Cleaner air linked to better cognitive development in young children, study finds

A 20-year study of more than 1,100 children found cognitive scores rose as air pollution fell in parts of New York

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Published: September 23, 2026 at 12:15 PM

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Cleaner air could be good news for children's developing brains, according to a long-running study in New York.

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Researchers at Columbia University followed more than 1,100 children and their mothers in Northern Manhattan and the South Bronx over more than two decades. They found that as exposure to several types of air pollution fell, children's scores on tests of cognitive development rose.

The findings add to growing evidence that reducing air pollution may have benefits for children's health and development, although the researchers stress that the study cannot prove that cleaner air alone caused the improvements.

What did the study find?

The research, published in Environmental Health, followed successive groups of mothers and children between 1998 and 2020.

Researchers looked at children's exposure before birth to three pollutants: fine particulate matter (PM2.5), nitrogen dioxide (NO2) and polycyclic aromatic hydrocarbons (PAH).

The children's development was assessed at ages one, two and three using a standardised test measuring areas including memory, sensory perception, problem-solving, speech and language comprehension.

Over the period studied, pollution levels fell substantially. Between 1998 and 2016, average prenatal exposure to PM2.5 fell by 51% and NO2 by 48%, while exposure to PAH fell by 66% between 1998 and 2020.

At the same time, children's cognitive development scores increased.

Prof Frederica Perera, who led the research with colleagues from the Columbia Center for Children's Environmental Health, said the team had previously found associations between prenatal exposure to air pollution and children's neurodevelopment.

“We tested cognitive processing including memory and sensory perception, problem-solving such as matching shapes, stacking blocks and communication, both speech and language comprehension. In the early years of the study, we reported significant associations between prenatal exposure to air pollution and neurodevelopment effects in the children. That was bad news.”

Children's scores improved as pollution fell

The researchers found that higher exposure to PM2.5, NO2 and PAH during pregnancy was associated with lower cognitive scores at ages one, two and three.

These associations remained after taking account of factors including maternal education, ethnicity, the child's sex, gestational age and exposure to tobacco smoke at home.

The clearest associations were seen among the earliest group of children, who experienced the highest levels of pollution. In this group, lower exposure to PM2.5 and PAH was significantly associated with higher cognitive scores at age three.

Prof Perera said the team wanted to know whether the improvements in air quality over time would be reflected in children's development.

The study found that cognitive scores improved as air pollution declined, particularly when children were aged two and three and during periods when pollution fell more sharply.

Can cleaner air be blamed for the improvement?

Not necessarily. The researchers say their findings show an association between improving air quality and better cognitive outcomes, but they cannot establish that falling pollution levels alone caused the change.

The children's circumstances also changed over the two decades. For example, the proportion of children living with a tobacco smoker fell from 34% to 18%, while the proportion of mothers who had graduated from high school increased by nine percentage points.

The researchers accounted for several of these factors in their analysis, but other changes in neighbourhoods and social conditions may also have played a role.

The study population was also largely Latina and African American, meaning the findings may not apply in exactly the same way to every population.

What does this mean for families?

The findings add to existing evidence that reducing air pollution can have health benefits for children.

New York introduced a number of measures targeting vehicle and building emissions during the study period, while pollution levels fell substantially. However, the researchers say the improvement cannot be attributed to any one policy.

Prof Perera also cautioned against assuming that today's pollution levels are necessarily best for children: “We cannot conclude that contemporary levels of air pollution are safe for the neurodevelopment of all children.”

The researchers say further studies are needed to understand the relationship between cleaner air and children's development.

“We need more studies such as ours to increase public awareness of the value of clean air and climate policies and motivate policymakers,” Prof Perera says.

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The study's authors conclude that the association between improved air quality and better cognitive outcomes provides further evidence that efforts to reduce emissions may benefit children's neurodevelopment.

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