Air pollution is a global crisis that has severe implications for the environment and human health. This article provides a comprehensive analysis of the most polluted cities around the world. We look at the main sources of pollution, analyse the efficiency of the measures that are being taken by governments to tackle the issue, and provide insights into the future of air quality.

“Clean air is a human right. Unfortunately, it is not a reality for a large proportion of the world’s population.” – Dr. Maria Neira, Director of the Public Health, Environment and Social Determinants of Health Department of the World Health Organization.

Why Should We Care About Air Pollution?

Air pollution is the greatest environmental threat to public health globally. Improving our air quality will bring health, development, and environmental benefits. With every breath we take, we suck in tiny particles that can damage our lungs, hearts, and brains and cause a host of other health problems. The most dangerous of these particles, which can include anything from soot, soil dust, to sulphates, are fine particles 2.5 microns or less in diameter – shortened as PM2.5.

According to Dr Maria Neira, Director of Environment, Climate Change and Health at the World Health Organization (WHO), about 9 out of 10 people are exposed to air pollution at levels above the WHO air quality guidelines. Researchers found that daily air pollution levels globally exceed 15 μg/m3 – the safe threshold value recommended by the WHO – for more than 70% of days in 2019. As a result, about 7 million people die every year due to ambient or household air pollution. This number is only the tip of the iceberg, as there is also a huge burden of sickness, hospitalisation, reduced life expectancy, and the associated social and economic impacts of lost productivity and healthcare costs. 

Mapping the Cities With the Most Dangerous Levels of Pollution

Mapping the most polluted cities and countries in the world helps identifying the primary sources of pollution and their causes, as well as understanding the consequences of high levels of pollution on human health and the environment.

According to IQAir’s 2022 World Air Quality Report, most of the world’s 50 most polluted cities are in Asia, particularly India and Pakistan. 

The following are the 10 most polluted cities in the world: 

1. Lahore, Pakistan

2. Hotan, China

3. Bhiwadi, India

4. Delhi (NCT), India

5. Peshawar, Pakistan

6. Darbhanga, India

7. Asopur, India

8. N’Djamena, Chad

9. New Delhi, India

10. Patna, India

While Indian cities top the world’s most polluted cities’ list, India does not place among the five most polluted countries globally. The latter are topped by nations much smaller in geographical area, which brings up the annual average PM2.5 concentration (μg/m³).

The following are the 5 most polluted countries in the world, according to IQAir

1. Chad

2. Iraq

3. Pakistan

4. Bahrain

5. Bangladesh

What is Air Pollution?

Ambient air pollution is caused by a number of air pollutants, including NOx, ozone, carbon monoxide, and sulphur dioxides.  PM2.5 is the air pollutant that has been most closely studied and is most commonly used as a proxy indicator of exposure to air pollution more generally. Particulate matter consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. 

The major components of PM are sulphates, nitrates, ammonia, sodium chloride, black carbon, mineral dust, and water. The most health-damaging particles are those with a diameter of 10 μm or less, which can penetrate and lodge deep inside the lungs. Both short- and long-term exposure to air pollutants have been associated with health impacts such as lung cancer, heart disease and stroke, according to the World Health Organization.

More on the topic here: What is Indoor Air Pollution?

What Are the Main Sources of Air Pollution?

The primary sources of pollution in each of the most polluted cities are residential pollution, mostly from cooking and heating using biomass, generating electricity from fossil fuels for our homes, and transport. Windblown dust is also a major source in portions of Africa and West Asia that are close to deserts. Windblown dust, emitted from the surface of the earth to the atmosphere, has significant impacts on atmospheric phenomena, air quality, and human health. 

Respiratory and cardiovascular disorders, meningococcal meningitis, conjunctivitis, and skin irritations are among the health problems that have been associated with exposure to dust. Specifically, airborne dust particles (in particular those finer than 10 microns in diameter, called PM10) can penetrate deep into the lungs and impair respiratory processes. Dust that contains heavy metals or other toxic compounds can also cause a wide range of acute and chronic health effects. 

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Where Are People Dying of Pollution?

Explore the map below to understand the impact of air pollution on human life in each country.

The most common health problems associated with air pollution include stroke, heart disease, lung disease, lower respiratory diseases, and cancer. Explore the map below to find out what percent of death in any given country can be attributed to outdoor fine particles.

Despite the grave health risks associated with air pollution, many countries still face challenges in meeting their clean air targets. However, some countries are making progress, such as the Philippines, Indonesia, and Brazil, among others. The global community needs to take action to reduce air pollution by making lifestyle changes, reducing energy consumption, and adopting environmentally conscious alternatives to wood-burning stoves, among others.

How Does Air Pollution Affect the Environment? 

Air pollution has significant negative impacts on the environment. Acid rain, caused by air pollutants such as sulphur dioxide and nitrogen dioxide, is harmful to natural ecosystems, interfering with the root’s cell division and ability to elongate, reducing essential nutrients for plants, and threatening wildlife, particularly aquatic animals. Eutrophication, the enrichment of a waterbody with minerals and nutrients that lead to excessive algae growth, blocks sunlight from underwater plants and consumes large amounts of oxygen in the water, resulting in the death of aquatic plants and animals. Human activities, such as energy production and fertiliser use, contribute significantly to eutrophication.

While air pollutants are distinguished from greenhouse gases, some air pollutants, such as ground-level ozone, possess warming power and can trap heat in the atmosphere. However, some air pollutants, like aerosol, have a positive effect on resisting climate change, as they possess cooling power by changing the amount of solar energy entering and leaving the atmosphere and forming clouds. Scientists are exploring the possibility of manipulating aerosols to slow down climate change, but controlling the number of airborne particles within a safe range remains a challenge. 

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What Can We Do?

nitrogen dioxide pollution impacts

Image: World Health Organization.

There are many ways individuals can reduce their personal air pollution footprint, including using public transportation, reducing energy consumption, moderating waste, and using air filtration and purification systems to improve indoor air quality. Additionally, people can limit outdoor activities when air quality is at unhealthy levels and stay informed about real-time air quality conditions using apps.

However, the problem of air pollution requires the collective efforts of individuals, communities, and governments worldwide. Governments can invest in energy-efficient power generation, improve waste management, and promote greener and more compact cities with energy-efficient buildings. Additionally, providing universal access to clean, affordable fuels and technologies and building safe and affordable public transport systems can help reduce air pollution. 

As we continue to map the most polluted cities in the world, let’s also work towards a future where clean air is a fundamental human right, and every individual has the opportunity to live a healthy and fulfilling life.

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