EnviroNearby

Elk County, Pennsylvania air quality history

Daily Air Quality Index summaries from EPA monitors in Elk, Pennsylvania, 1990–2025.

95%
Good days in 2025
36
Median daily AQI, 2025
0
Days above 100 in 2025
361
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Elk, Pennsylvania on 361 days. 344 of those days (95%) were in the Good range, and the median daily AQI was 36. That median is lower than the typical monitored county in Pennsylvania (median 40 across 38 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 361 days. Across the years with fuller monitoring, the share of Good days rose: an average of 77% in 1990–1992 versus 95% 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.

Share of monitored days in each AQI category, by year0%25%50%75%100%1990: Good 241 of 318 days1990: Moderate 56 of 318 days1990: Unhealthy for Sensitive Groups 17 of 318 days1990: Unhealthy 4 of 318 days19901991: Good 257 of 360 days1991: Moderate 70 of 360 days1991: Unhealthy for Sensitive Groups 22 of 360 days1991: Unhealthy 11 of 360 days1992: Good 300 of 361 days1992: Moderate 43 of 361 days1992: Unhealthy for Sensitive Groups 15 of 361 days1992: Unhealthy 3 of 361 days1993: Good 255 of 328 days1993: Moderate 45 of 328 days1993: Unhealthy for Sensitive Groups 26 of 328 days1993: Unhealthy 2 of 328 days1994: Good 291 of 361 days1994: Moderate 54 of 361 days1994: Unhealthy for Sensitive Groups 16 of 361 days1995: Good 197 of 263 days1995: Moderate 47 of 263 days1995: Unhealthy for Sensitive Groups 16 of 263 days1995: Unhealthy 3 of 263 days19951996: Good 168 of 208 days1996: Moderate 29 of 208 days1996: Unhealthy for Sensitive Groups 10 of 208 days1996: Unhealthy 1 of 208 days1997: Good 225 of 277 days1997: Moderate 41 of 277 days1997: Unhealthy for Sensitive Groups 11 of 277 days1998: Good 253 of 336 days1998: Moderate 57 of 336 days1998: Unhealthy for Sensitive Groups 20 of 336 days1998: Unhealthy 6 of 336 days1999: Good 276 of 363 days1999: Moderate 65 of 363 days1999: Unhealthy for Sensitive Groups 22 of 363 days2000: Good 292 of 353 days2000: Moderate 48 of 353 days2000: Unhealthy for Sensitive Groups 12 of 353 days2000: Unhealthy 1 of 353 days20002001: Good 267 of 353 days2001: Moderate 60 of 353 days2001: Unhealthy for Sensitive Groups 21 of 353 days2001: Unhealthy 5 of 353 days2002: Good 288 of 356 days2002: Moderate 47 of 356 days2002: Unhealthy for Sensitive Groups 18 of 356 days2002: Unhealthy 3 of 356 days2003: Good 301 of 359 days2003: Moderate 51 of 359 days2003: Unhealthy for Sensitive Groups 4 of 359 days2003: Unhealthy 3 of 359 days2004: Good 309 of 354 days2004: Moderate 39 of 354 days2004: Unhealthy for Sensitive Groups 6 of 354 days2005: Good 283 of 344 days2005: Moderate 50 of 344 days2005: Unhealthy for Sensitive Groups 11 of 344 days20052006: Good 312 of 355 days2006: Moderate 37 of 355 days2006: Unhealthy for Sensitive Groups 6 of 355 days2007: Good 297 of 361 days2007: Moderate 56 of 361 days2007: Unhealthy for Sensitive Groups 8 of 361 days2008: Good 298 of 344 days2008: Moderate 41 of 344 days2008: Unhealthy for Sensitive Groups 5 of 344 days2009: Good 317 of 343 days2009: Moderate 25 of 343 days2009: Unhealthy for Sensitive Groups 1 of 343 days2010: Good 305 of 358 days2010: Moderate 51 of 358 days2010: Unhealthy for Sensitive Groups 2 of 358 days20102011: Good 327 of 358 days2011: Moderate 30 of 358 days2011: Unhealthy for Sensitive Groups 1 of 358 days2012: Good 303 of 362 days2012: Moderate 54 of 362 days2012: Unhealthy for Sensitive Groups 4 of 362 days2012: Unhealthy 1 of 362 days2013: Good 332 of 361 days2013: Moderate 28 of 361 days2013: Unhealthy for Sensitive Groups 1 of 361 days2014: Good 343 of 364 days2014: Moderate 20 of 364 days2014: Unhealthy for Sensitive Groups 1 of 364 days2015: Good 324 of 347 days2015: Moderate 22 of 347 days2015: Unhealthy for Sensitive Groups 1 of 347 days20152016: Good 321 of 346 days2016: Moderate 22 of 346 days2016: Unhealthy for Sensitive Groups 3 of 346 days2017: Good 326 of 342 days2017: Moderate 16 of 342 days2018: Good 325 of 351 days2018: Moderate 26 of 351 days2019: Good 345 of 357 days2019: Moderate 12 of 357 days2020: Good 356 of 358 days2020: Moderate 2 of 358 days20202021: Good 340 of 358 days2021: Moderate 18 of 358 days2022: Good 353 of 363 days2022: Moderate 9 of 363 days2022: Unhealthy for Sensitive Groups 1 of 363 days2023: Good 343 of 363 days2023: Moderate 20 of 363 days2024: Good 343 of 358 days2024: Moderate 15 of 358 days2025: Good 344 of 361 days2025: Moderate 17 of 361 days2025
  • 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 and 90th-percentile daily AQI, by year0501001990: 90th percentile AQI 871991: 90th percentile AQI 1001992: 90th percentile AQI 711993: 90th percentile AQI 931994: 90th percentile AQI 711995: 90th percentile AQI 871996: 90th percentile AQI 771997: 90th percentile AQI 741998: 90th percentile AQI 901999: 90th percentile AQI 802000: 90th percentile AQI 642001: 90th percentile AQI 902002: 90th percentile AQI 842003: 90th percentile AQI 612004: 90th percentile AQI 582005: 90th percentile AQI 712006: 90th percentile AQI 582007: 90th percentile AQI 672008: 90th percentile AQI 542009: 90th percentile AQI 492010: 90th percentile AQI 612011: 90th percentile AQI 502012: 90th percentile AQI 582013: 90th percentile AQI 492014: 90th percentile AQI 482015: 90th percentile AQI 482016: 90th percentile AQI 502017: 90th percentile AQI 472018: 90th percentile AQI 482019: 90th percentile AQI 462020: 90th percentile AQI 442021: 90th percentile AQI 462022: 90th percentile AQI 452023: 90th percentile AQI 472024: 90th percentile AQI 462025: 90th percentile AQI 471990: Median AQI 391991: Median AQI 401992: Median AQI 351993: Median AQI 351994: Median AQI 381995: Median AQI 401996: Median AQI 351997: Median AQI 391998: Median AQI 391999: Median AQI 382000: Median AQI 382001: Median AQI 382002: Median AQI 372003: Median AQI 342004: Median AQI 342005: Median AQI 372006: Median AQI 352007: Median AQI 362008: Median AQI 362009: Median AQI 352010: Median AQI 372011: Median AQI 352012: Median AQI 372013: Median AQI 362014: Median AQI 362015: Median AQI 362016: Median AQI 372017: Median AQI 352018: Median AQI 342019: Median AQI 352020: Median AQI 342021: Median AQI 342022: Median AQI 352023: Median AQI 352024: Median AQI 342025: Median AQI 3619901995200020052010201520202025
  • 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.

