Large vans and minibuses which are more than 10 years old are facing a new charge of £100 a day in Greater London, if they fail to meet pollution limits.
It is the first time the vehicles have fallen under the Low Emission Zone, which covers most roads inside the M25.
From Tuesday, tougher restrictions will also mean £200 daily fees for lorries, buses and coaches which fall short of European Union standards on pollution.
The Green Party said the mayor should have enforced the charges sooner.
Also among the new regulations is a ban on black cabs which were produced more than 15 years ago.
This means about 2,600 vehicles, or 10% of the total fleet, will become unlawful as their licence plates expire.
And a "no-idling" campaign will be launched this month, to encourage all drivers to turn off their engines if stationary.
"Delivering cleaner air is key to my goal of creating a better quality of life for Londoners," said Mayor Boris Johnson.
Last April smog in London reached its highest level since 2003, official figures found.
But Darren Johnson, a Green Party member of the London Assembly, said the mayor had the chance to introduce the new rules 15 months ago.
Delaying their implementation had "contributed to London's appalling air pollution during the last year", and few incentives were available to cut the cost of replacing vehicles, he said.
"The mayor has failed to help out hard-pressed individuals and small businesses by funding a targeted scrappage and conversion scheme," Darren Johnson said.
"Black cabs have been promised help to update their cabs, but this has been done at the expense of funding ambitious plans for electric and hydrogen cabs in the future."