Jump to main content or area navigation.

Contact Us

Lead in Air

SIP Toolkit - Emission Inventories

You will need Adobe Acrobat Reader to view the Adobe PDF files on this page. See EPA's PDF page for more information about getting and using the free Acrobat Reader.

States must develop and periodically update a comprehensive, accurate, current inventory of actual emissions affecting ambient lead concentrations. The emissions inventory is used by states and EPA to determine the nature and extent of the specific control strategy necessary to help bring an area into attainment of the NAAQS. The EPA uses the data submitted by the states to develop the National Emission Inventory (NEI). The NEI is used by EPA to show national emission trends, as modeling input for analysis of potential regulations, and other purposes. Emission inventories should be based on measured emissions or documented emissions factors.

In the November 12, 2008 Lead Standard (PDF) (99pp, 665k) rulemaking, EPA finalized the guidance related to the emissions inventories requirements. The current regulations are located at 40 CFR 51.117(e) and include the following requirements.

  • States must develop and periodically update a comprehensive, accurate, current inventory of actual emissions affecting ambient lead concentrations.
  • The SIP inventory must be approved by EPA as a SIP element and is subject to public hearing requirements.
  • The emissions reporting requirements for lead nonattainment area SIPs stated in 40 CFR 51.117(e)(1) revised the source emission inventory reporting threshold from 5 tons per year to 0.5 tons per year.

On December 4, 2008 (73 FR 76539), EPA modified its requirements for collecting and reporting air emissions data. The EPA’s Air Emissions Reporting Rule (AERR) updates, consolidates, and harmonizes new emissions reporting requirements with preexisting sets of reporting requirements. The AERR is expected to be a means by which the Agency will implement additional data reporting requirements for the lead NAAQS SIP emission inventories. The AERR provides states with additional flexibility in the way they collect and report emissions data. Providing states with additional flexibility in how they submit air emission data increases the efficiency of operations of state and local programs. The final rule accelerates the reporting of air emissions data by state and local agencies which allows EPA to make the data available to the public and policymakers sooner. Additionally, the final rule unifies reporting dates for various categories of inventories and consolidates the emission inventory reporting requirements found in various parts of the Code of Federal Regulations.

EPA recognizes the discrepancy between the 0.5 tpy lead threshold for the December 27, 2010 Revisions to Lead Ambient Air Monitoring Requirements, commonly referred to as the “Lead Monitoring Rule” (75 FR 81126) and the NEI reporting threshold of 5 tpy. To resolve this inconsistency, EPA is considering proposing changes to align the thresholds by changing the Air Emissions Reporting Rule (AERR) that governs the reporting requirements for the NEI. Given the long rule making timeline, which can last from 1 to 2 years, EPA does not expect that any revision to the rule (if made) would occur in time to require the new threshold for the 2011 NEI (reporting for 2011 NEI is required by the end of 2012). However, given the discrepancy in the rules that currently exists, states are encouraged to voluntarily collect data on smaller Lead sources and report the data to EPA for the 2011 NEI. Note 40 CFR 51.117(e) states: “The point source inventory on which the summary of the baseline for lead emissions inventory is based must contain all sources that emit 0.5 or more tons of lead per year.” EPA realizes that sources below 0.5 tons of lead per year could also affect nonattainment (2008 Lead NAAQS Implementation Questions and Answers, July 8, 2011 (PDF) (9pp, 561k), question 10).

Emissions Inventory Questions and Answers (PDF) (6pp, 56k) - August 10, 2012

For more information see:


Jump to main content.