Daily Air Quality Index summaries from EPA monitors in Ascension, Louisiana, 1983–2025.
96%
Good days in 2025
33
Median daily AQI, 2025
1
Days above 100 in 2025
364
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Ascension, Louisiana on 364 days. 348 of those days (96%) were in the Good range, and the median daily AQI was 33. That median is lower than the typical monitored county in Louisiana (median 42 across 21 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 356 days. Across the years with fuller monitoring, the share of Good days rose: an average of 84% in 1983–1994 versus 91% in 2023–2025.
Years with fewer than 120 monitored days (1984) are shown in the table but left out of comparisons and trend statements.
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
Ozone
356
98%
Nitrogen dioxide (NO₂)
8
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
364
348
15
1
0
0
0
33
47
108
Ozone
2024
360
331
26
2
1
0
0
33
49
151
Ozone
2023
362
310
49
2
1
0
0
34
58
154
Ozone
2022
364
336
28
0
0
0
0
32
49
90
Ozone
2021
356
338
16
1
1
0
0
31
45
159
Ozone
2020
364
350
14
0
0
0
0
31
46
100
Ozone
2019
361
319
41
1
0
0
0
33
54
101
Ozone
2018
364
325
36
3
0
0
0
31
51
122
Ozone
2017
363
334
27
2
0
0
0
34
48
119
Ozone
2016
365
337
24
4
0
0
0
36
49
112
Ozone
2015
363
326
32
5
0
0
0
34
51
140
Ozone
2014
364
328
34
1
1
0
0
34
50
156
Ozone
2013
365
342
23
0
0
0
0
32
47
100
Ozone
2012
359
309
46
4
0
0
0
37
61
122
Ozone
2011
362
302
49
9
2
0
0
35
67
156
Ozone
2010
365
305
48
12
0
0
0
36
67
143
Ozone
2009
365
331
30
4
0
0
0
35
50
133
Ozone
2008
357
294
55
8
0
0
0
36
64
147
Ozone
2007
363
286
53
20
4
0
0
39
84
195
Ozone
2006
360
267
67
20
6
0
0
40
87
169
Ozone
2005
357
265
75
15
2
0
0
40
80
169
Ozone
2004
349
291
47
10
1
0
0
34
71
151
Ozone
2003
330
289
27
13
1
0
0
32
61
156
Ozone
2002
350
313
31
6
0
0
0
32
51
150
Ozone
2001
361
290
59
12
0
0
0
36
67
133
Ozone
2000
365
269
61
27
7
1
0
36
100
204
Ozone
1999
361
305
36
16
4
0
0
26
77
187
Ozone
1998
357
318
26
5
7
1
0
27
54
222
Ozone
1997
355
272
60
17
6
0
0
36
93
177
Ozone
1996
363
293
53
14
3
0
0
34
74
169
Ozone
1995
337
259
45
24
9
0
0
35
100
174
Ozone
1994
351
313
26
8
4
0
0
31
58
195
Ozone
1993
354
278
54
16
5
1
0
35
80
208
Ozone
1984
106
95
7
3
1
0
0
24
51
154
Ozone
1983
124
104
15
4
1
0
0
29
64
159
Ozone
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 Louisiana with a similar median AQI in 2025
