Data / Rankings / Highest daily Air Quality Index (US EPA) / Counties in Virginia

Counties in Virginia by highest daily Air Quality Index (US EPA)

Fairfax County had the highest highest daily Air Quality Index (US EPA) of 41 counties in 1991, at 243. Martinsville city had the lowest, at 47. The median was 146. Source: the U.S. Environmental Protection Agency.

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Highest243Fairfax County
Lowest47Martinsville city
Median14641 counties

Map of counties, 1991

Amherst County: 151 indexArlington County: 224 indexAugusta County: 147 indexBuchanan County: 146 indexCampbell County: 51 indexCarroll County: 63 indexCharles City County: 177 indexChesterfield County: 156 indexFairfax County: 243 indexFauquier County: 177 indexGiles County: 166 indexHanover County: 166 indexHenrico County: 192 indexKing William County: 57 indexLoudoun County: 49 indexMadison County: 164 indexPrince Edward County: 154 indexPrince William County: 179 indexRoanoke County: 154 indexSmyth County: 69 indexWarren County: 177 indexWythe County: 147 indexYork County: 52 indexAlexandria city: 206 indexBristol city: 60 indexCharlottesville city: 52 indexChesapeake city: 52 indexCovington city: 103 indexFairfax city: 205 indexFredericksburg city: 55 indexHampton city: 172 indexHopewell city: 53 indexLynchburg city: 68 indexMartinsville city: 47 indexNewport News city: 49 indexNorfolk city: 101 indexPortsmouth city: 49 indexRichmond city: 101 indexRoanoke city: 61 indexSuffolk city: 161 indexWinchester city: 53 index
  • Under 52
  • 52 to 62
  • 62 to 150
  • 150 to 160
  • 160 to 180
  • 180 and over
  • No data
index, 1991. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 1991

