In addition to the 25 worst cities for each pollutant listed above, the 25 most polluted counties for ozone and particle pollution are ranked in the tables below.
Thirty counties, listed alphabetically by state below, received failing grades for all three measures of pollution:
Arizona | Pinal |
California | Fresno, Imperial, Kern, Kings, Los Angeles, Madera, Merced, Orange, Riverside, Sacramento, San Bernardino, Stanislaus, Sutter, Tulare |
Illinois | Cook |
Indiana | Lake, Marion |
Michigan | Wayne |
Ohio | Butler, Cuyahoga |
Pennsylvania | Philadelphia |
Utah | Salt Lake |
Wisconsin | Milwaukee, Waukeshaw |
Page last updated: March 25, 2025