Matt Weiser, KQED SCIENCE
In 2014, scientists at the National Marine Fisheries Service published a study showing that two fire-retardant formulations are deadly to Chinook salmon, even when heavily diluted in streams.
Chemical fire retardants are considered a vital wildland firefighting tool, helping to slow the spread of flames while ground crews move into position. But as their use increases, the harmful side effects of these chemicals are coming under increasing scrutiny.
The chemicals, usually dropped from low-flying aircraft, largely consist of ammonia compounds, which are known toxins to fish and other aquatic life. Studies have shown retardants can kill fish, alter soil chemistry, feed harmful algae blooms and even encourage the spread of invasive plants. Yet there is little regulation of their use, and no safer alternatives on the market.
In California, state firefighting crews have applied 15.3 million gallons of chemical fire retardants so far this year, according to data provided by CalFire, the state’s wildland firefighting agency. That’s a new record, and double the amount used just three years ago.
CalFire applied 2.7 million gallons of retardant in a single one-week period starting October 9 – also a record. Of that amount, about 2 million gallons were used on the North Bay wildfires, which killed 43 people and burned more than 8,000 structures in October as they swept across several counties north of the San Francisco Bay Area, including Sonoma and Napa.