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Human Exposure and Atmospheric Sciences

Research in Action

Development of Reference and Equivalent Methods for measuring key air pollutants

EPA operates a nationwide air monitoring network to measure six primary air pollutants, including carbon monoxide, lead, sulfur dioxide, ozone, nitrogen dioxide, and particulate matter (PM10 and PM2.5) as part of its mission to protect human health and the environment.

The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS) for these criteria pollutants. Through accurate monitoring of criteria pollutants, EPA achieves the critical goal of regulating their ambient concentrations and protecting human health and the environment.

EPA scientists also conduct methods development research to develop ways of accurately and reliably measuring these six criteria pollutants in ambient air. These methods — called Federal Reference Methods (FRMs) — are used by states and other monitoring organizations to assess implementation actions needed to attain National Ambient Air Quality Standards. FRMs are the “gold standard” of air pollution monitoring systems, and ensure air quality data collected at different sites are accurate and can be used for purposes of inter-comparison.

To allow innovation and advance new technologies, EPA also reviews, tests, and approves other methods, called Federal Equivalent Methods (FEMs), which are based on different sampling and/or analyzing technologies than FRMs, but must be as accurate as FRMs.

EPA scientists review and establish NAAQS on a five-year cycle based on new health and environmental research data. Scientists in EPA’s Office of Research and Development review and ensure that methods are based on modern technology and have adequate instrument sensitivity to measure pollutants accurately.

Recently, EPA scientists reviewed the NAAQS for particulate matter and finalized revised standards and measurement methodologies for PM2.5. Other recent NAAQS reviews include revised methods and performance specifications for carbon monoxide (76 FR 54294) and sulfur dioxide (73 FR 66964). EPA scientists are currently evaluating technologies for ozone and nitrogen dioxide FRMs for future NAAQS reviews.

EPA researchers are continually evaluating potential new FRMs and FEMs to foster innovation and improved measurement of atmospheric pollutants. The scientists keep up-to-date on current air pollution sensor technologies, including availability and commercialization of emerging technologies. Adopting new technologies improves EPA’s ability to measure air pollution in new ways and locations.

Through EPA’s Reference and Equivalent Methods Program, EPA scientists are continually developing new FRMs and testing them for accuracy in the lab and field. EPA scientists also develop calibration protocols to assist states and regions in using FRMs with their air pollution monitoring systems.

Approved new methods are formally announced through publication in the Federal Register while approved modifications to existing FRMs and/or FEMs are announced through EPA’s public websites. EPA scientists provide air monitoring technical guidance to states, tribal organizations, other federal agencies, EPA regional offices, and key EPA program offices.

Results and Impact
EPA’s ongoing reviews and assessments of air quality data, and their health and ecological studies help EPA establish ambient standards to protect human health and the environment. EPA’s Reference & Equivalent Program ensures that air quality sampling and analysis instruments are evaluated and approved for making accurate, defensible compliance measurements. These collective activities provide states and regions with tools to protect public health and the environment from adverse effects of air pollution exposure.

Technical Contact
Robert Vanderpool, Ph.D.
Aerosol Research Engineer

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