PollutantDays as main pollutantShare of monitored days
Ozone361100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025361344170000364784Ozone
2024358343150000344667Ozone
20233633432000003547100Ozone
2022363353910003545101Ozone
2021358340180000344687Ozone
202035835620000344467Ozone
2019357345120000354680Ozone
2018351325260000344897Ozone
2017342326160000354790Ozone
20163463212230003750126Ozone
20153473242210003648101Ozone
20143643432010003648115Ozone
20133613322810003649105Ozone
20123623035441003758156Ozone
20113583273010003550112Ozone
20103583055120003761115Ozone
20093433172510003549108Ozone
20083442984150003654119Ozone
20073612975680003667136Ozone
20063553123760003558150Ozone
200534428350110003771129Ozone
20043543093960003458122Ozone
20033593015143003461182Ozone
200235628847183003784179Ozone
200135326760215003890197Ozone
200035329248121003864169Ozone
199936327665220003880150Ozone
199833625357206003990185Ozone
199727722541110003974133Ozone
199620816829101003577164Ozone
199526319747163004087156Ozone
199436129154160003871140Ozone
199332825545262003593156Ozone
199236130043153003571177Ozone
19913602577022110040100195Ozone
199031824156174003987174Ozone

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 Pennsylvania with a similar median AQI in 2025

All monitored counties in Pennsylvania

Source: U.S. EPA AirData, “Annual AQI by County” files for 1990–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem