Air pollution is the greatest external threat to human life expectancy on the planet. According to the Air Quality Life Index (AQLI) presented by the Energy Policy Institute at the University of Chicago (EPIC), air pollution is responsible for shortening the average global lifespan by 2.3 years. This translates to a cumulative loss of 17.8 billion life years.

According to the report, more than half of the total global life years lost due to elevated pollution can be attributed to South Asia, specifically accounting for 52.8 percent.

South Asia which is the global pollution epicenter, nearly all of the approximately 673.7 million inhabitants reside in regions where particulate pollution surpasses the standards set by the World Health Organization (WHO). As per the World Health Organisation (WHO) guidelines the annual average concentrations of PM2.5 should not exceed 5 µg/m3.

Across South Asia, air pollution reduces average life expectancy by 1.6 years relative to what it would be if the WHO guidelines was met.

In the 11 countries that make up the region, an estimated 1.1 billion total life years are lost due to air pollution.

How India fares | Indians are losing 5.3 years of life to air pollution. The official PM2.5 concentration benchmark in the country is set at 40µg/m3. However, India's yearly mean PM2.5 concentration reached 56.2 µg/m3 in 2020 and further increased to 58.7 µg/m3 in 2021.

Ranked as the world's most polluted megacity, Delhi contends with staggering levels of pollution. Its average yearly particulate pollution in 2021 reached 126.5 µg/m3, surpassing the WHO guidelines by over 25-fold.

How big a killer is air pollution? | A comparison of major global threats to life expectancy in selected South Asian countries.

If countries could meet WHO guidelines, the potential gains in life expectancy from permanently reducing PM2.5 from 2021 concentrations to the WHO guideline in the 10 most polluted countries in the world.