Air Pollution's Worst Victims: A Global Crisis

Air pollution is a serious global health and environmental problem. It is a leading risk factor for death, contributing to one in ten deaths globally. In 2024, only 17% of cities worldwide met the World Health Organization's annual PM2.5 guideline of less than 5 µg/m3, indicating that the vast majority of urban populations are exposed to unhealthy air. This is due to a combination of outdoor and indoor particulate matter and ozone, which can trigger asthma attacks, harm lung development in children, and even be deadly. Certain groups, including children, older adults, people with lung diseases, people of color, and those with lower incomes, are especially vulnerable to the effects of air pollution. In the United States, nearly half of the population lives in areas that received a failing grade for air quality in 2025. Los Angeles, California; Gary, Indiana; Bakersfield, California; and Chicago, Illinois are among the top five hotspots for fine particle air pollution in the country. Outside of the US, India is home to some of the world's most air-polluted cities, with Byrnihat and Delhi ranking among the highest in 2024.

Los Angeles, California

According to the 2019 State of the Air report, which compared data across 229 metropolitan areas, Los Angeles has the worst ozone air pollution in the United States. Ozone is a gas pollutant formed when sunlight reacts with nitrogen oxides and organic substances. Vehicle exhaust contains both the nitrogen oxides and reactive organic substances needed to form ozone, so traffic is frequently identified as a leading source. Like PM2.5, ozone can cause health effects ranging from respiratory infections and inflammation to premature death.

While air pollution levels in Los Angeles still far exceed federal standards, significant improvements have been made in the last two decades. California began addressing air pollution in 1967 when it established the California Air Resources Board (CARB), an organization whose mission is to unite local governments, businesses, and residents with the goal of researching and legislating effective air pollution policy. This board was later empowered by the legislative action of the federal government in 1970, which established the Clean Air Act. The Clean Air Act, along with the later 1977 and 1990 amendments, created federal air quality monitoring, emission control, and enforcement. The Clean Air Act has been deemed the most effective federal regulation for clean air, estimated to have prevented as many as 237,000 deaths from 1970 to 2020.

In addition to weather, extreme pollution events such as wildfires can cause significant spikes in LA's air quality. Such pollution events have become increasingly common in the area over the last few decades due to anthropogenic climate change. When smoke fills the LA Basin, the region's geography and weather conditions can make it difficult for the air pollution to disperse, resulting in slowly accumulating pollution levels until the emissions stop or the weather changes. During periods of unhealthy air quality, sensitive groups may experience symptoms such as difficulty breathing or throat irritation, and even healthy individuals may experience these symptoms with prolonged exposure. To protect against the health effects of air pollution, residents can check the air quality forecast in their community and avoid exercising or working outdoors when unhealthy air is expected.

Gary, Indiana

Air pollution is a serious health threat that affects people worldwide. It can trigger asthma attacks, harm lung development in children, and even be deadly. People of color and people with lower incomes are disproportionately affected by air pollution, putting them at higher risk for illness.

While air quality data for Gary shows fluctuations, with AQI levels ranging from "Good" to "Moderate", it is important to note that even short-term exposure to polluted air can have negative health effects. Sensitive groups, including individuals with respiratory conditions, children, and older adults, may experience symptoms such as difficulty breathing or throat irritation.

To protect themselves from the harmful effects of air pollution, residents of Gary, Indiana, can take proactive measures such as staying informed about air quality forecasts, limiting outdoor activities when air pollution levels are high, and investing in indoor air purification systems. Additionally, advocating for policies that address air pollution at the local and national levels is crucial to ensure that communities can breathe cleaner air.

It is worth noting that air pollution data and monitoring are subject to limitations and discrepancies. Real-time data may vary, and it is always advisable to refer to multiple sources and official recommendations to make informed decisions regarding your health and well-being.

Bakersfield, California

Bakersfield is located in a valley surrounded by mountains, including the Sierra Nevada mountains to the east and the California Coast Ranges to the west. This topography traps polluted air in the valley, preventing its dispersion. The city is a hub for high-emission industries, including agriculture and fossil fuel-based energy production. Kern County, of which Bakersfield is the county seat, is the most productive oil-producing county in California. The primary oil refinery in the area, Kern Oil, has been subject to numerous Clean Air Act violations due to excessive pollution. The oil fields, refineries, and freight trains hauling oil contribute significantly to the city's air pollution.

