Chad and Bangladesh  ranked as the most polluted countries in 2024, while Delhi, India was the most polluted capital city, according to the 2024 World Air Quality report produced by the Swiss-based IQAir.  But only seven countries worldwide met WHO air quality guidelines and Africa’s pollution levels remains under-reported. Pollution monitoring also fell victim to President Trump drastic cuts and rollbacks of environmental protections, as US embassies worldwide closed monitoring stations and disabled the US government’s airnow.gov data base.

Seventy-four of the 100 most polluted cities and towns are in India, according to the latest World Air Quality Report 2024, a slight improvement from 83 last year. Levels of a key microscopic pollutant, PM2.5,  declined 7% across the nation, averaging 50.6 micrograms/cubic metre or 10 times the World Health Organization’s (WHO) safe guideline.  Despite having the most polluted cities, India ranked fifth, globally, after Chad, Bangladesh, Pakistan, and the Democratic Republic of Congo in terms of national pollution levels.

Globally, only 17% of the almost 9,000 cities surveyed met the WHO air pollution standard, which is an annual average of 5 micrograms/cubic metre of the pollutant PM 2.5. This microscopic particulate matter, containing a cocktail of other pollutants that penetrate the blood and brain barrier, is the most widely tracked measure of air pollution.  Nationally, only seven countries: Australia, New Zealand, the Bahamas, Barbados, Grenada, Estonia and Iceland met WHO annual air quality levels, IQAir said.

However, a world map of pollution averages shows air pollution is primarily a Global South challenge. 

Most of the worst affected places are in Asia. Some in Africa, although only 24 out of 54 African countries or territories reported data in 2024. Still, this is a marked improvement since the first of these reports in 2017 had useable data from only three African countries. 

US State Department closes global air quality monitoring network

The rankings were released days after the new Trump administration’s move to shut down air quality monitoring at United States embassies worlwide.  In parallel,  the State Department deleted 17 years of  data from  US government’s airnow.gov data base – which had been a valuable source of reliable air quality data in resource-strapped countries like Chad.  This is likely to have a “profound” real-world impact on surveillance, according to the report’s scientists.

“The information collected at 80 global US embassies and consulates have proven to help protect public health and inform air quality policy… when US embassies began tracking local air pollution, host countries took action,” said Dr Christi Chester Schroeder, IQAir Air Quality Science Manager.

“IQAir estimates at least eight countries will completely lose access to all real-time air quality data because of this decision, nearly all of which are in developing countries.” 

In Asia, Iran and Afghanistan are not included in the report because of a lack of real-time data. 

The report is based on data from about 40,000 ground-level air quality monitors in 138 countries, although IQAir, a Swiss firm for air quality equipment, does not publicly provide a margin of error for PM2.5 concentrations used in this report. 

Why India isn’t the most polluted

While it dominates the top 100 most polluted cities and towns, India’s expansive air quality monitoring network also captures levels in more rural and less polluted aeras – and that brought it’s national average down in comparison to other heavily polluted coutries, experts said.  

So the reasons Pakistan and Bangladesh ranked higher in overall pollution levels may be related to the limited scope of their air quality monitoring network – which tend to capture urban areas only. Cities with high PM 2.5 concentrations thus have a disproportionate impact on the country’s annual average concentrations. Chad also returned to the 2024 rankings – after being excluded in 2023 for a lack of data. 

Regional airshed solution for South Asia

Either way, the report makes for bleak reading for India and the rest of South Asia. Bangladesh, Pakistan, India and Nepal are ranked at 2, 3, 5 and 7. The capitals of all these countries are also in the top 10 most polluted cities.

India continues to lead the region in government monitoring infrastructure, operating more than half of the total stations, the report points out. Despite this, many areas in India remain under-monitored, particularly in smaller cities and rural regions.

Cities like Delhi and Lahore frequently experience hazardous conditions with seasonal spikes in pollution leading to emergency measures such as school closures and public space shutdowns.

“Air pollution pays no regard to country borders. The trans-boundary nature of air pollution is a serious issue in many regions around the world, and is no different with India and Pakistan,” said Schroeder.

“Airsheds need to be treated as regional international issues, not national issues. Cities in India and Pakistan, as well as Bangladesh and Nepal, share common sources of pollution – industrial emissions, agricultural burning, vehicle pollution, dust, etc. Despite years of evidence of trans-boundary pollution, regional cooperation has been underwhelming.”

