Air Pollution: Cities With The Worst Air Quality

Air pollution is a pressing issue faced by urban populations worldwide, contributing to millions of premature deaths each year. According to the World Health Organization (WHO), air pollution kills nearly 9 million people worldwide annually, with 99% of the world's population living in areas exceeding WHO guideline limits. The biggest sources of air pollution are the burning of fossil fuels in power plants and vehicles, releasing harmful pollutants, emissions, and chemicals into the atmosphere. As of 2025, the top three most polluted cities in the world are Byrnihat, India; Delhi, India; and Karaganda, Kazakhstan. India, Pakistan, and other parts of Asia are home to most of the cities with the worst air pollution.

Cities in India, Pakistan and Asia dominate the list of the most air-polluted cities

Air pollution is a serious environmental issue that contributes to millions of premature deaths each year. In 2024, only 17% of cities worldwide met the World Health Organization's annual PM2.5 guideline of less than 5 µg/m3. This means that a large majority of the global urban population breathes unhealthy air.

In 2024, cities in India, Pakistan, and other parts of Asia dominated the list of the most air-polluted cities. India, in particular, accounted for 11 out of the top 20 cities with the worst PM2.5 levels. Byrnihat, a city in northeastern India, recorded the worst air pollution globally in 2024, with a PM2.5 concentration of 128.2 micrograms per cubic meter—a value that is over 25 times higher than the World Health Organization's recommended limit.

While N'Djamena, Chad, was the only non-Asian city among the top 20 most air-polluted cities, air pollution is a significant issue in other parts of the world as well. For instance, nearly half of the people in the United States live in areas where the air quality received a failing grade in the "State of the Air" report for 2025. More than 156 million people in the US live in counties that received a failing grade for either ozone or particle pollution, and over 42 million people live in counties that received a failing grade for all three air pollution measures.

Air pollution has severe health consequences, including an increased risk of premature birth, lower birth weight in newborns, asthma attacks, and harm to lung development in children. It can also be deadly, especially for vulnerable populations such as children, older adults, and people with lung diseases. To protect themselves from the harmful effects of air pollution, individuals can monitor their local air quality forecasts and avoid outdoor activities when unhealthy air quality is expected.

Byrnihat, India, recorded the worst air pollution in 2024

Air pollution is a deadly environmental threat that contributes to millions of premature deaths each year. In 2024, only 17% of cities worldwide met the World Health Organization's annual PM2.5 guideline of less than 5 µg/m3. This indicates that a large majority of the global urban population breathes unhealthy air.

India is home to many of the world's most polluted cities, with 11 of the top 20 most polluted cities in 2024. Byrnihat, a city in northeastern India, recorded the worst air pollution in the world in 2024. The PM2.5 concentration in Byrnihat was 128.2 micrograms per cubic meter, which is over 25 times higher than the World Health Organization's recommended limit.

The high levels of air pollution in Byrnihat and other Indian cities are likely due to a combination of factors, including industrial emissions, vehicle exhaust, dust, and the burning of fossil fuels and agricultural waste. These sources of pollution contribute to a mix of particulate matter and harmful gases in the air, including PM2.5, which are tiny particles that can penetrate deep into the lungs and cause serious health issues.

The effects of air pollution on human health are well-documented. Particulate matter and other pollutants can lead to respiratory and cardiovascular problems, including asthma attacks, lung cancer, and heart disease. Vulnerable populations, such as children, the elderly, and people with pre-existing health conditions, are especially at risk of experiencing the adverse health effects of air pollution.

Addressing air pollution in cities like Byrnihat requires a multi-faceted approach. This includes implementing stricter emission standards for industries and vehicles, improving waste management practices, and transitioning to cleaner energy sources. It is also crucial to raise awareness about the impacts of air pollution and encourage individuals to take action, such as reducing their personal vehicle usage and advocating for policies that support clean air and mitigate climate change.

N'Djamena, Chad, was the only non-Asian city in the top 20

Air pollution is a significant environmental threat, causing millions of premature deaths annually. In 2024, only 17% of cities worldwide met the World Health Organization's annual PM2.5 guideline of less than 5 µg/m3. This indicates that a large portion of the global population is exposed to unclean air.

India, Pakistan, and other parts of Asia are home to cities with the worst air pollution in 2024. Byrnihat, a city in northeastern India, recorded the worst air pollution globally in 2024, with a PM2.5 concentration of 128.2 µg/m3—over 25 times higher than the World Health Organization's recommended limit.

