Common firefighting chemicals severely hurt Aussie frog, says study

A new study has found that two commonly used bushfire fighting chemicals – who both markets themselves as environmentally friendly – can kill frogs or severely damage tadpoles’ development.

Although these chemicals are have recently replaced foams containing per- and poly-fluoroalkyl substances (PFASs) – more commonly known as forever chemicals – this new research shows there’s still issues with wildlife.

“There are currently around 15 fire retardants, 15 class A foams and 11 water enhancer formulations approved for bushfire management in Australia,” Griffith University ecotoxicologist Dr Chantal Lanctôt told Cosmos Science.

“We currently know very little about the effects of these formulations on most Australian aquatic taxa, including frogs.”

Researchers from Griffith University in Queensland looked at two firefighting chemicals – Phos-Chek LC95W and BlazeTamer380.

In 2022, Phos-Chek LC-95A was the most used fire retardant in the world. The product is marketed by retailers as “environmentally friendly”, and while Phos-Chek suggests that environmental precautions should be taken, “including preventing entry to sewers and public waters,” it also claims: “They are the safest, most effective, and environmentally friendly products available.“

BLAZETAMER380 has marketed itself as “non-toxic, non-corrosive and environmentally safe” as well as “proven harmless to humans, animals and vegetation”. It’s safety data sheet under “ecotoxicity” says: “Anionic polyacrylamide has no systemic toxicity to aquatic organisms or micro-organisms.”

The direct application of these chemicals into aquatic systems is prohibited, but according to the researchers “the contamination of aquatic habitats can occur through runoff, spills, dumping, or the unintentional application of firefighting chemicals over small waterbodies.”

The researchers looked at one specific Australian frog – the striped marsh frog (Limodynastes peronii).

They exposed 60 striped marsh frog tadpoles to either a control (no chemicals), or between 0.05 and 1 gram per litre of the firefighting solutions for 16 days. This was classed as either ‘high’ or ‘low’ exposure to the chemicals. 

The team found that both chemicals (in high or low concentrations) reduced tadpoles’ growth.

Growth for tadpoles exposed to BlazeTamer were 1.8 to 4.8 times lower compared to the controls, while both low and high Phos-Chek dilutions completely halted tadpole growth and development.

High concentration of Phos-Chek actually caused the death of most of the tadpoles in the experiment, with only 8% surviving the entire 16 days.

“We found that both formulations significantly delayed tadpole growth and development,” Lanctôt told Cosmos Science.

“Overall, our results show that application of the chemicals in and around small waterbodies (either via deliberate application, runoff or accidental spills) may have important ramifications for amphibians that breed and develop in these habitats.”

The chemicals can be used to build fire breaks in advance of fires, as well as dousing bushfires. Phos-Chek is used for deployment ahead of fires, while BlazeTamer is used as a fire suppressant during an active fire.

Although the researchers have only done this on one type of frog, the team think it’s ‘highly possible’ that other species of frogs will be affected in similar ways. The work is ongoing.

Of course, without these firefighting chemicals, many animals – including frogs – would be at risk from bushfires. However, finding chemicals that are both effective at stopping fires and not harmful for the animals they’re trying to protect is also important.

“Frogs are of particular concern because they’re subject to multiple threats. They are the fastest declining group of vertebrate animals globally, at least partly due to a disease caused by frog chytrid fungus,” Lanctôt told Cosmos Science.

“Understanding the impacts of these chemicals on Australian frogs, especially those already threatened by disease, will help inform adaptive management and conservation efforts to protect frogs threatened by disease and bushfires from extinction.” The research has been published in Aquatic Toxicology.