Not only is air pollution bad for our lungs and heart, it turns out it could actually be making us less intelligent, too. A recent study found that in elderly people living in China, long-term exposure to air pollution may hinder cognitive performance (things like our ability to pay attention, to recall past knowledge and generate new information) in verbal and maths tests. As people age, the link between air pollution and their mental decline becomes stronger. The study also found men and less educated people were especially at risk, though the reason why is currently unknown.

We already have compelling evidence that air pollution – especially the tiniest, invisible particulates in pollution – damages the brain in both humans and animals. Traffic pollution is associated with dementia, delinquent behaviour in adolescents, and stunted brain development in children who attend highly polluted schools.

In animals, mice exposed to urban air pollution for four months showed reduced brain function and inflammatory responses in major brain regions. This meant the brain tissues changed in response to the harmful stimuli produced by the pollution.

We don’t yet know which aspects of the air pollution particulate “cocktail” (such as the size, number or composition of particles) contribute most to reported brain deterioration. However, there’s evidence that nanoscale pollution particles might be one cause.