A new study from the University of Exeter has found that trees could be serve an additional function in the battle against air pollution.

The study found that in heavily polluted neighbourhood an increased number of trees actually reduced the amount of people who were admitted to hospital with asthma attacks.

Published in the journal Environment International, the study looked at over 650,000 serious asthma attacks over a 15 year period. It then compared emergency hospitalisations across 26,000 urban neighbourhoods in England.

In the worst polluted areas the data was loud and clear – trees made all the difference.

“We wanted to clarify how urban vegetation may be related to respiratory health.” explains Dr Ian Alcock, research fellow at the University of Exeter’s Medical School.

“We know that trees remove the air pollutants which can bring on asthma attacks, but in some situations they can also cause localised build-ups of particulates by preventing their dispersion by wind. And vegetation can also produce allergenic pollen which exacerbates asthma.”

What they found however was that despite these concerns, the increased vegetation did significantly more good than harm.

What’s interesting is that this only applies to trees in particular.

Increased use of parks, or green spaces can reduce asthma attacks but only at low pollution levels. Using them to combat high pollution areas just simply wasn’t effective.

Instead trees can very effectively remove pollutants from the air, even at extraordinarily high levels.

The team hope that their findings can help inform local councils in their urban planning policies – creating environments that balance each other out and ultimately result in a space that prioritises air quality.

There are public health implications as well, over 5.4 million people receive treatment for asthma in the UK which costs the NHS around £1 billion every single year.

While London continues to struggle with its own air pollution issues, cities like Paris have already started trialling projects to try and combat the global problem.

In 2016 Paris trialled a series of ‘smart trees’. The “trees” combine a vertically-installed moss culture with air pollution monitors and reduce fine dust and nitrous oxides 275 times more efficiently than normal trees, according to the manufacturer.