Delhi, Kolkata first, second globally in PM2.5 pollution: Report

Exposure to PM2.5 pollution tends to be higher in cities located in low- and middle-income countries, according to the report
A smoggy afternoon in Connaught Place, New Delhi. Photo: iStock
A smoggy afternoon in Connaught Place, New Delhi. Photo: iStock

Delhi and Kolkata have the highest and second-highest levels of pollution globally in terms of Particulate Matter (PM) 2.5, according to a new report released August 17, 2022.

The national capital had an ‘annual exposure level’ of 110 microgram per cubic metre (µg/m³), while Kolkata came second with 84 µg/m³, according to the report titled Air Quality and Health in Cities.

The report has been published by the US-based research organisation Health Effects Institute (HEI) and released by HEI’s State of Global Air Initiative.

It provides a comprehensive and detailed analysis of air pollution and global health effects for more than 7,000 cities around the world, according to a statement by HEI.

The analysis focussed on two of the most harmful pollutants — fine particulate matter (PM2.5) and nitrogen dioxide (NO2).

Dhaka in Bangladesh and Karachi in Pakistan were two other cities from the Subcontinent in the list of those most polluted due to PM2.5. Dhaka was ranked fifth with an annual exposure level of 71.4 µg/m³. Karachi stood eighth at 63.6 µg/m³.

Shanghai led the list of cities most polluted due to NO2, with an annual exposure level of 41.6 µg/m³. It was followed by Moscow (40.2), Tehran (39.8), St Petersburg (38.3) and Beijing (37.7).

Source: Air Quality and Health in Cities

“In 2019, 1.7 million deaths linked to PM2.5 exposure occurred in the 7,239 cities included in the analysis, with cities in Asia, Africa, and Eastern and Central Europe seeing the greatest health impacts,” the statement noted.

It added that the rapid urbanisation of the world placed the world’s top cities at the forefront of the battle to reduce the health effects of air pollution, especially in low- and middle-income countries.

The analysis used data from 2010 to 2019. It found that exposure to PM2.5 pollution tended to be higher in cities located in low- and middle-income countries.

Exposure to NO2 was found to be higher across cities in high-income as well as low- and middle-income countries.

The reason for this is that NO2 is produced mainly from the burning of fuels mostly in older vehicles, power plants, industrial facilities and residential cooking and heating.

As city residents tend to live closer to busy roads with dense traffic, they are often exposed to higher NO2 pollution than residents of rural areas.

“In 2019, 86 per cent of the more than 7,000 cities included in this report exceeded the WHO’s 10 µg/m3 guideline for NO2, impacting about 2.6 billion people.

While PM2.5 pollution tends to get more attention on known hot spots around the world, less data has been available for NO2 at this global scale,” the statement said.

Only 117 countries currently have ground-level monitoring systems to track PM2.5, according to the World Health Organization’s Air Quality Database. Fewer countries monitor NO2 levels (just 74).

“Strategic investments in ground-level air quality monitoring systems and expanded use of satellites and other emerging technologies in targeted regions can provide critical first steps toward cleaner air,” the statement said.

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