In recent years scientists have found that children who grow up surrounded by air pollution are more likely to have a broad range of “neuro-developmental” difficulties, including autism and various kinds of cognitive impairment. However, only a handful of studies have looked at the ways in which the noxious gases and microscopic particles that mothers and young children inhale affect the brain during critical stages of its growth.

A group led by Mònica Guxens, of the Barcelona Institute for Global Health, found that exposure to air pollution before birth appeared to have slowed the development of several brain regions that play an important role in people’s capacity for self-denial and sustained effort. This lack of inhibition could in turn cause “cognitive delays” when the children get older, the scientists argue in Biological Psychiatry.

“We need this function in our daily life,” Dr Guxens said. “It controls our impulses and our selective attention. Children need it to learn and for making decisions in later life. We’re interested to see what will happen: is there going to be an impact on their academic work, are there going to be clinical implications? It might be that this will lead to problems later.”

The results were drawn from MRI scans of 873 children between the ages of six and ten in Rotterdam. Even though 99.5 per cent of their mothers had lived with nanoparticle pollution levels well below EU legal limits while they were pregnant, the pollution still appeared to have taken its toll.

Children who had been exposed to more pollution in the womb did worse on a test of their ability to block out irrelevant stimuli. They also had thinner outer layers in the precuneus and the rostral middle frontal regions of their brains, both of which are involved in cognitive inhibition.

Experiments on animals show that so-called fine particles are able to pass through the placenta and affect the brain of the foetus. Dr Guxens said that there was probably no such thing as a safe concentration of air pollution.


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