This red retardant is crucial in the fight against wildfires. But is it also harming the environment?

Dropping fire retardant solutions from planes is a crucial strategy in wildfire fighting, but some experts are concerned about their impact on the environment, including aquatic ecosystems.

Once dropped, these retardants leave a rust-coloured or pinkish liquid coating on roads, roofs, and vegetation. This technique, commonly used since the mid 20th century, helps fire crews contain blazes by depriving flames of oxygen, explains Jen Baron, a postdoctoral researcher at the University of British Columbia's Centre for Wildfire Coexistence.

Since 2009, the B.C. Wildfire Service has relied on Phos-Chek LC-95A, a widely used retardant from Perimeter Solutions, a global manufacturer of firefighting products headquartered in the U.S. Its main ingredient, ammonium polyphosphate, is a common fertil