Motorists driving into central London face a new 'toxic tax' from today.
The £10 (NZ$17.90) fee mainly applies to diesel and petrol vehicles registered before 2006. Cars, vans, minibuses, coaches and other goods vehicles that don't meet clean-air standards will have to pay on top of the existing congestion charge.
London mayor Sadiq Khan says the tough new surcharge is aimed at reducing dangerously high pollution levels.
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"We've got a health crisis in London, we've got a situation where the air in London is a killer and makes people sick.
"We've got more than 9000 deaths prematurely each year, caused by the poor-quality air."
London is also one of 12 major cities around the world promising to buy zero-emission buses from 2025.
The cities also include Auckland, Paris, Los Angeles and Mexico - representing a cumulative population of almost 80 million.
C40 Cities Climate Leadership Group, made up of 40 countries that have committed to reverse climate change, estimates there are 59,000 buses of all types operating on the streets of the 12 cities.