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AP–42 Methods for Re-entrained Dust

Motor vehicle emissions inventories for PM10 and PM2.5 are comprised of four components: exhaust emissions, emissions from brake wear, emissions from tire wear, and re-entrained road dust. EPA's methodologies for estimating PM emissions from re-entrained road dust are found in Chapter 13 of Compilation of Air Pollutant Emission Factors, AP-42. The sections of AP-42 that address re-entrained road dust emissions are: Section 13.2.1 (Paved Roads) and Section 13.2.2 (Unpaved Roads).

State and local agencies currently use the latest versions of these sections of AP-42 for calculating re-entrained road dust in PM SIP development and regional conformity analyses, as applicable, unless EPA has approved an alternate method.

Policy & Guidance

• Federal Register Announcing EPA's Official Release of the January, 2011, AP-42 Method for Estimating Re-entrained Road Dust from Paved Roads and the Start of a 2-year Grace Period for Regional Conformity Analyses. On February 4, 2011, EPA officially approved the latest revision of the method for estimating re-entrained road dust emissions from cars, trucks, buses, and motorcycles on paved roads in AP-42 for use in PM10 and PM2.5 SIPs and regional emissions analyses for transportation conformity determinations. The Federal Register also starts a 2-year grace period for the 2011 AP-42 method to be used for regional conformity emissions analyses in PM10 and PM2.5 nonattainment and maintenance areas. At the end of the grace period, (i.e., after February 4, 2013), 2011 AP-42 method is required to be used in regional conformity analyses in PM10 nonattainment and maintenance areas and any PM2.5 nonattainment and maintenance areas where EPA regional administrator or the state air quality agency determined that re-entrained road dust is a significant contributor to the area's PM2.5 problem, or if the area has a PM2.5 motor vehicle emissions budget that includes re-entrained road dust.
• Policy Guidance on Use of November 2006 Update to AP-42 for Re-entrained Road Dust for SIP Development and Transportation Conformity (August 2007) - EPA guidance on changes made to the AP-42 methods for road dust and how and when to use them in PM2.5 SIPs and transportation conformity determinations. This guidance supersedes the AP-42 portions of EPA's February 2004 guidance, which addressed both MOBILE6.2 and AP-42. The portions of the February 2004 guidance addressing MOBILE6.2 remain in effect. Note that the portions of this guidance referring to paved re-entrained road dust are no longer in effect, as they have been replaced by EPA's February 4, 2011, Federal Register announcement.

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