Summary

Annual exposure to air pollution increases the risk of mortality in India indicating an urgent need to reduce the levels of air pollution across the country.

A new study published in the Lancet Planetary Health found that long-term exposure to PM_2.5 increased deaths by 1.5 million deaths per year in India compared to if it met the WHO guidelines. We observed that the risk is high even at lower air pollution levels, indicating the need to reduce air pollution levels across the country. The study included annual death data reported across all districts and PM_2.5 exposure from a spatio-temporal model built for India. 

Major findings:

1. Every 10 μg/m³ increase in annual PM_2.5 exposure is associated with an 8.6% increased risk for mortality across India.
2. Unlike previous studies, this study used PM_2.5 exposure from a fine spatio-temporal model built for India and annual mortality counts reported across all districts of India.
3. First Indian study to use difference-in-difference method, a causal methodology to isolate the effect of long-term PM_2.5 exposure (annual) and all-cause mortality.
4. During the study period (2009 to 2019), 25% of all deaths (~1.5 million deaths a year) were attributed to annual PM_2.5 exposure higher than the WHO guideline value of 5 μg/m³ across the country.
5. About 0.3 million annual deaths are attributed to annual exposure to PM_2.5 above the Indian National Ambient Air Quality Standards (NAAQS).
6. The exposure-response function revealed higher incremental risk for mortality at lower PM_2.5 concentrations and levelling off at higher PM_2.5 concentrations.

Implications:

• The study results highlight the extent of the mortality burden due to PM_2.5 pollution in the world’s most highly populated country. 
• The results underpin the need for stricter air pollution guidelines to prevent the excess mortality due to air pollution.

The results highlight a huge mortality burden and the need for stricter national ambient air quality standards in India. This research was conducted by members  from the CHAIR-India consortium comprising academic institutions in India (Centre for Health Analytics Research and Trends (CHART), Ashoka University, Sonipat, Haryana & Centre for Chronic Disease Control, New Delhi), Sweden (Karolinska Institutet, Stockholm), USA (Harvard University, Boston University, Boston, Icahn School of Medicine at Mount Sinai), Israel (Ben-Gurion University of the Negev) and Italy (Department of Epidemiology, Lazio Region Health Service/ASL Roma 1).