Scientific evidence shows that breathing polluted air can impair memory and reasoning, reduce academic performance and even lower intelligence. Here are three important examples of how air quality directly affects cognitive functioning:

1. Performance on standardized tests

Standardized tests have become increasingly important in education. Parents and educators already debate the potential impact of family income, cultural background, gender and other influences on test results. Now researchers are also looking closely at the impact of air quality on standardized test scores – and concluding that the impact is significant.

Multiple studies have identified a link between air quality and performance on standardized tests. For example, one study of school children in Southern California found that exposure to higher levels of fine particulate air pollution (known as PM2.5) is linked to consistently lower scores on standardized tests in math and reading.

In another study, researchers calculated that, for every increase of 2.5 micrograms per cubic meter (µg/m³) of PM2.5 surrounding the homes of the student subjects, their score for performance IQ, which measures reasoning and problem-solving abilities, dropped one point (1).

Ventilation rates in the classroom havebeen shown to impact standardized test scores.

One study found that for every ventilation rate increase of 1 liter per second per person, 2.9% more students were expected to pass a standardized math test, and 2.7% more students were expected to pass a standardized reading test (2).

In another study, for every increase in ventilation rate of one liter per second per person, the mean math scores of students rose by up to 11 points (3).

Researchers also found that in classrooms with high outdoor air ventilation rates, students scored up to 15 points higher on standardized tests than their counterparts in classrooms with low outdoor air ventilation rates (4).

2. Cognitive skills and aging

Evidence is growing that cognitive decline associated with aging is at least partially related to breathing air pollution. In one study, scientists administered math and memory tests to 780 people age 55 or older, then correlated scores with pollution levels where the participants lived. After adjusting the results for education, employment and other factors, the researchers still found significant differences in scores based on air quality. Participants in areas with high pollution levels had error scores that were 150% higher than those living in areas with low pollution.

A study conducted at the University of Southern California’s Davis School of Gerontology involved cognitive test scores of nearly 15,000 adults 50 years of age and older cross referenced with air pollution concentration maps (5). The research concluded that the brains of people residing in areas with the highest concentrations of air pollution aged three years faster than those who lived in areas with the lowest concentrations of air pollution.

Researchers at the Rush University Medical Center in Chicago studied women who were exposed, over long periods, to levels of air pollutants that were typical of many U.S. urban areas and found measurable declines in cognitive function (6) (7).

3. Memory

Scientists are gradually identifying the connection between air pollution and the brain. Neuroscience researchers exposed mice to high levels of particulate air pollution (similar to levels in Beijing or Mexico City) for a 10-month period. They observed that the mice exposed to high pollution levels took longer to navigate through a maze and made more mistakes.

Examining the brains of the mice exposed to pollution, the researchers found physical changes in the tips of neurons in the part of the brain responsible for memory. The researchers also found that the mice exposed to high levels of pollution showed increased levels of pro-inflammatory chemicals in the brain.

Brain development and prenatal exposure to air pollution

The harm to cognitive abilities caused by increased levels of air pollution begins in the womb.

Research has shown that the developing fetus is especially vulnerable to neurotoxicants, such as polycyclic aromatic hydrocarbons (PAHs), which are byproducts of fossil fuel combustion.

One study involved pregnant women and the air quality they were exposed to in two cities: New York City and Krakow, Poland. The children resulting from those pregnancies were given academic performance tests at five years old.

The children whose mothers had above-average exposure to PAHs during their pregnancies registered test scores nearly four points lower than those who had below-average exposure (8).

What you can do

We can each play an important role by taking action to clean the air we breathe indoors and outdoors. We can help reduce the sources of pollution, better ventilate our indoor environments, and help provide air filtration for schools and other indoor environments as needed. Here are a few examples of the positive steps we can each take to clean the air:

• Get involved:Schools with better indoor air quality have better attendance rates and test scores. If air quality is an issue in your local schools, ask your school principal, school board members or local chapter of the American Lung Association what you can do to get involved in improving classroom air quality.
• Avoid unnecessary exposure:Avoid unnecessary exposure to outdoor air pollution and use a high-performance air purifier such as the IQAir Atem Desk to keep the air clean at home. For rankings of the best and worst regions of the nation in terms of air pollution, and to check pollution levels where you live, follow IQAir’s AirVisual Air Quality Index.
• Reduce air pollution:Conserving energy, recycling, driving less or driving low-polluting vehicles — the choices you make can help reduce air pollution for everyone. Visit the U.S. Environmental Protection Agency website (www.epa.org) for more ideas.

How does the air quality rate in your area? Download the 2021 World Air Quality Report to find out.