EnviroNearby

Marion County, Texas air quality history

Daily Air Quality Index summaries from EPA monitors in Marion, Texas, 1998–2001.

59%
Good days in 2000
45
Median daily AQI, 2000
40
Days above 100 in 2000
360
Days with an AQI in 2000 (of 366)

In 2000, EPA reported a daily Air Quality Index (AQI) for Marion, Texas on 360 days. 211 of those days (59%) were in the Good range, and the median daily AQI was 45. That median is higher than the typical monitored county in Texas (median 42 across 27 counties), and about the same as the typical monitored U.S. county (44). The main pollutant was ozone on 274 days.

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 (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%1998: Good 190 of 245 days1998: Moderate 44 of 245 days1998: Unhealthy for Sensitive Groups 11 of 245 days19981999: Good 213 of 363 days1999: Moderate 103 of 363 days1999: Unhealthy for Sensitive Groups 40 of 363 days1999: Unhealthy 7 of 363 days19992000: Good 211 of 360 days2000: Moderate 109 of 360 days2000: Unhealthy for Sensitive Groups 29 of 360 days2000: Unhealthy 10 of 360 days2000: Very Unhealthy 1 of 360 days20002001: Good 76 of 109 days2001: Moderate 33 of 109 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 year0501001501998: 90th percentile AQI 801999: 90th percentile AQI 1052000: 90th percentile AQI 1122001: 90th percentile AQI 631998: Median AQI 401999: Median AQI 462000: Median AQI 452001: Median AQI 441998199920002001
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2000

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
Ozone27476%
Fine particles (PM2.5)7120%
Nitrogen dioxide (NO₂)154%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
200110976330000446377Ozone
200036021110929101045112205Ozone
19993632131034070046105182Ozone
199824519044110004080129Ozone

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 Texas

Source: U.S. EPA AirData, “Annual AQI by County” files for 1998–2001 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem