Cleaner air in New York City has been linked to improved cognitive development in young children, according to a study that tracked pollution exposure and developmental scores over more than two decades.
Researchers at Columbia University studied successive groups of mothers and children living in Northern Manhattan and the South Bronx between 1998 and 2020. They found that as exposure to several major air pollutants fell, children’s scores on tests of mental development rose.
The study, published in Environmental Health, looked at exposure during pregnancy to PM2.5, nitrogen dioxide and polycyclic aromatic hydrocarbons (PAH). Children’s cognitive development was assessed at ages one, two and three using a standardised test known as the Mental Development Index.
Pollution levels fell substantially over the period studied. Between 1998 and 2016, average prenatal exposure to PM2.5 dropped by 51% and NO2 by 48%, while PAH exposure fell by 66% between 1998 and 2020.
The researchers said the reductions coincided with the introduction of a series of clean-air and climate policies in New York, including measures targeting vehicle and building emissions. They cautioned, however, that the improvement in air quality could not be attributed to any single policy.
Children’s development scores also increased over time. Across the study groups, higher exposure to PM2.5, NO2 and PAH during pregnancy was associated with lower cognitive scores at ages one, two and three, even after researchers accounted for factors including maternal education, ethnicity, the child’s sex, gestational age and exposure to household tobacco smoke.
The strongest associations were found in the earliest group of children, who experienced the highest levels of pollution. Among these children, lower exposure to PM2.5 and PAH was significantly associated with higher cognitive scores at age three.
The researchers said the findings add to evidence that reducing air pollution may benefit children’s developing brains. But they stressed that the study does not establish that falling pollution levels alone caused the improvement in cognitive scores.
Other changes over the two decades, including differences in neighbourhoods and other social conditions, may also have influenced the results. The researchers also point out that the largely Latina and African American study population means the findings may not apply equally to all populations.
However, they conclude: ‘The associations we report here between the resultant improved air quality and benefits to cognitive outcomes provide new evidence that these policies are beneficial to children’s neurodevelopment and support such efforts to reduce emissions.’
The full research can be read here.
Photo: Annie Spratt
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