https://www.documentcloud.org/documents/3960562-201707181651.htmlWith more than 700 wildfires burning through British Columbia's forests since this spring, environmental experts fear the rising use of chemical fire retardants may put wild fish at risk.

The red plumes of the ammonia compound are a critical tool in aerial fire fighting, and it's expected to be needed more in coming decades if climate change causes more wildfires, according to B.C.'s Wildfire Management Branch.

The B.C. Wildfire Service says air tankers have already dropped eight million litres of retardant. That's a lot, considering the yearly average in the province is 9.4 million litres over the course of the entire wildfire season.

And B.C. pilots say sometimes it's accidentally dropped into streams and lakes.

While the fire retardant used in Canada is deemed safe for humans and animals — even if it's accidentally ingested — there is one exception outlined in product literature.

Ammonia compounds, which are an ingredient in fire retardant used in Canada, can kill aquatic life if they're not diluted or if it they aren't flushed out by moving water.

"The worst scenario would be a small static pond and a direct hit with an aircraft drop," says a product information sheet.

This concerns environmental advocates who say the fire retardant, which contains liquid fertilizer, can be toxic to fish in water.

This car was left in an area behind the Sage and Sands Trailer Park in Cache Creek, B.C. during the Elephant Hill wildfire. (Lien Yeung/CBC)

"Even with dilution in a river or a stream it can reach acutely toxic levels." said environmental engineer Joseph Dietrich of the National Oceanic and Atmospheric Administration (NOAA) in Oregon.

A 2014 NOAA study exposed fish to fire retardant chemicals for 96 hours. The study showed the chemicals can weaken or kill fish. They are especially toxic to smolting Chinook fry, which can die when they later enter sea water.

While an exposure this long is unlikely in running water, the risk of retardant hitting still water or getting stuck in an eddy increases the more it's used, Dietrich said.

However, it's not clear if the U.S. studies are comparable to the exposures and concentrations of the chemicals used in B .C.

While the U.S. Forest Service is studying the effects of wash-off into creeks and watersheds, it is clear current products are safer than in the past. Decades ago, formulations included cyanide, but that was stopped.

B.C. Wildfire crews drop red fire retardant close to homes burning in Lake Country, B.C. 0:25

Aiming for forest and grass

In Canada, most fire retardant that's dropped from the air is one of the various formulations branded as Phos-Chek, and overall it's deemed safe.

Once mixed, Phos-Chek LC95A contains about 85 per cent water and 15 per cent liquid fertilizer, which is made up of ammonia compounds, plus small amounts of clay, food-grade thickener and iron oxide for a bright red colour.

The red hue helps pilots aim strategic lines of chemical fireguard to slow fires and buy ground crews time. The thickener makes the retardant splat instead of blowing away.

In. B.C., most retardant lands on forest because it's most effective on fresh vegetation such as grass or trees. And pilots are careful to follow provincial guidelines, which follow U.S. standards to keep retardant at least 100 metres from any waterway.

But sometimes, they have no choice.

If wind or error causes the pilot to drop sprays beyond the target's perimeter or hit non-targeted bodies of water or houses, the incidents are reported.

This garden gnome was covered by red fire retardant at a B.C. home during the wildfires of 2017. (Lien Yeung/CBC)

'Better red than black'

Despite the concern expressed by Dietrich, many agree that fire retardants are crucial in B.C. where wildfires are a growing concern.

As for the splatter people find on their homes and cars, once dry, it's tough to remove, leaving a faded red stain. But in the face of fire many feel the risk is worth it.

Fred and Sylvia Gerwien returned to their Cache Creek, B.C., home after a wildfire evacuation to find windows and walls painted red with fire retardant, but expressed relief their house was not charred or worse.

"Better red than black," said Gerwien, a long-time fire-zone resident.

Fred and Sylvia Gerwien take the red coating all over their home and yard in stride. At least their Cache Creek B.C. home didn't burn, they say. (Gilbert Rowan/CBC)

Don MacKay, environmental health and safety manager for ICL Performance Products, the company that makes Phos-Chek, says it is safe, biodegradable and can be removed with soap and water.

When told of the NOAA studies that showed that retardant ingredients may harm fish, MacKay replied that the product is low risk.

"There is virtually almost no risk. It's very, very low risk," he said

He said the U.S. Department of Agriculture has tested the retardant on wildlife, aquatic life, vegetation, people and pets. He said the material is "just water-soluble fertilizer."

House in hills outside Cache Creek B.C. that was coated with fire retardant. (Gilbert Rowan/CBC)

In B.C. the scarlet plume is likely to remain a critical tool for fighting wildfires for the foreseeable future.

Michael Benson, superintendent of provincial air tanker operations said the retardant is widely used because it is efficient at halting wildfires.

Benson is aware that studies have shown that the material can be toxic to fish, and said it must be deployed judiciously.

He predicts there will be a market in the future for more environmentally-friendly retardants so it's no longer a choice between slowing a fire and potentially harming fish.