The bushfire smoke that enveloped the Canberra region over summer was so hazardous it killed a group of critically endangered native mice held in a breeding program more than 50 kilometres away from the fires.

Key points: Nine mice from the smoky mouse species, native to Australia, are the first animals to die due to bushfire smoke inhalation

Nine mice from the smoky mouse species, native to Australia, are the first animals to die due to bushfire smoke inhalation The mice were in a breeding program outside Canberra, 50 kilometres from the nearest fire

The mice were in a breeding program outside Canberra, 50 kilometres from the nearest fire The mice typically live in small, fragmented populations in Victoria, New South Wales and the Australian Capital Territory

The native Australian smoky mouse — so called because of their grey-tinged fur — has become the first recorded species to be killed because of bushfire smoke, researchers from Charles Sturt University (CSU) have found.

Nine mice, held at the Priam Psittaculture Centre's captive breeding facility near Canberra, died in the days following the first wave of hazardous smoke in January.

That same smoke saw Canberra's air quality deemed among the world's worst, and some national institutions, government departments and businesses temporarily close their doors. Canberra was surrounded by bushfires to the south, east and west for much of January.

"The bushfire that was producing the smoke that killed these animals would have been more than 50 kilometres away from the site," Dr Andrew Peters, an associate professor in wildlife health and pathology at CSU, told ABC Radio.

"This is the smoke that rolled over Canberra on New Year's Day and again four days later, so it gives you an idea just how hazardous that smoke was."

Parliament House in Canberra was surrounded by smoke from the NSW bushfires. ( ABC News: Penny Travers )

The mice started to die from "severe lung disease" three days after the bushfire smoke emerged. Large amounts of microscopic PM2.5 particles, which bushfire smoke produces, were found in their lungs.

"In the lungs of these mice we could actually see the smoke particles themselves," Dr Peters said.

"They were really abundant inside the lung tissue and surrounding that area we had lots of and lots of disease associated with smoke particles. It's exactly what we see in experimental cases of smoke inhalation."

The remaining smoky mice died days later from respiratory failure, when outside temperatures soared.

"There were other smoky mice that hung on despite their sickness, and it was only when temperatures spiked over 40 degrees Celsius that they were under enough stress to die from respiratory failure," Dr Peters said.

Findings mean wildlife toll could be much higher

Despite the smoky mouse population being in a breeding facility like this one, nine mice died after inhaling bushfire smoke. ( ABC News: Greg Nelson )

The CSU findings were submitted to the Journal of Wildlife Diseases, and are the first scientific reports of bushfire smoke causing wildlife deaths away from the burn zones.

"It's quite rare to actually have so much evidence that smoke can directly kill wildlife," Dr Peters said, suggesting the estimate that one billion animals died in the bushfires — already thought to be a conservative number — could be even bigger once smoke was taken into account.

"It would be really great to go in and see what the impact on wildlife populations are, but one of the problems is that most of the animals that would have been affected would have died by now, and their bodies would have been scavenged.

"Now that we know bushfire smoke can kill wildlife at large distances from the fires, it's possible wildlife have been impacted across far greater areas of Australia than previously thought."

The effect of bushfire smoke on other small animals is an area Dr Peters has pegged for further research, and not only because "Australia already has one of the worst track records in the world for small mammal extinctions".

"Birds are less likely to be impacted by smoke, we believe, because of the way their lungs are structured," he said.

"But certainly small mammals are likely to be the worst impacted … things like mountain pygmy possums and gliders.

"Before now, we've assumed this impact to be from the fires themselves, but now we know smoke is a potentially significant cause."

The smoky mouse is a critically endangered species. ( Photo supplied by Parks Victoria )

Dr Peters also said the smoky mouse deaths could have significance for how smoke affects human bodies.

"It's a real eye-opener to just how hazardous the smoke that we've been breathing in south-eastern Australia is," Dr Peters said.

"Because we will also have those smoke particles being laid down in our lungs with every breath that we take of this extremely hazardous bushfire smoke.

"It just shows you how little we know of the landscape impacts of bushfires of this scale."