Data / Median Air Quality Index (US EPA) / Barnstable County

Median Air Quality Index (US EPA) in Barnstable County

Median Air Quality Index (US EPA) in Barnstable County was 36 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024. That is the 11th highest of 13 counties in 2025.

2025, index36
Change on 20240
Rank11th of 13Counties in Massachusetts ranked
Series high461988
Series low342009

Next release: Tuesday, 13 July 2027, estimated by Invokely from past publication dates (low confidence), not announced by the publisher. Release calendar

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Median Air Quality Index (US EPA) in Barnstable County, 1987 to 2025

32.53537.54042.54547.519871993199920052011201720251987: 40 index1988: 46 index1989: 44 index1990: 40 index1991: 43 index1992: 41 index1993: 41 index1994: 44 index1995: 41 index1996: 43 index1997: 41 index1998: 40 index1999: 41 index2000: 36 index2001: 39 index2002: 41 index2003: 43 index2004: 41 index2005: 43 index2006: 43 index2007: 40 index2008: 43 index2009: 34 index2010: 40 index2011: 36 index2012: 37 index2013: 36 index2014: 35 index2015: 34 index2016: 36 index2017: 37 index2018: 36 index2019: 36 index2020: 36 index2021: 36 index2022: 36 index2023: 37 index2024: 36 index2025: 36 index303540455019872000201320251987: 40 index1988: 46 index1989: 44 index1990: 40 index1991: 43 index1992: 41 index1993: 41 index1994: 44 index1995: 41 index1996: 43 index1997: 41 index1998: 40 index1999: 41 index2000: 36 index2001: 39 index2002: 41 index2003: 43 index2004: 41 index2005: 43 index2006: 43 index2007: 40 index2008: 43 index2009: 34 index2010: 40 index2011: 36 index2012: 37 index2013: 36 index2014: 35 index2015: 34 index2016: 36 index2017: 37 index2018: 36 index2019: 36 index2020: 36 index2021: 36 index2022: 36 index2023: 37 index2024: 36 index2025: 36 index
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12, published 2026-07-13.
All 39 values
Periodindex
202536
202436
202337
202236
202136
202036
201936
201836
201737
201636
201534
201435
201336
201237
201136
201040
200934
200843
200740
200643
200543
200441
200343
200241
200139
200036
199941
199840
199741
199643
199541
199444
199341
199241
199143
199040
198944
198846
198740

Barnstable County compared with nearby places

Barnstable County: 36 indexBerkshire County: 38 indexBristol County: 38 indexDukes County: 35 indexEssex County: 40 indexFranklin County: 38 indexHampden County: 39 indexHampshire County: 36 indexMiddlesex County: 38 indexNorfolk County: 39 indexPlymouth County: 37 indexSuffolk County: 37 indexWorcester County: 39 index
  • Under 36
  • 36 to 38
  • 38 to 39
  • 39 and over
  • No data
Median Air Quality Index (US EPA), 2025, index. Barnstable County is outlined. Same source and period for every area shown. Source: U.S. Environmental Protection Agency. Boundaries: U.S. Census Bureau cartographic boundary files.

Rankings

Definition

Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries.

More on how it is measured
  • The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide).
  • Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.

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.

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How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median 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: median daily AQI (Median Air Quality Index (US EPA), Barnstable County, 1987 to 2025) [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: median daily AQI, Median Air Quality Index (US EPA), Barnstable County, 1987 to 2025. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/en/median-air-quality-index/barnstable-county-massachusetts. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Median Air Quality Index (US EPA), Barnstable County, 1987 to 2025. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/en/median-air-quality-index/barnstable-county-massachusetts.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Median Air Quality Index (US EPA), Barnstable County, 1987 to 2025 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/en/median-air-quality-index/barnstable-county-massachusetts (Accessed: 12 October 2026).

BibTeX
@misc{environmental_median_air_quality_index_2025,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Median Air Quality Index (US EPA), Barnstable County, 1987 to 2025}},
  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/en/median-air-quality-index/barnstable-county-massachusetts. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median 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: median daily AQI: Median Air Quality Index (US EPA), Barnstable County, 1987 to 2025
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/en/median-air-quality-index/barnstable-county-massachusetts
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/median-air-quality-index/barnstable-county-massachusetts.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Questions

What is the median Air Quality Index (US EPA) in Barnstable County?

Median Air Quality Index (US EPA) in Barnstable County was 36 in 2025, according to the U.S. Environmental Protection Agency. That is unchanged from 2024. That is the 11th highest of 13 counties in 2025.

Where does this figure come from?

U.S. Environmental Protection Agency. EPA AirData annual AQI by county: median daily AQI. Retrieved by Invokely on 2026-10-12.

What was the highest median Air Quality Index (US EPA) in Barnstable County?

46 in 1988, the highest value since 1987 in this series.

Related statistics for Barnstable County

All statistics for Barnstable County | Barnstable County in figures