One of India’s foremost air quality government scientists, Dr SN Tripathi, believes that in South Asia, India will have to take the lead in proposing and establishing some kind of agreement or arrangement with other countries.

Airsheds within India and ability to analyse how air pollution is moving from one region to another. Tripathi, Dean at Kotak School of Sustainability, IIT Kanpur, calls for a “multilateral airshed approach sooner than later  to deal with this menace.” 

Delhi is the air pollution capital

The report’s scientists point out that while India’s population is nearly identical to the entire African continent, it has significantly expanded its air quality monitoring network in recent years. Experts say more such data should help in tackling the crisis. 

The world’s most polluted place is Byrnihat, an industrial town in India’s north-eastern state of Meghalaya. The annual average PM2.5 concentration was 128.2 micrograms/cubic metre. 

However, 2024’s data puts the main focus back on Delhi. The capital area of New Delhi, which has a municipality separate from the rest of Delhi, was the world’s most polluted capital.

The larger area of Delhi ranked second among nearly 9,000 places. This is Delhi’s highest rank since the annual report began in 2017. (Although this is the 7th World Air Quality report, IQAir has produced eight rankings since 2017 ,which have been shared with Health Policy Watch for this article.)

In stark contrast to the national decline, the pollution level rose in Delhi by 6% to 108.3 micrograms/cubic metre last year, the highest since 2019. Ironically, that is the year India’s first national clean air programme (NCAP) was launched. 

The report attributes Delhi’s pollution to vehicular emissions, a leading contributor to fine particulate matter (PM2.5), exacerbated by traffic congestion and fuel adulteration, as well as industrial and construction activities and seasonal burning of agricultural residue.

Northern India dominates global ranking

All the 74 Indian cities in the top 100 list are in northern India with none from southern India. 

About 65 of these are in the northern plain called the Indo-Gangetic Plain (IGP), from Punjab in the west to Bengal 2,000 km in the east. This remains a pollution hotspot, where meteorological factors trap pollutants and exacerbate winter smog. 

The Indian government plans to coordinate air pollution control plans in the IGP with a population of about 600 million as one jurisdiction.

While India’s PM 2.5 averages 50.6 micrograms (population-weighted), a back-of-the-envelope calculation of average pollution in the IGP states shows the level of PM 2.5 to be higher by about a fifth. 

The challenge is that each state is a separate political entity but air pollution obviously moves across political boundaries.

Tripathi advocates the airshed approach as the framework “to approach the problem with common or shared resources.
To get more bang for the buck.” He estimates that pollution can come down by two-thirds if the burning of waste outdoors and of polluting fuels (like coal, dung and wood) inside homes is stopped. 

China’s Air Pollution Dips 

Pollution levels declined in over 320 cities in China, including major cities such as Beijing, Shanghai, Chengdu, Guangzhou, and Shenzhen. But levels rose in almost 130 other cities. 

Officials have set ambitious goals to lower the national annual average PM 2.5 concentration to below 28 µg/m³ by 2027 and below 25 µg/m³ by 2035. Special attention is being given to the Beijing-Tianjin-Hebei region at the provincial level.

Warning for Southeast Asia’s most polluted country

Air pollution in Indonesia decreased by 4% in 2024 compared to the previous year, averaging 35.5 micrograms. However, the report warns of a clean energy challenge.

The country is the world’s leading producer of nickel, a vital mineral for clean energy and storage but to extract it takes a lot of energy. And for this, it’s increasing its coal power capacity which grew 15% over a year till July 2024. 

Coal burning generates two-thirds of Indonesia’s electricity. Despite declining pollution, it remains the most polluted country in Southeast Asia. 

Vietnam air pollution’s cost

In Vietnam, air pollution has been estimated to cause a loss of around 4% of the GDP. Acute air pollution events in Vietnam have severely impacted daily life, with disruptions to air travel leading to flight diversions at multiple airports. In 2024, there was a small reduction in pollution from 29.6 to 28.7 micrograms. 

Vietnam’s government, international bodies and various organisations are empowering citizens through information campaigns to raise awareness, take preventive action and also expand air quality monitoring for public health action and academic research. 

Community initiatives are promoting sustainable agricultural practices, such as reducing straw burning, while advocating for responsible household waste disposal to minimize pollution.

The cleanest air was found in Hawaii’s Honaka’a, in the United States. It is ranked 8,954th and the PM 2.5 average was one microgram/cubic metre of air. 

Image Credits: Raunaq Chopra/ Climate Outreach, IQ Air, IQ Air, IQAir, Google maps, Aji Styawan / Climate Visuals.