EnviroNearby

York County, South Carolina air quality history

Daily Air Quality Index summaries from EPA monitors in York, South Carolina, 1980–2025.

76%
Good days in 2025
43
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 York, South Carolina on 361 days. 276 of those days (76%) were in the Good range, and the median daily AQI was 43. That median is about the same as the typical monitored county in South Carolina (median 43 across 13 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 195 days. Across the years with fuller monitoring, the share of Good days fell: an average of 74% in 1980–1984 versus 66% in 2023–2025.

Years with fewer than 120 monitored days (1982) are shown in the table but left out of comparisons and trend statements.

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%1980: Good 331 of 366 days1980: Moderate 32 of 366 days1980: Unhealthy for Sensitive Groups 3 of 366 days19801981: Good 314 of 362 days1981: Moderate 48 of 362 days1982: Good 95 of 100 days1982: Moderate 5 of 100 days1984: Good 73 of 158 days1984: Moderate 52 of 158 days1984: Unhealthy for Sensitive Groups 28 of 158 days1984: Unhealthy 5 of 158 days1985: Good 185 of 284 days1985: Moderate 69 of 284 days1985: Unhealthy for Sensitive Groups 25 of 284 days1985: Unhealthy 5 of 284 days1986: Good 95 of 133 days1986: Moderate 25 of 133 days1986: Unhealthy for Sensitive Groups 10 of 133 days1986: Unhealthy 2 of 133 days1986: Very Unhealthy 1 of 133 days19861987: Good 124 of 234 days1987: Moderate 56 of 234 days1987: Unhealthy for Sensitive Groups 44 of 234 days1987: Unhealthy 8 of 234 days1987: Very Unhealthy 2 of 234 days1988: Good 188 of 301 days1988: Moderate 65 of 301 days1988: Unhealthy for Sensitive Groups 29 of 301 days1988: Unhealthy 15 of 301 days1988: Very Unhealthy 4 of 301 days1989: Good 197 of 287 days1989: Moderate 72 of 287 days1989: Unhealthy for Sensitive Groups 17 of 287 days1989: Unhealthy 1 of 287 days1990: Good 199 of 331 days1990: Moderate 94 of 331 days1990: Unhealthy for Sensitive Groups 31 of 331 days1990: Unhealthy 7 of 331 days1991: Good 234 of 336 days1991: Moderate 76 of 336 days1991: Unhealthy for Sensitive Groups 23 of 336 days1991: Unhealthy 3 of 336 days19911992: Good 225 of 261 days1992: Moderate 27 of 261 days1992: Unhealthy for Sensitive Groups 9 of 261 days1993: Good 238 of 354 days1993: Moderate 87 of 354 days1993: Unhealthy for Sensitive Groups 21 of 354 days1993: Unhealthy 6 of 354 days1993: Very Unhealthy 2 of 354 days1994: Good 253 of 322 days1994: Moderate 57 of 322 days1994: Unhealthy for Sensitive Groups 9 of 322 days1994: Unhealthy 3 of 322 days1995: Good 171 of 257 days1995: Moderate 64 of 257 days1995: Unhealthy for Sensitive Groups 18 of 257 days1995: Unhealthy 3 of 257 days1995: Very Unhealthy 1 of 257 days1996: Good 220 of 291 days1996: Moderate 55 of 291 days1996: Unhealthy for Sensitive Groups 15 of 291 days1996: Unhealthy 1 of 291 days19961997: Good 212 of 310 days1997: Moderate 78 of 310 days1997: Unhealthy for Sensitive Groups 18 of 310 days1997: Unhealthy 2 of 310 days1998: Good 138 of 243 days1998: Moderate 76 of 243 days1998: Unhealthy for Sensitive Groups 24 of 243 days1998: Unhealthy 5 of 243 days1999: Good 119 of 274 days1999: Moderate 121 of 274 days1999: Unhealthy for Sensitive Groups 29 of 274 days1999: Unhealthy 5 of 274 days2000: Good 123 of 272 days2000: Moderate 126 of 272 days2000: Unhealthy for Sensitive Groups 22 of 272 days2000: Unhealthy 1 of 272 days2001: Good 137 of 255 days2001: Moderate 99 of 255 days2001: Unhealthy for Sensitive Groups 19 of 255 days20012002: Good 145 of 249 days2002: Moderate 64 of 249 days2002: Unhealthy for Sensitive Groups 27 of 249 days2002: Unhealthy 13 of 249 days2003: Good 185 of 248 days2003: Moderate 54 of 248 days2003: Unhealthy for Sensitive Groups 9 of 248 days2004: Good 185 of 251 days2004: Moderate 62 of 251 days2004: Unhealthy for Sensitive Groups 4 of 251 days2005: Good 175 of 244 days2005: Moderate 53 of 244 days2005: Unhealthy for Sensitive Groups 15 of 244 days2005: Unhealthy 1 of 244 days2006: Good 175 of 236 days2006: Moderate 52 of 236 days2006: Unhealthy for Sensitive Groups 8 of 236 days2006: Unhealthy 1 of 236 days20062007: Good 155 of 257 days2007: Moderate 91 of 257 days2007: Unhealthy for Sensitive Groups 11 of 257 days2008: Good 163 of 238 days2008: Moderate 61 of 238 days2008: Unhealthy for Sensitive Groups 14 of 238 days2009: Good 272 of 288 days2009: Moderate 16 of 288 days2010: Good 263 of 296 days2010: Moderate 33 of 296 days2011: Good 242 of 268 days2011: Moderate 26 of 268 days20112012: Good 196 of 240 days2012: Moderate 41 of 240 days2012: Unhealthy for Sensitive Groups 3 of 240 days2013: Good 227 of 251 days2013: Moderate 24 of 251 days2014: Good 270 of 277 days2014: Moderate 7 of 277 days2015: