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1 1 (December 23, 2020)

handle is hein.crs/govebau0001 and id is 1 raw text is: C i Res~an~h $erw~ fn ~:; ~ 4 I~t~ deb~ ~ ~ 9 Updated December 23,2020 Ozone and Particulate Matter Air Standards: EPA Review The Clean Air Act (CAA) requires the U.S. Environmental Protection Agency (EPA) to review standards for national ambient air quality every five years. In 2018, EPA announced strategies to expedite the National Ambient Air Quality Standard (NAAQS) review while concurrently disbanding a pollutant-specific scientific review panel that has historically advised agency s taff during their reviews. Although the CAA allows theEPA Administrator to specify the procedures for review of the NAAQS, past EPA reviews and revisions have garnered considerable congressional oversight. In December 2020, EPA completed the particulate matter (PM) NAAQS review andretainedthe standards. This In Focus discusses therecently completed PM NAAQS review and the ongoing ozone review. Background on Ozone and Particulate Matter Ozone and PM are two of six principalpollutants referred to as criteria pollutants for which EPA has promulgated NAAQS under the CAA (42 U.S.C. §7408(a)(1)). Ground-level ozone, theprimary component ofsmog, is formed when nitrogenoxides (NO.) react with volatile organic compounds (VOCs) in sunlight. Ground-level ozone is associated with health effects, such as aggravated as thma, chronic bronchitis, heart attacks, and premature death. EPA has identified natural and anthropogenic sources of ozone and ozoneprecursors (e.g., NO, and VOCs), including factories, lightning, power plants, vegetation, vehicles, volatile chemical products (e.g., paints and solvents), and wildfires. PM refers to a mixture of solid particles andliquid droplets in the atmosphere. PM components may include acids, organic chemicals, metals, and soil or dust particles. The size of PM varies, ranging fromtiny particles that canbe seen only through ahigh-power microscope to larger particles (e.g., soot). Exposure to PM has been associated with adverse health effects (e.g., aggravated asthma, chronic bronchitis, and premature death). PM has also been linked with haze formation and other ecological effects. Typical sources of fine PM (PM2.)-measured at 2.5 micrometers or less in diameter-include emissions from vehicles, smokestacks, and fires. Coarse PM (PMio)- generally measuring 10 micrometers or less in diameter-is often associated with dust fromp aved and unpaved roads, construction and demolition operations, certain industrial processes and agriculture operations, andbiomass burning. In addition, precursor emis sions (e.g., sulfur oxides, NOx, and VOCs) contribute to the formation ofsecondary PM. PM2.5 contains a much greater portion of secondary particles than PMio does. Notwithstanding air quality progress since 1970, ozone and PM concentrations currently exceed the NAAQS in some areas (nonattainmentareas). Table 1 lists these NAAQS and the estimated population in nonattainment areas. Table I . Selected NAAQS and the Estimated U.S. Population in Corresponding Nonattainment Areas Estimated U.S. Primary Population in NAAQS Standard Nonattainment Areas 2015 Ozone 70 ppb (8-hour) 122 million 2012 Fine PM 12.0 pg/m3 (Annual) 21 million 1987 Coarse PM 150 u/m3 (24-hour) 6 million Source: CRS, as adapted from EPA Green Book (May 31, 2020), which lists n onattain ment areas (https://www.epa.gov/green -book). Estimated population based on 2010, rounded to nearest million. Notes: Units of measure are parts per billion (ppb) and micrograms per cubic meter of air (fpg/m3). See 40 C.F.R. Part 50 for detailed NAAQS. Table presents the most recent PM and ozone NAAQS. NAAQS Statutory Requirements NAAQS do not directly limit emis sions. Rather, NAAQS are concentration-based standards for ambient (outdoor) pollution. Under the CAA, Congress mandated that EPA establish two types ofNAAQS for each criteriapollutant- a primary NAAQS, which must protect public health with an adequate margin of s afety, and a s econdary NAAQS, which must protectpublic welfare from any known or anticipated adverse effects (42 U. S.C. §7409(b)). Public welfare includes damage to crops, vegetation, property, building materials, and climate (42 U.S.C. §7602(h)). The CAA establishes a framework for EPA to set NAAQS based on the latest scientific knowledge through a notice- and-comment rulemaking process (42U.S.C. §§7408, 7409). The CAA requires EPA to review the NAAQS and the science upon which they are based every five years and then revise the NAAQS ifnecessary. TheCAA also requires EPA to appoint an independent scientific review committee composed ofseven members, which has beconr the Clean Air Scientific Advisory Committee (CASAC). The act directs CASAC to review the NAAQS every five years and recommend to the EPA Administrator any new national ambient air quality standards andrevisions ... as may be appropriate (42U.S.C. §7409(d)(2)). EPA's Review of the NAAQS Beyond the aforementioned CAA requirements, procedural aspects of the NAAQS review are generally at the discretion of the EPA Administrator. Historically, the agency has undertaken a multi-step process to review each NAAQS. Each NAAQS review typically begins with a planning phase in which EPA seeks public input and develops an Integrated Review Plan (IRP). The IRP maps

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