A new study has concluded as many as 660 million people or half of India's population could add 3.2 years to their lifespan, if air quality met the national safe standard. In other words, compliance with standards can save up to 2.1 billion life years alone in India.

Authored by Michael Greenstone, Director of the Energy Policy Institute at Chicago with prominent economists and public policy experts from Yale and Harvard University, the study looks at air quality data in different parts of the country from pollution control boards and satellite data.

The study using the 2011 census data estimates that 660 million people (54.5% of the population) live in regions that do not meet the annual PM 2.5 standard of 40 microgramme per cubic metre, and 262 million people (21.7% of the population) live in regions with air pollution levels more than twice this standard.

The study, however, arrived at the life expectancy figures using an earlier study by Greenstone conducted in China. Through this study, he was able to separate the effect of pollution to an extent from other factors of mortality. It had inferred that with every additional 100 micrograms of total suspended particulate matter per cubic meter in the atmosphere, life expectancy at birth was lowered by three years.