Fire retardant drops kill fish and cause algal blooms but have only 55% success rate

Aerial fire retardant (primarily ammonium phosphate-based Phos-Chek) is dropped on wildfires at a rate of millions of gallons per year. When it lands in or near waterways, the phosphorus triggers algal blooms that deplete dissolved oxygen and kill fish, amphibians, and aquatic invertebrates. A federal judge ruled in 2023 that retardant drops are polluting streams in violation of the Clean Water Act but allowed continued use because there is no viable alternative at scale. Meanwhile, research shows retardant drops intended to halt fire spread succeed only 55% of the time, and drops from Very Large Air Tankers (VLATs) suffer wind scatter at altitude, reducing accuracy further. Firefighters on the ground risk being hit by drops that can deliver thousands of gallons at impact velocities sufficient to cause injury or death. The problem persists because the Forest Service has used the same basic retardant chemistry since the 1960s, environmental review of alternatives is slow, and the political optics of 'doing something' with dramatic air drops override evidence that ground crews and prescribed fire are more cost-effective for most scenarios.