The Ultra Low Emission Zone (ULEZ) entered into force in central London.
Drivers of older, more polluting vehicles are taxed at any time to enter the congestion zone.
Transport for London (TfL) hopes that the move will reduce the number of polluting cars in the capital and estimates will affect around 40,000 vehicles every day.
London Mayor Sadiq Khan said it is "important that we make progress" in tackling the toxic air of the capital.
However, the Federation of Small Enterprises (FSB) said that many small businesses were very concerned about the future of their business & # 39; as a result of the & # 39; additional cost burden & # 39 ;.
Most non-compliant vehicles have to pay £ 12.50 for daily entry to the area on top of the congestion charge.
Vehicles can be checked using the TfL online checker, but in general they are non-compliant:
- Motorcycles that do not meet Euro 3 standards (vehicles from before 2007)
- Petrol cars & # 39; s and cars & # 39; s that do not meet Euro 4 standards (vehicles before 2006)
- Diesel cars and vans that do not meet the Euro 6 standards (vehicles before 2015)
- Buses, coaches and trucks must meet or exceed Euro 6 standards or pay £ 100 per day
Anyone who does not pay the costs will be fined £ 160, although a first offense can only be a warning letter.
The ULEZ will be expanded in 2021 to cover the entire area between the North and South Circular roads.
TfL estimates that the initial scheme will lead to a reduction of toxic emissions from road transport by around 45% in two years.
According to Khan, air pollution in London was a "public health emergency" and it was "the poorest Londoners suffering from the worst air quality".
Tom Edwards, BBC correspondent for transport in London
A very humid, foggy morning in London and most people will probably not notice that something has changed.
But London has taken a big step in trying to clear its air.
Given the start signal in 2013 by the former mayor Boris Johnson, Sadiq Khan brought the ULEZ a year ahead and plans to expand it in 2021.
According to the town hall, the ULEZ has already changed its behavior, with a fall in vehicles in central London and an increase in conforming vehicles before launch.
The plan is that the air in London in 2025 meets the legal limits.
Other cities are talking about diesel bans, but London has taken the radical step of placing it at the forefront of clean airships. Other cities keep a close eye on.
Sandra Green from the Clear Air Parents Network told BBC Breakfast that it was a "really big step forward".
"Air pollution caused by traffic, caused by individual cars, causes health problems for the next generation … and it's time we did something about it," she said.
City hall figures show that more than 60% of all vehicles that passed through the loading zone in March already met the new restrictions.
Nearly 27,000 non-compliant vehicles have been taken off the road in the last two months and the total number of cars entering central London has fallen by 11%.
However, some drivers have spoken of their anger that governments had previously recommended buying diesel cars that are now being attacked by the indictment.
Jim Parker, managing director of car collection company Boleyn, said the charge was "really unfair."
"It's not just us, it's all over the industry – everyone who owns a van or truck and makes money with it," he said.
"We have had a local company where the margins are so tight, they must now stop trading because they cannot get a retrofit set and they cannot afford new vehicles."
- London pollution & # 39; stunt lung capacity & # 39;
- Reality Check: what should owners of old diesels do?
Go Ultra Low, a government-sponsored electric vehicle campaign, said, "There has never been a better time for drivers to switch to electric switching."