment quality guidelines protective of aquatic life.

Approach/Activities:

Sediment and surface water samples were collected and analyzed for physical and chemical characteristics and whole sediment toxicity with sediment samples collected from six PFAS impacted areas in Michigan. A suite of 36 PFAS compounds (including PFOS) were measured in each collected sediment and surface water sample and 10 PFAS compounds in sediment porewater. Whole sediment toxicity tests were completed with sediment characterized by varying physical properties and at varying PFAS concentrations with each test organism. Hyalella azteca (H. azteca) and Chironomus dilutus (C. dilutus) were used to assess acute and chronic toxicity following written standard operating procedures (SOPs) which are based on the procedures outlined in U.S. EPA Method (EPA/600/R-99/064) Methods for Measuring the Toxicity and Bioaccumulation of Sediment-Associated Contaminants with Freshwater Invertebrates, Second Edition and American Society for Testing and Materials (ASTM) 1706-95B, Standard Test Methods for Measuring the Toxicity of Sediment Associated Contaminants with Freshwater Invertebrates. The survival and growth data for C. dilutus and H. azteca for each investigative sample were compared statistically (p= 0.05) to the corresponding site-specific reference sediment sample.

Results/Lessons Learned:

Neither H. azteca nor C. dilutus survival was significantly affected in either of the acute (10-day) or chronic (20-day C. dilutus and 28-day H. azteca) whole sediment toxicity tests with any sediment sample. However, H. azteca and C. dilutus growth was significantly affected in the acute (10-day) and chronic (20-day C. dilutus and 28-day H. azteca) whole sediment toxicity tests with the sediment samples.

Sediment threshold effect concentrations were exceeded for several metals, PAHs and total PCBs at some locations. Although there was measurable sublethal toxicity measured in five of the six whole sediment samples, effects on H. azteca and C. dilutus growth could not be attributed solely to PFAS compounds with three of the five sites, but rather due to a mixture of metals and PAHs that exceeded published Sediment Quality Guidelines and PFAS compounds. The concentration of total PFAS in whole sediment and in sediment porewater with those samples was not great enough to attribute the toxicity to PFAS compounds, yet the effect of PFAS, PAH and metal mixtures is largely unknown. Two of the six locations were relatively free of other contaminants and exhibited the greatest PFAS concentrations, the greatest porewater PFAS concentration and surface water concentrations.

These data support our conclusions that PFAS/PFOS compounds solely contributed toxicity in two of the six sediment samples. Collectively, these data also suggest, based on whole sediment toxicity test results and measured PFAS concentrations, that adverse ecological effects on freshwater invertebrates may be expected at organic carbon normalized PFAS concentrations between 999 µg/Kg-oc and 1,559 µg/Kg-oc. PFOS was the dominant PFAS compound measured in sediment and sediment porewater, thus the most likely contributor to whole sediment toxicity.

Mailee Garton

Affiliation

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Per- and Polyfluoroalkyl Substances (PFAS) Whole Sediment Toxicity