Human health and ecological risk assessments require data on the levels of contaminants in the both the abiotic and biotic environments. If such data are missing in the biotic environment, it is often possible to derive them, using abiotic concentrations and bioaccumulation factors (BAF).

For many organic contaminants, it is possible to derive BAFs from their octanol-water partitioning coefficient (KOW). However, this method is not suitable for those per- and polyfluoroalkyl substances (PFAS) compounds that are strong acids, such as strong acids in the perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonates (PFSAs) classes of compounds. These perfluoroalkyl acids (PFAAs) typically exist in nature as anionic species and the KOW method is not relevant. Furthermore, as many PFAS bind to proteins rather than to lipids, KOW would not be an appropriate measure of their bioaccumulation potential. Therefore, we derived BAFs using field measurements in a large watershed.

These measurements were used to assess the behaviour of PFAS in the environment and develop an understanding of the main parameters that control the transfer of PFAS from the abiotic to the biotic environment.

In particular, co-located samples of biota tissue and abiotic environmental media were used in the BAF calculations. The BAFs were only calculated for parameters with detected concentration in the abiotic samples (e.g., soil, surface water and sediment). The following biota tissue samples were collected and analyzed for PFCAs C4 to C14 and PFSAs C4, C6, C8 and C10 as well as perfluorooctane sulfonamide (PFOSA):

• Terrestrial plants species: grass, leaves, forage, and berries;
• Terrestrial invertebrates: earthworm;
• Aquatic plants species: cattail, macrophyte and grass;
• Aquatic invertebrate species: benthic and crayfish; and,
• Fish: 10 fish species.

The following BAFs were developed for PFAS parameters: 1) soil to terrestrial plants; 2) soil to earthworms (BAF soil-plants); 3) surface water to fish (BAFfish); 4) sediment to fish (BSAFfish); 5) surface water to aquatic plants; 6) surface water to aquatic invertebrates; and, 7) sediment to aquatic invertebrates.

The main results indicate the following:

The derived BAFs suggest an increasing bioaccumulation potential of PFAS with increasing chain length. This has been a general observation across biological species and confirms previous studies.

For fish, the BAFs were estimated based on both whole fish and fillet analysis, making them useful for ecological and human health risk assessment, respectively. The results indicate significant accumulation of PFAS in internal organs resulting in higher whole-body BAFs compared to fillet.

It was interesting to note that PFSAs generally show a higher bioaccumulation potential than PFCAs.

The results of the current study also confirm previous trends indicating that accumulation of PFOS in large bodied fish are greater than in small fish.

Nava Garisto, National Discipline Leader and a Risk Group Manager, ARCADIS
Dr. Nava Garisto is an internationally recognized risk expert with over 33 years of project experience managing large scale and complex environmental risk projects in Canada, Europe and the USA. Nava has managed human health and ecological risk assessments for a variety of industries and contaminated sites, including PFAS contaminated sites, nuclear generating stations (e.g., Pickering, Darlington, Bruce Power and New Brunswick Power) and fuel refining and manufacturing (e.g., Cameco facilities) and sites of potential future waste disposal, former refineries and municipal works.

The uptake of selected per- and polyfluoroalkyl substances (PFAS) by terrestrial plants and soil invertebrates was evaluated through a sampling program in support of an ecological risk assessment conducted at a former firefighter training area (FFTA). Fire training activities at the assessment location occurred from approximately the early 1960’s to early 1990’s, during which PFAS containing aqueous film forming foam (AFFF) application occurred during all or a portion of the FFTA operational time period and resulted in the present day occurrence of PFAS in a variety of media at the FFTA property, including biological tissues. Risk assessment modelling uncertainty related to tissue uptake of PFAS was reduced by measuring co-located plant-invertebrate-soil sample concentrations of PFAS to identify site specific uptake factors. Soil to tissue bioconcentration factors (BCF) were calculated for soil invertebrates (“earthworms” and “white grubs” consisting of Phyllophaga species) and above ground vegetative portions of plants. BCFs for 13 PFAS, consisting of nine C4 to C12 perfluoroalkyl carboxylic acids (PFCAs) and four C4 to C8 perfluoroalkyl sulfonic acids (PFSAs), including perfluorooctane sulfonamide (PFOSA), were calculated for soil-plant tissue and soil-soil invertebrate sample pairs.

Median dry weight-basis terrestrial plant BCFs exceeded unity, except for perfluorodecanoic acid (PFDA) (C10 PFCA with a BCF of 0.9), and decreased over an approximate 2.8 order of magnitude range from a maximum median BCF associated with perfluorobutanoic acid (PFBA) (C4 PFCA). Similarly, median dry weight-basis plant PFSA BCFs exceeded unity and decreased within an order of magnitude range from perfluorobutane sulfonic acid (PFBS) (C4 PFSA) to perfluorooctane sulfonate (PFOS) (C8 PFSA).

