Brain fog Short-term exposure to pollution impacts memory research finds

Even short-term exposure to air pollution can have a measurable impact on brain function, especially memory, new analysis has revealed.

Researchers from the University of Queensland and Carnegie Mellon University in the United States made the discovery by looking at the performance of more than 100,000 people who used a “brain training” phone app.

Smoke haze choked many of Australia’s major cities in late 2019, including Brisbane.Credit:Jocelyn Garcia

They then matched the performances with data about the air quality in their location on the days they used the app.

One of the lead authors, Andrea La Nauze from UQ’s School of Economics, said they found a clear correlation between areas with higher levels of pollution and poorer performance in the app.

“There is existing research which shows pollution affects the cognitive ability of young people and older people and we wanted to test whether that was also true of people in the ‘middle’ who make up the bulk of the workforce,” Dr La Nauze said.

“We found the effects are larger for younger people, so for someone under 30 we find the effect of a high-pollution day is the equivalent of ageing about 15 years in terms of cognitive ability.”

On average the researchers found exposure to high levels of fine particulate matter (particles less than 2.5 microns in size) caused a player to drop by almost six points in a 100-point scale where 100 represents the score of the top 1 per cent of cognitive performers.

Dr La Nauze said they found the effect dwindled as people got older, and people over 50 did not display much noticeable decline in cognitive ability on high pollution days compared with days with lower pollution levels.

She said they also found memory seemed to be particularly affected out of seven cognitive functions targeted by the study, which also included verbal ability, attention, flexibility, maths ability, speed and problem-solving.

That had implications, Dr La Nauze suggested, for the types of work which could be affected by high pollution levels.

“That’s short-term working memory, so in particular when we’re thinking about productivity it’s going to be people who rely on short-term memory for their work, people like nurses, teachers, doctors and so on,” she said.

“It wouldn’t necessarily affect people who work in fields like agriculture or manufacturing where something like attention is going to be the most important determinant of their productivity.”

The findings come after the World Health Organisation changed its air quality guidelines in September this year, lowering the acceptable levels of pollution significantly.

Dr La Nauze said the stronger guidelines were a good thing, but even at levels equivalent to the new revised WHO standards they were still seeing cognition effects from pollution.

The researchers looked at data from US-based users of the app Lumosity, but Dr La Nauze said the findings have a lot of relevance for Australia, especially with large-scale bushfires becoming more common.

“Fundamentally it comes down to government policy â€" reducing vehicle emissions, targeting sources of air pollution such as bushfires and revising air-quality standards,” she said.

“Air-quality standards in Australia and around the world should take into account the cognitive effects and their downstream productivity impacts.”

The study has been published in the journal National Bureau of Economic Research.

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