The latest report on air quality reveals the world's 20 most polluted cities.

The latest report on global air quality has revealed the list of the top 20 most polluted cities in the world, with all but one located in Asia.

On November 14, 2024, a man was observed feeding seagulls amidst the smog-laden waters of the Yamuna River in New Delhi, India.

According to a recent study, nearly all of the world's 20 most polluted cities last year were situated in Asia, with the exception of one. Thirteen of these cities are found in India, the most populous nation, where rapid economic development is primarily driven by coal, resulting in extensive traffic congestion in its megacities.

Additionally, four cities are located in neighboring Pakistan, while one city each is in China and Kazakhstan. The sole city outside Asia on the list is N'Djamena, the capital of Chad in central Africa, which has been identified as having the worst air quality in the country.

In North America, the cities with the highest pollution levels were all situated in California.

The report, published by IQAir, a Swiss organization that monitors global air quality, focused on fine particulate matter, or PM2.5, which is among the smallest yet most harmful pollutants.

PM2.5 originates from various sources, including fossil fuel combustion, dust storms, and wildfires. These particles are so minuscule—one-twentieth the width of a human hair—that they can bypass the body's natural defenses, entering the lungs or bloodstream.

These particles can lead to irritation and inflammation and have been associated with respiratory issues and chronic kidney disease. Prolonged exposure may result in cancer, strokes, or heart attacks and has been linked to an increased risk of depression and anxiety.

On November 20, 2024, a bird was seen navigating through a dense layer of smog in New Delhi, India.

The World Health Organization (WHO) recommends that average annual PM2.5 levels should not exceed 5 micrograms per cubic meter. However, Byrnihat, an industrial town in northeast India, recorded a PM2.5 concentration of 128.2 last year, which is over 25 times the WHO's guideline.

"It is disheartening and frustrating that Byrnihat continues to rank at the top of this list," a local resident remarked.

Suman Momin, 26, a resident of Byrnihat, expressed her deep sorrow and sense of helplessness regarding the city's persistent position at the top of pollution rankings. She attributed the deteriorating air quality to the numerous factories in the vicinity, the rapidly expanding construction sector, and the deforestation occurring in the area.

On a foggy winter morning, commuters in Greater Noida, India, faced increasing air pollution levels on November 19, 2024. Momin remarked, "The pollution is particularly severe at the moment; visibility is poor, dust is pervasive, and my eyes are burning." She emphasized the necessity of wearing a mask whenever she leaves her home.

India has twelve cities listed among the top twenty most polluted globally, with New Delhi being recognized as the most polluted capital for the sixth consecutive year, recording a PM2.5 concentration of 91.8. The report also identified six satellite cities—Faridabad, Loni, Delhi, Gurugram, Noida, and Greater Noida—as part of this troubling list.

In November of the previous year, a thick layer of smog enveloped Delhi, causing flight disruptions, obscuring buildings, and leading the city's chief minister to declare a "medical emergency."

Despite this, India, now the world's most populous nation with 1.4 billion residents, improved its ranking from third to fifth place compared to the previous year. However, the report highlighted that air pollution continues to pose a significant health risk, reducing life expectancy by an estimated 5.2 years.

The report indicated that India's neighboring countries, Bangladesh and Pakistan, ranked as the second and third most polluted nations globally in terms of PM2.5 levels.

China, which previously held the top position in global air quality rankings, has shown slight improvements, according to the report.

A dense layer of smog was observed enveloping Kartavya Path during the early morning hours following Diwali on November 13, 2023, in New Delhi, India.

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According to the report, China's national annual average PM2.5 concentration has decreased from 32.5 micrograms per cubic meter to 31, indicating improvements in air quality in major cities such as Beijing, Shanghai, Chengdu, Guangzhou, and Shenzhen.

Although China is the largest emitter of carbon dioxide globally, it has recently undertaken significant measures to combat air pollution, particularly in urban areas that have driven its economic development, and has made substantial investments in solar and wind energy.

However, last month, two clean-energy organizations expressed concern regarding plans by China's power sector to construct nearly 100 gigawatts of new coal plant capacity, marking the highest level of new coal development in almost a decade.

The IQAir report revealed that all 20 of the most polluted cities worldwide last year surpassed WHO PM2.5 guidelines by more than tenfold.

Data gaps 
"Air pollution continues to pose a serious threat to human health and environmental stability, yet many individuals remain unaware of their exposure levels," stated Frank Hammes, Global CEO of IQAir.

Iran and Afghanistan were not included in this year's report due to insufficient data availability.

The report also highlighted significant issues with air quality monitoring in Southeast Asia, where nearly all countries exhibit "substantial gaps in government-led initiatives."

In 2024, 173 out of 392 cities in the region were reported to lack government monitoring stations, with Cambodia having none.

These challenges are expected to worsen following the recent announcement by the United States to cease sharing air quality data collected from its embassies and consulates globally due to "funding constraints," as reported by the Associated Press.

"Air quality data saves lives," emphasized Hammes.

It raises essential awareness, informs policy-making, directs public health initiatives, and empowers communities to take measures aimed at reducing air pollution and safeguarding future generations.

In North America, the cities identified as having the most severe air pollution include Ontario, Bloomington, and Huntington Park, all located in California, according to the report.

The United States experienced a notable decrease in PM2.5 levels last year, with the annual average declining by 22% compared to 2023.

On March 10, 2023, vehicles were seen traversing a highway during a dust storm amidst significant pollution in Beijing.

North America has historically maintained robust air quality monitoring systems, accounting for 56% of the total number of ground-based air quality monitoring stations featured in the IQAir report. This infrastructure supports ongoing scientific research on air quality and assists policymakers in making informed public health decisions.

Only 12 countries, regions, and territories reported PM2.5 concentrations that fell below the WHO guidelines, with the majority located in Latin America, the Caribbean, or Oceania.

The report urged governments to allocate funding for renewable energy initiatives and to enhance emission standards for vehicles and industrial operations.

Suman expressed her hope that authorities in Byrnihat would take action to prevent her city from ranking among the most polluted areas again next year.

"Residents have developed respiratory issues over the years as well," she shared with CNN.

"This is my birthplace. I am a local. I do not wish to leave this area. We want the governments to take more action, unite, and work on our behalf."

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