A new study from Karolinska Institutet shows that long-term exposure to air pollution contributes to millions of deaths in India. The research, published in The Lancet Planetary Health, emphasizes the need for stricter air quality regulations in the country.

Air pollution consisting of particles smaller than 2.5 micrometers in diameter, PM_2.5, can enter the lungs and bloodstream and is a major health risk in India. Researchers have now examined the link between these particles and mortality over a 10-year period. The study is based on data from 655 districts in India between 2009 and 2019.

“We found that every 10 microgram per cubic meter increase in PM_2.5 concentration led to an 8.6% increase in mortality,” says Petter Ljungman, last author and researcher at the Institute of Environmental Medicine at Karolinska Institutet.

The research analyzed the relationship between changes in air pollution levels and mortality. The results show that around 3.8 million deaths over the period can be linked to air pollution levels above India’s own air quality guidelines of 40 micrograms per cubic meter.

When compared to the stricter guidelines recommended by the World Health Organization (WHO)—only 5 micrograms per cubic meter—the figure rises to 16.6 million deaths. That’s almost 25% of all mortality during the study period.

The study also highlights that the entire population of India lives in areas where PM_2.5 levels exceed WHO guidelines. This means that almost 1.4 billion people are exposed year after year to air pollution that can negatively affect health. In some regions, levels of up to 119 micrograms per cubic meter were measured, significantly higher than what both the WHO and India consider safe.

“The results show that current guidelines in India are not sufficient to protect health. Stricter regulations and measures to reduce emissions are of the utmost importance,” said Petter Ljungman.

The Indian government has been running a national air pollution control program since 2017 to improve air quality, but the study shows that PM_2.5 concentrations have continued to increase in many areas. The researchers emphasize the importance of both reducing emissions locally and taking into account the long range of air pollution—PM_2.5 particles can travel hundreds of kilometers.

“Our study provides evidence that can be used to create better air quality policies, both in India and globally,” says Petter Ljungman.

Air pollution in India linked to millions of deaths