Air Pollution: Which City Suffers The Most?

Air pollution is a serious issue that affects cities worldwide, with 99% of the global population living in areas where the air quality exceeds the World Health Organization's (WHO) guideline limits. Burning fossil fuels, vehicular traffic, diesel generators, and industrial work are significant contributors to poor air quality. The health implications of air pollution are severe, ranging from respiratory illnesses to premature births and increased mortality from stroke, heart disease, and lung cancer. This introduction will discuss the critical issue of air pollution, its causes, and its impact on human health, with a specific focus on identifying the most polluted city in the world.

New Delhi, India: the most polluted capital

New Delhi, India, is widely considered one of the most air-polluted cities globally, with the air quality deteriorating further in recent years. In August 2022, an assessment of 7000 cities worldwide by the US-based Health Effects Institute deemed New Delhi the most polluted capital in the world. The city's poor air quality has irreversibly damaged the lungs of 2.2 million children, with air pollution being the fifth-largest cause of death in India.

The primary sources of New Delhi's air pollution include power plants, stubble burning, lit garbage, road dust, factories, and vehicles. On 7 November 2016, the PM2.5 levels in New Delhi reached 999, far exceeding the recommended limit of 60 micrograms. This hazardous air quality resulted in low visibility, causing accidents, including a 24-vehicle pile-up on the Yamuna Expressway. The high pollution levels also led to the cancellation and delay of public transport services.

New Delhi's air quality has continued to be a severe issue in recent years, with the city recording its worst air quality of 2024 on 18 November. The 24-hour AQI reading of 491 was classified as "severe plus," indicating hazardous conditions with significant health impacts, especially for vulnerable populations. This prompted the Supreme Court of India to reprimand the central and state governments, urging them to implement stricter measures to reduce pollution.

To address the poor air quality, the Delhi Government has taken several steps, such as banning the entry of commercial petrol and diesel vehicles in 2021 and deciding to stop providing fuel to vehicles older than 15 years from April 2025. Additionally, embassies and international businesses in New Delhi are considering measures like reducing staff tenures and providing high-end air purifiers to mitigate the impact of air pollution.

China: 1.25 million die from air pollution

Air pollution is a serious issue affecting many countries worldwide. According to the World Health Organization (WHO), air pollution kills nearly 9 million people worldwide annually, with 99% of the global population living in areas with air quality that exceeds WHO guideline limits. While China has made significant progress in reducing air pollution-related deaths, it still faces challenges in this area.

China has experienced a high number of deaths attributed to air pollution, with 1.25 million people dying prematurely each year due to poor air quality. However, it is important to note that China has made notable improvements in recent years. A study revealed that annual deaths from air pollution peaked in 2013 and have since declined to levels below those recorded in 1990. This positive development is a result of concerted efforts by major Chinese cities to address particle pollution.

One of the key strategies employed by Chinese cities has been the reduction of industrial and traffic-related pollution. For instance, the city of Beijing banned coal heating, opting instead for natural gas as a cleaner alternative. Additionally, there has been a push toward the use of clean energy sources across the country. China is also investing significantly in solar energy, accounting for 45% of global investment in this sector. By 2024, China is expected to generate twice as much power from solar energy as the United States.

Another factor contributing to the reduction in air pollution-related deaths is the decrease in the use of solid fuels for cooking. In 2005, 61% of Chinese households relied on coal or wood for cooking, which posed significant health risks due to indoor air pollution. However, by 2017, this number decreased to 32%, indicating a positive shift toward cleaner cooking fuels. These efforts to improve air quality have had a tangible impact on the health and well-being of China's population.

While China has made significant strides in combating air pollution, it is important to recognize that the problem is not unique to this country. According to Earth.Org, 12 out of the 15 most polluted cities globally are located in India. The Lancet estimates that air pollution in India causes over 1 million deaths annually, highlighting the urgency of addressing this issue in that country as well. Nevertheless, China's progress in reducing air pollution serves as a testament to the effectiveness of implementing cleaner technologies and fuels.

US: 42 million live in counties with air pollution

Air pollution is a serious global health threat, causing increased mortality from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer, and acute respiratory infections. According to the World Health Organization (WHO), around 9 million people die prematurely each year due to air pollution from coal, oil, and gas-burning sources. Alarmingly, 99% of the world's population lives in areas where the air quality exceeds the recommended guideline limits set by the WHO.

