DWER also included screening assessment of PFAS levels in a number of waterways within the footprint of the 2016 Yarloop fires, as part of a larger study investigating the environmental impact of bushfire and fire‑control. PFOS was found in surface water at concentrations ranging between 0.027 and 0.057 micrograms per litre at two upper catchment sites. These sites were in forested catchments above development, but within the footprint of the fire and the area of fire control measures. PFAS were not found in surface waters of reference sites (outside of the fire affected area), or in lower catchment sites with mining, agriculture and peri‑urban land use.

https://www.der.wa.gov.au/images/documents/our-work/community-updates/PFAS/WA_Government_Statement_PFAS.pdf