Testing along West End Lane showed many residents were being exposed to nitrogen dioxide levels more than 50 per cent above permitted levels.

Volunteers joined members of the Fortune Green and West Hampstead Neighbourhood Development Forum to test pollution levels along West End Lane and at other points throughout the neighbourhood last November.

The experiment was spawned after a member, Helena Paul, witnessed the road becoming more and more crowded with traffic often at a stand-still during the morning and evening rush.

Using nitrogen dioxide diffusion tubes, the forum selected 12 sites; one on Mill Lane close to the turn-off to Beckford Primary School, one on West End Lane close to Emmanuel Primary School, two on Finchley Road, five on West End Lane with another on Hilltop Road.

A further tube was positioned on Iverson Road not far from the junction with West End Lane along with another site on Lymington Road at the junction with Alvaney Road.

Ms Paul reported that all the results, bar the tube on Hilltop Road, were above the maximum legal level of 40g/m3.

Along West End Lane, readings ranged between 60g/m3 and 67g/m3 which is 50 per cent above the maximum legal limit.

Readings in Mill Lane registered 57g/m3.

“At the junction of Fortune Green Road and Finchley Road, they were 165.4g/m3 which is close to the highest I have seen recorded in London,” Ms Paul said.

“It should be noted that there are a lot of people living around this junction and a lot of new building taking place there as well.

“This means that along West End Lane, Mill Lane, Lymington Road and Iverson Road, people – including primary school children – are being exposed to 50 per cent over the maximum permitted levels of nitrogen dioxide and on Finchley Road it is four times the legal level.

“We think that action in London to control air pollution is really urgent and these results just underline this fact.”

Air pollution can significantly impact health, causing nearly 9,500 premature deaths every year in London, and is linked to conditions such as heart and lung disease, cancer and asthma.

Camden Council held an air quality conference during the same month attended by more than 100 residents, businesses and community groups.

Cabinet Member for Sustainability and Environment Cllr Meric Apak confirmed Camden would work towards meeting the six key priorities of introducing car-free days, moving toward becoming a diesel-free borough, promoting electric vehicles, having more trees and green spaces, working towards more measurement and target setting in Camden’s Clean Air Action Plan and working more closely with schools to tackle air quality.