More than 7 per cent of daily deaths in 10 major Indian cities are linked to air pollution caused by PM2.5 concentrations that exceeded the World Health Organisation's (WHO) safe limits for safe exposure, according to a study published in The Lancet Planetary Health journal.
The study analysed data from cities including Ahmedabad, Bengaluru, Chennai, Delhi, Hyderabad, Kolkata, Mumbai, Pune, Shimla and Varanasi. It revealed that levels of PM2.5, tiny pollutants that can penetrate deep into the lungs and bloodstream, exceeded the WHO's safe limits of 15 micrograms per cubic metre on 99.8 per cent of the days.
Delhi has the highest fraction of daily and yearly deaths attributable to PM2.5 air pollution, which comprises particles 2.5 micrometres or less in diameter, the study said. These harmful particles stem mainly from vehicular and industrial emissions.
Annually, the national capital records around 12,000 deaths linked to air pollution, amounting to a staggering 11.5 per cent of its total deaths.
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 possibly be causing these fatalities.
An alarming finding of the study indicated that a 10 microgram per cubic metre increase in PM2.5 concentration, measured over two days, correlates with a 1.4 per cent rise in daily mortality. This risk factor doubles to 2.7 per cent when observations are restricted to levels below the Indian air quality standards, which are notably less stringent than WHO guidelines.
The WHO recommends a safe exposure limit of 15 micrograms per cubic metre over a 24-hour period, while the Indian standard allows for 60 micrograms per cubic metre.
City-specific data revealed a 0.31 per cent rise in daily mortality per a 10 microgram per cubic metre increase in PM2.5 levels in Delhi, compared to a 3.06 per cent rise in Bengaluru.
The link between daily exposure to PM2.5 and locally produced pollutants was stronger in the causality models used by the researchers, indicating that local pollutants could be significantly contributing to these deaths.
The study also highlighted that the causal effects were particularly strong in cities with lower overall air pollution levels, such as Bengaluru, Chennai, and Shimla.
The research, which is the first multi-city time series analysis of short-term exposure to PM2.5 and daily mortality in India, analysed around 36 lakh daily deaths across ten Indian cities from 2008 to 2019. The other cities involved in the study included Ahmedabad, Hyderabad, Kolkata, Pune, Shimla and Varanasi.
The international team for the study included researchers from Varanasi’s Banaras Hindu University and the Centre for Chronic Disease Control, New Delhi.
Joel Schwartz from Harvard University, a co-author of the study, emphasised that lowering and enforcing stricter air quality limits "will save tens of thousands of lives per year".
He stressed that effective methods for controlling pollution were already in use in other parts of the world and needed to be implemented urgently in India.
The WHO has asserted that almost everyone on Earth is exposed to higher levels of air pollution than recommended, posing severe health risks. Prolonged exposure to PM2.5 particles can trigger strokes, heart disease, lung cancer and various other respiratory ailments.
