Air Pollution: America's Worst Cities Revealed

Air pollution is a serious health threat that can trigger asthma attacks, harm lung development in children, and even be deadly. While the Clean Air Act has driven pollution reduction over the past 50 years, climate change and other factors have made it increasingly difficult to maintain air quality. In 2025, nearly half of Americans (approximately 156 million people) lived in areas with failing grades for unhealthy levels of ozone or particle pollution. This article explores where air pollution is worst in the USA, highlighting the cities and states with the poorest air quality and the factors contributing to this issue.

California's Central Valley

The Central Valley's air pollution is influenced by a combination of factors, including its topography, agricultural burning, and industrial activities. The surrounding mountain ranges trap air pollutants, exacerbating the effects of pollution sources such as heavy truck traffic, diesel-burning locomotives, tractors, and irrigation pumps. The region is also home to large-scale oil, agriculture, and warehouse distribution industries, which contribute significantly to air pollution.

Despite some improvements in air quality over the years, climate change is now threatening to reverse this progress. California's record-breaking drought has led to an increase in agricultural burning, and the state's wildfire seasons have been intensifying, with 4 of the 5 largest wildfires in California's history occurring in 2020 and 2021. The smoke from these wildfires poses significant health risks, especially in the Central Valley, where many residents work outdoors.

Efforts to improve air quality in the Central Valley have been met with challenges. Activists argue that the influence of polluting industries has hindered progress in implementing stricter air quality regulations. However, the EPA has been working with local organizations to reduce PM2.5 levels through regulatory action, clean-vehicle programs, and enforcement. The San Joaquin Valley Air Pollution Control District has also received funding for innovative air emission reduction technologies through the Clean Air Technology Initiative.

Los Angeles

According to the 2019 State of the Air report, Los Angeles had the worst ozone air pollution in the country. Ozone is a gas pollutant that forms when sunlight reacts with nitrogen oxides and organic substances found in vehicle exhaust. As a result, traffic is a leading source of ozone pollution in Los Angeles, with an estimated 6.5 million vehicles in the city. The large population of Los Angeles, with 4 million residents and an additional 6 million in the surrounding county, also contributes significantly to the city's air pollution. Heavy vehicular emissions and traffic congestion are major issues that impact the air quality.

In addition to vehicle emissions, other factors contributing to Los Angeles' air pollution include the burning of fossil fuels by ships, planes, and manufacturing industries, as well as wildfires. The city's geographic location in Southern California makes it particularly susceptible to warm weather and harmful pollutants, exacerbating the air quality issues. The summer months of June, July, and August tend to have higher levels of pollution compared to other months.

Despite the challenges, there have been notable improvements in Los Angeles' air quality over the years. The yearly average of fine particle pollution has declined, and residents are exposed to unhealthy ozone levels for significantly fewer days per year compared to the year 2000. The COVID-19 pandemic lockdown measures also resulted in a prolonged period of clean air in March 2020, as non-essential businesses closed and residents stayed at home. Additionally, the city has set sustainability goals to increase the number of zero-emission vehicles, aiming for 25% by 2025 and 100% by 2050.

Bakersfield

According to the American Lung Association's "State of the Air" report, Bakersfield has consistently ranked high in annual particle pollution, 24-hour particle pollution, and high ozone days among metropolitan areas in the country. The city's average reading of fine particulate matter (PM2.5) in a 24-hour period can be as high as 40.5 micrograms per cubic meter, significantly higher than the recommended levels by the World Health Organization (WHO) of no more than 5 µg/m3.

The health impacts of air pollution in Bakersfield are significant. It is estimated to cost the region approximately $3 billion, or about $1,000 per person, per year. The high levels of pollution disproportionately affect children, the elderly, and those with pre-existing heart and lung conditions. About 70,000 residents in the wider metropolitan area are reported to have asthma, with additional cases of cardiovascular disease and chronic obstructive pulmonary disease.

While there have been some improvements in recent years through stricter air quality standards and technological advancements, the election of administrations opposed to air quality regulations threatens to undo this progress. Bakersfield's struggle with air pollution highlights the urgent need for policymakers to address this issue and protect the health of its residents.

Overall, Bakersfield's air pollution is a complex issue influenced by its geographical location, industrial activities, and policy decisions. The city has made some progress in improving air quality, but it continues to face challenges in ensuring clean air for its residents.

Wildfires

The impact of wildfire smoke on air quality has been significant, eroding years of progress in improving air quality across the nation. Between 2000 and the 2010s, air quality improved in 41 states, with a notable decrease in health-damaging tiny particles. However, since 2016, wildfire smoke has either slowed or reversed these positive trends in 35 states. The Western states, including California, Washington, and Oregon, have been particularly affected, with smoke-laden days becoming an annual occurrence.

California, for instance, experienced devastating wildfires in 2020, with skies over cities shrouded in orange-colored smoke. The particles produced by these fires can be up to ten times more harmful to human health than particles from other sources. While California has made strides in reducing pollution from vehicles and industrial sources, the worsening wildfires have become a growing concern.

The Clean Air Act, a landmark environmental law, has played a crucial role in improving air quality over the past five decades. However, it has been less effective in regulating the risks posed by smoke from wildfires, which can drift across state borders and affect areas far from the fire's origin. As a result, there is a growing need for new approaches to address this evolving challenge and mitigate the impact of wildfires on air quality.

To address the increasing threat of wildfires, a combination of strategies is necessary. This includes implementing forest and fire management policies, such as prescribed burns, to reduce the risk of catastrophic wildfires. Additionally, adapting to climate change and mitigating its impacts is crucial, as climate change intensifies the conditions that fuel wildfires. By addressing the underlying drivers of wildfires and improving air quality management strategies, it may be possible to mitigate the adverse effects of wildfires on the health of communities across the United States.

Communities of colour

While air pollution is a widespread issue across the United States, it is important to recognise that it disproportionately affects communities of colour. Research has found that people of colour in the United States breathe more particulate air pollution on average, regardless of income level or region. This is due to the systemic racism that has led to people of colour being pushed closer to sources of pollution, such as factories, congested roadways, and shipping routes. As a result, communities of colour experience a higher burden of diseases linked to air pollution, with higher rates of pediatric asthma and a greater risk of premature death.

A study by researchers at the EPA-funded Center for Air, Climate, and Energy Solutions found that African Americans, Hispanics, Asians, and other people of colour are exposed to a regulated air pollutant called fine particulate matter (PM2.5). This pollutant has serious public health implications, as it can cause lung and heart problems, especially for vulnerable populations such as children and the elderly. The same study also revealed that nearly all emission sectors, including industry, agriculture, vehicles, and construction, contribute to the disproportionate exposure to air pollution faced by communities of colour.

The health disparities caused by air pollution are not limited to physical health issues but also extend to mental health concerns. Studies have found that chronic stress resulting from discrimination can play a significant role in the increased risk of health issues within communities of colour. Additionally, socioeconomic factors, such as low income and limited access to healthcare, can further exacerbate the impact of air pollution on these communities.

It is worth noting that the Environmental Protection Agency (EPA) has played a crucial role in monitoring and regulating air pollution in the United States. However, recent staffing and funding cuts threaten their ability to continue this vital work. To address environmental injustice effectively, it is essential to consider the intersection of race and income when designing regulations and policies aimed at improving air quality and protecting the health of all communities, especially those that have been historically marginalised.

While air pollution is a pressing issue for all Americans, it is undeniable that communities of colour bear a heavier burden. Addressing this disparity requires a multifaceted approach that tackles systemic racism, ensures equitable access to healthcare and environmental decision-making processes, and strengthens regulations to protect air quality. By prioritising these actions, policymakers can work towards creating a healthier and more equitable future for all Americans.

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