PM2.5 exposure leads to 1.5 million deaths in India every year
Fine particulate matter, a common measure of air pollution, refers to particles in the air that are 2.5 microns or less in diameter
Long-term exposure to PM2.5 pollution concentration higher than the 5 μg/m³ annual average recommended by the World Health Organization (WHO) ambient air quality guidelines is potentially associated with 1.5 million deaths a year in India, according to a study published in The Lancet Planetary Health on Wednesday.
Fine particulate matter, a common measure of air pollution, refers to particles in the air that are 2.5 microns or less in diameter. The unit μg/m³ denotes micrograms of the pollutant per cubic metre of air.
According to the analysis, the entire 1.4 billion population in India lives in areas with PM2.5 concentration above that recommended by the WHO guidelines. Also, 1.1 billion (81.9% of the total population) live in areas with PM 2.5 concentration above the national air quality standard of 40 µg/m³.
The evidence supporting the association between long-term exposure to outdoor air pollution and deaths in India, however, is scarce and inconsistent with studies in other countries, the authors said.
The study looked at annual deaths from 2009 to 2019 at the district level in India and obtained annual PM2.5 concentrations by a machine learning-based model using satellite data as well as ground-monitoring observations of air pollution levels across 1,056 locations.
The range of PM2.5 pollution exposure was quite large across the years, with the lowest annual PM2.5 concentration of 11.2 μg/m³ observed in the Lower Subansiri district, Arunachal Pradesh, in 2019 and the largest annual figure of 119.0 μg/m³ observed in Ghaziabad, Uttar Pradesh, and Delhi in 2016. A 10 µg/m³ increase in annual PM2.5 concentration was associated with an 8·6% higher annual mortality, according to the model results of the study.
Based on the Indian annual air quality standard, a total of 3·8 million premature deaths may have occurred between 2009 and 2019, which were attributable to PM2.5, amounting to 5% of total mortality, the paper estimated.
When the WHO guidelines were considered, a total of 16·6 million deaths were attributable to PM2.5, amounting to 24·9% of total mortality.
It’s important to note that the authors used two different safety standards to look at two scenarios – the Indian national standard ≤40 µg/m³ and the WHO guideline of ≤5 µg/m³ – for annual means.
“We used the Indian NAAQS (National Ambient Air Quality Standards) to motivate policy makers regarding the current guidelines and aid in understanding the need for revising guidelines, without necessarily implying that these two concentrations are safe,” said the paper.
In the background, the authors said in 2019, the Global Burden of Diseases, Injuries, and Risk Factors Study attributed 0·98 million deaths to ambient air pollution in India based on potentially inappropriate exposure-response functions from countries with low air pollution levels. Instead, using data from India, they investigated long-term exposure to PM2.5 and all-cause mortality with a causal inference method.
In India, people living in urban and several rural areas are exposed to high PM2.5 concentrations throughout the year. According to the paper, population-weighted mean PM2.5 exposure (2000 to 2019) across India was reported at 57·3 µg/m³, with higher concentrations observed from 2010 to 2019. WHO revised the air quality guidelines for PM2.5 concentrations in 2021 based on mounting evidence of major health effects even at low exposure concentrations, resulting in stricter recommendations, going from not exceeding 10 µg/m³ to not exceeding 5 µg/m³ annual mean PM2.5 concentration.
The Indian NAAQS are currently less than or equal to 40 µg/m³ for annual mean PM2.5 concentration.
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