If you look at the smudged skylines of Los Angeles, California or Beijing, China, the haziness creates the illusion of cities shrouded in perpetual gray. That smog is driven by a pollutant that doesn’t just ruin the view — it worms its way into the brain, influencing the health of people exposed.
In a new study, scientists find another reason why air pollution is bad for the brain — this time zeroing in on the effect it has on men’s brain health. The study examines the negative effect of fine particulate matter, also known as PM 2.5 pollution. You might know it as black carbon or “soot.”
“Our study is the first one that demonstrates that exposure to PM2.5, even just over a few weeks, can impair cognitive performance,” lead author Xu Gao tells Inverse. Gao is an assistant professor at Peking University and a researcher affiliated with Columbia University.
What’s new — Scientists are increasingly unearthing new information about how the tainted air we breathe harms our bodies, whether it’s worsening the severity of Covid-19 or reducing men’s sperm count.
Gao and colleagues found air pollution is associated with considerable negative short-term effects on cognitive health in a sample of older white men. This finding was published Monday in the journal Nature Aging.
The study suggests PM 2.5 levels not usually considered hazardous can still cause individuals to suffer from cognitive decline due to short-term air pollution. This implies “there is no safe zone for PM 2.5,” Gao says.
Interestingly, the researchers found that men who take what’s known as non-steroidal anti-inflammatory drugs (NSAIDS) did not suffer as many harmful effects from PM 2.5 pollution. These anti-inflammatory medications include pills like aspirin.
This finding emerged although NSAIDs don’t have any known relationship to cognitive performance. The researchers suspect NSAIDs have a “modifying effect” on the inflammatory responses prompted by inhaling polluted air.
These findings are preliminary — Gao says it’s too early to endorse taking NSAIDs as a way to protect oneself from air pollution. However, he does venture to say people on these medications “may have additional benefits.”
Why is air pollution bad for health?
Air pollution is associated with an ever-growing laundry list of health risks, including:
- Increased risk of heart attacks
- Decreased lung function and increased risk of chronic lung disease
- Premature death
- Increased risk of Alzheimer’s disease
PM 2.5 pollution is especially harmful. These tiny air particles are 2.5 microns or less in size — for comparison, human hair is roughly 70 microns in diameter. This category of pollution is why you see gray horizons in cities like Los Angeles — it’s associated with smog and poor air quality. It’s arguably the greatest environmental risk factor for human mortality.
But there is some good news amidst all this doom and gloom. Some recent studies, for example, suggest exercise can offset some of the harmful effects of air pollution — even in urban areas.
Air pollution deaths have also declined by half between 1990 and 2010, correlating with improved federal regulations on air quality.
But it can still do considerable short-term and long-term damage to the human mind, according to this latest Nature Aging study.
How they did it — The scientists analyzed data from 954 men in the Boston area between 1995 and 2021. The average age of a man in the study data was 69-years-old. None had chronic health conditions, but 64 percent were former smokers.
The participants were also questioned about their use of NSAIDs, including aspirin. They also took cognitive tests, including tests on their ability to remember words and repeat numbers, as well as screening exercises used to test for dementia.
“We found that both short and long exposures were related to cognitive function.”
The researchers also analyzed this data in conjunction with information on weather patterns in the Boston area, since air pollution varies by season and is greater in the winter.
Finally, they obtained data on air pollution from a Harvard University supersite, which they used as a baseline to measure air pollution in the Greater Boston areas.
Using this information, the researchers were able to paint a picture of cognitive health that correlates with short-term air pollution and also study any potential effects of NSAIDs on cognitive performance.
Why it matters — Media and policymakers have focused, rightly so, on the number of deaths resulting from air pollution each year, which now number 200,000 annually in the U.S — and that’s just from the air that meets EPA standards.
Much less attention has been paid to air pollution’s impacts on short-term and long-term cognitive performance. The research that has been done has found air pollution can impair the cognitive performance of children, and influence cognitive decline in older adults.
Although this new study focuses on short-term effects, the researchers also conducted a sensitivity analysis to include the effects of long-term exposure to air pollution. And while preliminary, the findings don’t bode well for the human mind’s ability to withstand air pollution in the long run.
“We found that both short and long exposures were related to cognitive function,” Gao says.
But the study has limitations — The study team acknowledges that their work is just a starting point. Much more research needs to be done to expand on their intriguing findings — and go beyond the scope of the study’s design.
For example, the study only focuses on older white men, “which suggests the possibility that the results might not be generalizable to other ethnic groups and/or women” the team writes.
Gao would like to conduct further research involving people of different ages, races, and genders to confirm whether similar effects would occur among various demographics.
“We believe that younger people may have a better adaptive response to air pollution than the elderly. Females are also different from males with respect to health outcomes,” Gao says.
Meanwhile, scientists have long known that communities of color suffer disproportionately from air pollution. A recent Science study found Black and Hispanic individuals experience particularly high levels of PM 2.5 pollution — the subject of this study.
What’s next — Ultimately, what’s needed is more information on both the long-term impacts of air pollution on cognitive health and the relationship between NSAIDs and air pollution. This research could be used to inform future policy, both in the U.S. and abroad.
And while Gao suggests NSAIDs could be helpful in treating the cognitive effects of air pollution, it is not a replacement for policies that reduce the actual source of pollution. Recent efforts by the Biden administration to move toward electric vehicles, as well as California’s stricter vehicle emissions standards, could help shift the tide against air pollution.
“Although our study shows that taking NSAIDs may be a solution to air pollution’s harm, [it’s] definitely not the final answer to the threats of air pollution. Changing our policies of air pollution towards a more restrictive manner is still warranted,” Gao says.
But it’s data that drives policy forward — evidence that pollution isn’t just a topic on our minds, it literally influences the brain.
Abstract: Air pollution, especially fine particulate matter (PM2.5), may impair cognitive performance1–3, but its short-term impact is poorly understood. We investigated the short-term association of PM2.5 with the cognitive performances of 954 white males measured as global cognitive function and Mini-Mental State Examination (MMSE) scores and further explored whether taking nonsteroidal anti-inflammatory drugs (NSAIDs) could modify their relationships. Higher short-term exposure to PM2.5 demonstrated nonlinear negative associations with cognitive function. Compared with the lowest quartile of the 28-d average PM2.5 concentration, the 2nd, 3rd and 4th quartiles were associated with 0.378, 0.376 and 0.499 unit decreases in global cognitive function score, 0.484, 0.315 and 0.414 unit decreases in MMSE score and 69, 45 and 63% greater odds of low MMSE scores (≤25), respectively. Such adverse effects were attenuated in users of NSAIDs compared to nonusers. This study elucidates the short-term impacts of air pollution on cognition and warrants further investigations on the modifying effects of NSAIDs.