Address: Watkins Mill Road
Lawson, MO 64062
County: Clay
Date established: Jan. 1, 1975
Pollutant monitored: Ozone (O3)
Pollutant no longer monitored: Nitrogen dioxide (NO2)
(To ask for information, go to
Site coordinates:
* Latitude: 39.407419°
* Longitude: -94.265142°
EPA site ID: 29-047-0003

Established in 1975, the air monitor at Watkins Mill State Park is one of the state's longest-running stations. The park lies about 40 miles northwest of the Kanas City line, and the monitor helps determine ozone exposure of a population segment in the the Kansas City metropolitan statistical area. The state park is adjacent to the Watkins Woolen Mill State Historic Site. The park and historic site bear the name of entrepreneur Waltus Watkins.

The federal ozone season runs from March 1 through October 31.
Ground-level ozone forms when pollutants emitted by cars, factories, power plants and other sources react chemically in the presence of heat and sunlight. Ozone at ground level is a harmful air pollutant as opposed to ozone in the upper atmosphere, which protects us from ultraviolet light.

As of 2015, the federal standard for ground-level ozone is 70 parts per billion, or 0.070 parts per million. An area is in compliance if the design value is at or below this standard. A design value for ozone incorporates data from three years. The department and EPA calculate the design value by 1) ranking the daily eight-hour ozone values for three consecutive years; 2) extracting the fourth-highest value for each year; and 3) averaging the three figures.

Weekly summary of preliminary data from all ozone sites
• Eight-hour ozone design values
• Four highest eight-hour ozone values from beginning of ozone season
• Running list of exceedances from beginning of season
• Monthly number of exceedances, 2016 and 2017
• Daily maximum average eight-hour concentration for each site from beginning of season

Preliminary data from Watkins Mill in parts per million
• "P" stands for primary monitor; "S" for secondary monitor.
• Data from 10 days ago through current date
• Central Standard Time

Preliminary eight-hour forward-rolling averages from all ozone sites in parts per million
• Hourly data equal to average of that hour and the following seven hours.
• Data from 10 days ago through current date
• Central Standard Time

Preliminary one-hour ozone averages in parts per million from all sites

• Data from 10 days ago through current date
• Central Standard Time

2016 list of exceedances from all ozone monitors

* Technical issues can affect ability to deliver quality data.
Access a table of symbols indicating technical issues.