Project Summary/Abstract This project will undertake the analysis of bioaccumulation of PFAS at the entry level for food-chain, focusing on freshwater insects. The project will explore the relationship between freshwater insects? taxonomic groups and various PFAS compounds. The research focus will be placed on the following taxa: Ephemeroptera, Plecoptera, Trichoptera and Odonata. These insects encompass a variety of trophic functions, which reflect different exposure levels and uptake pathways of contaminants. These insects feeding types cover carnivores, omnivores, detritivores (fine detritivores, coarse detritivores) and periphytivores. These taxa are near the base of the trophic chain and constitute the gateway to chemical biomagnification throughout the food web. They are also of low mobility, which allows the characterization of sites relative to pollution load. Also, given these taxa are commonly used in biomonitoring, this study will evaluate their potential use as bioindicators for PFAS contamination. Specifically, this project will analyze how the concentration of PFAS varies within and among freshwater insects? taxa and the relationship between aquatic insect taxonomic and trophic groups and concentration of PFAS. The relationship of freshwater insects? diversity and PFAS compounds and concentration in water will also be examined. Additionally, the bioaccumulation factors (BAFs), the ratio of PFAS concentration in insects to that in water, will be calculated. The BAFs will be mapped on the insect phylogeny and trophic trees to understand better these relationships. Finally, this study will provide an understanding on whether novel PFAS that continue to be used and released into the environment are equally environmentally persistent and toxic as the phased-out compounds (PFOA, PFOS among others). This will pioneer and evoke further predictions on the effects of such emerging organic pollutants in freshwater ecosystems and potential public health threats. This project will further inform regulation on PFAS and conservation of freshwater ecosystems in the U.S. This project will leverage the passive samplers developed by URI-STEEP Project 4. It also aligns with the overall goals of STEEP Project 4, by investigating the presence of PFAS, and their bioaccumulation in biota. The project will critical to support the characterization of PFAS sources and determining human health risks in relation to contaminated waterways and bioaccumulation in aquatic biota, case of insects.