Published: 8 April 2026 | Author: Team JanVayu | Reading time: 4 min
For years, studies in India showed that higher PM2.5 went with higher mortality. Critics, including some in government, answered that correlation is not causation. Poverty, diet, smoking and access to healthcare, they said, could explain the pattern.
Two studies published in The Lancet Planetary Health in 2024 (July and December) make a strong case against that argument. They use causal methods borrowed from economics, and they find that PM2.5 pollution directly causes excess deaths in India, on a very large scale.
The first study: districts compared over time
The first study (Jaganathan et al. 2024, Lancet Planetary Health), used India's district-level mortality data and a difference-in-differences approach, a method common in economics for separating cause from other influences. The authors compared districts where pollution changed with districts where it did not, while allowing for economic conditions, weather and demographic trends. They estimated that long-term PM2.5 exposure causes approximately 1.5 million additional deaths per year in India compared to a scenario where the country met the WHO annual guideline of 5 micrograms per cubic metre. Update: the Lancet Countdown 2025 (published October 2025) attributes 1.72 million deaths to anthropogenic PM2.5 in India in 2022. That measures something different from the 1.5 million figure here and does not revise it. The 1.5 million figure is the Jaganathan et al. estimate, kept as the causal-study reference.
This is a model-based estimate, not a head-count. It takes a regression coefficient (8.6% higher mortality per 10 µg/m³), estimated from observed district mortality, and applies it to India's PM2.5 exposure above the WHO guideline (95% confidence interval 1.1 to 1.9 million). The method controls for the very factors that governments have cited to dismiss health burden estimates as speculative.
The second study: ten cities, day by day
The second study examined short-term exposure across ten Indian cities using causal modelling techniques. It found statistically significant increases in daily mortality associated with day-to-day PM2.5 changes. The risk per 10 µg/m³ was steeper below the Indian 24-hour standard (2.7%) than overall.
Short-term studies capture acute effects such as heart attacks, strokes and asthma crises, which occur within hours or days of a pollution spike. Earlier Indian studies relied on time-series correlations. This one gives much stronger evidence that deaths on high-pollution days come from the pollution itself, and not from cold weather, seasonal illness or other coincident factors.
Why the difference matters
Correlation and cause lead to different policies. When the evidence is correlational, policymakers can argue that cleaner air might not reduce deaths, and that better hospitals or more doctors could do more. Causal evidence removes that argument: cleaning the air saves lives, and the saving can be measured.
The 1.5 million figure (a separate estimate; the Lancet Countdown 2025 counts 1.72 million PM2.5-attributable deaths in 2022 on a different method) sits against the government's position in Parliament that there is "no conclusive data" on deaths exclusively due to air pollution (Lok Sabha reply, 9 December 2022).
Who gains from cleaner air
A complementary study published in Science Advances added a finding on fairness: the air quality improvements India has achieved in recent years have been shared unequally. Using improved daily PM2.5 satellite estimates, the researchers showed that wealthier areas, which have higher average PM2.5, saw larger recent falls (about 8.1% for the wealthiest against 3.6% for the poorest).
India's aggregate pollution statistics show small improvements on some measures, and they hide a widening gap between who breathes cleaner air and who does not. The communities with the least political power carry the greatest health burden.
What this means for policy
Taken together, these studies settle the scientific case for reducing air pollution. The open question for policymakers is how many deaths to accept while action stays slow.
The National Clean Air Programme, now at its 2026 deadline, was designed around a 40% reduction in PM10 concentrations. These studies, though, measure PM2.5, the fraction most strongly linked to mortality, while NCAP's target is for PM10. Even modest reductions in fine particulate matter would save hundreds of thousands of lives annually.