Air Quality in Selected U.S. Cities, 1990–2000

Updated April 8, 2022 | Infoplease Staff

(number of days with AQI values greater than 100)1

Metropolitan statistical area 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
Atlanta, Ga. 42 23 20 36 15 35 25 31 50 61 26
Baltimore, Md. 29 50 23 48 41 36 28 30 51 40 16
Boston, Mass.-N.H. 7 13 9 6 10 8 2 8 7 5 1
Chicago, Ill. 4 25 6 3 8 23 7 9 10 14 0
Cleveland/Lorain/Elyria, Ohio 10 23 11 17 24 27 18 13 22 21 5
Dallas, Tex. 24 2 12 14 27 36 12 20 28 23 20
Denver, Colo. 9 6 11 6 2 3 0 0 7 3 2
Detroit, Mich. 11 27 7 5 11 14 13 11 17 15 3
El Paso, Tex. 19 7 10 7 11 8 7 4 6 6 3
Houston, Tex. 51 36 32 27 38 65 26 47 38 50 42
Kansas City, Mo.-Kans. 2 11 1 4 10 23 10 17 15 5 10
Los Angeles/Long Beach, Calif. 173 168 175 134 139 113 94 60 56 27 48
Miami, Fla. 1 1 3 6 1 2 1 3 8 5 0
Minneapolis/St. Paul, Minn.-Wis. 4 2 1 0 2 5 0 0 1 0 0
New York, N.Y. 36 49 10 19 21 19 15 23 17 24 12
Philadelphia, Pa.-N.J. 39 49 27 62 37 38 38 38 37 32 18
Phoenix/Mesa, Ariz. 12 11 11 15 10 22 15 12 14 10 10
Pittsburgh, Pa. 19 21 9 13 19 25 11 21 39 23 4
St. Louis, Mo.-Ill. 23 24 14 9 32 36 20 15 23 29 14
San Diego, Calif. 96 67 66 59 46 48 31 14 33 16 14
San Francisco, Calif. 0 0 0 0 0 2 0 0 0 0 0
Seattle/Bellevue/Everett, Wash. 9 4 3 0 3 0 6 1 3 1 1
Washington, DC-Md.-Va.-W.Va. 25 48 14 52 22 32 18 30 47 39 11
1. AQI—Air Quality Index. AQI measures how polluted air is by measuring five major pollutants: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen oxide. Based on the amount of each pollutant in the air, the AQI assigns a numerical value to air quality as follows: 0 to 50 (good); 51 to 100 (moderate); 101 to 150 (unhealthy for sensitive groups); 151 to 200 (unhealthy); 201 to 300 (very unhealthy); 301 to 500 (hazardous).
Source: U.S. Environmental Protection Agency, Office of Air Quality Planning & Standards.

 

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