Daily Air Quality Index summaries from EPA monitors in St. Charles, Louisiana, 1980–2014.
93%
Good days in 2014
31
Median daily AQI, 2014
0
Days above 100 in 2014
365
Days with an AQI in 2014 (of 365)
In 2014, EPA reported a daily Air Quality Index (AQI) for St. Charles, Louisiana on 365 days. 341 of those days (93%) were in the Good range, and the median daily AQI was 31. That median is lower than the typical monitored county in Louisiana (median 44 across 22 counties), and lower than the typical monitored U.S. county (42). The main pollutant was ozone on 365 days. Across the years with fuller monitoring, the share of Good days rose: an average of 79% in 1980–1983 versus 93% in 2012–2014.
The most recent year with data for this county is 2014; EPA's files for 2015–2025 contain no row for it, which usually means its monitors stopped reporting.
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, 2014
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
365
100%
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
2014
365
341
24
0
0
0
0
31
47
97
Ozone
2013
365
348
17
0
0
0
0
31
46
87
Ozone
2012
347
308
38
1
0
0
0
36
54
119
Ozone
2011
358
314
40
4
0
0
0
34
61
115
Ozone
2010
361
306
45
10
0
0
0
35
61
129
Ozone
2009
363
321
39
3
0
0
0
34
54
122
Ozone
2008
340
306
32
2
0
0
0
32
51
105
Ozone
2007
363
314
39
7
3
0
0
35
64
172
Ozone
2006
347
274
59
13
1
0
0
37
77
159
Ozone
2005
349
262
77
10
0
0
0
38
75
136
Ozone
2004
360
310
40
9
1
0
0
31
64
161
Ozone
2003
364
302
47
13
2
0
0
32
67
177
Ozone
2002
363
325
33
5
0
0
0
32
51
147
Ozone
2001
363
309
41
12
1
0
0
33
61
156
Ozone
2000
355
272
52
23
7
1
0
36
97
202
Ozone
1999
354
274
53
24
3
0
0
38
97
161
Ozone
1998
360
291
51
14
4
0
0
34
74
179
Ozone
1997
359
283
59
15
2
0
0
34
80
185
Ozone
1996
358
304
44
9
1
0
0
33
64
190
Ozone
1995
358
276
51
26
5
0
0
37
93
182
Ozone
1994
358
302
42
12
1
1
0
33
71
203
Ozone
1993
361
287
62
11
1
0
0
36
77
164
Ozone
1992
355
307
34
13
1
0
0
31
61
195
Ozone
1991
287
245
35
7
0
0
0
30
61
122
Ozone
1986
335
262
54
17
2
0
0
25
84
164
Ozone
1985
195
191
4
0
0
0
0
19
36
74
Ozone
1984
122
122
0
0
0
0
0
22
38
50
Ozone
1983
172
134
25
12
1
0
0
33
87
154
Ozone
1981
179
146
28
5
0
0
0
32
65
115
NO2
1980
209
165
32
12
0
0
0
32
69
131
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.
