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Equivalent Test Methods/Clean Air Act: U.S. Environmental Protection Agency Designates Two New Equivalent Methods (PM2.5/PM10-2.5)

April 09, 2025

By: Walter G. Wright

Category: Arkansas Environmental, Energy, and Water Law

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The United States Environmental Protection Agency (“EPA”) published an April 7th Federal Register notice announcing that it has designated the following:

  • One new equivalent method for measuring concentrations of PM2.5.
  • One new equivalent method for measuring PM10-2.5.

Sampling ambient air conditions is an important part of the process for determining whether an area is and/or will remain in compliance with the Clean Air Act National Ambient Air Quality Standards (“NAAQS”).

Pursuant to the authority of the Clean Air Act and in accordance with regulations 40 C.F.R. Part 53, EPA evaluates methods for monitoring the concentrations of the NAAQS as set for in 40 C.F.R. Part 50. Such monitoring methods must meet certain specific requirements for adequacy as either reference or equivalent for utilizations by states to determine compliance with the applicable NAAQS.

EPA typically announces approval of an equivalent test or monitoring method as it is approved.

The new equivalent method for PM2.5 is described as an automated method (monitor) utilizing the measurement principle based on beta attenuation analysis.

The new equivalent method for PM10-2.5 is described as an automated method (monitor) utilizing the measurement principle based on beta attenuation analysis.

A copy of the Federal Register can be downloaded here.

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