Agricultural activities in and around Bakersfield also play a significant role in air pollution. Farmland machinery, crop burning, pesticides, and wind-blown dust release particulate matter and gases like nitrogen dioxide, a precursor to ozone pollution. The city's growing population and increasing residential emissions further exacerbate the problem. Residential emissions from private motor vehicles, wood stoves, fire pits, and BBQs are traditional contributors to air pollution in US cities.

The regulatory rollbacks on high-emitting industries initiated by the Trump administration, climate change, frequent California wildfires, and population growth have made it challenging to achieve sustained reductions in air pollution and meet federal air quality targets. Bakersfield's air pollution has serious health implications for its residents. About 70,000 people in the wider metropolitan area are estimated to have asthma, with air pollution triggering asthma attacks and causing other respiratory issues.

Addressing Bakersfield's air pollution requires stronger environmental regulations and a comprehensive approach that involves industry, government, and community collaboration. The city's ranking as the most polluted in the nation underscores the urgent need for action to improve air quality and protect the health of its residents.

Chicago, Illinois

One of the key pollutants in Chicago's air is ozone, which is a major respiratory health hazard. Ozone is formed when sunlight reacts with pollutants from vehicle emissions and industrial sources, and it is of particular concern during the summer months when temperatures are high and sunlight is strong. The American Lung Association's report on air pollution might provide more insight into the status of Chicago as one of the most ozone-polluted cities in the US.

In addition to ozone, particulate matter (PM) pollution is also a significant issue in Chicago. PM2.5, which refers to tiny particles less than 2.5 microns in diameter, can penetrate deep into the lungs and even enter the bloodstream, causing serious health problems. Sources of PM2.5 include vehicle emissions, industrial processes, and construction activities. According to the US Environmental Protection Agency (EPA), Chicago's PM2.5 levels likely exceed the national standard, posing risks to the respiratory and cardiovascular health of residents.

The impact of air pollution in Chicago is probably not felt equally across the city's diverse communities. Low-income communities and communities of color are often disproportionately affected by poor air quality. For example, the predominantly Black and Latinx neighborhood of Little Village, located on the city's southwest side, has long been burdened by industrial pollution. The neighborhood is home to a high concentration of heavy industries, including coal-fired power plants and steel mills, which likely contribute to elevated levels of air pollutants such as sulfur dioxide and particulate matter.

To address these issues, the city of Chicago has likely implemented or considered initiatives and policies to improve air quality and protect residents' health. For instance, stricter emissions standards for industrial sources and targets for reducing ozone and PM pollution might be part of the strategy. Additionally, promoting the use of electric vehicles, cleaner fuels, and energy efficiency in buildings could also be among the approaches to mitigate air pollution in Chicago.

St Louis, Missouri

Air pollution is a critical global health issue, causing approximately 4.5 million premature deaths in 2019. It is a "silent killer", as it is rarely the direct cause of death, but rather a contributing factor. According to the World Air Quality Report of 2024, 91% of countries and regions worldwide exceeded the World Health Organization's (WHO) annual PM2.5 guideline value of 5 µg/m3.

In the United States, St. Louis, Missouri, is one of the cities most affected by air pollution. The region's air quality is impacted by several energy plants that still burn coal, with three of the top ten most polluting power plants in the nation located in the area. The neighbourhoods with the highest levels of PM2.5 tend to be north of Delmar Boulevard, the racial and socioeconomic dividing line known as the "Delmar Divide". These areas have a higher percentage of Black residents compared to other parts of the same counties, and their residents experience negative health effects due to the poor air quality.

The air pollution in St. Louis has led to health warnings for sensitive groups, including people with lung diseases such as asthma and COPD, children, and older adults. On certain days, these individuals are advised to reduce their time spent outdoors and limit physical activity to prevent symptoms such as throat irritation and difficulty breathing.

The high levels of air pollution in St. Louis are influenced by the city's industrial activity and power generation sources. The burning of coal and other fossil fuels releases nitrogen oxides (NOx), hydrogen sulfide, volatile organic compounds (VOCs), and particulate matter, which contribute to ozone layer depletion and smog formation. Additionally, transportation emissions from cars, trucks, and other vehicles also elevate fine particulate matter levels in the region.

To address the air quality issues in St. Louis, policymakers and environmental organisations are advocating for regulatory changes and the adoption of cleaner energy sources. However, the success of these initiatives depends on cooperation from energy companies and support from government agencies like the U.S. Environmental Protection Agency, which plays a critical role in monitoring and enforcing air pollution standards.

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