(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.