Median dry weight-basis terrestrial invertebrate BCFs exceeded 10. For PFCA, a “U-shaped” median BCF vs. increasing PFCA chain length relationship was identified, with the maximum BCFs associated with perfluoroundecanoic acid (PFUnA) (C10 PFCA) and perfluorododecanoic acid (PFDoA) (C12 PFCA). The median PFSA BCFs decreased with increasing PFSA carbon chain length, with the lowest BCF associated with PFOS.

The PFAS uptake pattern in terrestrial plants and soil invertebrates related to PFAS carbon chain length were similar to literature based associations, although most notably, the site specific BCFs were typically much higher in magnitude than literature based values. This discrepancy may in part be a product of differences in soil properties and initial soil PFAS concentrations at the site relative to literature studies.

These results demonstrate the importance of site specific uptake factor derivation in risk assessment rather than reliance on literature based BCFs when biomagnification modelling is conducted. When calculating a PFAS site specific target level (SSTL) based on literature BCFs, evaluation of the test conditions under which the BCF was derived relative to site conditions, and the applicability of the vegetative compartment used to derive the literature BCF relative to the ingestion route of exposure in the risk assessment require consideration to avoid inadvertently over or underestimating the SSTL.

David Tarnocai, Senior Risk Assessor, SNC-Lavalin Inc.
David Tarnocai, M.Sc., P.Geo., is a Senior Risk Assessor with over 25 years of experience. David is a Qualified Person for conducting Environmental Site Assessments (QPESA) and Risk Assessments (QPRA) in the province of Ontario, Canada. He has extensive expertise in environmental site assessment and remediation, human health and ecological risk assessment (HHERA) and environmental project management. His specific areas of expertise include contaminant hydrogeology, site remediation, HHERA, contract document preparation and tendering related to environmental works. David is experienced in the assessment of both terrestrial and aquatic sites and the assessment and remediation of properties contaminated with various contaminants including perfluoroalkylated substances (PFOS, PFOA and other perfluorocarboxylates and perfluoroalkyl sulfonates). He has evaluated environmental conditions at over 200 sites, including active and former industrial properties (power generation facilities, petroleum packaging facilities, railway facilities), firefighter training areas, explosive ordinance disposal areas, firing ranges, petroleum storage and dispensing facilities (service stations, bulk fuel terminals, airports, trucking facilities, marinas/ports) waste disposal sites, and domestic landfills. David has managed or conducted environmental projects in Canada, the Middle East and South America in environments ranging from high-density urban, desert, tropical jungle and remote northern locations.

In Canada, investigation of per- and polyfluoroalkyl substances (PFAS) to date has largely been focused on fire training areas (specifically those associated with airports and military bases) due to the use of aqueous film-forming foam (AFFF); however, consideration of the presence and potential risks associated with these parameters is now expanding beyond these sites to include assessment in support of waste management (e.g., landfill leachate and biosolids) and brownfield redevelopment. The potential presence of PFAS at brownfield sites has implications for their redevelopment as the means of evaluating the risks associated with these emerging contaminants, and processing the sites through applicable regulatory frameworks, is largely undefined. While research, data, and information are evolving quickly on PFAS toxicology, as well as the fate and transport of these parameters in the environment, regulatory screening values and risk assessment approaches are largely lagging.

This presentation will examine the approach by which human health and ecological risk assessment can be completed for a brownfield site in Ontario at which AFFF was applied during a historic fire. Currently, the brownfield regulation in Ontario does not include guidance or regulatory standards specific to PFAS. The review will outline the screening levels and toxicity values that may be applied to support the assessment of risk, as well as the conceptual human health and ecological exposure models needed to complete risk evaluations. By stepping through the risk assessment process for the site, a viable framework for assessing and addressing PFAS at brownfield sites can be established.

Krista Barfoot, Principal Brownfield Technologist, Jacobs
Dr. Krista Barfoot is a Principal Brownfield Technologist with over 23 years of industry experience. She is a Qualified Person for Risk Assessment under Ontario Regulation 153/04, the Chair of the Ontario Environmental Industry Association (ONEIA) Brownfields Committee, a member of ONEIA’s Excess Soils Sub-Committee, and a Board Member for the Canadian Brownfields Network. Krista’s technical expertise includes human health risk assessment, vapour intrusion, management of excess soil, non-aqueous phase liquid (NAPL), risk mitigation measures, and stakeholder communication. She is actively leading the development of the strategic approach for revitalizing several large, high-profile brownfield sites in Ontario.