Air monitoring is required under the federal Clean Air Act (CAA). Code of Federal Regulations, 40 C.F.R. Part 50 and 40 C.F.R. Part 58, establish the design criteria for the ambient air monitoring network. These regulations detail the siting and operating of air monitoring sites and operating air monitoring instruments in a way to ensure that the data collected is valid.
The Missouri Department of Natural Resources operates an extensive network of ambient air monitors to comply with the Clean Air Act and its amendments. The Ambient Air Quality Monitoring Network for Missouri includes State and Local Air Monitoring Stations (SLAMS), special purpose monitors (SPMs) and a National Core (NCore) network station consistent with requirements in federal regulation.
State and Local Air Monitoring Stations (SLAMS)
The State of Missouri operates a network of about 50 ambient air monitoring sites, called State and Local Air Monitoring Stations (SLAMS). The main purpose of this air monitoring network is to determine whether areas in Missouri are meeting the primary National Ambient Air Quality Standards (NAAQS). These standards are established by EPA to protect human health effects and are available in the NAAQS Table.
Data from the monitoring network are sent to EPA’s national database of air monitoring data, called the Air Quality System (AQS). This data also helps develop information about air quality for the citizens of Missouri. Concentrations of most air pollutants are measured continuously, with hourly averages reported. A detailed description of the air monitoring network and demonstration that it is intended to meet all the ambient air monitoring federal requirements are included in an annual monitoring network plan.
Special Purpose Monitors (SPM)
In addition to the basic required monitoring sites, Missouri also operates special purpose monitors (SPM). These sites may be established for many different purposes, such as compliance evaluation, air quality research and characterization, short-term air quality studies, air quality investigation and monitoring method or instrument evaluation. For example, monitoring for trends in concentrations of toxic air pollutants at a site in St. Louis as a part of the National Air Toxics Trends Sites (NATTS) network.
Industrial Monitors
Some industrial facilities in Missouri also conduct air monitoring near their facilities. This monitoring is done under an approved industrial monitoring Quality Assurance Project Plan (QAPP), reviewed and approved by the state. The department periodically reviews (audits) site operation and instrument performance at these sites. These industrial sites are identified in the annual monitoring network plan. Data from these sites are also reported to the AQS database.