Drivers with older more polluting cars will face a £12.50 charger per day to enter the centre capital.
The £12.50-a-day Ultra-low emission zone charge has come into force as of today (8 April).
Diesel cars must be less than roughly four years old to avoid the charge, while petrol cars must be less than about 13 years old.
He claimed the Ulez will “help clean our air and reduce harmful road transport emissions”.
Mr Khan commissioned a study by King’s College London and Imperial College London which found that poor air quality leads to about 1,000 London hospital admissions for asthma and serious lung conditions every year.
He said: “As someone who developed adult-onset asthma over the last few years, I know from personal experience that London’s toxic air is damaging people’s health.
“This study is a stark reminder that air pollution disproportionately affects the most vulnerable Londoners and I’m doing everything in my power to protect children, the elderly and those with respiratory conditions from our filthy air.”
The Ulez initially covers the same area as the congestion charge zone, but will be extended to the whole of inner London within the North and South Circular roads from October 2021.
Charges apply at all times and are on top of the congestion charge, which is £11.50 between 7am and 6pm on weekdays.
All vehicle types apart from black taxis are liable for the Ulez charge unless they meet certain emissions standards or exemptions.
