Per- and polyfluoroalkyl substances (PFASs) are a group of persistent manmade compounds used in aqueous film forming foam (AFFF). The extensive use of AFFF has led to widespread environmental PFAS contamination and exposures of firefighters. Compared to the general population, elevated serum PFAS concentrations have been reported in Australian firefighters where AFFF has been used in the past. There is currently no longitudinal data on the PFAS exposure to firefighters in Australia, and this is what my PhD project aims to provide. We aim to determine the current PFAS serum concentrations in Australian firefighters and investigate trends of PFAS exposure in association with work history. We also estimate the serum elimination half-lives of PFAS and assess associations with potential health outcomes. This will provide information necessary to evaluate the success of attempts to control exposure and provide data important for epidemiological studies and risk assessments.