The toxic gas nitrogen dioxide (NO2) can lead to respiratory disease and can cause the lining of the lungs to become inflamed.
The government is the subject of legal action after failing to deal with the high level of the toxic gas in the country's cities.
Most British cities have plans to reduce traffic fumes to within the legal limit by 2020, however London has insisted that it could not meet the NO2 targets set for it in 1999 until at least 2025.
London has the highest levels of NO2 of any European capital city and the UK has the highest proportion of zones breaching legal limits.
More top news
Ria Chatterjee spoke to a former prisoner convicted of manslaughter. He claims the key to rehabilitation is mental health support.
The Met Police chief said that if artificial intelligence could help identify potential terrorists most people would want them to use it.
Sadiq Khan's Tory rival in May's election claimed scrapping the free pass would release £44m to spend on tackling knife crime.