Professor in respiratory biology at the University of Technology in Sydney, Brian Oliver, said more research was needed to determine the medium and long-term health effects of bushfire smoke inundating Canberra and other parts of Australia the past few months.

"We don't know a whole lot," he said.

"People being exposed to bushfire smoke for more than one or two days is a whole new phenomena."

Read more: Australians urged to visit 'Huskisson over Hawaii' as coast gets the all clear

He said the effectiveness of protective gear like P2 masks was not fully known, and they had to be fitted perfectly to work.

He said he believed P1 masks, while more difficult to get, would be more effective. "But my feeling is some smoke mask is better than no smoke mask," he said.

It comes as Canberra Hospital says it has had about 120 respiratory presentations to its emergency department since December 31, likely attributed to the smoke.

Professor Oliver said if a major population health study of people exposed to the smoke was undertaken, the results would not be known for 10 to 20 years. "By the time you can measure, the horse has already bolted," he said.

He said a shorter term solution could be to experiment on cells to try to predict what the medium and longer term health effects would be. But professor Oliver said the research from countries with pollution from biomass smoke suggested there were serious long term effects from smoke.

"It causes very similar diseases to if you were smoking cigarettes," he said. "We have to work out how similar the bushfires are (to biomass smoke)."

He said wood smoke contained chemicals that could be carcinogens, but said different forests produced different fumes.

While it appeared bushfire smoke could cause cancer, it would likely take 20 or 30 years of exposure to do so, he said.

At the worst periods of smoke haze within Canberra, air quality rankings deemed it to have the most hazardous air pollution in the world. Professor Oliver said while the smoke was a different kind of pollution to those seen in places like China and India, each provided their own risks.

"Sometimes the pollution in Delhi is caused by crops burning and other times it's due to traffic pollution," he said.

"I think the air quality index is a good gauge to work out where are you most likely to have serious health effects."

So when Canberra was ranked higher than somewhere like Delhi, it gave a good indication that the health effects in Canberra were also worse.

Professor Oliver said a US study of air quality in China showed that every 20 units of PM2.5 particulate matter (like that seen in Canberra) was equivalent to smoking one cigarette.

"If you've only got only day's worth of exposure it's not going to have a big influence in the scheme of your life." he said.

"But now people have had two or three months of exposure there would be measurable health effects in the future."