Among the top 20 most polluted cities, N'Djamena, Chad, was the only non-Asian city. N'Djamena's air quality index (AQI) is often rated as "very unhealthy," with PM2.5 levels reaching over 16 times the World Health Organization's annual guideline value. Wildfires near the city contribute to the poor air quality, and residents are advised to follow health recommendations to protect themselves from the smoke.

The high levels of air pollution in N'Djamena highlight the need for urgent action to improve air quality and protect the health of its residents. It is essential for individuals in the area to stay informed about the air quality forecast and take necessary precautions, such as avoiding outdoor activities when unhealthy air quality is expected.

Particle pollution is linked to an increased risk of premature birth and lower birth weight

Air pollution is a serious environmental threat, contributing to millions of premature deaths annually. In 2024, only 17% of cities worldwide met the World Health Organization's (WHO) annual PM2.5 guideline of less than 5 µg/m3. This means that a significant proportion of the global population is exposed to unclean air.

Particle pollution, or air pollution, is linked to an increased risk of premature birth and lower birth weight. A study by the Stockholm Environment Institute (SEI), the London School of Hygiene and Tropical Medicine, and the University of Colorado concluded that approximately 3.4 million premature births across 183 countries could be attributed to fine particulate matter, a prevalent air pollutant. This type of pollution is composed of minuscule particles from various emissions, such as diesel emissions and agricultural fires, which can infiltrate the lungs and impact the pulmonary and cardiovascular systems.

The association between particle pollution and premature births has been observed in multiple regions. In Guangdong, China, a study examined the relationship between specific air pollutants (PM2.5, PM10, SO2, NO2, CO, and O3) and preterm birth/low birth weight. The results indicated significant correlations between exposure to these pollutants during pregnancy and adverse birth outcomes. Similar findings were reported in a study conducted in the United States, where air pollution was found to have a substantial impact on unborn children, resulting in economic costs of $4.33 billion in 2010.

South Asia has been identified as the region with the highest number of preterm births associated with particulate matter pollution, with up to 1.6 million associated births. China, despite having a relatively low rate of preterm births, still had an estimated 521,000 preterm births potentially linked to air pollution due to high concentrations of particulate matter.

The effects of particle pollution on birth outcomes extend beyond preterm births. Studies have suggested that exposure to air pollution in utero may negatively impact babies' birth weight. For instance, in the SEI study, it was found that an increase of 10 μg/m3 in NO2 levels in the last month of pregnancy was associated with an increased risk of low birth weight, with an odds ratio of 1.059 (95% CI 1.02-1.10) for PM2.5.

Nearly half of the US population lives in areas with failing air quality

Air pollution is a significant environmental threat, causing millions of premature deaths annually. In 2024, only 17% of cities worldwide met the World Health Organization's annual PM2.5 guideline of less than 5 µg/m3. This indicates that a large portion of the global urban population breathes unhealthy air.

In the United States, air quality is a pressing issue, with nearly half of the population, approximately 156 million people, living in areas with failing air quality. This problem is not isolated to a few cities but is widespread across the country. The American Lung Association's "State of the Air" report for 2025 revealed that more than 156 million people resided in counties that received a failing grade for either ozone or particle pollution. Over 42 million people lived in counties that failed in all three air pollution measures: ozone, year-round particle pollution, and short-term particle pollution.

Several factors contribute to the failing air quality in the United States. One significant factor is climate change, which enhances the formation of ozone pollution and makes it more challenging to mitigate in communities with high ozone levels. Climate change also increases the frequency and intensity of wildfires, which produce smoke that contains small particles that can penetrate the lungs and enter the bloodstream, causing serious health issues. The impact of wildfires on air quality is evident, with the 2023 Canadian wildfires causing the most smoke exposure per person in modern US history.

Additionally, the deliberate location of heavy industry, landfills, and highways in communities of color has resulted in environmental racism, leading to poor air quality for these communities. People of color are disproportionately affected by air pollution, with Hispanic individuals being nearly three times as likely as white individuals to live in areas with high levels of air pollution. This disparity highlights the environmental justice issues that are intertwined with air quality concerns.

The consequences of air pollution on human health are significant. It can trigger asthma attacks, harm lung development in children, and even lead to premature deaths. The impact is particularly severe for vulnerable groups, including children, older adults, and individuals with lung diseases such as asthma and COPD. Those who live or work near busy highways or spend time outdoors are also at higher risk of experiencing the detrimental effects of air pollution.

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