Per‐ and polyfluoroalkyl substances (PFAS) are highly fluorinated compounds, with a variety of industrial and consumer uses, including stain resistant coatings, plastics, fire‐resistant coatings, and fire‐fighting fluids. PFAS are the active ingredient in aqueous film‐forming foam (AFFF) use to extinguish fuel-based fires. Potential links between the occupational use of AFFF by firefighters and certain negative health outcomes have not been sufficiently studied. As the overall objective of this study is to investigate the influence of PFAS newly identified in AFFF on reproductive health of firefighters, we will fully delineate PFASs composition found in AFFF and use by firefighters during their duties. We intend to characterize the composition of individual PFASs and their precursors in AFFF using unique analytical set up consisting of liquid chromatography-inductively coupled plasma tandem mass spectrom¬etry (LC-ICPMSMS) followed by high resolution mass spectrometry (LC-OrbiTrap -MS). We will perform sampling and analysis of blood and semen in newly recruited group of firefighters after their first exposure to AFFF to monitor the change in concentration levels of the compounds identified in the AFFF and evaluate the relations with fertility parameters (sperm count, morphology, motility), as firefighters are at higher risk to be diagnosed with male infertility. To directly compare in vivo observations and verify our findings we will set up in vitro experiments to elucidate the effects of these compounds on steroidogenesis and spermatogenesis pathways. The proposed interdisciplinary study is a major step in elucidating the role of PFAS originating from AFFF in male reproductive health. Moreover, these findings will also support efforts designed to introduce a more rigorous regulatory framework tackling PFAS collectively rather than on a compound-specific basis.