Air pollution was measured for two decades
Cuts in air pollution in US cities over recent decades have added an average of five months of life to their inhabitants, research suggests.
The New England Journal of Medicine study matched air pollution and life expectancy statistics from 51 cities between 1980 and 2000.
Scientists found people living 2.72 years longer by 2000 - 15% of which they attributed to falls in pollution.
Studies have found poor air quality can worsen lung and heart disease.
In the UK, official estimates have suggested that air pollution still reduces lifespan by an average of eight months, despite increases in air quality in recent years.
Meeting stricter emissions targets may reduce this burden by nearly a half, some experts have suggested.
The study, carried out between Brigham Young University and Harvard School of Public Health, used advanced statistical models to separate out the various other factors behind changes in life expectancy, such as smoking and wealth, as well as to account for migration to and from the cities studied.
The research focused on "PM 2.5" pollution - which measured levels of tiny particles with a diameter one-twentieth of the width of a human hair.
These fine particles can travel deeply into the lungs, and have been linked with the worsening of asthma and heart disease.
The researchers found that in those cities with the biggest shift from polluted to clean air, this had yielded an average of 10 more months lifespan to its residents.
For every decrease of 10 micrograms per cubic metre of particulate pollution, life expectancy increased by more than seven months.
In some of the previously heaviest-polluted cities, such as Pittsburgh and Buffalo, the fall was close to 14 micrograms per cubic metre.
Dr C Arden Pope, one of the study researchers, said it was a "remarkable" increase.
"We find that we're getting a substantial return on our investments in improving our air quality.
"Not only are we getting cleaner air that improves our environment, but it is improving our public health."
Professor Jonathan Ayres, a specialist in the medical effects of air pollution based at the University of Birmingham, said that similar studies had not been carried out in the UK or Europe because the necessary data had been gathered only in recent years.
However, he said that the lifespan estimates "seemed a little high".
"There's no doubt there are differences in the way that people in the US respond to air pollution compared to people in the UK.
"However, the research is a strong justification for the efforts that have been made to reduce pollution over the past couple of decades."
He said that work to improve air quality in the UK had made "good progress", with the areas of highest pollution targeted and car manufacturers persuaded to develop cleaner engines.
Despite this, he said there was some concern that levels of some types of pollution might actually rise over the next few years.