The Dirtiest Cities in the U.S.

What We’re Showing

The top 10 dirtiest cities in the U.S. as ranked by Lawnstarter’s proprietary score. Data is updated as of June 2024.

Lawnstarter scored cities based on four main categories, including pollution, infrastructure, living conditions and resident dissatisfaction.

Some metrics included in the score calculations include: air quality index, greenhouse gas emissions per capita, water quality violations, quantity of waste in landfills per capita, population density, and share of overcrowded rooms.

San Bernardino Ranked Dirtiest City

San Bernardino County, which also includes the fifth-ranked city Ontario, consistently ranks first in the country for the worst ozone and particulate pollution.

The county is a major shipping hub, and home to multiple freight and warehouse corridors. Heavy diesel truck traffic passes through its roadways everyday and contributes to poor air quality.