Air pollution remains a serious public health concern across the United States, with some cities experiencing alarmingly high levels of fine particulate matter (PM2.5).
This list of the 20 most polluted cities in America ranks urban areas based on their annual PM2.5 concentrations in 2025, comparing them to safety guidelines from the American Lung Association and World Health Organization.
From California’s smog-filled valleys to wildfire-prone regions in Oregon, these cities highlight the urgent need for cleaner air policies.
If you’re concerned about your health and environment, knowing where pollution is worst can help guide informed decisions.
1. Bakersfield, California
Bakersfield is identified as the most polluted city in the U.S., with an annual PM2.5 concentration of 18.8.
This level significantly surpasses both the American Lung Association’s recommended limit of 9.0 and the World Health Organization’s guideline of 5.0, indicating a substantial health risk.
Located within California’s San Joaquin Valley, Bakersfield is impacted by major warehouse distribution, oil, and agriculture production.
The San Joaquin Valley has a long history of non-compliance with EPA air pollution standards, spanning approximately 25 years.
Environmental groups have initiated legal action against the EPA to compel faster intervention for air quality improvement in this highly affected region.
2. Visalia, California
Visalia, California, holds the second spot on the list of most polluted cities, reporting an annual PM2.5 concentration of 18.4.
This concentration far exceeds the recommended safe levels set by both the American Lung Association (9.0) and the World Health Organization (5.0), highlighting significant air quality challenges.
Like Bakersfield, Visalia is situated in the San Joaquin Valley, a region consistently struggling with air pollution.
The Valley’s industrial activities, including major warehouse distribution, oil production, and agriculture, contribute to the high particulate matter levels.
The ongoing failure to meet EPA standards in this area underscores the persistent environmental and health concerns.
3. Fresno, California
Fresno, California, ranks as the third most polluted city, with an annual PM2.5 concentration of 17.5.
This level is considerably higher than the 9.0 recommended by the American Lung Association and the 5.0 suggested by the World Health Organization, signifying a potential negative impact on health.
As another city within the San Joaquin Valley, Fresno shares the environmental burdens associated with the region’s prominent industries, such as warehouse distribution, oil, and agriculture.
The San Joaquin Valley has not complied with EPA air pollution standards for about 25 years, prompting environmental groups to sue the EPA for more decisive action to improve air quality.
4. Eugene, Oregon
Eugene, Oregon, is ranked the fourth most polluted city, with an annual PM2.5 concentration of 14.7.
This concentration exceeds the American Lung Association’s guideline of 9.0 and the World Health Organization’s guideline of 5.0, indicating unhealthy air.
Eugene is one of two Oregonian cities in the top ten, with wildfires identified as the primary cause of poor, smoky air quality in the region.
Increased hot and dry conditions have recently exacerbated these poor air conditions in the state. While Oregon faces current pollution challenges, its overall air quality has shown improvement since the 1970s.
5. Bay Area, California
The Bay Area, California, is listed as the fifth most polluted, with an annual PM2.5 concentration of 14.3.
This concentration is well above the levels considered safe by the American Lung Association (9.0) and the World Health Organization (5.0), suggesting potential health risks from airborne particulate matter.
While not explicitly stated to be in the San Joaquin Valley, California is noted as the most polluted state overall, with six cities in the top ten.
The state’s struggles with pollution, influenced by factors like car usage, industrial businesses, and wildfires, contribute to areas like the Bay Area experiencing poor air quality.
6. Los Angeles, California
Los Angeles, California, ranks as the sixth most polluted city, with an annual PM2.5 concentration of 14.0.
This level is significantly higher than the 9.0 recommended by the American Lung Association and the 5.0 by the World Health Organization, indicating a concerning level of particulate matter pollution.
Los Angeles contributes to California’s distinction as the most polluted state in America, with numerous cities appearing on this list.
Air quality issues in the state can stem from various sources, including extensive car usage on major highways, which is particularly relevant for a large metropolis like Los Angeles.
7. Sacramento, California
Sacramento, California, is the seventh most polluted city, showing an annual PM2.5 concentration of 13.8.
This concentration exceeds the recommended safe levels of 9.0 by the American Lung Association and 5.0 by the World Health Organization, indicating potentially detrimental health impacts from airborne particles.
Sacramento’s inclusion on this list further solidifies California’s position as the most polluted state, with many of its cities facing significant air quality challenges.
Urban pollution often arises from factors such as car usage along major highways and industrial activities, contributing to hazy vistas and poor air.
8. Medford, Oregon
Medford, Oregon, ranks as the eighth most polluted city, with an annual PM2.5 concentration of 13.5.
This concentration is considerably higher than the 9.0 recommended by the American Lung Association and the 5.0 by the World Health Organization, suggesting potential negative health impacts from the tiny particles.
Medford is one of two Oregonian cities in the top ten most polluted, with wildfires being a leading cause of the region’s smoky and poor air quality.
The state has experienced an increase in poor air conditions recently, largely due to rising hot and dry weather that fosters wildfires.
9. Phoenix, Arizona
Phoenix, Arizona, ranks as the ninth most polluted city in the U.S., recording an annual PM2.5 concentration of 12.4.
This level surpasses both the American Lung Association’s recommended maximum of 9.0 and the World Health Organization’s guideline of 5.0, indicating a significant presence of airborne particulate matter that can be detrimental to health.
The existence of cities like Phoenix on this list highlights that air quality challenges are present across various states.
While sources of pollution can include car usage, wildfires, and industrial businesses, the specific causes for Phoenix’s ranking are not detailed.
