Story at a glance

  • Wild bushfires are consuming large areas of Australia.
  • Short-term health hazards include smoke inhalation and breathing problems.
  • Long-term health problems could include lower cardiovascular and immune function, as well as potentially mental health issues.

In Australia, ongoing bushfires have burned about 10.3 million hectares (103,000 sq km). Residents of Sydney have had to deal with smoke covering their city for weeks, according to the BBC. The wild bushfires have been ongoing in Australia for several months at this point, and with the southern hemisphere just getting into summer there doesn’t seem to be an end in sight. The fires are a humanitarian, environmental and health emergency.

Twenty-seven people died, and many more are displaced. There are stories of koalas screeching as they are burned alive, and one expert estimates that as many as 1 billion animals may have been killed in the fires. For humans, besides the physical danger of being near fire, there are short- and long-term health hazards related to the smoke and ashes that come from the fires.

The short-term health hazards

Smoke inhalation is the most significant short-term health hazard. “Any smoke that is produced as the by-product of something burning is noxious and bad,” says Brian Oliver of the University of Technology, Sydney to the BBC. People who breathe in smoke or smoggy air may experience symptoms of asthma and generally difficulty breathing. Other health problems can include eye irritation, pneumonia and headaches.

The long-term health hazards

Particulate matter (PM) are the molecules that are products of the burning process. PM can move with the winds and travel across continents. For example, 2018 imagery from NASA shows smoke from fires in California stretching across the middle of the country. Another similar natural event that ejects organic materials into the air is a volcano eruption. In 2010, when the Iceland volcano erupted, planes were grounded because of the ash in the air.

Air pollution may have long-lasting effects on health, and research suggests that even small increases in PM concentration in the air can be detrimental to cardiovascular health. Exposure to air pollutants may impair the immune system by inducing an inflammatory response, and it can alter certain genes that affect production of immune cells, although the researchers don’t know how long those changes may last.

Research on children who were exposed to higher PM when they were in utero suggests that their lung capacity is lower at ages five or six. A study in adolescent macaques that were exposed to wildfire smoke as infants suggests that the changes to the immune system and lung function may persist for years afterwards.

PM exposure may also affect mental health. Recent studies have shown a link between increases in PM and emergency room visits for psychiatric reasons. Experts aren’t sure what might be the mechanism for how that happens, but they have some ideas for why rogue particles in our bodies are a bad thing.

What’s happening in the body

It’s not yet understood how air pollutants or PM cause health problems. However, researchers think that PM can wreak havoc because they can enter our bodies and bloodstreams, sometimes also passing through cell membranes. The particles may be reacting with other compounds in the body or binding to tissue that they shouldn’t be binding to. PM can travel as far in the body as the brain, according to studies in rats, which could be related to the mental health issues discussed earlier.

Researchers are focusing on discovering what happens when rats and mice are exposed to ultrafine particles to try to understand what might be happening in people. Once more is known in an animal model, experts can begin to find a solution to treat people who have been exposed to high amounts of air pollutants. What’s also not well understood is how the identity of the PM comes into play, like what kind of chemical compound it is, such as a sulfate or nitrate or some other chemical compound.

What to do and where to find more information

Wearing masks can provide some protection against PM, but it’s not a perfect solution. With PM, size matters. There are a few cutoff sizes that experts worry about: 2.5 micrometers (μm) and 0.1 μm for the diameter of particles. PM smaller than 2.5 μm (PM2.5) are what many air quality agencies measure and report.

One of the best masks available is the N95 mask, which is said to be able to filter out 95 percent of particles up to 0.3 μm in size. But the smallest particles may still be able to get through, and when PM concentration is very high that could mean a lot of particles are penetrating. That’s why air pollution researchers are concerned about PM smaller than 0.1 μm, or ultrafine particles.

Air filtration machines may not be a huge help, but they may be crucial in the worst situations. There have been studies in Mongolia that show such machines can improve indoor air quality. But that air quality still has many times higher health risks than in places in the U.S. like Los Angeles. If the air quality is very bad, masks and air filtering machines may be necessary to try to bring air quality closer to a healthy level.

The best defense may be to completely avoid areas with high PM counts and stay indoors on really bad days if possible. People currently in Australia are advised to get out of the path of the fires, wear protective clothing and footwear, cover all exposed skin and seek shelter away from heat. People are also advised to not exercise outdoors.

Globally, you can find a real-time map of heat detection provided by NASA, although not all signals are fires. For Australia, the BBC developed a map that shows where active fires have been reported and government updated websites for New South Wales and other provinces like Victoria have additional maps or information. The government of Australia tracks the Air Quality Index and other measurements for towns across the country, for example PM2.5 readings in and around Sydney.

In the U.S., you can find up-to-date air quality information at For more health information, check out the Centers for Disease Control and Prevention’s website on wildfires.

Published on Jan 10, 2020