polluted city

5 Most Polluted Cities in the U.S.

Steve Russell - February 22, 2023

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Inclement weather and frequent natural disasters have made it clear that we can no longer bat an eye to climate change. As a result, cities across the United States — some of the highest emissions producers in the nation — have spearheaded climate resilience plans to mitigate the impacts of global warming. 

Despite these efforts, some cities have lagged in reducing emissions. According to the American Lung Association, more than 137 million Americans live where there’s unhealthy particulate matter (PM2.5) and ozone, equivalent to 40% of the U.S. population. 

Celebrity spotting on Hollywood Boulevard and catching a couple of Broadway shows are top draws for some of America’s beloved tourist destinations. However, they may not be the cleanest places to visit. Here are five of the most polluted cities in the U.S. 

1. Los Angeles, California

Despite California’s comprehensive climate policies, the state’s most populous city has struggled to reduce emissions. For instance, following 2020’s major wildfires and excessive heatwaves, Los Angeles recorded the highest ozone pollution at 185 parts per billion in 26 years.

The U.S. Census Bureau maintains that 9,829,544 people reside in LA, which means more cars on the road. The city is also home to a robust financial, real estate, and entertainment hub with several notable corporations headquartered downtown. 

Between vehicle emissions and outdated commercial spaces, it’s no wonder LA is one of the most polluted cities in the U.S. In fact, 22% of its carbon emissions derive from commercial buildings and facilities.  

Fortunately, LA has begun constructing new green buildings that run on renewables with zero emissions and retrofitting existing buildings for energy efficiency.

2. New York City

Air pollutants have dire implications for lung cancer, respiratory infections, cardiovascular disease, and increased mortalities. In fact, high PM2.5 concentrations resulted in 1.8 million deaths in 2019. 


Due to New York City’s growing population, industrial areas, increasing traffic, and building density, PM2.5 has been a significant concern for its health and sustainability departments. 

While the city reduced its PM2.5 concentrations by 43% from 2009 to 2020 — assisted partly by a new requirement for buildings to switch to cleaner heating oils — NYC still has a long way to go to reach safe air quality.

3. Pittsburgh, Pennsylvania

Unlike its ultra-populated counterparts, 60% of Pittsburgh’s air pollution comes from steel plants and other industrial sources. In 2017, reports indicated 232 deaths directly resulted from Pittsburgh’s poor air quality.

Despite some slight improvements in recent years, the American Lung Association has given the city “F” ratings for ozone and PM2.5 yearly, followed by 57 days of unsafe levels of atmospheric pollutants in 2020. 

Nevertheless, Pittsburgh’s Climate Action Plan has set out to achieve zero-waste, 100% renewables at City facilities and a 50% decrease in vehicle emissions. 

4. Bakersfield, California

Situated nearly two hours north of LA in Kern County, Bakersfield has some of the worst air quality in the U.S. 

Mining and petroleum industries, transportation, wildfires, and agriculture are the leading PM2.5 sources throughout Kern County, with Bakersfield experiencing a 20.9% dip in air quality in 2020.

The San Joaquin Air Pollution Control District controls strategic planning to address air pollution in Bakersfield and the surrounding towns. According to its 2018 PM2.5 Plan, local businesses have invested $40 billion in 20 years for pollution control. 

Approximately $2 billion in grants have also been awarded to residents, citywide agencies, schools, and businesses for cleaner equipment and to adopt stronger public health strategies.

5. Phoenix, Arizona

Arizona’s capital is nicknamed “the hottest city in America,” with good reason. Phoenix sees an annual average of 111 days surpassing 100° F, with a documented 145 days in 2020.

As a result of excessive heatwaves, the city was above safe levels of PM2.5 and ozone for 149 days in 2020. The combination of ozone and extreme temperatures can make breathing difficult for people and lead to sickness.

Phoenix began a beautification program to cool the city down by planting trees to increase shading and sequester carbon dioxide. In collaboration with American Forests, the city hopes to reach “tree equity” by 2030 to ensure even distribution to enhance residents’ quality of life.

Reducing Air Pollution: An Ongoing Problem for U.S. Cities

Even the most polluted cities in the U.S. have plans to reduce emissions and improve their citizens’ air quality. Unfortunately, emissions from booming population growth and industrialization are challenging to overcome. Taking the necessary precautions when visiting or moving to a polluted city, such as staying indoors and closing the windows during record ozone, can protect your health.


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About the author

Steve Russell

Steve is the Managing Editor of Environment.co and regularly contributes articles related to wildlife, biodiversity, and recycling. His passions include wildlife photography and bird watching.