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Particle Pollution Designations

Particle Pollution Designations Guidance and Data

We provided guidance for the particle pollution designations process in the preamble for the National Ambient Air Quality Standards (NAAQS) final rulemaking (40 FR 3086; January 15, 2013). On April 16, 2013, the EPA provided additional information on the timeline for designating areas and identified where key designation – related subjects can be found in the PM2.5 NAAQS preamble.

On this page:

  1. EPA Guidance on the Area Designations for the 2012 Annual PM2.5 NAAQS
  2. Five-Factor Analysis
  3. Designations Mapping Tool

Datasets Provided by EPA to Support the Five-Factor Analysis:

Dataset Availability Date

Current annual PM2.5 design values (excel spreadsheet)(334 K)

July 3, 2014

CSN speciation data (SANDWICHED) (excel spreadsheet)(293 K)

May 22, 2014

IMPROVE speciation data (SANDWICHED) (excel spreadsheet)(320 K)

May 22, 2014

Urban Increments (see design value spreadsheet above)

July 3, 2014

NEI emissions summaries (excel spreadsheet)(6 MB)

July 11, 2014

Quarterly emissions summaries (excel spreadsheet)(6 MB)

July 3, 2014

Gridded emissions*

May 2013

Wind speed/direction data (zip file)(39 MB)

July 3, 2014

Wind roses*

May 2013

HYSPLIT trajectory endpoint data

Sept 18, 2013

Vehicle Miles Traveled (excel spreadsheet)(649 K)

June 13, 2014

Population (excel spreadsheet)(364 K)

March 27, 2014

* Provided as part of web-based mapping tool.

A. EPA Guidance on the Area Designations for the 2012 Annual PM2.5 NAAQS
States and tribes should refer to the April 2013 guidance for area designations for the 2012 Annual PM2.5 NAAQS when preparing their recommendations on area designations

B. Five-Factor Analysis
The five factors identified in the April 2013 Guidance for Area Designations for the 2012 Annual PM2.5 NAAQS are listed below, along with data and data sources that may be useful in evaluating each area on a case-by-case and in making boundary recommendations. The following is not an exclusive list of factors, data, or sources of data that could be considered in assessing an area. The EPA is providing this list as a useful tool for the designations process, and it should not be construed as representing a decision by the EPA to rely solely on this list for final designation determinations.

The EPA intends, at a minimum, to evaluate these factors, data and/or data sources in making final determinations regarding area designations for the 2012 Annual PM2.5 NAAQS. States and tribes should refer to the designations guidance for more complete information about these factors and the factor analysis. We recognize that consideration of the 5 factors for an assessment can be resource intensive. In addition to providing the relevant data to facilitate the analyses, the EPA provided a PM2.5 Mapping Tool to assist air agencies in developing their area designation and nonattainment boundary recommendations.

Factor 1: Air Quality Data - The air quality analysis is an examination of available ambient PM2.5 air quality monitoring data, including the annual design value calculated for each area based on air quality data for a 3-year period.

For additional information about PM2.5 air quality data, visit EPA's Air Trends site.

Factor 2: Emissions and Emissions-Related Data - The emissions analysis examines emissions of identified sources of direct PM2.5, the major components of direct PM2.5 (organic mass, elemental carbon, crustal material (and/or individual trace metal compounds)), primary nitrate and primary sulfate, and precursor gaseous pollutants (e.g., SO2, NOX, total VOC, and NH3). Emissions data are derived from the 2011 NEI version 1, and are given in tons per year. Emissions data indicate the potential for a source to contribute to observed violations, making it useful in assessing boundaries of nonattainment areas. More information about the NEI.

Factor 3: Meteorology - The evaluation of meteorological data helps to determine the effect on the fate and transport of emissions contributing to PM2.5 concentrations and to identify areas potentially contributing to the monitored violations. One basic meteorological analysis involves assessing potential source-receptor relationships in the area using summaries of emissions, wind speed, and wind direction data. A more sophisticated assessment involves modeling air parcel trajectories.

Factor 4: Geography/Topography - The geography/topography analysis includes an examination of physical features of the land that might define the airshed and, therefore, affect the formation and distribution of PM2.5 over an area. Mountains or other physical features may influence the fate and transport of emissions and PM2.5 concentrations. Additional analyses may consider topographical features that cause local stagnation episodes via inversions. Valley-type features can cause local cold-air drainage patterns and vertical temperature inversions that effectively “trap” air pollution. Under these conditions emissions can accumulate leading to periods of elevated PM2.5 concentrations. These air drainage patterns and inversions may be limited in extent and therefore may need to be separated from regions with more conventional air flow and PM2.5 concentration patterns.

Factor 5: Jurisdictional Boundaries - The analysis of jurisdictional boundaries identifies the planning and organizational structure of an area to provide insights into how air quality planning and enforcement in a potential nonattainment area can be carried out. Examples of jurisdictional boundaries include counties, air districts, areas of Indian country, metropolitan planning organizations (MPOs), and existing nonattainment areas.

C. PM2.5 Designations Mapping Tool

The PM2.5 Mapping Tool gave air agencies access to air quality data, emissions data, and jurisdictional boundaries to assist in designations for the 2012 Particle pollution NAAQS. We have removed the link to the PM2.5 Designations Mapping Tool because we developed the tool specifically for the initial area designations for the 2012 annual PM2.5 NAAQS, which we issued in December 2014 and March 2015, and the tool no longer represents current conditions. Much of the data used to populate the mapping tool is still available through the above links. All data used to support the initial area designation decisions are included in the docket for this action (EPA-HQ-OAR-2012-0918).