US federal Department of the Interior Opinion suggests wildfire chemicals have limited impacts on ecosystems and species. The revised opinion, based on extensive consultation, updates previous documents and specifically considers a significant number of threated plant, animal and insect species. The wildfire fire retardant chemicals used for some fifty years now are nearly all phosphorus- or phosphorus and ammonium- based, with some magnesium and chloride salts. The Opinion concludes that, as used to fight wildfires, these chemicals are not likely to jeopardise survival of the species considered nor adversely modify the critical habitats considered. Action will continue to limit applications susceptible to impact protected species or habitats and to monitor impacts in the field. Wildfire retardant chemicals are subject to specific approval protocols, for example France CEREN CCTP2010, Spain UNE 23.530 (both accepted in several Mediterranean countries), US Forest Service Specification FS 5100-304d (valid also in Australia, New Zealand).
“2023 Revised Final Biological Opinion for the U.S. Forest Service Programmatic Nationwide Aerial Application of Fire Retardant on National Forest System Land”, United States Department of the Interior, Fish and Wildlife Service, 13 February 2023 https://www.fs.usda.gov/sites/default/files/2023-02/Fire-Retardant-FWS-Biological-Op.pdf