When planning a trip to a new place, it is essential to be completely aware of all aspects of the destination. Knowing the local reality in depth, including its positive and negative points, ensures that the traveler is well prepared and informed.
A survey carried out in 2025 by the Lawnstarter platform ranked the dirtiest cities in the United States. To compose this list, several elements that contribute to environmental and social degradation were considered, such as high levels of pollution, poor sanitation infrastructure and the population’s negative perception of living conditions. The research analyzed 500 large urban centers, discarding 197 due to lack of complete information, and evaluated the remaining 303.
Once the studies and analyzes were completed, the team responsible for the ranking identified San Bernardino, California, as the location with the greatest cleaning and pollution challenges throughout the country.
The Californian city stood out negatively for having the highest percentage of residents dissatisfied with pollution, reaching 75% of those interviewed. Furthermore, San Bernardino shares with nine other cities in California the distinction of having the worst air quality average.
These are the five dirtiest cities in the United States according to LawnStarter’s 2025 ranking, with emphasis on California’s dominance.
The gardening services platform analyzed data on pollution, housing conditions, waste infrastructure and resident satisfaction in the country’s largest cities. San Bernardino, California, repeated first place for the second year in a row.
San Bernardino has worse air quality and greater dissatisfaction
The city recorded the highest percentage of residents dissatisfied with pollution, reaching 75%. This rate is made worse by the presence of more than 850 large warehouses in the county, which raise nitrogen dioxide levels by around 20% nearby.
Los Angeles suffers from traffic and overcrowded housing
In second place comes Los Angeles, also in California. Almost 40% of residents live near high-traffic roads, and the city has one of the highest rates of overcrowded homes, over 11%.
Detroit and Reading complete the top 4
Detroit, Michigan, came in third, with 54% of residents dissatisfied with pollution and a smoking rate of nearly 24% among adults. Reading, in Pennsylvania, occupies fourth position, penalized by the strong industrial presence and the worst score in environmental risk indicators due to toxic emissions.
Ontario closes the top 5 with similar problems
Ontario, also in California, completes the list of the five worst. Like San Bernardino, it ties for the worst average air quality index, with more than 60% of residents reporting dissatisfaction with pollution levels.
- 1. San Bernardino (CA)– worse pollution and dissatisfaction
- 2. Los Angeles (CA)– traffic and overcrowded housing
- 3. Detroit (MI)– pollution and high smoking
- 4. Reading (PA)– toxic industrial emissions
- 5. Ontario (CA)– poor air quality
Cleaner cities contrast with the negative ranking
At the other extreme, South Bend (Indiana) was considered the least polluted, followed by Wilmington (North Carolina) and Des Moines (Iowa). Others well positioned include Davenport (Iowa), Athens (Georgia), Winston-Salem (North Carolina), Fargo (North Dakota), Frederick (Maryland), Pleasanton (California) and Lynchburg (Virginia). They stand out for their good air and water quality, low excessive fuel consumption and high resident satisfaction.