In the United States, the "State of the Air" report for 2025 revealed that nearly half of the country's population, approximately 156 million people, reside in counties that received a failing grade for either ozone or particle pollution. Even more concerning, over 42 million people live in counties that were given an F for all three air pollution measures, indicating a severe air quality issue.

The primary sources of air pollution worldwide are the burning of fossil fuels in power plants and the use of fossil fuel-based vehicles and other transportation modes. The combustion process releases harmful pollutants, emissions, and chemicals into the atmosphere. These pollutants, particularly nitrogen oxides, react with ultraviolet radiation from the sun to form smog, which poses significant risks to respiratory health.

Climate change exacerbates the problem by creating conditions that promote ozone pollution and making it more challenging to improve air quality in communities with high ozone levels. Additionally, climate change increases the risk of wildfires, which release dangerous particle pollution into the atmosphere.

It is worth noting that vulnerable populations, including children, older adults, and individuals with lung diseases, are at heightened risk from the effects of air pollution. People of color and those with lower incomes are also disproportionately impacted by air pollution, facing higher risks of associated illnesses.

Fossil fuels: the biggest source of air pollution

While it is difficult to pinpoint the single most air-polluted city in the world, the World Health Organization (WHO) has compiled a list of the top 500 cities by PM2.5 annual mean concentration measurement. This list was compiled from air quality monitoring data from almost 5,390 towns and cities in 63 countries between 2010 and 2022.

Regardless of which city is the most polluted, fossil fuels are a major contributor to air pollution globally. The burning of fossil fuels releases nitrogen oxides into the atmosphere, contributing to smog and acid rain formation. Fossil fuel combustion also emits particulate matter (PM 2.5), which has been linked to various health risks, including respiratory infections, asthma attacks, and harm to lung development in children. According to research by Harvard University and other institutions, air pollution from burning fossil fuels was responsible for about one in five deaths worldwide in 2018, or approximately 8 million people.

Fossil fuel-related activities, such as coal mining, oil extraction, and fracking, also contribute to air pollution. Coal mining operations can contaminate water sources with toxic runoff, while oil spills and leaks during extraction or transport can jeopardize freshwater and ocean ecosystems. Drilling and fracking operations generate enormous volumes of wastewater, which can be laden with heavy metals and other pollutants, further contributing to environmental degradation and air pollution.

The transition from fossil fuels to renewable energy sources is crucial to reducing air pollution and its associated health risks. Improving energy efficiency, investing in renewable energy sources, and implementing corporate energy management programs can help reduce greenhouse gas emissions and improve air quality. Additionally, individuals can play a role in reducing air pollution by conserving energy, limiting driving, and supporting policies that prioritize clean energy and pollution reduction.

While the most air-polluted city may vary based on changing conditions and data availability, the overarching issue of fossil fuel-induced air pollution remains a pressing global concern, requiring collective efforts to mitigate its impact on human health and the environment.

Air pollution: kills 9 million people annually

Air pollution is a pressing issue that claims the lives of around 9 million people annually. It is caused by a variety of sources, including residential energy use for cooking and heating, vehicles, power generation, agriculture/waste incineration, and industry. According to the World Health Organization (WHO), nearly everyone on Earth (99%) breathes air that exceeds their guideline limits and contains high levels of pollutants, with low- and middle-income countries suffering the highest exposures.

Outdoor and indoor air pollution cause respiratory and other diseases and are significant factors in morbidity and mortality worldwide. Particles in the air can be smaller than 1/30th the diameter of a human hair, penetrating deep into the body and causing harm. Ozone and particle pollution are linked to an increased risk of premature births and lower birth weights in newborns. Those who live or work near busy highways or exercise outdoors are at greater risk of adverse health effects from air pollution.

Certain groups are especially vulnerable to the impacts of air pollution. This includes children, older adults, and people with lung diseases such as asthma and COPD. Additionally, people of color and individuals with lower incomes are disproportionately affected by air pollution, facing higher risks of illness due to their exposure. The combined effects of ambient and household air pollution are associated with approximately 7 million premature deaths each year.

Household combustion devices, motor vehicles, industrial facilities, and forest fires are significant contributors to air pollution. Major pollutants of concern include particulate matter, carbon monoxide, ozone, nitrogen dioxide, and sulfur dioxide. While air pollution is a global issue, certain regions are more severely affected. China and India, home to two of the world's fastest-growing economies, bear a significant brunt of air pollution-related deaths, accounting for more than half of the global total. Brazil, Pakistan, and Japan have also experienced increases in pollution-related deaths in recent decades.

Frequently asked questions