EnviroNearby

Stark County, North Dakota air quality history

Daily Air Quality Index summaries from EPA monitors in Stark, North Dakota, 1985–2001.

94%
Good days in 1986
24
Median daily AQI, 1986
0
Days above 100 in 1986
177
Days with an AQI in 1986 (of 365)

In 1986, EPA reported a daily Air Quality Index (AQI) for Stark, North Dakota on 177 days. 167 of those days (94%) were in the Good range, and the median daily AQI was 24. That median is lower than the typical monitored county in North Dakota (median 28 across 8 counties), and lower than the typical monitored U.S. county (39). The main pollutant was coarse particles (PM10) on 177 days.

EPA did not report an AQI for every day of 1986 here (177 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 2001; EPA's files for 2002–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (1995, 1996, 1997, 1998, 2000, 2001…) 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%1985: Good 129 of 132 days1985: Moderate 3 of 132 days19851986: Good 167 of 177 days1986: Moderate 10 of 177 days1987: Good 32 of 35 days1987: Moderate 3 of 35 days19871989: Good 30 of 30 days1990: Good 60 of 61 days1990: Moderate 1 of 61 days19901991: Good 56 of 56 days1992: Good 60 of 60 days19921993: Good 61 of 61 days1994: Good 58 of 58 days19941995: Good 57 of 57 days1996: Good 58 of 58 days19961997: Good 49 of 49 days1998: Good 58 of 59 days1998: Moderate 1 of 59 days19982000: Good 56 of 59 days2000: Moderate 3 of 59 days2001: Good 27 of 31 days2001: Moderate 4 of 31 days2001
  • 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 year0501001985: 90th percentile AQI 431986: 90th percentile AQI 441987: 90th percentile AQI 411989: 90th percentile AQI 311990: 90th percentile AQI 271991: 90th percentile AQI 211992: 90th percentile AQI 191993: 90th percentile AQI 161994: 90th percentile AQI 191995: 90th percentile AQI 211996: 90th percentile AQI 151997: 90th percentile AQI 181998: 90th percentile AQI 212000: 90th percentile AQI 492001: 90th percentile AQI 551985: Median AQI 251986: Median AQI 241987: Median AQI 191989: Median AQI 191990: Median AQI 141991: Median AQI 121992: Median AQI 101993: Median AQI 101994: Median AQI 91995: Median AQI 91996: Median AQI 61997: Median AQI 91998: Median AQI 102000: Median AQI 282001: Median AQI 2719851987199019921994199619982001
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 1986

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
Coarse particles (PM10)177100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2001312740000275565PM2.5
2000595630000284957PM2.5
1998595810000102153PM10
199749490000091826PM10
199658580000061547PM10
199557570000092137PM10
199458580000091934PM10
1993616100000101625PM10
1992606000000101931PM10
1991565600000122135PM10
1990616010000142760PM10
1989303000000193131PM10
1987353230000194166PM10
1986177167100000244480PM10
198513212930000254359PM10

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.

All monitored counties in North Dakota

Source: U.S. EPA AirData, “Annual AQI by County” files for 1985–2001 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem