Part 1: Cause and effect
Every year, approximately 195,000 Australians set aside their usual lives to keep us safe during fire season, volunteering with our six state and two territory bushfire services. As climate change makes bushfires more frequent and intense, these firefighters and support staff are being pushed to the extreme.
The flames aren’t the only danger – bushfire smoke contains high levels of hazardous air pollutants, which have been shown by many studies to affect human health.
Just last year, researchers realised that the health impacts of the terrifying Black Summer of 2019–20 were more extensive than previously thought. They found undocumented health problems – from coughing to eye and throat irritation to anxiety and depression – among the general population of Canberra, which was choked with bushfire smoke for weeks on end.
This raises the question: how do bushfires affect the health of firefighters on the frontlines, who are often most severely exposed? How are we studying the health risks they face?
How can bushfires harm our health?
The immediate physical risk of a fire is obvious, but smoke poses a more insidious threat.
The danger of smoke is in the detail: the small specks of fine particulate matter, and in particular pieces with a diameter of 2.5 micrometres or less (a few thousandths of a millimetre). Referred to as PM 2.5, these are so small that they can get into the lungs and bloodstream.
These are present in low concentrations in almost all air we breathe, and in higher concentration in polluted or smoky air. But not all particulate matter is created equal.
“The sort of mix that you get in a bushfire or a coal mine fire is different to what you get in what’s called urban background air pollution, which is mostly generated by motor vehicles and industry, and in particular contains heavy metals,” explains Professor Michael Abramson, an epidemiologist from Monash University.
“The common element in both sorts of particles are the polycyclic aromatic hydrocarbons. These are known to be carcinogenic – the International Agency for Research in Cancer has classified air pollution as a class one carcinogen.”
The surrounding community was showered in smoke and ash for 45 days until the fire was finally extinguished.
Abramson is the Principal Investigator of the Hazelwood Health Study, one of the only studies to examine the long-term health effects of smoke from a landscape fire. In particular, it’s looking to detect an excess of cancers in people exposed to the Hazelwood coal mine fire.
In 2014, after a bushfire hit the mine in Victoria’s Latrobe Valley, it started to burn and didn’t stop. The surrounding community was showered in smoke and ash for 45 days until the fire was finally extinguished.
A study was rapidly commissioned to find out the health effects of this prolonged smoke on the local towns. Residents’ health was compared to people in a town 50 kilometres down the road, which hadn’t been affected by the smoke.
Abramson says that the study has already made it clear that exposure to smoke affected people’s respiratory health.
“We’ve found worse asthma control; we’ve found evidence of chronic obstructive pulmonary disease, or COPD; we’ve found changes in lung mechanics – that is, the people who were exposed have less stretchy lungs, equivalent to having aged several years, just from their exposure to the smoke,” he says.
Researchers still don’t know the full long-term effects; the study is ongoing.
They also looked at cardiovascular health and found that the smoke didn’t have as much of an effect on heart attacks or strokes as they initially thought, but there were significant psychological effects.
Many questions remain unanswered – including whether smoke exposure is linked to an increased risk of cancer.
“We will eventually know whether there was or wasn’t an excess of cancer associated with the fire and smoke, [but] those cancers have very long latency,” Abramson says. “You wouldn’t expect to see it within five years or even 10 years.”
This study is producing results that are also relevant to the impacts of bushfires, as coal mine fires and bushfires create smoke with similar compositions.
“Broadly speaking, they [both] fit in a class we call landscape fires, and we’re going to have a lot more of those,” Abramson says. “Cities like Canberra, Sydney and Melbourne were exposed to high concentrations for weeks as a consequence of the Black Summer bushfires. I think our findings are going to be relevant more broadly than just this particular community and the Latrobe Valley.
“And in future, I fear everybody’s going to be exposed at some point.”
“We’ve found worse asthma control; we’ve found evidence of chronic obstructive pulmonary disease; we’ve found changes in lung mechanics.”
Michael Abramson, Monash University
Although the Hazelwood study has many transferrable lessons, its main focus is not firefighters – it’s the entire community.
“In fact, this is my regret,” Abramson reflects. “The most exposed people were professional and volunteer firefighters, who were in the mine for 45 days. We know that on the first couple of days they had to be very careful with work practices because they were getting high concentrations of carbon monoxide, so they had to rotate people more frequently and so on.”
Recognising this, he and his team called for a specific study on firefighters during an inquiry set up by the Victorian government.
“They appointed some consultants who ran their cost-benefit analysis over it and said any possible benefit would be outweighed by costs, and the government said, ‘Thank you very much, we’re not going to do the study on firefighters’,” Abramson says. “So that’s my regret.”
The Australian Firefighters’ Health Study
A decade ago, the International Agency for Research on Cancer (IARC) published a monograph acknowledging that firefighting comes with a risk of exposure to carcinogens. This drew on international studies that found excesses of certain types of cancers in firefighters.
“That came out in 2010 and that, I think, was what prompted some of our epidemiological research on firefighters in this country,” says Associate Professor Deborah Glass, from Monash University.
In 2011, the Australasian Fire and Emergency Service Authorities Council (AFAC) commissioned Monash’s School of Public Health and Preventive Medicine to investigate cancer, mortality and other possible health impacts in Australian firefighters. Called the Australian Firefighters’ Health Study, it was the first large-scale study of its kind in the country.
Glass headed up the team, which was given names and job histories from the personnel records of the majority of fire agencies around Australia. The records ranged from 1976 to 2003 and included 18,032 full-time, 13,701 part-time, and 201,056 volunteer firefighters.
“Our study was one of the first and I think only one that really looked at volunteers,” Glass says.
By linking the personnel records to the Australian Cancer Database and the National Death Index, the team could find the rates of cancers (overall and specific cancers) and the death rates of firefighters, and then compare them to the general population.
Firefighting comes with a risk of exposure to carcinogens.
Crucially, they looked at cancer incidence and death rates among different types of firefighters, separately analysing the data about full-time career, part-time paid, and volunteer firefighters – something that most previous studies hadn’t done.
Released in a final report in November 2014, the results found that the overall mortality risk for firefighters (paid and volunteer) was decreased by 30% compared to the general population. Causes of death like heart or lung diseases were also lower than expected.
Glass explains that these results likely stem from the “healthy worker effect”.
“You almost always find that people in the working population are healthier than the general population – and that’s because if you’re in work, you’re selected not to be sick,” she says.
This is particularly relevant in firefighting, as workers – including volunteers – need to be physically fit.
When looking specifically at volunteer firefighters, the report found that those who had attended more fire incidents had a higher risk of death, particularly from heart disease.
In terms of cancers, cancer risk in male full- and part-time firefighters was higher than the general Australian population – particularly melanoma and prostate cancer, and particularly among firefighters employed long-term.
In volunteers, however, there was no overall trend of increased cancer risk, even for long-term volunteers. But there was an increased risk of cancer when volunteers attended a greater number of fire incidents. Plus, there was an increased risk of prostate cancer overall, most strongly in men who had volunteered for more than 10 years.
In general, the study didn’t look at the specific exposures – that is, why firefighters are more at risk of certain cancers.
But new research is covering this ground. Glass is currently studying the effects of per- and polyfluorinated alkyl substances (PFAS), which were used for a long time in some water-based firefighting foams and are potentially linked to cancers; results are expected by the end of 2022.
Meanwhile, Glass’s colleague at Monash, occupational physician and epidemiologist Malcolm Sim, is looking at the health impacts of smoke exposure on professional and volunteer firefighters during Black Summer, and on other first responders and outdoor workers involved in the aftermath.
Both studies secured funding in the wake of the 2019–20 fires, six years after the Firefighters’ Health Study issued its final report.
Cancer risk in male full- and part-time firefighters was higher than the general Australian population.
Since then, a systematic review of international firefighter cancer studies has been released, appearing in 2020 in the journal International Archives of Occupational and Environmental Health.
It looked at the large-scale trends over time and geographical regions, and found that the cancer risk of professional firefighters was similar to the general population. However, there was an increased mortality risk for melanoma and prostate cancer.
The researchers suggest that this is due to improved firefighting techniques and personal protective equipment, providing a safer working environment, as well as an increase in medical checkups and screenings leading to a higher rate of diagnosis.
But that study was only looking at paid firefighters, most of whom fight structural fires in more urban environments, while Australia has a disproportionately large number of volunteer firefighters who battle blazes in the bush.