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Seventy trade groups sent an October 31st letter to Mr. Jeffrey Zients who serves as Chief of Staff in the White House addressing the Clean Air Act National Ambient Air Quality Standard (“NAAQS”) for fine particulate matter (PM2.5).

The organizations request that the United States Environmental Protection Agency (“EPA”) maintain the existing NAAQS for PM2.5.

EPA announced on January 6th a proposed rule which would strengthen the NAAQS for PM2.5. It had previously announced in 2022 that it was reconsidering the Trump Administration’s prior decision to retain the PM2.5 NAAQS. Note that the particulate matter standard includes both fine particles PM2.5 and coarse particles (PM10).

Particulate matter is a generic term for a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplets or solids) over a wide range of sizes. It is composed of two major components.

Primary particulates or soot are emitted directly into the atmosphere. Secondary particulates can also be formed through a secondary process. They might be formed from condensation of high-temperature vapor from vapors generated as a result of chemical reactions involving gas-based precursor.

Larger particulates (PM10) are generally the result of mechanical, evaporative, and suspension processes. Particulates designated PM2.5 typically consist of sulfates, nitrates, elemental carbon, organic carbon, compounds and metals. Because of their small size, these particulates can remain in the air for significant periods of time.

Sections 108 and 109 of the Clean Air Act require EPA to identify air pollutants utilizing certain criteria and set NAAQS for each. Particulates are one of the six air pollutants currently designated as criteria air pollutants and subject to NAAQS. Section 109 requires that EPA promulgate primary NAAQS for the pollutants identified under Section 108.

Section 109(b)(1) defines a primary standard as one “the attainment and maintenance of which, in the judgment of the Administrator, based on the criteria and allowing an adequate margin of safety, are requisite to protect the public health.” Further, Section 109(d)(1) of the Clean Air Act requires a periodic review of each NAAQS.

Depending on the results of the review, EPA must determine whether the existing air quality criteria and NAAQS must be revised. EPA’s review of the PM2.5 is an example of this review process.

Note that states are primarily responsible for ensuring attainment and maintenance of a NAAQS once EPA has established or revised them. Each state is therefore required to formulate, subject to EPA approval, an implementation plan (i.e., “SIP”) designed to achieve each NAAQS.

The SIPs will contain the measures and actions the state proposes to undertake to attain each NAAQS. This will include emission limits imposed on stationary sources.

The October 31st letter from the various trade organizations states that a revision of the PM2.5 NAAQS could put nearly 40% of the United States population in areas of nonattainment.

Concern is expressed that:

. . . Doing so would risk jobs and livelihoods by making it even more difficult to obtain permits for new factories, facilities and infrastructure to power economic growth.

The October letter also argues that members of the referenced organizations have:

. . . innovated and worked with regulators to lower PM2.5 concentrations significantly, and further progress is being made as part of the energy transition investments.

Cited is EPA data which they state indicates PM2.5 concentrations have declined by 42% since 2000.

The organizations object to a revision of the current standard for PM2.5 set at 12 µg/m3 and a revision to an EPA proposed standard as low as 8 µg/m3.

The letter also argues that approximately 84% of PM2.5 emissions in the United States come from fires, road dust, agriculture, and other nonpoint sources that are described as “difficult and costly to control.” Therefore, concern is expressed that the cost of complying with the PM2.5 revision would fall predominantly on the private sector.

A copy of the October 31st letter can be downloaded here.