Just a few hours of exposure to dense traffic pollution is enough to impair human brain function, research has revealed.
Air pollution is a constant presence in the lives of most Australians. We have one of the most highly urbanised countries on the planet, with around 70 per cent of the total population living in just five metropolitan areas.
Solid, liquid and gas pollutants fill the air over urban regions, causing a number of health issues for those exposed for long periods and is responsible for an estimated 5000 deaths per year. The pollutants come from a range of sources, but the majority are caused by industrial processes and the burning of fossil fuels for energy, especially car fumes.
A study published in the journal Environmental Health demonstrates that as little as two hours’ exposure to diesel exhaust fumes causes a noticeable decrease in brain function.
In the experiment, researchers briefly exposed 25 healthy adults to diesel exhaust fumes and clean filtered air at different times in a lab setting. Participants’ brain activity was measured before and after each exposure using functional magnetic resonance imaging (fMRI).
The researchers were looking for changes in what’s known as the brain’s default mode network (DMN), which is a set of interconnected regions of the brain that play an integral role in memory and thought.
The results showed a definite decrease in the functional connectivity of the DMN when participants were exposed to the diesel fumes.
Dr Jodie Gawryluk, lead author of the study, says lower connectivity between DMN regions is also associated with depression and anxiety.
“We know that altered functional connectivity in the DMN has been associated with reduced cognitive performance and symptoms of depression, so it’s concerning to see traffic pollution interrupting these same networks,” she said.
“While more research is needed to fully understand the functional impacts of these changes, it’s possible that they may impair people’s thinking or ability to work.”
The results echo a University of Queensland (UQ) study that looked at the effects of all types of air pollution on cognitive function.
Read: How safe is the air quality in your home?
The UQ research team collected data from Luminosity brain training games and cross-referenced that against participants’ home addresses to find any correlation between lower game scores and areas of higher pollution.
Air pollution generally is measured in ‘particulate matter’, or PM, which refers to tiny solid and liquid particles suspended in the air. The PM level is accompanied by a number indicating particle size in microns.
A rating of between PM10 means the particles have a diameter of between 2.5 and 10 microns. At this size, the particles are small enough to pass through the throat and nose and enter the lungs.
A PM2.5 rating means the particles are smaller than 2.5 microns and can penetrate deep into the bloodstream.
“The games we studied targeted seven cognitive functions: memory, verbal ability, attention, flexibility, maths ability, speed and problem-solving,” says Dr Andrea La Nauze, co-author of the study.
“We found that exposure to moderately high levels of fine particulate matter (PM2.5) caused a player to drop by almost six points in a 100-point scale.”
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The biggest effects were on memory, meaning occupations that rely heavily on memory function are likely to be most affected.
Whether you live in the city or country, exposure to bushfire smoke in summer is common. Bushfires fill the air with thick smoke, meaning even more dangerous particulate matter. In the 2019–20 bushfire season, it was found that smoke from the fires caused 12 times more deaths than the fires themselves.
“We believe our research has real implications for the average working-age Australian adult, particularly as bushfires become more frequent and contribute to air pollution levels,” Dr La Nauze says.
“The 2019–2020 bushfire crisis subjected millions of Australians to the worst air pollution in the world.”
Read: Chemical pollution causing infertility, smaller penises
In 2021, the World Health Organization (WHO) updated its guidelines on air pollution levels, lowering them significantly to protect human health. The WHO strongly encouraged governments and businesses to focus on policies and investments supporting cleaner transport, energy-efficient homes, power generation, industry and better municipal waste management would reduce key sources of outdoor air pollution.
Dr La Nauze agrees and says the Australian government could be setting better policies with cleaner air in mind.
“Although Australia’s air is pretty clean by international standards, the average Australian is still exposed to higher levels of air pollution than the latest WHO recommendations,” she says.
“Fundamentally though, it comes down to government policy: reducing vehicle emissions, targeting sources of air pollution such as bushfires and revising air-quality standards.”
How is the air quality in your area? Should the government be doing more to protect the health of Australians? Let us know in the comments section below.
