EnviroNearby

Chatham County, North Carolina air quality history

Daily Air Quality Index summaries from EPA monitors in Chatham, North Carolina, 1987–2015.

93%
Good days in 2015
38
Median daily AQI, 2015
0
Days above 100 in 2015
212
Days with an AQI in 2015 (of 365)

In 2015, EPA reported a daily Air Quality Index (AQI) for Chatham, North Carolina on 212 days. 197 of those days (93%) were in the Good range, and the median daily AQI was 38. That median is lower than the typical monitored county in North Carolina (median 43.5 across 42 counties), and lower than the typical monitored U.S. county (41). The main pollutant was ozone on 212 days. Across the years with fuller monitoring, the share of Good days rose: an average of 65% in 1987–1992 versus 87% in 2013–2015.

EPA did not report an AQI for every day of 2015 here (212 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

The most recent year with data for this county is 2015; EPA's files for 2016–2025 contain no row for it, which usually means its monitors stopped reporting.

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%1987: Good 105 of 195 days1987: Moderate 59 of 195 days1987: Unhealthy for Sensitive Groups 24 of 195 days1987: Unhealthy 7 of 195 days19871989: Good 116 of 197 days1989: Moderate 67 of 197 days1989: Unhealthy for Sensitive Groups 14 of 197 days1992: Good 133 of 164 days1992: Moderate 30 of 164 days1992: Unhealthy for Sensitive Groups 1 of 164 days19921994: Good 153 of 186 days1994: Moderate 29 of 186 days1994: Unhealthy for Sensitive Groups 4 of 186 days1995: Good 141 of 237 days1995: Moderate 66 of 237 days1995: Unhealthy for Sensitive Groups 27 of 237 days1995: Unhealthy 3 of 237 days19951996: Good 147 of 231 days1996: Moderate 65 of 231 days1996: Unhealthy for Sensitive Groups 17 of 231 days1996: Unhealthy 2 of 231 days1997: Good 109 of 238 days1997: Moderate 90 of 238 days1997: Unhealthy for Sensitive Groups 32 of 238 days1997: Unhealthy 7 of 238 days19971998: Good 87 of 214 days1998: Moderate 77 of 214 days1998: Unhealthy for Sensitive Groups 42 of 214 days1998: Unhealthy 8 of 214 days1999: Good 134 of 250 days1999: Moderate 94 of 250 days1999: Unhealthy for Sensitive Groups 18 of 250 days1999: Unhealthy 4 of 250 days19992000: Good 122 of 256 days2000: Moderate 120 of 256 days2000: Unhealthy for Sensitive Groups 14 of 256 days2001: Good 122 of 261 days2001: Moderate 125 of 261 days2001: Unhealthy for Sensitive Groups 14 of 261 days20012002: Good 108 of 261 days2002: Moderate 110 of 261 days2002: Unhealthy for Sensitive Groups 31 of 261 days2002: Unhealthy 12 of 261 days2003: Good 153 of 257 days2003: Moderate 97 of 257 days2003: Unhealthy for Sensitive Groups 6 of 257 days2003: Unhealthy 1 of 257 days20032004: Good 147 of 263 days2004: Moderate 115 of 263 days2004: Unhealthy for Sensitive Groups 1 of 263 days2005: Good 133 of 259 days2005: Moderate 111 of 259 days2005: Unhealthy for Sensitive Groups 15 of 259 days20052006: Good 136 of 262 days2006: Moderate 123 of 262 days2006: Unhealthy for Sensitive Groups 3 of 262 days2007: Good 126 of 259 days2007: Moderate 122 of 259 days2007: Unhealthy for Sensitive Groups 11 of 259 days20072008: Good 167 of 263 days2008: Moderate 91 of 263 days2008: Unhealthy for Sensitive Groups 4 of 263 days2008: Unhealthy 1 of 263 days2009: Good 204 of 263 days2009: Moderate 58 of 263 days2009: Unhealthy for Sensitive Groups 1 of 263 days20092010: Good 178 of 257 days2010: Moderate 77 of 257 days2010: Unhealthy for Sensitive Groups 2 of 257 days2011: Good 179 of 261 days2011: Moderate 82 of 261 days20112012: Good 218 of 263 days2012: Moderate 44 of 263 days2012: Unhealthy 1 of 263 days2013: Good 221 of 260 days2013: Moderate 39 of 260 days20132014: Good 211 of 258 days2014: Moderate 47 of 258 days2015: Good 197 of 212 days2015: Moderate 15 of 212 days2015
  • 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 year0501001501987: 90th percentile AQI 1121989: 90th percentile AQI 931992: 90th percentile AQI 611994: 90th percentile AQI 771995: 90th percentile AQI 1051996: 90th percentile AQI 1001997: 90th percentile AQI 1151998: 90th percentile AQI 1261999: 90th percentile AQI 912000: 90th percentile AQI 902001: 90th percentile AQI 902002: 90th percentile AQI 1222003: 90th percentile AQI 772004: 90th percentile AQI 732005: 90th percentile AQI 922006: 90th percentile AQI 772007: 90th percentile AQI 842008: 90th percentile AQI 722009: 90th percentile AQI 582010: 90th percentile AQI 692011: 90th percentile AQI 662012: 90th percentile AQI 542013: 90th percentile AQI 542014: 90th percentile AQI 542015: 90th percentile AQI 491987: Median AQI 501989: Median AQI 451992: Median AQI 391994: Median AQI 341995: Median AQI 451996: Median AQI 461997: Median AQI 541998: Median AQI 641999: Median AQI 492000: Median AQI 522001: Median AQI 522002: Median AQI 542003: Median AQI 452004: Median AQI 452005: Median AQI 492006: Median AQI 492007: Median AQI 512008: Median AQI 452009: Median AQI 392010: Median AQI 442011: Median AQI 442012: Median AQI 392013: Median AQI 342014: Median AQI 392015: Median AQI 381987199219951997199920012003200520072009201120132015
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2015

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
Ozone212100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2015212197150000384964Ozone
2014258211470000395487Ozone
2013260221390000345480Ozone
20122632184401003954151Ozone
20112611798200004466100Ozone
20102571787720004469108Ozone
20092632045810003958101Ozone
20082631679141004572162Ozone
2007259126122110005184140Ozone
200626213612330004977126Ozone
2005259133111150004992147Ozone
200426314711510004573112Ozone
20032571539761004577161Ozone
200226110811031120054122197Ozone
2001261122125140005290136Ozone
2000256122120140005290147Ozone
199925013494184004991174Ozone
199821487774280064126174Ozone
1997238109903270054115172Ozone
1996231147651720046100177Ozone
1995237141662730045105164Ozone
19941861532940003477122Ozone
19921641333010003961101Ozone
198919711667140004593143Ozone
1987195105592470050112179Ozone

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 North Carolina with a similar median AQI in 2015

All monitored counties in North Carolina

Source: U.S. EPA AirData, “Annual AQI by County” files for 1987–2015 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem