Philadelphia County, Pennsylvania air quality history
Daily Air Quality Index summaries from EPA monitors in Philadelphia, Pennsylvania, 1980–2025.
50%
Good days in 2025
50
Median daily AQI, 2025
8
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 Philadelphia, Pennsylvania on 365 days. 184 of those days (50%) were in the Good range, and the median daily AQI was 50. 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 226 days. Across the years with fuller monitoring, the share of Good days rose: an average of 16% in 1980–1982 versus 40% 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)
226
62%
Ozone
132
36%
Nitrogen dioxide (NO₂)
7
2%
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
184
173
8
0
0
0
50
73
147
PM2.5
2024
366
173
183
10
0
0
0
52
77
136
PM2.5
2023
365
83
268
9
3
1
1
58
84
331
PM2.5
2022
365
155
206
4
0
0
0
52
71
113
PM2.5
2021
365
137
217
9
2
0
0
54
77
153
PM2.5
2020
366
212
149
5
0
0
0
47
63
119
PM2.5
2019
365
193
166
6
0
0
0
49
72
140
PM2.5
2018
365
152
203
9
1
0
0
54
74
156
PM2.5
2017
365
96
257
10
2
0
0
56
74
166
PM2.5
2016
366
111
246
9
0
0
0
55
77
147
PM2.5
2015
365
103
246
14
2
0
0
56
86
161
PM2.5
2014
365
50
306
8
1
0
0
59
78
151
PM2.5
2013
365
97
258
10
0
0
0
58
79
122
PM2.5
2012
366
72
266
25
3
0
0
60
91
154
PM2.5
2011
365
103
242
13
7
0
0
58
87
172
PM2.5
2010
365
125
212
24
4
0
0
57
96
172
PM2.5
2009
365
96
261
8
0
0
0
56
79
147
PM2.5
2008
366
63
275
23
4
1
0
60
97
285
PM2.5
2007
365
91
234
31
8
1
0
61
103
205
PM2.5
2006
365
93
228
38
6
0
0
61
103
177
PM2.5
2005
365
97
229
31
8
0
0
60
101
197
PM2.5
2004
366
89
247
22
8
0
0
60
96
172
PM2.5
2003
365
93
233
34
5
0
0
60
101
197
PM2.5
2002
365
70
236
36
17
6
0
61
126
213
PM2.5
2001
365
58
256
35
13
2
1
67
108
328
PM2.5
2000
366
90
247
23
5
1
0
61
93
212
PM2.5
1999
365
109
221
22
11
2
0
59
100
214
PM2.5
1998
365
152
166
35
12
0
0
55
115
200
NO2
1997
365
167
153
24
19
2
0
52
119
215
NO2
1996
366
166
145
38
12
4
1
57
122
333
NO2
1995
365
156
144
45
12
8
0
57
122
243
NO2
1994
365
136
159
47
20
2
1
57
119
419
NO2
1993
365
169
124
40
26
4
2
57
143
481
NO2
1992
366
187
145
23
10
1
0
48
100
205
NO2
1991
365
167
130
40
20
8
0
57
136
224
NO2
1990
365
182
139
28
12
4
0
51
105
219
NO2
1989
365
143
178
34
9
1
0
57
103
203
NO2
1988
366
133
172
22
20
19
0
57
161
259
NO2
1987
363
89
203
39
19
13
0
68
143
232
NO2
1986
365
113
193
35
19
5
0
61
133
217
NO2
1985
365
125
165
41
25
9
0
57
143
235
NO2
1984
366
83
216
41
21
5
0
68
133
234
NO2
1983
365
80
189
52
25
19
0
68
164
234
NO2
1982
365
57
230
52
18
8
0
68
133
226
NO2
1981
365
53
235
55
17
5
0
68
126
226
NO2
1980
366
69
203
42
34
18
0
68
169
235
NO2
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
