Air Pollution: Cities With The Dirtiest Air

Air pollution is a critical threat to human health and environmental stability, and it is one of the deadliest environmental threats, causing millions of premature deaths each year. The World Health Organization (WHO) has set an annual PM2.5 guideline of less than 5 µg/m3, but in 2024, only 17% of cities worldwide met this standard. This article will discuss the cities with the most polluted air, including those with high levels of particle pollution and ozone pollution, and the factors contributing to poor air quality.

Byrnihat, India: The most polluted city in 2024

Air pollution is a deadly environmental threat, causing 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 large majority of the global population is exposed to unclean air.

India, in particular, is home to some of the world's most polluted cities, with 11 of the top 20 polluted cities in 2024. 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. This figure is over 25 times higher than the WHO's recommended limit.

The poor air quality in Byrnihat and other Indian cities is a result of several factors, including burning fossil fuels, agricultural practices, vehicle emissions, and rapid urbanization. These activities contribute to chemical reactions in the atmosphere, leading to air pollution. According to the WHO, exposure to PM2.5 pollutants can have severe health consequences, including respiratory and viral infections, asthma, cancer, stroke, and lung disease.

The Indian government and relevant authorities must address this issue by implementing measures to reduce pollution levels and mitigate the health risks faced by residents. This may include transitioning to cleaner energy sources, regulating agricultural and industrial practices, promoting sustainable transportation, and raising awareness about the impacts of air pollution on human health and the environment.

By taking decisive action and adopting sustainable practices, Byrnihat and other polluted cities in India can improve their air quality, protect the health of their citizens, and contribute to global efforts to combat climate change.

Delhi, India: Second-worst air pollution in 2024

Delhi, India, has long struggled with poor air quality, and in 2024, it was reported to have the second-worst air pollution in the world. The city's air pollution is a complex issue with a variety of contributing factors, and it poses significant health risks to its residents.

In November 2024, Delhi recorded its worst air quality of the year, with a 24-hour AQI reading of 491, classified as "severe plus". This hazardous level indicated significant health risks, particularly for vulnerable populations. The primary cause of this spike in pollution was the increased fire activity in the surrounding states and Pakistan's Punjab region, as farmers burned excess straw and crop residues, leading to a dense smog that engulfed the city.

Delhi's air pollution is a year-round issue, but it tends to worsen during the winter months. Cold temperatures, stagnant winds, and temperature inversion trap toxic particles close to the ground, making the smog denser and more persistent. Various factors contribute to Delhi's poor air quality, including vehicle emissions, industrial activities, power plants, construction, and household cooking and heating practices. The burning of crop residues, such as rice stubble, in nearby states also significantly impacts the city's air quality. Despite efforts to reduce the number of farm fires, the air pollution in Delhi remains stubbornly high.

The Indian government has faced criticism for not allocating enough resources to combat this pressing issue. While some measures have been implemented, such as spraying mist to capture fine particles and restricting motor vehicles, the effectiveness of these initiatives has been questioned. The city of Delhi has also invested in "smog towers," giant outdoor air purifiers, but their impact on improving air quality has been disputed by scientific consensus.

The health implications of Delhi's air pollution are severe. According to the World Health Organization, India has the highest death rate from chronic respiratory diseases and asthma. It is estimated that air pollution in India kills about 2 million people annually, and in Delhi alone, poor air quality has irreversibly damaged the lungs of 2.2 million children. As scientific understanding of the far-reaching health impacts of air pollution advances, the urgency of implementing effective solutions becomes increasingly critical.

Los Angeles, California: Worst air pollution in the US

Los Angeles, California, has some of the worst air pollution in the United States. According to the 2019 State of the Air report, Los Angeles has the worst ozone air pollution in the country. The city's ozone levels are due to a combination of geographical factors and human activities.

The Los Angeles basin is surrounded by mountains to the west and north, with the Pacific Ocean to the west and several mountain ranges with 11,000-foot peaks to the east and south. A daily breeze blows pollutants from west to east toward the mountains, and the high-pressure system that sits over the basin 95% of the year traps the air below the mountain tops. As a result, pollution builds up in the basin over several days until strong winds or a change in the pressure system allows it to clear. The region's geography and weather conditions, such as warm, dry weather and low rainfall, also contribute to the formation of ozone and the accumulation of fine particles and dust.

Human activities have exacerbated the problem. Diesel engines, ports, motor vehicles, and industries are major sources of air pollution in Los Angeles. Traffic is frequently identified as a leading source of ozone pollution, as vehicle exhaust contains nitrogen oxides and reactive organic substances that react with sunlight to form ozone. Residential wood combustion, such as burning wood in fireplaces, is the largest source of PM 2.5 pollution. In addition, extreme pollution events such as wildfires, which have become more common due to anthropogenic climate change, can cause significant spikes in air pollution levels in Los Angeles.

The air pollution in Los Angeles has had detrimental effects on the health of its residents. A 2008 economic study found that more than 3,800 people die prematurely each year in the Los Angeles Basin due to air pollution levels that violate federal standards. Exposure to PM 2.5, which is widely regarded as one of the most harmful pollutants, has been linked to heart disease, respiratory illness, and premature death. Fine particle pollution has also been associated with health conditions such as asthma.

