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Top 10 Most Polluted Cities in the US in 2024

Pollution is a serious problem in many cities across the United States. It occurs when harmful substances like chemicals and tiny particles enter the air, making breathing unsafe. Pollution can lead to various health issues for people, such as respiratory problems, heart disease, and even premature death. Many of the most polluted cities in the US are located in states like California, Texas, and Pennsylvania. 

Sometimes, things still get bad like in 2023 when wildfires in Canada made the air in places like New York and Washington DC dangerous to breathe. Here is the list of the top 10 most polluted cities in the US.

List of Top 10 Most Polluted Cities In The USA

  1. Los Angeles
  2. Bakersfield
  3. Fresno
  4. Visalia
  5. San Francisco
  6. Sacramento
  7. San Diego
  8. Modesto
  9. Riverside
  10.  Phoenix

1. Los Angeles

Los Angeles has a concerning track record, holding the title of the city with the highest ozone pollution for 23 out of the last 24 years. In 2009, reports indicated that it had the highest levels of ozone pollution in the nation, exceeding national standards and posing risks to residents’ health. This consistent ranking highlights the ongoing challenge of air quality in the region. This pollution primarily stems from vehicle emissions, industrial activities, and geographical factors that trap pollutants.

The impact of this pollution on public health is significant, with studies linking it to increased rates of respiratory illnesses, cardiovascular diseases, and premature deaths. Los Angeles has some of the most polluted air in the US. It is a huge city with over 10 million people, surrounded by mountains and the ocean. This geography can trap pollution, making the air worse. Cars, trucks, and factories are the main sources of this pollution, which can cause health problems for residents like asthma and heart issues. Efforts are being made to clean up the air, like making rules for cleaner vehicles and using cleaner energy. Still, more work is needed to keep the air safe, especially on hot days when pollution gets stuck in the city. Everyone in Los Angeles can help by using public transport, sharing rides, and supporting clean energy. 

2. Bakersfield

Bakersfield, located in California’s San Joaquin Valley took the lead in 2016 for having the highest level of airborne pollutants among all cities in the United States. In 2021, the American Lung Association’s “State of the Air” report listed Bakersfield as the city with the worst year-round particle pollution in the country. 

Furthermore, Bakersfield has struggled with high ozone levels, with the same report highlighting it as the fourth-worst city for ozone pollution. Ozone, a major component of smog, can cause respiratory problems and exacerbate existing health conditions.

The city’s topography exacerbates its pollution problems, as surrounding mountains trap pollutants, leading to stagnant air and higher concentrations of harmful substances. Bakersfield is a hub for agricultural activities and oil production, both of which are significant sources of air pollution. Pesticides and fertilizers used in agriculture. Emissions from vehicles and machinery contribute to the city’s air quality challenges.

Despite efforts to improve air quality through emission regulations and cleaner technologies, Bakersfield continues to face challenges in combating its pollution levels and ensuring the well-being of its residents. Addressing these issues requires ongoing collaboration and innovative solutions to reduce pollution sources and protect public health.

3. Fresno

Fresno ranked as the 6th most polluted city in terms of short-term particle pollution, known as PM2.5, and the 10th most polluted city for year-round particle pollution. The city’s pollution woes stem from a mix of factors, including heavy traffic contributing to vehicle emissions, agricultural activities releasing dust and pollutants, and geographic conditions that trap pollutants in the region. These factors combine to create significant challenges for maintaining clean air.

In addition to PM2.5, Fresno faces challenges with ozone pollution, particularly during hot summer months. The region’s topography and weather patterns exacerbate ozone formation, leading to respiratory problems and health concerns for residents. 

Despite these initiatives, Fresno continues to grapple with persistent air pollution issues, highlighting the ongoing need for comprehensive measures to address environmental challenges and protect public health in the city.

Read Also: Top Universities in California

4. Visalia

Visalia, in California’s agricultural San Joaquin Valley, has a population of 141,384 per the 2020 census. It’s the fifth-largest city in the valley and the 40th in California. 