10. Fairbanks, Arkansas
Fairbanks, Arkansas, is listed as the tenth most polluted city, with an annual PM2.5 concentration of 12.2.
This concentration is notably higher than the safe thresholds set by the American Lung Association (9.0) and the World Health Organization (5.0), indicating unhealthy levels of particulate matter.
The inclusion of Fairbanks on this national list underscores that significant air pollution is not confined to just a few states but affects communities across different regions of the U.S.. Such high levels of PM2.5 are known to have a negative impact on human health.
11. Indianapolis, Indiana
Indianapolis, Indiana, ranks as the eleventh most polluted city, reporting an annual PM2.5 concentration of 11.9.
This concentration exceeds the American Lung Association’s recommended limit of 9.0 and the World Health Organization’s guideline of 5.0, indicating that residents are exposed to unhealthy levels of particulate matter.
The presence of Indianapolis on this list reflects that various factors, including potentially car usage along major highways and industrial businesses, contribute to air quality issues in diverse urban areas across the country. Such concentrations of PM2.5 can be detrimental to health.
12. Yakima, Washington
Yakima, Washington, is listed as the twelfth most polluted city, with an annual PM2.5 concentration of 11.8.
This concentration is above the guidelines of 9.0 from the American Lung Association and 5.0 from the World Health Organization, signaling a concerning level of fine particulate matter in the air.
While the specific reasons for Yakima’s pollution are not detailed, air quality issues in various cities can stem from sources like car usage, wildfires, or industrial activities. These tiny particles are known to have a detrimental impact on health.
13. Detroit, Michigan
Detroit, Michigan, ranks as the thirteenth most polluted city, with an annual PM2.5 concentration of 11.7.
This concentration surpasses both the American Lung Association’s recommended limit of 9.0 and the World Health Organization’s guideline of 5.0, indicating unhealthy levels of particulate matter.
As a major industrial and urban center, Detroit’s air quality may be influenced by factors such as industrial businesses and car usage along major highways, which are common contributors to pollution in parts of the country. High PM2.5 levels can negatively impact health.
14. Chico, California
Chico, California, is listed as the fourteenth most polluted city, with an annual PM2.5 concentration of 11.6.
This concentration exceeds the 9.0 recommended by the American Lung Association and the 5.0 by the World Health Organization, indicating a concerning level of fine particulate matter.
Chico’s inclusion contributes to California’s status as the most polluted state, with several of its cities ranking highly due to widespread air quality challenges.
Pollution in California can be attributed to factors like industrial businesses, vehicle emissions, and, in some regions, wildfires.
15. Spokane, Washington
Spokane, Washington, ties with Chico, California, as the fifteenth most polluted city, also reporting an annual PM2.5 concentration of 11.6.
This level is higher than both the American Lung Association’s recommended 9.0 and the World Health Organization’s 5.0, indicating unhealthy air quality.
While the specific pollution sources for Spokane are not detailed in the sources, air pollution across the U.S. can originate from various factors, including car usage, wildfires, and industrial businesses. The presence of such concentrations of PM2.5 poses a potential negative impact on health.
16. El Centro, California
El Centro, California, ranks as the sixteenth most polluted city, with an annual PM2.5 concentration of 11.1.
This concentration is above the 9.0 recommended by the American Lung Association and the 5.0 by the World Health Organization, signifying unhealthy levels of particulate matter.
As another Californian city on the list, El Centro contributes to California’s designation as the most polluted state, with a high number of its urban areas facing significant air quality issues.
The cumulative impact of pollution sources throughout the state contributes to these elevated PM2.5 levels.
17. Reno, Nevada
Reno, Nevada, is listed as the seventeenth most polluted city, reporting an annual PM2.5 concentration of 11.0.
This concentration exceeds the American Lung Association’s recommended maximum of 9.0 and the World Health Organization’s guideline of 5.0, indicating that residents are exposed to unhealthy levels of particulate matter.
While the specific causes for Reno’s pollution are not detailed, air quality issues in cities can stem from factors such as car usage along major highways, wildfires in surrounding regions, or industrial businesses. These tiny particles are known to be detrimental to human health.
18. Pittsburgh, Pennsylvania
Pittsburgh, Pennsylvania, ranks as the eighteenth most polluted city, with an annual PM2.5 concentration of 10.9.
This concentration is higher than both the American Lung Association’s recommended 9.0 and the World Health Organization’s 5.0, signaling unhealthy air quality due to fine particulate matter.
Pittsburgh’s history as an industrial center might contribute to its current air quality status, as industrial businesses are noted as a source of pollution in some parts of the country. High levels of PM2.5 are directly linked to negative impacts on human health.
19. Kansas City, Kansas
Kansas City, Kansas, ties with Las Vegas, Nevada, as the nineteenth most polluted city, with an annual PM2.5 concentration of 10.8.
This level is higher than both the American Lung Association’s recommended 9.0 and the World Health Organization’s 5.0, indicating unhealthy air quality from particulate matter.
The presence of a Midwestern city like Kansas City on this list highlights that air pollution challenges are widespread across the United States.
Such concentrations of PM2.5, which are tiny particles in the air, are considered detrimental to health.
20. Las Vegas, Nevada
Las Vegas, Nevada, ties with Kansas City, Kansas, as the twentieth most polluted city, also reporting an annual PM2.5 concentration of 10.8.
This concentration surpasses both the American Lung Association’s recommended 9.0 and the World Health Organization’s 5.0, indicating that residents are exposed to unhealthy levels of particulate matter.
Air quality issues in cities can stem from various sources, including car usage along major highways and local industrial activities.
These high concentrations of PM2.5 are deemed likely to have a negative impact on the health of residents.
Alicia Richards