Firefighting aqueous film forming foam composition, properties and toxicity: a review

Global warming and urbanization are likely to increase fires in natural and urbanized areas, requiring advanced fire management techniques such as the use of aqueous film forming foams. However, these foams contains in particular toxic fluorinated compounds that belongs to the class of the so-called ‘forever chemicals’. Here we review aqueous film forming foams with focus on classification, film forming, composition, toxicity, and standards. Foams are classified into aqueous film forming foams, alcohol-resistant foams, and fluoroprotein foams. Foams contain hydrocarbon surfactants, fluorosurfactants, organic solvents, and additives such as pH buffers, stabilizers, salts, corrosion inhibitors, and anti-freeze agents. Firefighting foams are aggregates of small bubbles that efficiently combat liquid fuel fires by forming a vapor-suppressing blanket over the fuel surface. Aqueous film forming foams contain 2–15% of stable perfluorinated molecules. Concerning toxicity, perfluorooctanoic acid has a half-life of more than five years in adult humans. Alternative compounds such as perfluorobutane sulfonate has a shorter half-life of 45 days in adult humans, yet its impact on soil and aquatic ecosystems is not fully understood. The proprietary nature of the aqueous film forming foam formulations is a challenge in developing sustainable firefighting foams.