There is no safe level of air pollution. Every day, children are exposed to air pollutants during their journeys to and from school and in playgrounds and classrooms. Exposure to these harmful pollutants is linked to an ever-growing list of health problems, including asthma and other respiratory diseases.
More recently it has become clear that air pollution also has significant effects on the brain. This can result in cognitive impairments in children and increase the risk of dementia in the elderly. Children are both more at risk of exposure to air pollution and more vulnerable to its effects. We need to take urgent action to clean up air quality around schools and protect the health, wellbeing and development of children.
Combustion of fuels, such as from diesel engines and burning of wood, causes the release of air pollutants, including very fine particulates and gases such as NO2. When inhaled, very fine particles in the air can transfer to the bloodstream via the lungs to other parts of the body, including the brain, or directly to the brain from the nose through the olfactory nerve.
Exposure levels at school can have a significant effect on children’s cognitive development. Children spend up to eight hours a day at school and a worrying number of schools across the UK are surrounded by dangerous levels of air pollution. A recent report from Global Action Plan found that 27 per cent of UK schools are above World Health Organisation air pollution limits. The main source of air pollutants around schools are traffic related, largely from engine exhaust and brake and tyre wear. Road transportation releases vast quantities of harmful pollutants including fine and very fine particulate matter (PM10 and PM2.5), polycyclic aromatic hydrocarbons (PAHs) and nitrogen oxides (NOx).
A recent Manchester University study indicates that exposure to air pollution can have a negative impact on cognitive functioning in children. Traffic-related air pollutants such as nitrogen dioxide (NO2) and PM2.5 cause the greatest adverse effects on working memory and attention control.
Working memory is the ability to keep information in mind temporarily and to use it for the completion of mental tasks, and attention control is the ability to focus attention on specific stimuli or a wider goal for an extended period, and to ignore distractions. Both attention control and working memory have rapid trajectories of development during childhood. These skills are essential for effective learning in schools, and levels of working memory can affect later academic achievement. Exposure to air pollution can harm this developmental trajectory, especially over longer periods of time.
Our modelling exercise showed that if we can reduce pollution in and around schools by 20 per cent, then children’s working memory – a key feature of cognitive development – will improve by an additional 6 per cent, equivalent to an extra three weeks of learning in a 12-month period. If we can reduce pollution by 50 per cent, children’s working memory will improve similar to an extra seven weeks of learning in a 12-month period.
Childhood development represents a critical time window, when children are vulnerable to air pollution because important organs, such as lungs and brains, are developing. In addition to the immediate damage to health, including causing asthma, this can also affect health in later life. There is evidence that exposure to air pollution in early life can increase the risk of neurodegenerative disease in older age.
It is vital that local authorities and schools work closely to minimise children’s exposure to air pollution by reducing traffic around schools and implementing the Clean Air for Schools Framework. The recently announced Greater Manchester Clean Air Zone is a fantastic step towards tackling poor air quality, and other initiatives around the north are important, but we must maintain an additional level of focus on roads near schools if we want to protect children in their critical developmental years.
Martie van Tongeren is professor of occupational and environmental health at Manchester University