“The significant effects we are observing even below the Indian air quality limits are alarming,” said Bhargav Krishna, fellow at the Sustainable Futures Collaborative and the study’s lead author, “suggesting that perhaps we have set our standards higher than they should be.”
New Delhi: The death toll from India’s air pollution is elevated even in cities previously thought to have relatively clean air, underscoring how the problem extends beyond megacities such as Delhi, according to a study in the journal The Lancet Planetary Health.
Thursday’s report shed new light on the pervasive nature of the country’s air-quality crisis. It found that a significant share of the 33,000 yearly deaths attributable to air pollution in 10 cities examined was recorded in coastal centers like Bangalore, Chennai, Kolkata and Mumbai, where air quality is considered to be moderate.
On average, 7.2 per cent of all daily deaths in 10 of the largest and most polluted cities in India, including Delhi, Bengaluru and Mumbai, were linked to PM2.5 levels higher than World Health Organization (WHO) guidelines for safe exposure, according to a study published in The Lancet Planetary Health journal.
“The significant effects we are observing even below the Indian air quality limits are alarming,” said Bhargav Krishna, fellow at the Sustainable Futures Collaborative and the study’s lead author, “suggesting that perhaps we have set our standards higher than they should be.”
The researchers looked at 3.6 million deaths between 2008 and 2019 across the sample areas, and overlapped them with a detailed map of the distribution of PM 2.5, a compound of cancer-causing pollutants so small they can penetrate the bloodstream.
Delhi was found to have the largest fraction of daily and yearly deaths attributable to PM2.5 air pollution, caused by particles sized 2.5 micrometres or less in diameter.
Sources of such pollution include vehicular and industrial emissions.
Researchers said that daily exposure to PM2.5 pollution in Indian cities is linked with a higher risk of death, and locally created pollution could be possibly causing these deaths.
The international team included researchers from Varanasi’s Banaras Hindu University and the Centre for Chronic Disease Control, New Delhi.
They found that an increase of 10 micrograms per cubic metre in the average of fine particulate matter (PM2.5) pollution measured over two days (short-term exposure) was related to 1.4 per cent higher daily mortality.
The death risk was found to be doubled (2.7 per cent) per a 10 microgram per cubic metre increase, when the researchers restricted their analysis to observations below Indian standards of air quality, less stringent than WHO guidelines for safe exposure, which prescribe 15 micrograms per cubic metre of PM2.5 over a 24-hour period.
Indian air quality standards prescribe 60 micrograms per cubic metre of PM2.5 over a 24-hour period.
City-wise, the authors found a 0.31 per cent rise in daily mortality per a 10 micrograms per cubic metre increase in PM2.5 in Delhi, while in Bengaluru, the rise was 3.06 per cent.
The links between daily exposure to PM2.5 pollution and locally created pollutants were found to be stronger in models which the researchers used to explore cause-and-effect relationships.
Therefore, it was possible that the locally generated pollutants were causing these excess deaths, the authors said.
“The causal effects were especially strong in cities with lower concentrations of air pollution, such as (Bengaluru), Chennai, and Shimla,” the authors wrote.
Agencies