Wildland Fire Retardants and Foams in the Megafire Era: Ecotoxicological Risks and a GIS-Based Decision Framework

Increasingly extreme fire weather is expanding the aerial use of fire retardants and firefighting foams, yet their environmental effects rarely inform operational decisions. This review assesses their ecotoxicological risks to forest soils, freshwaters and coastal waters. We synthesized 150 sources from four bibliographic databases (Scopus, Web of Science, PubMed and Google Scholar) and official EFFIS/GWIS datasets, calculated un-ionized ammonia fractions across pH 6.5–9.0 and 10–30 °C, and overlaid Greek burned-area and protected-area data. Ammonium-based retardants act mainly through un-ionized ammonia toxicity and nutrient loading, with effects on fish, cladocerans and amphibian larvae that depend on formulation, temperature, pH and exposure duration. Surfactant-based foams, including fluorine-free replacements for PFAS foams, are often more toxic per unit mass. In soils, retardants raise salinity and nutrients, shift microbial communities and favor weeds. Most evidence comes from cool, circumneutral waters, whereas warm, alkaline Mediterranean streams can raise the un-ionized fraction roughly 14- to 50-fold. In Greece, 29.8% of the area burned in 2016–2026, and 43.5% in 2023, lay within protected areas. A GIS-based framework combining exposure, receptor sensitivity, water chemistry and product hazard into tiered application zones, with safe-by-design criteria for new suppressants, can make application location central to risk management.