Allegheny County, Pennsylvania air quality history
Daily Air Quality Index summaries from EPA monitors in Allegheny, Pennsylvania, 1980–2025.
46%
Good days in 2025
52
Median daily AQI, 2025
4
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Allegheny, Pennsylvania on 365 days. 168 of those days (46%) were in the Good range, and the median daily AQI was 52. That median is higher than the typical monitored county in Pennsylvania (median 40 across 38 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 184 days. Across the years with fuller monitoring, the share of Good days rose: an average of 38% in 1980–1982 versus 42% in 2023–2025.
How the days broke down each year
Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.
Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous
Typical and high-end AQI over time
The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.
Median daily AQI
90th-percentile daily AQI
Main pollutant by day, 2025
On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.
Pollutant
Days as main pollutant
Share of monitored days
Fine particles (PM2.5)
184
50%
Ozone
181
50%
Year-by-year data
Annual AQI summary by year
Year
Days with AQI
Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous
Median AQI
90th pct.
Max AQI
Main pollutant
2025
365
168
193
4
0
0
0
52
78
129
PM2.5
2024
366
175
182
9
0
0
0
52
77
129
PM2.5
2023
365
121
227
15
1
1
0
56
84
237
PM2.5
2022
365
129
225
10
1
0
0
56
84
151
PM2.5
2021
365
118
240
6
1
0
0
57
84
154
PM2.5
2020
366
138
218
10
0
0
0
54
77
128
PM2.5
2019
365
67
287
7
4
0
0
59
80
165
PM2.5
2018
365
92
260
12
1
0
0
58
84
154
PM2.5
2017
365
111
235
18
1
0
0
58
87
168
PM2.5
2016
366
103
243
19
1
0
0
56
84
152
PM2.5
2015
365
105
241
18
1
0
0
58
90
157
PM2.5
2014
365
99
256
9
1
0
0
58
80
157
PM2.5
2013
365
98
254
12
1
0
0
57
82
190
PM2.5
2012
366
76
246
40
4
0
0
61
108
172
PM2.5
2011
365
64
259
38
4
0
0
63
103
186
PM2.5
2010
365
50
254
46
15
0
0
69
117
200
PM2.5
2009
365
20
312
28
5
0
0
65
99
181
PM2.5
2008
366
9
299
47
11
0
0
68
116
164
PM2.5
2007
365
25
273
45
22
0
0
68
133
185
PM2.5
2006
365
33
267
50
15
0
0
67
128
183
PM2.5
2005
365
58
230
54
22
1
0
69
131
202
PM2.5
2004
366
58
247
44
17
0
0
66
117
178
PM2.5
2003
365
53
256
38
16
2
0
66
119
218
PM2.5
2002
365
58
232
42
30
3
0
67
139
209
PM2.5
2001
365
50
232
59
24
0
0
72
136
197
PM2.5
2000
366
51
258
45
12
0
0
69
119
195
PM2.5
1999
365
92
199
50
22
2
0
64
129
219
PM2.5
1998
365
182
122
35
23
3
0
51
129
212
NO2
1997
365
201
122
27
11
4
0
47
105
213
NO2
1996
366
181
141
34
9
1
0
51
108
207
NO2
1995
365
173
143
29
11
9
0
51
115
221
NO2
1994
365
170
149
31
11
4
0
52
112
205
NO2
1993
365
200
124
33
5
3
0
48
102
207
NO2
1992
366
219
129
13
5
0
0
46
77
182
NO2
1991
365
180
139
31
11
4
0
51
108
204
NO2
1990
365
186
150
22
7
0
0
50
90
190
NO2
1989
365
201
122
26
13
3
0
48
105
213
NO2
1988
366
180
118
26
19
22
1
51
161
531
NO2
1987
365
156
150
36
18
5
0
54
126
223
NO2
1986
365
149
166
43
6
1
0
55
114
206
NO2
1985
365
186
143
27
9
0
0
50
98
195
NO2
1984
366
145
174
41
6
0
0
54
108
182
NO2
1983
365
116
170
40
31
8
0
62
154
230
CO
1982
364
124
173
45
19
3
0
58
128
219
CO
1981
365
136
164
45
15
5
0
61
119
224
NO2
1980
366
155
136
46
18
11
0
55
135
247
CO
What this data can and can’t tell you
It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.
It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.
Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.
Counties in Pennsylvania with a similar median AQI in 2025
