Cleaner air in the US during the last two decades has given an average American 21 weeks of life extension. Cleaner air refers to reducing fine particles emitted by automobiles, diesel engines, steel mills and coal-fired plants.

Changes in smoking habits have also made a major impact on the longevity. Improved socio-economic conditions were also a contributing factor in increasing the life expectancy.

Researchers at Brigham Young University conducted a study which shows that reduction in smoking and improved socio-economic factors contribute towards an increased life span. But decrease in pollution is a major factor. Decrease of every 10 micrograms of pollutant particles per cubic meter of air was associated with an increase of more than seven months in average life expectancy.

Areas such as Akron, Ohio, and Philadelphia in particular showed that kind of drop in air pollution.

The bigger the decline, the better were living conditions for residents. In some areas like Buffalo, New York and Pittsburgh the fine-particle counts dropped by 13 to 14 micrograms. This means that the average life span has been increased by about 43 weeks.