Air Pollution: The World's Worst Offenders

Air pollution is a significant global health problem, causing more than 10% of worldwide deaths, according to The Lancet. It affects nearly every organ and system in the human body and is particularly harmful to vulnerable groups, such as children, older adults, and those with respiratory conditions. In 2024, only 17% of cities worldwide met the World Health Organization's annual PM2.5 guideline, indicating that the vast majority of urban populations breathe unhealthy air. India is home to some of the world's most polluted cities, with Byrnihat, in the northeast, recording the worst air quality in 2024. However, the issue is not limited to India, as air pollution is a pressing concern in many emerging and developing countries, where environmental standards can be challenging to meet.

Cities with the worst air pollution in 2024

Air pollution is a pressing issue faced by urban populations worldwide. In 2024, the World Health Organization's (WHO) guidelines and Air Quality Index (AQI) provided valuable insights into the environmental health risks faced by various nations. While the AQI rankings for individual cities are not available, here is a list of countries with the worst air pollution in 2024, with a focus on the cities contributing to their poor air quality:

Bangladesh

Bangladesh topped the list of countries with the worst air pollution in 2024, with a dangerously high average AQI score of 140, indicating severe pollution levels. Dhaka, the capital city, recorded a PM2.5 concentration of 114.5 µg/m3, over ten times the recommended limit.

India

India held the third spot in the AQI rankings for 2024, with an average AQI of 111. Indian cities accounted for 11 of the top 20 most polluted cities globally in 2024. Byrnihat, a city in northeastern India, recorded the worst air pollution globally, with a PM2.5 concentration of 128.2 µg/m3. Delhi, the capital territory, recorded the second-worst air pollution levels, experiencing severe winter air pollution driven by crop burning, stagnant cold air, and weak wind patterns. Mumbai also experiences unhealthy levels of air pollution.

Kyrgyzstan

Kyrgyzstan faced poor air quality in 2024, with a PM2.5 level of 44 µg/m³, surpassing WHO guidelines.

Bahrain

Bahrain ranked fourth in 2024 with an AQI average of 103, indicating unhealthy air quality for sensitive individuals.

It is worth noting that Africa and South America may also have cities with high air pollution levels, but there are fewer public air quality monitoring stations in these regions, making it difficult to obtain accurate data.

Indian cities with severe air pollution

India has a low per capita emission of greenhouse gases, but the country is the third-largest producer of greenhouse gases in the world. A 2013 study on non-smokers found that Indians have 30% weaker lung function than Europeans. While air quality remains a critical environmental challenge in India, with significant variations across different cities, evaluating cities across India highlights the stark contrast between them.

In 2019, India was home to 13 of the world's 20 most polluted cities. In 2024, this number increased to 11 out of the top 20. Delhi, the capital of India, recorded the second-worst air pollution levels in 2024. The city experiences the worst winter air pollution of any major city, driven by crop burning in nearby states, stagnant cold air, and weak wind patterns that trap and concentrate smog over the capital. Delhi's air quality index (AQI) was placed under the "severe-plus category" when it touched 574, by the System of Air Quality and Weather Forecasting and Research. In May 2014, the World Health Organization announced New Delhi as the most polluted city in the world. Kolkata and Mumbai are other major cities with high levels of air pollution.

The main contributors to India's particulate air pollution include industrial and vehicular emissions, construction dust and debris, dependence on thermal power for electricity, waste burning, and the use of wood and dung by low-income and rural households for cooking and heating. 51% of India's air pollution is caused by industrial pollution, 27% by vehicles, 17% by crop burning, and 5% by other sources. Traffic gridlock in Delhi and other Indian cities is extreme, resulting in a buildup of local pollution, particularly under stagnant conditions. At such low speeds, vehicles in India emit air pollutants 4 to 8 times more than they would with less traffic congestion.

To tackle this issue, the Indian government launched the National Clean Air Programme in 2019, with a tentative national target of 20%-30% reduction in PM2.5 and PM10 concentrations by 2024, considering 2017 as the base year for comparison. It will be rolled out in 102 cities that are considered to have air quality worse than the National Ambient Air Quality Standards.

US cities with poor air quality

Air pollution is a critical issue in the United States, affecting the health and well-being of millions of Americans. While air quality has improved in recent years due to the increasing use of cleaner energy sources, certain US cities continue to grapple with poor air quality, posing risks to public health and the environment. Here is an overview of US cities with poor air quality and the factors contributing to this issue:

Bakersfield, California

Bakersfield has been identified as the most polluted city in the US by year-round air quality measures. It ranks first for high-pollution days and third for ozone exposure. The city's poor air quality is a result of emissions from the energy and agriculture industries, a dry and dusty climate, and its low-lying geography, which traps polluted air in the valley.

Los Angeles, California

Los Angeles, known for its heavy traffic and industrial presence, is the country's worst city for ozone pollution or smog. The high levels of ozone are attributed to a combination of factors, including vehicle emissions, industrial activities, and wildfires. The Los Angeles-Long Beach area is particularly affected by poor air quality.

