Metals and PFAS concentrations in aquatic environments and fish of the Brooks Range, Alaska

In Alaska, fish are an important subsistence resource for Indigenous and rural residents. Additionally, they can serve as bioindicators that respond to ecosystem changes. Resource development, such as mining, and climate change-impacted natural phenomena like permafrost thaw can introduce contaminants into aquatic systems. Consequently, quantification of contaminant concentrations in aquatic media is needed to track ecosystem and fish health in order to characterize current conditions and identify potential threats. To address gaps in fish contaminant data in northern Alaska, we assessed metals and per- and polyfluoroalkyl substances (PFAS) concentrations in waterbodies along the Dalton Highway associated with a 2026 land use change, and in three rivers of the western Brooks Range potentially affected by the proposed Ambler Road. Metal concentrations in aquatic media were not substantially elevated at most sites. In fish muscle tissue, mercury levels were largely below thresholds for consumption advice except for a subset of large-bodied individuals. PFAS were either not detected, or at trace concentrations (< 3 µg/kg) in most fish. However, perfluorooctanesulfonic acid (PFOS) was elevated in fish at one lake along the Dalton Highway near industrial infrastructure, with maximum observed concentrations reaching thresholds that would trigger further investigation or consumption advisories in at least 45 other US states and countries. Given the possible health implications for people and fish from PFAS exposure, we recommend further investigation of this site and similar industrial infrastructure outposts throughout Alaska, as well as call for PFAS fish consumption guidance to be formalized at the Alaska and US federal level.