EXPOSURE to air pollution is linked to an increased severity of mental illness, a new study suggests.

The research, published in the British Journal of Psychiatry, found that even a small amount of exposure to nitrogen dioxide (NO₂) – emitted by diesel vehicles – leads to an 18 per cent rise in the risk of hospital admission.

The danger is also significant for small-particle pollution, which is produced by burning any fossil fuel, according to the study. 

Scientists stressed that the findings, likely to apply to most cities across the world, showed that cutting air pollution was essential to greatly reduce human suffering and the high economic costs caused by long-term mental disorder.

Research lead Ioannis Bakolis, of Kings College London, welcomed the introduction of low-emissions zones that have seen air pollution rates fall in cities such as London, but he warned: “Even at low levels, you can observe this kind of very important effect.”

The study tracked patients in the south of the capital from their first contact with mental health services and used high-resolution estimates of air pollution in their neighbourhoods.

The quarterly average NO₂ levels in the study area varied by between 18 and 96 micrograms per cubic metre (µg/m³).

Researchers found that people exposed to 15µg/m³ higher levels of pollution had an 18 per cent greater risk of needing admission to hospital and a 32 per cent greater risk of needing outpatient treatment 12 months later. 

The results, which could not be explained by other factors, confirm the findings of recent research that established a link between air pollution and significant rises in depression, anxiety and suicide rates.

A global review in 2019 concluded that emissions may be damaging every organ in the human body, especially the heart and lungs. The World Bank estimates that the problem also costs the global economy a staggering $5 trillon (£3.6tn) a year. 

The University of Bristol’s Joanne Newbury, part of the research team, said: “Air pollution is modifiable. We know there are interventions that can be used, such as expanding low-emission zones.

“Mental health interventions at the individual level are actually quite difficult.”

Professor Kevin McConway of the Open University said it was “not easy for people to avoid pollution,” so to tackle the problem, “communal action on a broad scale” was required. 

A Labour for a Green New Deal spokesperson said: “For a long time it’s been clear that damaging our environment has severe effects on our own health, from the effects of excess temperatures to pandemics becoming more likely.

“This is more evidence in this vein, and it further strengthens the case for taking the environment out of the market’s hands.”