Air pollution can throw off your chess game, a new study finds. That's bad news, especially if you already struggle with chess, but it's also even worse than it sounds.

Since most of us now breathe polluted air, and we know air pollution can harm our brain, impaired chess players may be canaries in the coal mine, hinting at risks to our cognitive health.

The new study found that when the concentration of fine particulate matter in the air increased by a certain amount, chess players made a greater number of errors in tournament matches. What's more, those errors increased in severity, as determined by software using artificial intelligence to analyze games.

To be specific, when the level of fine particulate matter increased by 10 µg/m3, the odds of chess players making a mistake grew by 2.1 percentage points, while the magnitude of their errors rose by 10.8 percent.

"We find that when individuals are exposed to higher levels of air pollution, they make more mistakes, and they make larger mistakes," says co-author Juan Palacios, an economist in the Sustainable Urbanization Lab at the Massachusetts Institute of Technology.

Particulate matter (PM) is an airborne cocktail of solid particles and liquid droplets, featuring diverse substances like dust, soot, smoke, organic matter, and various chemicals. It's often a byproduct of combustion, lingering in the air after something burns.

Some PM comes from natural sources like volcanoes or fires, but much of the air pollution in cities (and elsewhere) has anthropogenic sources like power plants, vehicles, or agriculture.

PM is categorized by particle size, with smaller pieces posing bigger risks. The smallest group, called fine particulate matter or PM 2.5, includes particles with a diameter of 2.5 microns or less – a size that enables passage deeper into respiratory tracts and beyond.

Air pollution leads to millions of premature deaths globally every year, according to the World Health Organization. It's infamous for contributing to cancer, heart disease, and other health problems, but a growing field of research also seeks urgent insight into its cognitive effects.

For the new study, researchers tracked 121 players at three eight-week chess tournaments in Germany from 2017 to 2019, recording more than 30,000 moves. Artificial intelligence helped them judge each move, identify optimal decisions, and flag errors.

They also used sensors inside tournament venues to record PM 2.5 levels, plus carbon dioxide and temperature. Outdoor conditions can affect those factors, the authors note, even indoors.

Indoor PM 2.5 levels during the tournaments ranged from 14 to 70 micrograms per cubic meter of air, the study found, comparable to the air in many urban areas.

All signs point to PM 2.5 as the culprit for poorer performance, the researchers report, with other variables like temperature, CO2, and noise levels showing no similar links with the player's decisions.

The researchers also accounted for the quality of players' opponents, using standardized chess ratings to assess whether dips in performance could just point to tougher competition.

And the study included an instrumental variable analysis, a statistical method for estimating causal relationships to help rule out other explanations.

"It's pure random exposure to air pollution that is driving these people's performance," Palacios says. "Against comparable opponents in the same tournament round, being exposed to different levels of air quality makes a difference for move quality and decision quality."

The combination of air pollution and time pressure made things even worse, the study found. When players were forced to race the clock at a critical part of the match, the extra load of particulates raised the likelihood of an error even further by 3.2 percentage points, and the magnitude of errors by 20.2 percent.

"When these players do not have the ability to compensate [for] lower cognitive performance with greater deliberation, [that] is where we are observing the largest impacts," Palacios says.

While this study is limited to chess players, the health risks of PM are not. The study uses chess to help illustrate what air pollution can do not only to lungs and hearts, but also to brains.

There could be much broader implications, the researchers note, if air pollution has similar cognitive effects in other contexts, quietly impairing our judgment at key moments.

More research is needed on air pollution and cognition, but this study already sheds valuable light on how air quality affects decision-making quality in complex settings, the researchers say.

"There are more and more papers showing that there is a cost with air pollution, and there is a cost for more and more people," Palacios says.

"And this is just one example showing that even for these very [excellent] chess players, who think they can beat everything – well, it seems that with air pollution, they have an enemy who harms them," he adds

The study was published in Management Science.