Air pollution poses the biggest environmental risk to human health worldwide. Scientific evidence has linked air pollution to respiratory conditions like asthma and cardiovascular conditions including an enlarged heart.

The pollutant most responsible for these health problems is fine particulate matter known as PM2.5 .

Poor air quality undermined intellectual performance and decreased a person's productivity.

People's exposure to PM2.5 over 24 hours should be less than 15 micrograms of particulate matter in one cubic meter of air, according to guidelines recommended by the World Health Organization, with recommended average annual concentrations set at 5 micrograms per cubic meter.

These limits may be too generous, however. A team of British scientists has found that even brief exposure to PM2.5 can affect a person's ability to focus on a task, avoid distractions and behave appropriately. “Our study provides compelling evidence that even short-term exposure to particulate matter can have immediate negative effects on brain functions essential for daily activities, such as doing the weekly supermarket shop,” Thomas Faherty, a coauthor on the study and a postdoctoral researcher at the University of Birmingham, said in a statement.

The results revealed that poor air quality undermined intellectual performance and decreased a person's productivity. In a high-tech world requiring a high level of cognitive functioning, this can have significant consequences. “Decreased productivity impacts economic growth, further highlighting the need for stricter air quality regulations to combat the harmful effects of pollution on brain health,” Francis Pope, a co-author on the study and a professor at the University of Birmingham, pointed out.

Twenty-six people participated in the study. Each completed four sessions of cognitive tests, followed by a one-hour period of exposure to either clean air or PM2.5 from a burning candle. This was followed by a four-hour delay and then a second round of cognitive tests.

Even short-term exposure to particulate matter in polluted air can have immediate negative effects on the brain functions needed for daily activities, such as going to the supermarket.

The cognitive functioning measured by the tests encompassed a variety of the mental processes needed for everyday tasks. They measured:

  • Selective attention, helps focus decision-making and goal-directed behavior. It enables you to, for example, prioritize items on your shopping list and ignore other products and resist impulse buys.
  • Working memory makes tasks that need simultaneous processing, such as planning a schedule to accommodate several variables or juggling multiple conversations, possible.
  • Socio-emotional cognition enables us to perceive and interpret our own emotions and those of others. It helps guide socially acceptable behavior.

Keep in mind that these cognitive skills are not strictly separate. They work together.

The study was designed to separate out the effects of exposure to air pollution on mental abilities. Each participant was exposed to clean air for two sessions and to particulate matter from the candle for two sessions. The concentration of particulate matter during exposure to the candle was significantly higher than during exposure to clean air.

Participants had to breathe through their mouths for two sessions because their ability to breathe through their noses was restricted by nose clips like those worn by swimmers. They had no breathing restrictions for the other two sessions.

The inflammation brought on by fine particles is likely behind the reductions in cognitive function.

Selective attention and the ability to recognize different emotions were negatively affected by exposure to particulate matter, regardless of whether participants were wearing nose clips. Working memory was not affected, however, suggesting some brain functions are less affected than others by short-term air pollution exposure.

It's likely that the inflammation caused by particulate matter is behind the reductions seen in cognitive function, the researchers say. But more studies are needed to better understand how air pollution exposure affects cognition.

The long-term effects of exposure to air pollution on vulnerable populations, including seniors and children, are well known, and seniors may be particularly at risk for cognitive issues if they live in areas with air pollution. As co-author Gordon McFiggans, a professor at the University of Manchester said, “[We] need to look at the effects of different sources of pollution on brain health in vulnerable older members of society.”

The study is published in Nature Communications.