Good 321 of 337 days2015: Moderate 16 of 337 days2016: Good 295 of 325 days2016: Moderate 29 of 325 days2016: Unhealthy for Sensitive Groups 1 of 325 days20162017: Good 275 of 307 days2017: Moderate 31 of 307 days2017: Unhealthy for Sensitive Groups 1 of 307 days2018: Good 271 of 354 days2018: Moderate 80 of 354 days2018: Unhealthy for Sensitive Groups 3 of 354 days2019: Good 210 of 365 days2019: Moderate 148 of 365 days2019: Unhealthy for Sensitive Groups 7 of 365 days2020: Good 303 of 366 days2020: Moderate 63 of 366 days2021: Good 257 of 360 days2021: Moderate 103 of 360 days20212022: Good 253 of 363 days2022: Moderate 109 of 363 days2022: Unhealthy for Sensitive Groups 1 of 363 days2023: Good 213 of 365 days2023: Moderate 149 of 365 days2023: Unhealthy for Sensitive Groups 3 of 365 days2024: Good 226 of 363 days2024: Moderate 136 of 363 days2024: Unhealthy for Sensitive Groups 1 of 363 days2025: Good 276 of 361 days2025: Moderate 85 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 year0501001501980: 90th percentile AQI 491981: 90th percentile AQI 551982: 90th percentile AQI 451984: 90th percentile AQI 1261985: 90th percentile AQI 1051986: 90th percentile AQI 971987: 90th percentile AQI 1291988: 90th percentile AQI 1191989: 90th percentile AQI 971990: 90th percentile AQI 1051991: 90th percentile AQI 971992: 90th percentile AQI 611993: 90th percentile AQI 931994: 90th percentile AQI 741995: 90th percentile AQI 931996: 90th percentile AQI 841997: 90th percentile AQI 841998: 90th percentile AQI 1081999: 90th percentile AQI 1082000: 90th percentile AQI 962001: 90th percentile AQI 972002: 90th percentile AQI 1292003: 90th percentile AQI 802004: 90th percentile AQI 772005: 90th percentile AQI 842006: 90th percentile AQI 802007: 90th percentile AQI 842008: 90th percentile AQI 902009: 90th percentile AQI 462010: 90th percentile AQI 512011: 90th percentile AQI 502012: 90th percentile AQI 712013: 90th percentile AQI 502014: 90th percentile AQI 442015: 90th percentile AQI 472016: 90th percentile AQI 502017: 90th percentile AQI 542018: 90th percentile AQI 582019: 90th percentile AQI 642020: 90th percentile AQI 532021: 90th percentile AQI 612022: 90th percentile AQI 582023: 90th percentile AQI 672024: 90th percentile AQI 642025: 90th percentile AQI 581980: Median AQI 231981: Median AQI 251982: Median AQI 231984: Median AQI 581985: Median AQI 431986: Median AQI 381987: Median AQI 481988: Median AQI 441989: Median AQI 411990: Median AQI 461991: Median AQI 411992: Median AQI 311993: Median AQI 411994: Median AQI 381995: Median AQI 441996: Median AQI 391997: Median AQI 441998: Median AQI 471999: Median AQI 552000: Median AQI 532001: Median AQI 482002: Median AQI 462003: Median AQI 392004: Median AQI 392005: Median AQI 422006: Median AQI 402007: Median AQI 472008: Median AQI 442009: Median AQI 312010: Median AQI 352011: Median AQI 382012: Median AQI 412013: Median AQI 382014: Median AQI 332015: Median AQI 332016: Median AQI 392017: Median AQI 382018: Median AQI 392019: Median AQI 472020: Median AQI 392021: Median AQI 442022: Median AQI 442023: Median AQI 472024: Median AQI 462025: Median AQI 431980198619911996200120062011201620212025
  • 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
Ozone19554%
Fine particles (PM2.5)16646%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025361276850000435893Ozone
202436322613610004664112PM2.5
202336521314930004767115PM2.5
202236325310910004458126PM2.5
20213602571030000446197Ozone
2020366303630000395393PM2.5
201936521014870004764133PM2.5
20183542718030003958115Ozone
20173072753110003854105Ozone
20163252952910003950105Ozone
20153373211600003347100Ozone
2014277270700003344100Ozone
2013251227240000385087Ozone
20122401964130004171143Ozone
2011268242260000385097Ozone
2010296263330000355197Ozone
2009288272160000314680Ozone
200823816361140004490122Ozone
200725715591110004784150Ozone
20062361755281004080166Ozone
200524417553151004284151Ozone
20042511856240003977147Ozone
20032481855490003980129Ozone
20022491456427130046129190Ozone
200125513799190004897147Ozone
2000272123126221005396156Ozone
19992741191212950055108185Ozone
1998243138762450047108182Ozone
199731021278182004484161Ozone
199629122055151003984169Ozone
199525717164183104493203Ozone
19943222535793003874166Ozone
199335423887216204193213Ozone
19922612252790003161136Ozone
199133623476233004197190Ozone
1990331199943170046105185Ozone
198928719772171004197151Ozone
19883011886529154044119242Ozone
1987234124564482048129214Ozone
19861339525102103897203Ozone
1985284185692550043105197Ozone
198415873522850058126172Ozone
19821009550000234562CO
1981362314480000255595CO
19803663313230002349148CO

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 2025

All monitored counties in South Carolina

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem