Emerging Contaminants Summit

Spring 2020

larsonEmily Larson
Geosyntec Consultants 

Emily Larson has over 7 years of consulting experience modeling the bioaccumulation of semivolatile compounds and metals in ecological systems, modeling exposure to human and ecological receptors and preparing human health and ecological risk assessments. Emily also has environmental field experience including sampling soil, surface water, groundwater, and vegetation, and has participated in a multi-year fish population study. Emily has experience with Superfund (CERCLA) as well as several state led programs specifically in the Inter Mountain West and Pacific Northwest regions. She has worked with several different clients in both the private and the public (state and federal) sector. Ms. Larson has provided support on projects evaluating the risks associated with dibenzo-p-dioxin (dioxin) and dibenzofuran (furan) in soil, sediments, and surface water. Emily’s current research focuses on evaluating avian exposure through an ecological risk model to seven prominent perfluorinated compounds using data from five Aqueous Film Forming Foam (AFFF) sites.




Modeling Avian Exposures to Perfluoroalkyl Substances in Aquatic Habitats Impacted by Historical Aqueous Film Forming Foam Releases

Releases of Perfluoroalkyl and Polyfluoroalkyl Substances (PFASs) associated with Aqueous Film Forming Foams (AFFFs) have the potential to impact on-site and downgradient aquatic habitats.  Dietary exposures of aquatic-dependent birds were modeled for seven PFASs (PFHxA, PFOA, PFNA, PFDA, PFHxS, PFOS, and PFDS) using five different scenarios based on measurements of PFASs obtained from five investigations of sites historically-impacted by AFFF.  Exposure modeling was conducted for four avian receptors representing various avian feeding guilds: lesser scaup (Aythya affinis), spotted sandpiper (Actitis macularia), great blue heron (Ardea herodias), and osprey (Pandion haliaetus).  For the receptor predicted to receive the highest PFAS exposure (spotted sandpiper), model-predicted exposure to PFOS exceeded a laboratory-based, No Observed Adverse Effect Level exposure benchmark in three of the five model scenarios, confirming that risks to aquatic-dependent avian wildlife should be considered for investigations of historic AFFF releases.  Perfluoroalkyl sulfonic acids (PFHxS, PFOS, and PFDS) represented 94% (on average) of total PFAS exposures due to their prevalence in historical AFFF formulations, and increased bioaccumulation in aquatic prey items and partitioning to aquatic sediment relative to perfluoroalkyl carboxylic acids.  Sediment-associated PFASs (rather than water-associated PFASs) were the source of the highest predicted PFAS exposures, and are likely to be very important for understanding and managing AFFF site-specific ecological risks.  Additional considerations for research needs and site-specific ecological risk assessments are discussed with the goal of optimizing ecological risk-based decision making at AFFF sites and prioritizing research needs


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