Temporary rises in air pollution may impair memory and thinking in older men, according to research that indicates even short-term spikes in airborne particles can be harmful to brain health.
Scientists found that the men’s cognitive performance fell following rises in air pollution during the month before testing, even when peak levels remained below safety thresholds for toxic air set by the World Health Organization and national regulators.
The findings build on growing evidence that exposure to fine particulate matter in the air, largely from road vehicles and industry, is harmful not only to the heart and lungs, but also to delicate neural tissues in the brain.
Researchers in the US and China compiled multiple cognitive test scores from nearly 1,000 men living in the Greater Boston area and checked them against local levels of PM2.5s – airborne particles smaller than 2.5 micrometres across. The men involved in the study were white and had an average age of 69.
Writing in Nature Aging, the scientists describe how higher levels of PM2.5s up to four weeks before testing were linked to poorer cognitive performance on tasks ranging from word memory to number recall and verbal fluency. The effect was clear even when concentrations of PM2.5s stayed below 10 micrograms per cubic metre, the WHO guideline level which is routinely breached in London and many other cities.
Intriguingly, the study found evidence that test scores were less affected by short-term rises in air pollution if the men were taking aspirin or other non-steroidal anti-inflammatory drugs, known as NSAIDs. “Our study indicates that short-term air pollution exposure may be related to short-term alterations in cognitive function and that NSAIDs may modify this relationship,” the authors write. According to one line of thinking, such painkillers may help by reducing inflammation that is triggered by fine particles getting into the brain.
While the WHO says levels of PM2.5s should not exceed an annual mean of 10 micrograms per cubic metre, the UK has adopted a higher limit of 25 micrograms per cubic metre. The government’s air quality index regards PM2.5 levels below 35 micrograms per cubic metre as “low”.