Fairfax County: 243 indexFairfax County243Arlington County: 224 indexArlington County224Alexandria city: 206 indexAlexandria city206Fairfax city: 205 indexFairfax city205Henrico County: 192 indexHenrico County192Prince William County: 179 indexPrince William County179Charles City County: 177 indexCharles City County177Fauquier County: 177 indexFauquier County177Warren County: 177 indexWarren County177Hampton city: 172 indexHampton city172Giles County: 166 indexGiles County166Hanover County: 166 indexHanover County166Madison County: 164 indexMadison County164Suffolk city: 161 indexSuffolk city161Chesterfield County: 156 indexChesterfield County156Prince Edward County: 154 indexPrince Edward County154Roanoke County: 154 indexRoanoke County154Amherst County: 151 indexAmherst County151Augusta County: 147 indexAugusta County147Wythe County: 147 indexWythe County147Buchanan County: 146 indexBuchanan County146Covington city: 103 indexCovington city103Norfolk city: 101 indexNorfolk city101Richmond city: 101 indexRichmond city101Smyth County: 69 indexSmyth County69Lynchburg city: 68 indexLynchburg city68Carroll County: 63 indexCarroll County63Roanoke city: 61 indexRoanoke city61Bristol city: 60 indexBristol city60King William County: 57 indexKing William County57Fredericksburg city: 55 indexFredericksburg city55Hopewell city: 53 indexHopewell city53Winchester city: 53 indexWinchester city53Charlottesville city: 52 indexCharlottesville city52Chesapeake city: 52 indexChesapeake city52York County: 52 indexYork County52Campbell County: 51 indexCampbell County51Loudoun County: 49 indexLoudoun County49Newport News city: 49 indexNewport News city49Portsmouth city: 49 indexPortsmouth city49Martinsville city: 47 indexMartinsville city47Fairfax County: 243 indexFairfax County243Arlington County: 224 indexArlington County224Alexandria city: 206 indexAlexandria city206Fairfax city: 205 indexFairfax city205Henrico County: 192 indexHenrico County192Prince William County: 179 indexPrince William County179Charles City County: 177 indexCharles City County177Fauquier County: 177 indexFauquier County177Warren County: 177 indexWarren County177Hampton city: 172 indexHampton city172Giles County: 166 indexGiles County166Hanover County: 166 indexHanover County166Madison County: 164 indexMadison County164Suffolk city: 161 indexSuffolk city161Chesterfield County: 156 indexChesterfield County156Prince Edward County: 154 indexPrince Edward County154Roanoke County: 154 indexRoanoke County154Amherst County: 151 indexAmherst County151Augusta County: 147 indexAugusta County147Wythe County: 147 indexWythe County147Buchanan County: 146 indexBuchanan County146Covington city: 103 indexCovington city103Norfolk city: 101 indexNorfolk city101Richmond city: 101 indexRichmond city101Smyth County: 69 indexSmyth County69Lynchburg city: 68 indexLynchburg city68Carroll County: 63 indexCarroll County63Roanoke city: 61 indexRoanoke city61Bristol city: 60 indexBristol city60King William County: 57 indexKing William County57Fredericksburg city: 55 indexFredericksburg city55Hopewell city: 53 indexHopewell city53Winchester city: 53 indexWinchester city53Charlottesville city: 52 indexCharlottesville city52Chesapeake city: 52 indexChesapeake city52York County: 52 indexYork County52Campbell County: 51 indexCampbell County51Loudoun County: 49 indexLoudoun County49Newport News city: 49 indexNewport News city49Portsmouth city: 49 indexPortsmouth city49Martinsville city: 47 indexMartinsville city47
index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties1991
index		Change on 1990
1Fairfax County243+31
2Arlington County224+16
3Alexandria city206+21
4Fairfax city205+5
5Henrico County192-8
6Prince William County179+138
7Charles City County177-25
7Fauquier County177+13
7Warren County177+18
10Hampton city172+13
11Giles County166+5
11Hanover County166+7
13Madison County164-5
14Suffolk city161-21
15Chesterfield County156-31
16Prince Edward County154-18
16Roanoke County154+25
18Amherst County1510
19Augusta County147-4
19Wythe County147-17
21Buchanan County146+68
22Covington city103+44
23Norfolk city101+19
23Richmond city101-1
25Smyth County69+16
26Lynchburg city68+19
27Carroll County63+10
28Roanoke city61-1
29Bristol city60+5
30King William County57+5
31Fredericksburg city55-6
32Hopewell city53-6
32Winchester city53-8
34Charlottesville city52-8
34Chesapeake city52+3
34York County52-1
37Campbell County51+11
38Loudoun County49-8
38Newport News city49+4
38Portsmouth city49-3
41Martinsville city47+2

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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. 19 counties with data in other periods have no value for 1991 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: highest daily AQI. 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: highest daily AQI (Counties in Virginia by highest daily Air Quality Index (US EPA), 1991) [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: highest daily AQI, Counties in Virginia by highest daily Air Quality Index (US EPA), 1991. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/virginia-counties?period=1991. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Virginia by highest daily Air Quality Index (US EPA), 1991. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/virginia-counties?period=1991.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Virginia by highest daily Air Quality Index (US EPA), 1991 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/virginia-counties?period=1991 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_virginia_by_1991,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in Virginia by highest daily Air Quality Index (US EPA), 1991}},
  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/highest-daily-air-quality-index/virginia-counties?period=1991. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. 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: highest daily AQI: Counties in Virginia by highest daily Air Quality Index (US EPA), 1991
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/highest-daily-air-quality-index/virginia-counties?period=1991
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/virginia-counties?period=1991.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Rank Counties in Virginia by highest daily Air Quality Index (US EPA) using official data, and cite the source.
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Questions

Which county has the highest highest daily Air Quality Index (US EPA)?

Fairfax County, with 243 in 1991, according to the U.S. Environmental Protection Agency.

Which county has the lowest highest daily Air Quality Index (US EPA)?

Martinsville city, with 47 in 1991.

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: highest daily AQI. Retrieved 2026-10-12. 19 counties have no value for 1991 and are not ranked.

Highest daily Air Quality Index (US EPA): other rankings

Counties in Virginia: more rankings