Chester County, South Carolina air quality history
Daily Air Quality Index summaries from EPA monitors in Chester, South Carolina, 1980–2007.
57%
Good days in 2007
48
Median daily AQI, 2007
12
Days above 100 in 2007
249
Days with an AQI in 2007 (of 365)
In 2007, EPA reported a daily Air Quality Index (AQI) for Chester, South Carolina on 249 days. 141 of those days (57%) were in the Good range, and the median daily AQI was 48. That median is about the same as the typical monitored county in South Carolina (median 47 across 21 counties), and about the same as the typical monitored U.S. county (46). The main pollutant was ozone on 249 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 64% in 1980–1982 versus 62% in 2005–2007.
EPA did not report an AQI for every day of 2007 here (249 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.
The most recent year with data for this county is 2007; EPA's files for 2008–2025 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, 2007
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
249
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
2007
249
141
96
11
1
0
0
48
84
151
Ozone
2006
229
151
71
6
1
0
0
44
84
151
Ozone
2005
227
143
57
24
3
0
0
45
105
164
Ozone
2004
228
166
60
2
0
0
0
43
80
136
Ozone
2003
232
165
54
13
0
0
0
42
84
147
Ozone
2002
231
125
61
33
12
0
0
48
136
192
Ozone
2001
235
126
76
32
1
0
0
49
115
164
Ozone
2000
210
112
73
25
0
0
0
50
105
150
Ozone
1999
233
104
77
37
14
1
0
58
126
214
Ozone
1998
233
101
85
34
12
1
0
58
136
203
Ozone
1997
226
109
91
21
5
0
0
54
105
182
Ozone
1996
228
136
71
19
2
0
0
46
97
161
Ozone
1995
242
129
84
23
5
1
0
50
105
204
Ozone
1994
312
249
55
7
1
0
0
39
64
154
Ozone
1993
346
240
86
17
2
1
0
41
87
203
Ozone
1992
332
243
74
13
2
0
0
39
84
154
Ozone
1991
319
247
68
4
0
0
0
38
67
133
Ozone
1990
324
215
82
21
6
0
0
43
97
190
Ozone
1989
324
247
61
15
1
0
0
37
77
182
Ozone
1988
317
219
60
29
8
1
0
40
108
227
Ozone
1987
330
209
79
32
8
2
0
43
112
217
Ozone
1986
335
223
79
25
7
1
0
41
100
206
Ozone
1985
323
232
70
21
0
0
0
41
93
140
Ozone
1984
349
246
72
28
3
0
0
41
97
174
Ozone
1983
337
204
66
45
19
3
0
44
129
210
Ozone
1982
350
245
63
34
7
1
0
40
108
201
Ozone
1981
347
234
77
29
6
1
0
41
101
206
Ozone
1980
257
139
55
50
11
2
0
47
129
205
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 South Carolina with a similar median AQI in 2007
