As we brace for months of polluted air, concerns extend beyond respiratory illnesses. Research suggests that prolonged exposure to air pollution, particularly during pregnancy and early childhood, may affect brain development, cognitive abilities and behaviour.
Air pollution is often linked to coughing, wheezing, asthma, and other respiratory problems. But its effects may extend much further, potentially affecting one of a growing child's most important organs: the brain.
A growing body of research suggests that exposure to fine particulate matter (PM2.5) and other air pollutants during pregnancy and childhood may interfere with brain development, affecting processes involved in learning, memory, attention, and emotional regulation.
The concern is particularly significant for children living in cities such as Delhi, where pollution levels can remain high for prolonged periods. The developing brain is especially vulnerable because it changes rapidly from pregnancy through adolescence, as neural connections form and strengthen.
How does pollution reach the brain?
PM2.5 particles are small enough to penetrate deep into the lungs. Some ultrafine particles and pollution components may enter the bloodstream, while others can trigger inflammatory responses that affect organs beyond the respiratory system.
Scientists believe air pollution can affect the brain through several mechanisms, including inflammation, oxidative stress and damage to the blood-brain barrier, which normally protects the brain from harmful substances.
A 2021 study, How air pollution alters brain development: the role of neuroinflammation, published in Translational Neuroscience, says Air pollution can damage the body's natural protective barriers, including those in the nose, lungs, and gut. It can also weaken the blood-brain barrier, which normally prevents harmful substances from entering the brain. When these barriers are damaged, toxic particles from polluted air can enter the body and potentially reach the brain.
“Fine particulate matter (PM2.5), one of the most harmful components of air pollution, is small enough to penetrate deep into the lungs. Some ultrafine particles and pollutant components can cross biological barriers or trigger systemic inflammatory responses that affect the brain,”.
How does it damage the brain
The researchers say, once inside, these pollutants can trigger inflammation in the brain, known as neuroinflammation. This inflammation can damage or kill brain cells and may affect children's memory, learning, attention and other thinking abilities.
The effects may be subtle at first, but research suggests they can affect children and adults and may have long-term consequences for brain health. Some researchers believe that these changes could be early signs of processes linked to neurodegenerative diseases.
These processes may interfere with the formation of neural connections and the development of white matter, the nerve fibres that connect different regions of the brain and help them communicate.
A 2022 study published in Environmental Pollution used advanced neuroimaging (magnetic resonance imaging or MRI) to show that exposure to PM 2.5 during pregnancy and childhood alters white matter microstructure and changes brain volumes by the time children reach ages 9 to 12.
White matter acts as the brain's "communication wiring"; when its microstructure changes, the brain's speed and efficiency in processing information are disrupted.
Why is the developing brain particularly vulnerable?
A child's brain does not develop all at once. Different regions mature at different stages, with the brain continuing to develop through adolescence and into early adulthood. During this period, nerve cells form connections, neural networks become more specialised, and the brain develops the ability to process information, control emotions, maintain attention and make decisions.
Pollution may affect IQ and cognitive abilities.
A systematic review and meta-analysis published in Environmental Health in November 2024 examined the relationship between PM2.5 exposure and children's intelligence.
The researchers analysed six studies involving 4,860 children across North America, Europe and Asia. They found that every 1 microgram per cubic metre increase in PM2.5 exposure was associated with a 0.27-point reduction in full-scale IQ scores.
Research from the Kalinga Institute of Industrial Technology (KIIT) in Odisha, presented at the World Conference on Lung Health, found that children aged 6–8 living in heavily polluted areas scored nearly 20 points lower on intelligence quotient (IQ) tests than peers in cleaner environments.
A study highlighted by the Institute of Economic Growth showed that a 1 μg/m³ increase in average \(PM_{2.5}\) exposure over 12 months is associated with a 10–16 percentage-point drop in mathematics scores and a 7–9 percentage-point drop in reading performance among children.
"We have evidence suggesting that air pollution can affect cognitive development. A study from Barcelona found that children attending schools in areas with higher air pollution had poorer working memory than children studying in areas with lower pollution,” says Dr Taneja.
"Think about that for a moment. The pollution levels in those parts of Barcelona are still considerably better than what children in Delhi are exposed to. "We do not fully understand what prolonged exposure to such high levels of pollution is doing to a child's developing brain.
What about attention and behavioural problems?
Researchers have also examined the relationship between prenatal pollution exposure and behavioural development.
A 2015 study published in JAMA Psychiatry investigated children exposed to polycyclic aromatic hydrocarbons (PAHs), pollutants produced by the incomplete combustion of fuels and other organic materials.
The researchers found that prenatal exposure was associated with disturbances in the development of white matter, slower information-processing speed and more behavioural problems, including symptoms associated with ADHD. Postnatal exposure was also associated with additional changes in brain development.
While these findings do not establish that air pollution causes ADHD, they add to concerns about the possible effects of prolonged exposure during critical stages of childhood development.
Air pollution also affects blood vessels and can cause stroke
Dr Sudhir Kumar, neurologist at Apollo Hospitals, Hyderabad, says air pollution is increasingly being recognised as an important risk factor for cardiovascular and neurological diseases.
"Traditionally, we talk about diabetes, hypertension and cholesterol when discussing stroke risk. However, research published in major journals, including The Lancet, has highlighted the growing contribution of environmental factors such as air pollution," he says.
Explaining how pollution damages blood vessels, he says: "The underlying mechanisms include inflammation and endothelial damage. The endothelium is the inner lining of blood vessels. According to Dr Kumar, pollutants entering the bloodstream can contribute to inflammation and damage this lining, promoting platelet accumulation, narrowing of blood vessels, and clot formation. Over time, these changes can increase the risk of cardiovascular events, including heart attacks and strokes.
Protecting children requires cleaner air.
For children, the concern is that exposure can begin during pregnancy and continue through infancy, school years and adolescence. Even when children are kept indoors, outdoor pollutants can enter homes.
Reducing exposure during severe pollution episodes, using appropriately sized HEPA air purifiers and modifying outdoor activities can help. Pregnant women and young children also need particular protection.
But individual precautions cannot substitute for cleaner air.
The danger is that the consequences may not be immediately visible. A child may have no obvious respiratory symptoms while exposure to polluted air affects biological processes essential for learning, memory, and development. Protecting children from air pollution, therefore, is not just about helping them breathe better today; it is about safeguarding their developing brains and their health in the years ahead.