Watch our animated version on BBC Reel: How dirty air is polluting our minds

It was in 2011 that Sefi Roth, a researcher at the London School of Economics was pondering the many effects of air pollution. He was well aware of the negative outcome on health, increased hospital admissions and also mortality. But maybe, he thought, there could be other adverse impacts on our lives.

To start with, he conducted a study looking at whether air pollution had an effect on cognitive performance.

Roth and his team looked at students taking exams on different days – and also measured how much pollution was in the air on those given days. All other variables remained the same: The exams were taken by students of similar levels of education, in the same place, but over multiple days.

He found that the variation in average results were staggeringly different. The most polluted days correlated with the worst test scores. On days where the air quality was cleanest, students performed better.

“We could see a clear decline [of performance] on days that were more highly polluted,” says Roth. “Even a few days before and a few days after, we found no effect – it’s really just on the day of the exam that the test score decreased significantly.”

To determine the long-term effects, Roth followed up to see what impact this had eight to 10 years later. Those who performed worst on the most polluted days were more likely to end up in a lower-ranked university and were also earning less, because the exam in question was so important for future education. “So even if it’s a short-term effect of air pollution, if it occurs in a critical phase of life it really can have a long-term effect,” he says. In 2016 another study backed up Roth’s initial findings that pollution can result in reduced productivity.

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These insights are what led to Roth’s most recent work. In 2018 research his team analysed two years of crime data from over 600 of London’s electoral wards, and found that more petty crimes occurred on the most polluted days, in both rich and poor areas.

Although we should be wary of drawing conclusions about correlations such as these, the authors have seen some evidence that there is a causal link.