Water safety after fires

[95389]

There have been many fires in the Sierra recently. Using chemicals is part of fire fighting. Can these chemicals contaminate the water and or the soil? Does this pose any risks to backpackers, hikers, and fishermen?

[rlown]

https://en.wikipedia.org/wiki/Fire_retardant

One has to draw their own conclusions.

[dave54]

The red fire retardant is mostly ammonia phosphate or ammonia sulfate (2 different manufacturers). These are basically the same chemicals used in home fire extinguishers, and also are fertilizers. The red color is iron oxide dye added for visibility. A plant based gum thickener is added to increase viscosity. A few other chemicals in very small amounts as stabilizers, increase shelf life, etc. None are toxic.

Any new formulation is tested and approved by the research branch of the Forest Service before use. Testing includes fire effectiveness and environmental/health effects. Not 100% benign, but not a significant health risk.

The stuff is toxic to aquatic life -- fish, invertebrates, etc. The fire agencies know this, and efforts are made to minimize dropping into lakes and streams if not necessary. Still, some drift does go into waterways. These are noted and monitoring is part of the post-fire rehabilitation and recovery plans. Many of the air tanker pilots are cropdusters in the off season. As cropdusters, they have all the state certifications for pesticide applications and use. They usually know more about drift rates and soil half-lifes than their critics.

Not a health concern. Streams will flush and dilute any residue quickly. Small lakes and tarns could get some level of concern, but I doubt the level would ever rise to impact a human stomach.

[Jimr]

Being Nitrogen based fertilizers, you'd think that any body of water like a lake that truly took a hit would start showing signs of a green hue.

[balzaccom]

Avoid yellow snow and orange lakes.

[95389]

Thank you for all your answers.