Daily Air Quality Index summaries from EPA monitors in Cass, Missouri, 1983–2025.
78%
Good days in 2025
41
Median daily AQI, 2025
1
Days above 100 in 2025
362
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Cass, Missouri on 362 days. 281 of those days (78%) were in the Good range, and the median daily AQI was 41. That median is about the same as the typical monitored county in Missouri (median 41 across 19 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 197 days. Across the years with fuller monitoring, the share of Good days fell: an average of 82% in 1983–1985 versus 76% 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)
197
54%
Ozone
165
46%
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
362
281
80
1
0
0
0
41
55
123
PM2.5
2024
366
280
85
1
0
0
0
42
58
107
Ozone
2023
332
242
85
5
0
0
0
44
64
143
Ozone
2022
360
287
73
0
0
0
0
40
56
88
Ozone
2021
365
267
97
1
0
0
0
42
59
108
PM2.5
2020
362
300
60
2
0
0
0
39
54
105
PM2.5
2019
365
289
76
0
0
0
0
42
57
93
PM2.5
2018
364
266
98
0
0
0
0
41
61
97
Ozone
2017
359
253
104
2
0
0
0
43
58
115
PM2.5
2016
364
294
70
0
0
0
0
39
54
80
PM2.5
2015
336
206
129
1
0
0
0
45
64
103
PM2.5
2014
341
147
193
1
0
0
0
53
70
102
PM2.5
2013
361
201
160
0
0
0
0
48
63
97
PM2.5
2012
364
100
244
19
1
0
0
57
82
161
PM2.5
2011
363
173
184
6
0
0
0
52
71
122
PM2.5
2010
365
161
204
0
0
0
0
53
71
100
PM2.5
2009
285
204
79
1
1
0
0
42
62
154
Ozone
2008
262
174
87
1
0
0
0
45
61
129
Ozone
2007
262
157
101
4
0
0
0
46
77
136
Ozone
2006
263
140
113
10
0
0
0
49
84
150
Ozone
2005
262
133
118
9
2
0
0
50
90
164
Ozone
2004
261
182
78
1
0
0
0
43
61
133
Ozone
2003
321
177
123
20
1
0
0
47
93
179
Ozone
2002
263
130
110
22
1
0
0
51
100
156
Ozone
2001
262
141
115
6
0
0
0
49
77
126
Ozone
2000
296
158
115
20
3
0
0
48
97
185
Ozone
1988
235
132
71
22
10
0
0
44
108
174
Ozone
1987
344
264
68
12
0
0
0
35
80
129
Ozone
1986
342
292
47
2
1
0
0
32
58
156
Ozone
1985
350
302
39
7
2
0
0
33
64
172
Ozone
1984
343
268
62
12
0
1
0
33
80
203
Ozone
1983
279
224
50
4
1
0
0
35
71
151
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 Missouri with a similar median AQI in 2025
