According to a study published in The Lancet Planetary Health journal, an average of 7.2 per cent of daily deaths in 10 of India's largest and most polluted cities, including Delhi, Bengaluru, and Mumbai, were associated with PM2.5 levels exceeding the World Health Organization (WHO) guidelines for safe exposure.
Delhi has the highest proportion of daily and annual deaths linked to PM2.5 air pollution, which consists of particles 2.5 micrometres or smaller in diameter. The primary sources of this pollution are emissions from vehicles and industries.
An international research team, including scientists from Banaras Hindu University in Varanasi and the Centre for Chronic Disease Control in New Delhi, found that daily exposure to PM2.5 pollution in Indian cities is associated with an increased risk of death. They suggest that locally generated pollution might be a contributing factor to these fatalities.
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 researchers found that the death risk doubled, reaching 2.7%, for every 10 microgram per cubic metre increase in PM2.5 levels. This analysis was restricted to observations that met Indian air quality standards, which are less stringent than the WHO guidelines. The WHO recommends a safe exposure limit of 15 micrograms per cubic metre of PM2.5 over a 24-hour period.
Indian air quality standards set a limit of 60 micrograms per cubic meter of PM2.5 over a 24-hour period. The study revealed that in Delhi, there was a 0.31% increase in daily mortality for every 10 micrograms per cubic meter rise in PM2.5. In contrast, Bengaluru experienced a 3.06% increase. The researchers discovered stronger correlations between daily PM2.5 exposure and locally produced pollutants using models designed to investigate 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.
The study, "the first multi-city, time series analysis of short-term exposure to PM2.5 and daily mortality in India," looked at roughly 36 lakh daily deaths across ten Indian cities between 2008 and 2019. Other cities included in the analysis were Ahmedabad, Hyderabad, Kolkata, Pune, Shimla and Varanasi.
(with PTI inputs)
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