Children in New York City appear to have benefited cognitively as the air around them became cleaner, according to new research spanning more than two decades.
The study followed more than 1,100 children born between 1998 and 2020 in Northern Manhattan and the South Bronx. Researchers compared children’s exposure to air pollution during pregnancy with their scores on standard tests of early cognitive development.
The pollutants studied included PM2.5, nitrogen dioxide and polycyclic aromatic hydrocarbons (PAHs). These pollutants can come from traffic, heating systems and the burning of fossil fuels.
Over the study period, exposure to all three pollutants fell substantially. Previous research by the same team found that, between 1998 and 2016, average prenatal exposure to PM2.5 fell by 51% and nitrogen dioxide by 48%. PAH exposure fell by 66% between 1998 and 2020. The researchers linked these improvements to the combined effects of New York City’s clean-air and climate policies.
At the same time, children’s cognitive scores increased. The researchers used the Mental Development Index, a standardized measure in which higher scores indicate better cognitive performance. Across the study population, scores rose at ages 1, 2 and 3. The increase was particularly notable at age 3, when scores rose by about 1.4 points for each year across the study period.
The researchers also found that children exposed to higher levels of pollution during pregnancy generally had lower cognitive scores. For example, when the researchers combined the cohorts, higher prenatal PM2.5 exposure was significantly associated with lower scores at ages 1, 2 and 3. Similar patterns were found for nitrogen dioxide and PAHs.
The findings are especially notable in the earliest group of children, who experienced the highest pollution levels and the largest reductions. In that group, prenatal exposure to PM2.5, nitrogen dioxide and PAHs was significantly associated with lower cognitive scores at age 3. Later children experienced lower pollution levels, and the relationships were generally weaker.
The study does not prove that cleaner air directly caused the improvement in cognitive scores. The researchers acknowledge that other changes over the 20-year period, such as differences in neighbourhoods and other social factors, could also have played a role.
Still, the authors say the results add to growing evidence that reducing air pollution can benefit children’s developing brains.
Frederica Perera, Professor Emerita of Environmental Health Sciences at Columbia Mailman School, concluded: ‘This study in over a thousand children enrolled over a twenty-year period provides new evidence that policies to reduce fossil fuel emissions benefit developing brains and strongly supports continued efforts to reduce these emissions.’
The full research can be read here.
Photo: Patrick Tomasso
Leave a Reply