London saw 13% fall in nitrogen dioxide levels in 2019 but its still worst in UK
It comes after Sadiq Khan introduced an Ultra Low Emission Zone in April 2019
But a list of 800 most-polluted roads has revealed 600 are currently in London
Landmark inquest ruled air pollution contributed to nine-year-old girl s death
33 out of 43 UK air quality zones still have nitrogen dioxide above legal limits
The Marylebone Flyover in London is the most-polluted spot in the country