Address: 100 Branch St.
St. Louis, MO 63102
County: St. Louis City is not part of a county.
Pollutants monitored: Fine particulate matter (PM2.5) and particulate matter (PM10)
Date established: Oct. 1, 2006
Site coordinates
* Latitude: 38.65643°
* Longitude: -90.18977°
EPA site: 29-510-0093

The air monitoring station stands in an industrial area of St. Louis. Recycling facilities for metal surround a large portion of the site; an active railroad lies to the east; and Interstate 70 lies to the west. All of these are potential sources of air pollution. The Branch Street station helps determine public exposure to air pollutants from these sources.

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Taken from the air monitoring station, this picture shows the St. Louis Gateway Arch in the distance. Note the monitor's condensation trap on the left; it helps stabilize conditions to ensure accurate data.

However, due to its particular industrial location, EPA considers the Branch Street station a unique middle-scale site, and monitoring agencies cannot compare its data to the annual standard for PM2.5. The department does compute annual PM2.5 values for Branch Street — See the weekly summary, for example — but it cannot use these figures to determine attainment.

Fine Particulate Matter (PM2.5) Data*

PM2.5 refers to microscopic particulate matter 2.5 microns in diameter and smaller. It comes directly from emissions and from atmospheric reactions. Airborne particulate matter can have adverse effects on the respiratory and circulatory systems.

EPA uses two ways to determine compliance with PM2.5 federal standards. One looks at data over a 24-hour period, and the other takes into account data from a whole year. Since December 2012, the annual PM2.5 standard has been 12 micrograms per cubic meter, based on the three-year average of annual means. EPA bases the 24-hour PM2.5 standard of 35 micrograms per cubic meter on the 98th percentile of 24-hour measurements, averaged over three years.

Weekly summary of preliminary data from all PM2.5 sites
• Annual and 24-hour design values
• Map of current monitoring sites

Preliminary one-hour averages from Branch Street
• PM2.5 data in the last column on the right
• Pages of hourly data from 10 days ago through today
• Central Standard Time

Preliminary up-to-date one-hour averages from all PM2.5 sites
• Data from past three days through current date
• Central Standard Time

Department webpage about particulate matter
• Description of PM2.5 and PM10
• Information about 1997, 2006 and 2012 EPA standards plus related documents

Graph of annual design values from St. Louis sites, beginning in 2003

Graph of 24-hour design values from St. Louis sites, beginning in 2003

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


Particulate Matter (PM10) Data*

PM10 refers to particulate matter smaller than 10 micrometers in diameter. People may inhale these airborne particles but cannot see them. By comparison, the average human hair is seven times thicker than the biggest of these particles.

EPA's standard is 150 micrograms per cubic meter of ambient air (150 µg/m3), averaged over a 24-hour day. A site does not meet this standard if it exceeds the level more than once per year, averaged over a three-year period. Monitoring agencies quantify a site's PM10 data by determining the expected number of days exceeding the standard. The word expected indicates that a monitoring agency may not measure PM10 every day.

Quarterly summary of preliminary PM10 data
• Information about standard and monitoring
• Expected number of exceedance days in a year
• Map of PM10 monitoring stations

Preliminary one-hour averages from Branch Street
• PM10 data in the fourth column from the left
• Pages of hourly data from 10 days ago through today
• Central Standard Time

Preliminary data from all PM10 sites
• Data from past three days through current date
• Central Standard Time

Graph of expected number of days exceeding the standard, beginning in 2003

Department webpage about particulate matter
• Description of PM2.5 and PM10
• Information about 2006 EPA standards plus related documents

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

Related Links

Related Links

Missouri's network of air monitoring sites

The department's annual network plans typically mention the unique stature of the Branch Street monitoring station with respect to the annual PM2.5 standard. Go to dnr.mo.gov/env/apcp/airpollutants.htm to access these plans.

National standard for pollutants

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

The department's webpage about air quality provides information about air quality forecasts and current air quality in three Missouri cities as well as tips for reducing air pollution and handing days with high pollution.

Daily Air Quality Forecast (AirNow) shows how current readings at air monitoring sites rate on the EPA's Air Quality Index. Users can access forecasts from across the country.
Click on Missouri in the state box at the top of the home page to access information.

EPA's Air Sensor Toolbox for Citizen Scientists