Efforts have been made to improve air quality in Los Angeles. California established the California Air Resources Board (CARB) in 1967 to unite local governments, businesses, and residents in researching and legislating effective air pollution policies. The Clean Air Act, along with subsequent amendments, created federal air quality monitoring, emission control, and enforcement. While air pollution levels in Los Angeles still exceed federal standards, significant improvements have been made in the last two decades. The yearly average of fine particle pollution has declined, and residents are exposed to unhealthy ozone levels for fewer days per year compared to the year 2000.

Climate change: Increases risk of wildfires, which spread particle pollution

Air pollution is a deadly environmental threat, causing millions of premature deaths each year. In 2024, only 17% of cities met the World Health Organization's annual PM2.5 guideline, indicating that most urban populations breathe unhealthy air. India is home to some of the world's most polluted cities, with Byrnihat, a city in northeastern India, recording the worst air pollution in 2024. Other cities with poor air quality include Delhi, N'Djamena in Chad, and Los Angeles.

Climate change is closely linked to air pollution and wildfires, creating a vicious cycle. Human activities, such as burning fossil fuels, transportation, and industrial processes, release greenhouse gases and black carbon emissions, contributing to climate change. These emissions trap heat in the atmosphere, raising global temperatures and disrupting weather patterns. As a result, the risk and impact of wildfires increase, particularly in forests with dry organic matter and drought conditions. Climate change has doubled the number of large fires in the western United States between 1984 and 2015, and warmer temperatures make it harder to control fires.

Wildfires release a range of harmful pollutants, including black carbon, carbon monoxide, nitrogen oxides, and particulate matter. These pollutants have severe impacts on human health and the environment, and when combined with existing air pollution, they pose even greater threats. For example, black carbon from wildfires can intensify heatwaves, alter weather patterns, accelerate the melting of ice and snow, and further perpetuate climate change. The East Siberian wildfires from 2019 to 2021 led to elevated black carbon levels in the Arctic, and Amazonian fires increased glacier melting by 3-4%.

To break this vicious cycle, governments must address the interconnectedness between climate change, air pollution, and wildfires. Reducing emissions and implementing fire prevention strategies are crucial. Communities can discourage residential developments near fire-prone forests, increase space between structures and vegetation, and incorporate fire-resistant design features. Additionally, removing potential fuels, such as dead trees, from at-risk forests can help reduce the likelihood and impacts of wildfires. By taking a comprehensive approach, policymakers can protect public health, mitigate climate change, and minimize the harmful effects of wildfires on the environment.

Health risks: Air pollution is linked to premature births and lower birth weights

Air pollution is a serious environmental threat, contributing to millions of premature deaths each year. In 2019, air pollution was linked to almost 6 million premature births and nearly 3 million underweight babies worldwide. A study by the University of California, San Francisco (UCSF) and the University of Washington found that air pollution is a major cause of preterm birth and low birth weight. The analysis, published in PLOS Medicine, is the most comprehensive examination of how air pollution affects several key indicators of pregnancy, including gestational age at birth, birth weight, and preterm birth.

The study also found that the global incidence of preterm birth and low birth weight could be reduced by up to 78% if air pollution were minimized in Southeast Asia and sub-Saharan Africa, regions with high rates of indoor pollution and preterm births. Additionally, the study quantified the effects of air pollution on early life mortality, concluding that it contributed to the deaths of 500,000 newborns in 2019. These findings highlight the urgent need to address air pollution to protect newborn health and reduce infant morbidity and mortality rates.

Outdoor air pollution is a significant issue, with more than 90% of the world's population breathing polluted air. However, indoor air pollution is also a critical concern, with half of the global population exposed to it due to burning coal, dung, and wood inside their homes. In 2024, only 17% of cities met the World Health Organization's annual PM2.5 guideline, indicating that most urban populations breathe unhealthy air. India, for example, had 11 of the top 20 most air-polluted cities in 2024, with Byrnihat ranking as the city with the worst air pollution globally. Delhi, India's capital, recorded the second-worst air pollution levels in the same year.

Various factors contribute to air pollution in these cities, including industrial emissions, vehicle exhaust, and the burning of crops in nearby states. Additionally, weak regulations and seasonal weather patterns can worsen the problem. Climate change also plays a role, increasing the risk of wildfires, which produce dangerous particle pollution. Particle pollution, such as ozone and fine particulate matter (PM2.5), is linked to increased risks of premature birth and low birth weight. These particles are small enough to bypass the body's natural defenses, causing harm to both mothers and their unborn children.

To address these health risks, policymakers must take steps to clean the air, such as implementing and enforcing air quality standards and regulations. The Clean Air Act in the United States, for example, has successfully driven pollution reduction for over 50 years. However, ongoing staffing and funding cuts to organizations like the U.S. Environmental Protection Agency endanger the progress made in improving air quality and protecting public health. Therefore, it is crucial to prioritize and support initiatives that aim to reduce air pollution and mitigate its harmful health impacts.

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