BATHINDA: A new study published in the Lancet Planetary Health finds that even levels of air pollution below current Indian air quality standards lead to increased daily mortality rates in India. The study examines 10 Indian cities (Ahmedabad, Bengaluru, Chennai, Delhi, Hyderabad, Kolkata, Mumbai, Pune, Shimla, and Varanasi) and finds that 33,000 deaths annually are attributable to air pollution levels exceeding WHO guidelines. Notably, significant deaths occurred even in cities not typically associated with high air pollution. The authors analyzed PM2.5 exposure data and daily mortality counts from 2008 to 2019 to reach these conclusions.
7.2% of all deaths (~33,000 each year) across all 10 of these cities could be linked to short-term PM2.5 exposure higher than the WHO guideline value of 15 μg/m3 according to the study. Also, each 10 μg/m3 increase in short-term PM2.5 exposure was associated with a 1.42% increase in daily deaths. This estimate nearly doubled to 3.57% when we used a causal modelling approach that isolates the impact of local sources of air pollution. The risk of death rises sharply at lower PM2.5 concentrations and diminishes at higher levels, with notable impacts seen even below the current National Ambient Air Quality Standard of 60 μg/m³ for 24-hour exposure.
This groundbreaking study offers a new understanding of air pollution and health in India. It is the first multi-city study to assess the relationship between short-term air pollution exposure and mortality across diverse air pollution levels and agro-climatological zones.
Novel causal modelling techniques that isolate the heightened impact of local sources of air pollution such as waste burning and vehicular emissions among others are utilised in this study.
The results suggest that national air quality standards should be more stringent and efforts to control air pollution should be intensified. Conducted by researchers from institutions including Ashoka University, the Centre for Chronic Disease Control, Karolinska Institutet, Harvard University, and Boston University, many of whom are part of the CHAIR-India consortium.
The study also offers crucial policy insights, highlighting that air pollution policy should extend beyond 'non-attainment cities' that fail to meet Indian standards. These standards are four times higher than the WHO guideline value of 15 μg/m³, making many more regions vulnerable. The findings emphasize the need to expand remedial actions beyond the currently designated 'non-attainment cities.'
The study emphasizes the need for year-round action on air pollution, not just during seasonal extremes. A significant portion of mortality risk occurs at low to moderate PM2.5 levels, with risk tapering off at higher levels. Current policies, like the Graded Response Action Plans, primarily target extreme pollution levels and should be recalibrated to address air quality consistently throughout the year.
The study also helps develop policy instruments to effectively address dispersed local sources of air pollution, which are complex but crucial for health improvements. These sources regularly impact most people and require focused attention beyond ambient concentrations. Targeting these everyday exposure sources would yield significant health benefits.
Dr. Bhargav Krishna, Fellow at the Sustainable Futures Collaborative and a lead author on the study said “The results of this first-of-its-kind multi-city study show us that reducing air pollution is a nationwide challenge. Our analyses highlight air pollution’s substantial effects on death even in cities previously considered less polluted such as Mumbai, Bengaluru, Kolkata and Chennai. The significant effects observed below the current Indian standards have implications for what we consider acceptable air quality, and emphasise the need for stringent year-round action across the whole country”.
Dr. Jeroen de Bont, a Postdoctoral researcher at Karolinska Institutet and a lead author, emphasised the significance of our first multi-city study. “Spanning data from 2008 to 2019 across India’s largest cities, our findings support the evidence that approximately 7.2% of all deaths in India are attributable to daily PM2.5 exposure. As efforts to combat air pollution intensify, addressing dispersed local sources becomes crucial alongside existing strategies”, he said.
“This unique study accounted for a diverse air quality profile across 10 Indian cities and demonstrates for the first time that the risk of mortality is significant even at lower levels of air pollution. The insights signal an urgent need to revisit our air quality management strategies that currently focus only on ‘non-attainment cities’, rethink current air quality standards accounting for the lower risk thresholds and shift from addressing regional to local sources to effectively protect human health”, said Dr. Poornima Prabhakaran, Director of the Centre for Health Analytics Research and Trends (CHART) at the Trivedi School of Biosciences, Ashoka University and India lead of the CHAIR-India consortium.
“The levels of air pollution we see in India are really extremely high and this study clearly shows how day-to-day variations in these levels lead to considerable mortality. Interestingly we saw that local pollution sources are likely to be more toxic than more distant sources which has implications for policymakers addressing this highly relevant threat to human health," said Dr. Petter Ljungman, Associate Professor at the Karolinska Institutet, and one of the researchers involved in the study.
Professor Joel Schwartz of Harvard University, a co-author of the study said “Lowering and enforcing Indian air quality standards will save tens of thousands of lives per year. Methods for controlling pollution exist and are used elsewhere. They urgently need to be applied in India.”
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