London (AFP) - Air pollution was the cause of the early deaths of almost 9,500 people in Britain's capital city in 2010, according to research by King's College London.
The study showed for the first time the impact of nitrogen dioxide from exhaust fumes and fossil fuel burning, and showed the problem was far greater than previously thought.
According to the study for Transport for London and the Greater London Authority, in 2010 there were 3,537 premature deaths in London due to particulate matter, and 5,879 due to nitrogen dioxide.
The knock-on cost to the economy was estimated at Â£3.7 billion.
"In one of the busiest cities in the world people are at greater risk of being killed by the air they breathe than in a car accident," said Dr Penny Woods, chief executive of the British Lung Foundation.
"These figures suggest that, every year, six times as many people are killed by air pollution in London as are killed in road traffic accidents across the entire country."
But London Mayor Boris Johnson said the data was five years out of date and did not reflect a series of measures undertaken to clean the air like hybrid buses and scrapping old taxis.
"This is a snapshot of the true impact of air pollutants on our health," Johnson said.
"My greatest priority remains to protect the well-being and environment of Londoners, and this scientific evidence will ensure we have all the information needed to continue delivering comprehensive measures that bring real change."