India was the third most polluted country globally in 2023 with regard to air pollution, according to the sixth Annual World Air Quality Report released on Tuesday by the Swiss technology company IQAir.

Bangladesh was the top ranking country followed by Pakistan.

The report said that Delhi was the most polluted national capital, while Bihar’s Begusarai was the most polluted metropolitan area of 2023 globally.

India is home to 12 out of the world’s top 15 ranked cities with regard to air pollution. These are: Guwahati, Greater Noida, Siwan, Saharsha, Goshaingaon, Katihar, Bettiah, Samastipur, Muzaffarnagar, Gurugram, Arrah and Dadri.

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The report analysed PM2.5 data from 7,812 cities across 134 countries, regions and territories. PM2.5 refers to tiny airborne particles that are about 30 times smaller than the width of a human hair and can easily be breathed into the lungs and the bloodstream.

The volume of such particles is measured in micrograms per cubic metre of air (μg/m³). One µg/m3 means that one cubic metre of air contains one microgram of suspended particulate matter.

PM2.5 is one of six common airborne pollutants that are monitored and regulated by environmental agencies worldwide, including by India’s Central Pollution Control Board, due to its significant impacts on human health and the environment.

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Common components of PM2.5 include sulfates, black carbon, nitrates and ammonium. Human-made sources of PM2.5 include combustion engines, industrial processes, power generation, burning of coal and wood, agricultural activities and construction.

IQAir’s report found that the average annual concentration of PM2.5 in India exceeded the World Health Organization’s prescribed annual threshold by more than 10 times. The World Health Organization’s Global Air Quality Guidelines prescribed a “safe” annual average PM2.5 concentration of 5μg/m³.

The annual average concentration of PM2.5 in India stood at 54.4μg/m³ in 2023, a marginal increase from 53.3μg/m³ in 2022, according to IQAir’s analysis.

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In 2023, the annual average concentration of PM2.5 in Bangladesh was 79.9μg/m³. In Pakistan, this figure stood at 73.7μg/m³.

In India, the spike in pollution levels in 2023 posed significant health risks to an estimated 1.36 billion people living in the country.

In the National Capital Region, the report flagged an alarming surge in PM2.5 levels that rose by 10% compared to the previous year and peaked at a monthly average concentration of 255 μg/m3 in November.

“The data indicates pressing environmental challenges that India faces, posing significant health risks to its vast population,” Avinash Chanchal, the campaign manager at Greenpeace India, said. “Vehicle emissions continue to play a significant role in exacerbating air pollution, accounting for 40% of PM2.5 emissions in the nation’s capital.”

In contrast, the countries that met the World Health Organization’s annual PM2.5 guideline, of an average concentration of 5μg/m³ or less, were: Australia, Estonia, Finland, Grenada, Iceland, Mauritius and New Zealand.