Children exposed to higher levels of air pollution in their homes from birth to age three may develop weaker connections between key brain regions, with potentially long-lasting effects on future learning, behavior, and health, according to one of the first studies of its kind.
The study is one of the first to explore how air pollution affects neurological connections when the brain is not actively engaged in a task, using brain scans taken multiple times in a large population-based group of children from birth, says lead author Michelle Kusters. Published recently [February 2025] in Environment International, the researchers found:
- More exposure to air pollution was linked to weaker connections between different brain networks.
- Early exposure affected the connection between the amygdala (a region involved in emotional regulation) and brain regions involved in attention, movement and sensation, and hearing (hippocampus and caudate nucleus). This was especially true of exposure to PM2.5, which can penetrate deep into the lungs.
- Ongoing exposure, particularly to PM10, a larger particle size, caused changes in the connections between brain networks (salience and medial-parietal networks) responsible for higher thinking and decision-making.
“These associations persist throughout adolescence, which may indicate persistent disruptions in the normal development of brain networks due to pollution exposure,” says Mònica Guxens, ICREA research professor at ISGlobal and co-author of the study. “This could affect emotional processing and cognitive functions.”
Young brains vulnerable to pollution harms
The findings add to growing evidence that air pollution can have long-term consequences for brain health, especially in children. Particles from air pollution can enter the brain through the nose and lungs, where scientists suspect they trigger inflammation and oxidative stress, which harms cells. They can also often carry heavy metals like lead, cadmium, arsenic, and other toxic substances.
For this study, researchers from the Barcelona Institute for Global Health (ISGlobal) focused on five common pollutants: fine particulate matter (PM2.5, or tiny pollutant particles of 2.5 micrometers or less, and PM10), nitrogen dioxide (NO2), and nitrogen oxides (NOX), all of which are primarily linked to traffic-related emissions.
Increased exposure to outdoor air pollution in early life, for instance, has been shown to make it harder for children to learn and process information, especially in terms of critical thinking and non-verbal tasks. Exposure to air pollution during pregnancy and early childhood can also lead to lasting changes in the brain’s white matter, research suggests.
The structure of many brain networks begins to form around the age of 2, but development continues as the brain matures. In newborns and young children, basic brain networks develop quickly in the first few years.
The amygdala, for example, grows by 105% in the first year and 15% in the second, which may make it particularly vulnerable to the effects of air pollution. Other networks involved in higher-level thinking usually develop later in childhood.
Pollutants also shown to affect brain volume
For this study, the researchers studied data from 3,626 children in Rotterdam, Netherlands. The children were scanned twice: once around age 10 and again at age 14, while they were resting (not doing any tasks).
The researchers looked at pollution exposure during two periods—from birth to age three and in the year before the brain scans—and used statistical models to estimate pollution exposure, combining actual measurements with local environmental information. They noted several limitations of the study, including that it did not include air pollution data for schools or repeated measurements for all children in the study.
Another related study from the same research team examined how air pollution during pregnancy and childhood affects brain volume (the amount of space the brain occupies) through adolescence. Based on data from 4,243 children from a large Dutch population-based birth cohort, the study found that exposure to PM2.5 and copper (from vehicle brake and tire wear) during pregnancy was linked at age 8 to smaller hippocampal volume.
However, the hippocampus appeared to show “catch-up growth” over time, between 8 and 17 years, suggesting plasticity in this area of the brain might mitigate the adverse effects of early life air pollution. While some brain regions may adapt, the researchers say ongoing disruptions in functional brain networks could have long-term effects.
More research is needed, along with better protection for children, they say.
“Given the widespread exposure to air pollution, these results reinforce the importance of policies aimed at reducing pollution levels, particularly in urban environments, to safeguard children’s brain development,” Kusters says.
Reference
Kusters MSW, Granés L, Petricola S, Tiemeier H, Muetzel RL, Guxens M. Exposure to residential air pollution and the development of functional connectivity of brain networks throughout adolescence. Environment International. 2025;196:109245. doi:10.1016/j.envint.2024.109245
