Pacific Monitoring Station Image

Address: 18701 Old Highway 66
               Pacific, MO 63039
County: Saint Louis     
Pollutant monitored: Ozone (O3)
Site coordinates
   * Latitude: 38.49011°
   * Longitude: -90.70509°
EPA Site ID: 29-189-0005

Ozone (O3) Data*

The federally mandated monitoring season for ground-level ozone 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 is 70 parts per billion. 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 sites with exceedances from beginning of season
   • Monthly number of exceedance
   • Map of Missouri's ozone monitoring sites
   • Daily maximum average eight-hour concentration for each site from beginning of season

Preliminary up-to-date one-hour averages from Pacific
   • Ozone data in third and fourth columns
      -- "P" stands for primary monitor. "S" stands for secondary monitor.
   • Data from 10 days ago through current date
   • Central Standard Time
   • Concentrations of pollutant in parts per million (ppm)

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

Preliminary up-to-date one-hour ozone averages from all sites

   • Data from 10 days ago through current date
   • Central Standard Time
   • Concentration of ozone in parts per million (ppm)

Department's webpage about ground-level ozone
   • Description
   • Health effects
   • Tips to reduce ozone
   • 2008 and 2015 standards plus related documents

Graph of design values for ozone sites in St. Louis area, beginning in 2003

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

Related Links

Missouri's mapped network of air monitoring sites

National standard for pollutants

Real-time views from cameras in Kansas City and St. Louis

Department's webpage about air quality
   • Air quality forecasts for St. Louis, Kansas City and Springfield during ozone season: March 1 through October 31
   • Tips for improving air quality
   • Tips for breathing better when air quality is forecasted to be unhealthy for sensitive groups (orange) or unhealthy (red)

Daily Air Quality Forecast (AirNow
) gives air quality forecasts for cities nationwide.

EPA's Air Sensor Toolbox for Citizen Scientists

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