Bushfire smoke is everywhere in our cities. Here's exactly what you are inhaling
- Written by Gabriel da Silva, Senior Lecturer in Chemical Engineering, University of Melbourne
As bushfire smoke blankets large parts of Australia, it’s time to examine what this complex chemical mixture is made of, to better understand what it’s doing to both our bodies and the planet.
I research the chemical processes that create pollutants in flames, and what happens when they are released into the air we breathe.
Bushfires are not the only source of smoke we are exposed to in our everyday lives. We breathe smoke from cigarettes, wood-fired heaters, coal-fired power stations and vehicles.
But smoke stemming from the bushfires is accumulating over cities in concentrations rarely seen before in Australia, badly affecting cities including Sydney, Melbourne and Canberra. This poses risks to public health and the environment. Read on to find out exactly what you’re breathing in.
Lukas Coch/AAPIt’s largely water
First, there is a lot of water in bushfire smoke. When fire rips through a forest it burns off the water held in the trees, sending rolling clouds of steam up into the atmosphere.
Water might seem harmless, but it actually enables bushfires to form their own weather. Water vapour condenses on smoke particles and forms huge pyrocumulonimbus clouds. We saw these storms in the current fire crisis. They can complicate firefighting efforts by producing wind and lightning strikes but unfortunately rarely bring rain.
Read more: Even for an air pollution historian like me, these past weeks have been a shock
These clouds also inject smoke high into the atmosphere from where it can circle the globe. We recently saw this when smoke from bushfires in Australia’s south-east drifted to New Zealand and then on to South America. Smoke lofted into the stratosphere influences the climate by blocking the movement of light and heat, and can even interfere with chemistry in the ozone layer.
AAP/Erik AndersonThe climate effect
Smoke also contains gases, most notably carbon monoxide (CO) and carbon dioxide (CO₂). Carbon dioxide is the end-product of combustion and is the most significant contributor to man-made global warming.
Forests sequester massive amounts of carbon as wood and other organic matter and much of this is released back into the atmosphere as carbon dioxide when burned.
Within about a year, these molecules could be anywhere in Earth’s atmosphere. CO₂ is so long-lived that many of these same molecules will remain circling the globe for hundreds of years.
Read more: We know bushfire smoke affects our health, but the long-term consequences are hazy
This bushfire season, more than 10 million hectares of land has already burned. Estimates based on satellite data put the subsequent CO₂ release at 400 million tonnes. This is close to Australia’s total annual greenhouse gas emissions of around 500 million tonnes of CO₂ equivalent.
Our planet’s climate emergency is already making Australia hotter and drier, with more frequent extreme weather events. The ensuing fires are in turn releasing carbon back into the atmosphere, forming a dangerous positive feedback loop.
NASA Earth ObservatoryThe poisonous sibling
Whereas CO₂ presents a long-term threat to us all, its poisonous sibling carbon monoxide (CO) is a more immediate concern to those directly exposed to smoke. Carbon monoxide forms when combustion is interrupted on its way to make carbon dioxide.
At the high concentrations found in smoke, carbon monoxide can be deadly. It binds strongly to our haemoglobin – the molecule in red blood cells that carries oxygen around the body. At around 100 parts per million in air it can starve the human body of oxygen, asphyxiating its victims.
Carbon monoxide poisoning through smoke inhalation is a direct concern to firefighters and those sheltering from flames. Those fighting bushfires often work long shifts, sometimes over several weeks, with face masks that offer limited protection.
Authors: Gabriel da Silva, Senior Lecturer in Chemical Engineering, University of Melbourne