Fresno and Visalia, California

Both Fresno and Visalia, located in California's Central Valley, score poorly across all three measures of pollution tracked by the ALA. Fresno is the second-worst city for year-round particulate matter pollution, while Visalia ranks fifth for most high-pollution days and second for ozone exposure. The air pollution in these cities impacts a significant number of people of color.

Pittsburgh, Pennsylvania

Pittsburgh is another US city facing air quality challenges. The constant use of coal in power stations has led to poor air quality in the region. The demand for electricity has remained relatively unchanged, and air pollution from coal combustion continues to negatively affect the area.

Grants Pass and Medford, Oregon

Grants Pass and Medford, located in southern Oregon, have high levels of air particulate matter pollution. This pollution affects a population of approximately 309,000 people, including over 61,000 people of color.

It is important to note that air pollution disproportionately affects people of color and low-income communities, putting them at higher risk for various health issues, including respiratory problems, heart disease, and cancer. Climate change further exacerbates air pollution, creating conditions favorable for ozone formation and increasing the frequency of wildfires, which release hazardous particulate matter into the atmosphere.

Particle pollution and health risks

Air pollution is one of the most significant health issues of modern industrial society, causing over 10% of worldwide deaths annually (approximately 4.5 million premature deaths in 2019). Particle pollution, or particulate matter (PM), is a major contributor to poor air quality and poses serious health risks. PM2.5, or fine particles, are 2.5 microns or smaller in diameter and are of particular concern due to their ability to penetrate deep into the respiratory tract and lungs. These fine particles are primarily produced by industrial emissions, vehicle exhaust, and the burning of fossil fuels and wood.

The health risks associated with particle pollution are extensive. Short-term exposure to high levels of PM2.5 can trigger cardiovascular events, hospitalisations, and even mortality. Long-term exposure to low levels of PM2.5 has been linked to an increased risk of strokes, coronary heart disease, and premature death. Particle pollution has also been associated with respiratory issues such as asthma, bronchitis, and reduced lung function. Studies have found a correlation between particle pollution and adverse pregnancy and birth outcomes, including preterm birth, low birth weight, and fetal and infant mortality.

The size of particulate matter plays a crucial role in its potential for causing health issues. Smaller particles, such as PM2.5, are more harmful than larger particles (PM10-2.5) because they can penetrate deeper into the lungs and even enter the bloodstream. These fine particles can cause irritation to the eyes, nose, throat, and lungs, as well as coughing, sneezing, and shortness of breath. People with pre-existing heart or lung conditions, children, older adults, and individuals from minority and low socioeconomic backgrounds are more susceptible to the health risks associated with particle pollution.

The World Health Organization (WHO) has set a recommended limit for PM2.5 concentration in the air of 10 micrograms per cubic meter. However, many countries, particularly emerging and developing nations, do not meet this standard. India, for example, had 11 cities in the top 20 most air-polluted cities in 2024, with Byrnihat recording a PM2.5 concentration of 128.2 micrograms per cubic meter—over 25 times the WHO limit. Other countries with high air pollution levels include Pakistan and other parts of Asia, with N'Djamena in Chad being the only non-Asian city in the top 20.

The health risks associated with particle pollution highlight the importance of implementing measures to reduce air pollution and improve air quality. This includes regulating industrial emissions and vehicle exhaust, transitioning to cleaner energy sources, and promoting the use of air purification systems. By addressing particle pollution, we can mitigate its harmful health effects and improve the overall well-being of populations worldwide.

Global environmental standards and developing countries

Air pollution is a significant issue in emerging and developing countries, where global environmental standards are often not met. India, for instance, is home to some of the world's most polluted cities, with 11 of the top 20 cities with the worst PM2.5 levels in 2024. Other countries with severe air pollution include Pakistan and other parts of Asia.

Developing countries face challenges in meeting global environmental standards due to various factors. One of the main obstacles is their financial ability and domestic energy demands, which hinder their ability to transition to renewable energy sources and implement ambitious environmental commitments. For instance, fossil fuels remain a crucial source of affordable electricity for developing countries, even as they strive to increase their renewable energy capacity, as seen in China's case.

Additionally, weak regulation and enforcement in developing countries can exacerbate the problem. The lack of stringent environmental regulations and the priority given to economic growth and production goals can result in high levels of industrial emissions and vehicle exhaust, contributing to air pollution.

To address these issues, a more equitable approach to tackling climate change may be necessary. This involves recognizing the differing responsibilities and capabilities of developed and developing countries. Developed countries can provide financial assistance and share their experience in setting up effective environmental policies. Developing countries, on the other hand, can learn from the mistakes of developed nations and strive to adopt modern and clean technologies, potentially skipping the dirty phases of industrialization.

Furthermore, corporations have a responsibility to uphold environmental standards in their global operations and supply chains. By understanding the practices of leading firms, developing countries can gain insights into managing foreign investors and encouraging compliance with environmental regulations. A tiered approach to environmental policy, starting with simple discharge-control technology requirements and building regulatory capacity over time, can also help developing countries make gradual progress without losing sight of the ultimate environmental goals.

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