Between 1980 and 2000, Americans' average life span increased almost three years, and researchers believe that nearly 5 months of that increase is the result of dramatic improvements in air quality. Residents of cities that were most successful in reducing air pollution showed the biggest jump in life span. People living in Pittsburgh, Pennsylvania, for example, could expect to live an extra 10 months with their cleaner air. Many other factors also boost life expectancy, including improved socioeconomic status and reduction in smoking prevalence.