EnviroNearby

Calhoun County, Michigan air quality history

Daily Air Quality Index summaries from EPA monitors in Calhoun, Michigan, 1985–2001.

82%
Good days in 1988
29
Median daily AQI, 1988
0
Days above 100 in 1988
273
Days with an AQI in 1988 (of 366)

In 1988, EPA reported a daily Air Quality Index (AQI) for Calhoun, Michigan on 273 days. 225 of those days (82%) were in the Good range, and the median daily AQI was 29. That median is lower than the typical monitored county in Michigan (median 34 across 14 counties), and lower than the typical monitored U.S. county (42). The main pollutant was coarse particles (PM10) on 273 days.

EPA did not report an AQI for every day of 1988 here (273 of 366 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 (1996, 1997, 1998, 1999, 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 58 of 66 days1985: Moderate 8 of 66 days19851986: Good 89 of 115 days1986: Moderate 26 of 115 days1987: Good 97 of 113 days1987: Moderate 15 of 113 days1987: Unhealthy for Sensitive Groups 1 of 113 days19871988: Good 225 of 273 days1988: Moderate 48 of 273 days1989: Good 44 of 52 days1989: Moderate 8 of 52 days19891990: Good 43 of 48 days1990: Moderate 5 of 48 days1991: Good 53 of 60 days1991: Moderate 7 of 60 days19911992: Good 58 of 60 days1992: Moderate 2 of 60 days1993: Good 58 of 60 days1993: Moderate 2 of 60 days19931994: Good 56 of 58 days1994: Moderate 2 of 58 days1995: Good 57 of 59 days1995: Moderate 2 of 59 days19951996: Good 59 of 61 days1996: Moderate 2 of 61 days1997: Good 58 of 58 days19971998: Good 49 of 51 days1998: Moderate 2 of 51 days1999: Good 50 of 51 days1999: Moderate 1 of 51 days19992000: Good 38 of 40 days2000: Moderate 2 of 40 days2001: Good 15 of 15 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 531986: 90th percentile AQI 601987: 90th percentile AQI 531988: 90th percentile AQI 571989: 90th percentile AQI 541990: 90th percentile AQI 521991: 90th percentile AQI 521992: 90th percentile AQI 401993: 90th percentile AQI 371994: 90th percentile AQI 411995: 90th percentile AQI 461996: 90th percentile AQI 311997: 90th percentile AQI 351998: 90th percentile AQI 441999: 90th percentile AQI 412000: 90th percentile AQI 452001: 90th percentile AQI 451985: Median AQI 341986: Median AQI 291987: Median AQI 311988: Median AQI 291989: Median AQI 281990: Median AQI 241991: Median AQI 211992: Median AQI 241993: Median AQI 191994: Median AQI 211995: Median AQI 201996: Median AQI 181997: Median AQI 191998: Median AQI 201999: Median AQI 192000: Median AQI 232001: Median AQI 18198519871989199119931995199719992001
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 1988

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)273100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2001151500000184546PM10
2000403820000234551PM10
1999515010000194158PM10
1998514920000204458PM10
1997585800000193545PM10
1996615920000183163PM10
1995595720000204655PM10
1994585620000214160PM10
1993605820000193756PM10
1992605820000244056PM10
1991605370000215270PM10
1990484350000245270PM10
1989524480000285463PM10
1988273225480000295777PM10
1987113971510003153123PM10
198611589260000296077PM10
1985665880000345378PM10

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 Michigan

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