It ranked as the third most polluted city in terms of short-term particle pollution and the seventh most polluted city in terms of year-round particle pollution.

The main sources include vehicle emissions, agricultural activities, and industrial processes. The city’s geographical location exacerbates the problem, as it is surrounded by mountains, creating a bowl-like effect that traps pollutants in the air.

Visalia is facing pollution problems that need fixing. Pollution comes from cars, factories, and farms. We can fix it by using cleaner cars, making factories cleaner, and farming smarter. Planting more trees can help clean the air, and using solar and wind power can reduce pollution from energy. Recycling and managing waste better are also important. Everyone needs to learn about pollution and work together to stop it. We must check pollution levels regularly and make sure rules are followed. 

Sustained efforts are needed to continue improving air quality in Visalia, including ongoing monitoring of pollution levels, implementing innovative technologies to reduce emissions, and promoting public awareness and participation in environmental conservation efforts. These actions are essential to protect public health and create a healthier environment for current and future generations in Visalia.

5. San Francisco

San Francisco, despite its reputation for environmental consciousness, contends with significant pollution challenges. In recent years, it has been labeled as one of the most polluted cities in the USA. According to data from the Environmental Protection Agency (EPA), San Francisco has struggled with air quality issues, notably high levels of ozone and particulate matter.

The city’s topography, surrounded by water and hills, contributes to trapping pollutants within its boundaries. Vehicle emissions from both personal and commercial transportation are major contributors to pollution levels. Furthermore, industrial activities and the burning of fossil fuels further degrade air quality.

Efforts to combat pollution include initiatives like promoting electric vehicles, expanding public transportation, and implementing stricter emissions standards. Despite these measures, San Francisco continues to face air quality challenges, especially during periods of heavy traffic or weather inversions that trap pollutants close to the ground. Continued efforts and community involvement are essential to improving the city’s environmental health.

6. Sacramento

Sacramento, the capital of California, sits where two rivers meet. It is home to about 525,000 people, making it a big city in Northern California and the state’s capital. The area was once inhabited by indigenous groups before the Spanish came. They named the Sacramento River, and later, the city grew under Swiss-born John Augustus Sutter. It is one of the most polluted cities in the US. 

Data from the Environmental Protection Agency (EPA) shows that Sacramento experiences high levels of ozone pollution, a significant health concern associated with respiratory illnesses and cardiovascular problems. The region’s topography and climate exacerbate these issues, creating stagnant air conditions that trap pollutants.

Efforts to combat pollution include stricter emission standards for vehicles, promotion of public transportation, and investment in clean energy initiatives. However, ongoing challenges persist, emphasizing the ongoing importance of sustainable urban development and environmental stewardship in Sacramento and beyond.

7. San Diego

San Diego, where the Pacific meets vibrant culture, is a bustling coastal city near the Mexico border. Its rich history, from Native American roots to Spanish colonial influence, marks it as the birthplace of California. Today, San Diego thrives as a hub for innovation in biotechnology, defense, and tourism, embodying the California dream under its perennial sunny skies. Despite this, it is also the most polluted city in the US. 

In recent years, San Diego has experienced an increase in unhealthy air days, with ozone levels exceeding federal standards. Part of the pollution issue stems from vehicular emissions due to the city’s large population and significant traffic congestion. Industrial activities and wildfires in the surrounding areas have also contributed to air pollution challenges in San Diego.

Efforts to address these issues include stricter emission standards for vehicles, promotion of public transportation, and initiatives to reduce industrial emissions. Despite these measures, continued vigilance and innovative solutions are needed to combat pollution effectively and safeguard the health of San Diego residents.

Also Read: Cold Places In the USA

8. Modesto

Modesto, the largest city in Stanislaus County, California, has around 218,000 residents. It’s located in the Central Valley, surrounded by farms that produce things like milk and almonds. Modesto is known for the Gallo Family Winery and being a Tree City USA. It’s a relaxed place with a strong connection to agriculture and nature. A major issue in this city is pollution. 

Modesto ranked among the most polluted cities in terms of short-term and year-round particle pollution, highlighting the severity of the air quality issues.

In recent decades, efforts have been made to address pollution in Modesto. The city has implemented stricter regulations on vehicle emissions, encouraged the use of public transportation, and promoted the adoption of cleaner technologies in industries. Despite these measures, Modesto continues to face air quality challenges due to its geographical location and the prevalence of pollutants from surrounding areas.

The community’s awareness and advocacy for cleaner air have grown, leading to initiatives aimed at reducing greenhouse gas emissions and improving overall environmental quality. While progress has been made, ongoing efforts are crucial to mitigate pollution and safeguard the health and well-being of Modesto’s residents.

9. Riverside

Riverside, located in Southern California, has faced significant challenges with pollution over the years. As of 2021, it stands as one of the most polluted cities in the United States, particularly concerning air quality. According to data from the American Lung Association, Riverside has regularly ranked among the top cities with high levels of particulate matter pollution, notably PM2.5, which poses severe health risks.

The city’s industrial activities, coupled with its geographical location that traps pollutants in the air basin, contribute to this environmental concern. Efforts to address pollution have included stricter emissions regulations for industries and vehicles, along with initiatives promoting cleaner energy sources. Despite these measures, Riverside continues to grapple with air pollution, impacting the health and well-being of its residents.

In recent years, community organizations and governmental agencies have intensified efforts to raise awareness about pollution’s detrimental effects and implement sustainable solutions. These endeavors aim to safeguard public health and preserve Riverside’s natural environment for future generations.

Also Read: Tallest Buildings In Washington DC

10. Phoenix

Phoenix, the capital of Arizona, grapples with significant pollution challenges that impact its residents and environment. According to the American Lung Association’s “State of the Air” report in 2021, Phoenix ranked among the top 10 most ozone-polluted cities in the United States, highlighting the severity of air quality issues. The city’s rapid urbanization and transportation demands have contributed to high levels of particulate matter and ozone pollution, posing health risks such as respiratory illnesses and cardiovascular diseases.

Data from the Maricopa County Air Quality Department reveals that in 2020, Phoenix experienced numerous days of unhealthy air quality, exceeding federal standards for pollutants like PM2.5 and ozone. The region’s reliance on automobiles, coupled with its geography and climate, creates conditions conducive to smog formation, exacerbating air pollution challenges.

Efforts to mitigate pollution include stricter emissions standards, increased public transportation options, and initiatives promoting clean energy alternatives. However, ongoing urban development and population growth necessitate continued vigilance and proactive measures to address Phoenix’s pollution issues effectively.


Tackling pollution in cities like Los Angeles, Bakersfield, and Fresno is crucial for a healthier environment. We need to work together, from individuals to governments and businesses, to implement cleaner practices and reduce pollution levels. By prioritizing sustainability and investing in green technologies, we can create cleaner and safer cities for everyone to enjoy.


Is America More Polluted Than Europe?

In Europe, pollution is mainly concentrated in specific regions. While Europe’s overall pollution levels surpass those of the United States, northern Europe, including Scandinavia and the Baltic States, has similar average pollution levels to the US.

Does Texas Have Good Air Quality?

Texas has beautiful skies and sunny days, but hot weather and pollution from vehicles and factories can make the air dirty and harmful, especially for Texans who are sensitive to it.

Is The US Heavily Polluted?

Some parts of the US have a lot of pollution from cities and industries with improved air quality. Around 85 million Americans lived where pollution levels exceeded primary NAAQS in 2022.

What Are the Most Common Pollutants?

The six primary pollutants are carbon monoxide, lead, nitrogen oxides, ground-level ozone, particulate matter (particle pollution), and sulfur oxides, each contributing to environmental and health concerns through air contamination.

Which Are the Cleanest Countries?

Countries like Switzerland, Sweden, and Finland are often cited among the cleanest due to their strict environmental regulations, effective waste management systems, and commitment to renewable energy sources.

Oleksandra Mamchii

Working as a academic lead at Best Diplomats.

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