Counties in Mississippi by share of days with good air quality (US EPA AQI)

Coahoma County had the highest share of days with good air quality (US EPA AQI) of 20 counties in 1999, at 100%. Forrest County had the lowest, at 10.2%. The median was 40.4%. Source: EPA.

Highest100Coahoma County

Lowest10.2Forrest County

Median40.420 counties

Map of counties, 1999

Under 18
18 to 38
38 to 49
49 to 58
58 and over
No data

%, 1999. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 1999

%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

Rank	Counties	1999 (%)	Change on 1998
1	Coahoma County	100	0 pts
1	Washington County	100	+3.8 pts
3	Panola County	94	+39.6 pts
4	Yalobusha County	60.9	-6.2 pts
5	Hinds County	57.3	-18.6 pts
6	Madison County	55.1	+0.3 pts
7	Hancock County	54.6	-11.1 pts
8	DeSoto County	54.5	-0.6 pts
9	Warren County	45.4	-24.1 pts
10	Jackson County	41.7	-17.6 pts
11	Adams County	39.1	-15.3 pts
12	Harrison County	37.8	n/a
13	Lauderdale County	37.2	-27.4 pts
14	Lee County	33.7	-18.8 pts
15	Bolivar County	30.9	n/a
16	Scott County	19	n/a
17	Jones County	15.9	-84.1 pts
18	Rankin County	13.1	n/a
19	Lowndes County	12.4	n/a
20	Forrest County	10.2	n/a

Other periods

About this ranking

Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.

United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 9 counties with data in other periods have no value for 1999 and are left out rather than filled from another source. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts (Counties in Mississippi by share of days with good air quality (US EPA AQI), 1999) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Mississippi by share of days with good air quality (US EPA AQI), 1999. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/mississippi-counties?period=1999. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Counties in Mississippi by share of days with good air quality (US EPA AQI), 1999. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/mississippi-counties?period=1999.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Mississippi by share of days with good air quality (US EPA AQI), 1999 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/mississippi-counties?period=1999 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_mississippi_by_1999,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Mississippi by share of days with good air quality (US EPA AQI), 1999}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/mississippi-counties?period=1999. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}

RIS

TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Mississippi by share of days with good air quality (US EPA AQI), 1999
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/good-air-quality-days-share/mississippi-counties?period=1999
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/mississippi-counties?period=1999.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -

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Questions

Which county has the highest share of days with good air quality (US EPA AQI)?

Coahoma County, with 100% in 1999, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

Forrest County, with 10.2% in 1999.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 9 counties have no value for 1999 and are not ranked.