Analysis in the latest study found that for every decrease of 10 micrograms per cubic meter of particulate pollution in a city, the average life expectancy of residents in the city grew by more than seven months.
The average PM2.5 levels in the 51 cities studied dropped from 21 to 14 micrograms per cubic meter during the 1980s and 1990s. Health gains were also found in cities that initially had relatively clean air but then made further improvements in reducing air pollution.
