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  • Where can I download hourly emissions data from continuous monitoring?

    Hourly emissions data files are available from the Clean Air Markets Division of EPA, collected as part of 40 CFR Part 75. The download location has changed in February, 2023. The new location is https://campd.epa.gov/data/bulk-data-files . Once on this new site, use the menu (at the left) and the Keyword…

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  • What sources make up the Tier 1 categories used in the emissions trends?

    Tier 1 categories are assigned by source classification codes (SCCs) that are the most specific processes available in the NEI. The latest SCC list with the Tier 1 assignments can be downloaded from the EPA SCC website in Comma Separate Values (CSV) format.

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  • What is the cause of the large decrease in electric utility emissions, particularly sulfur dioxide, starting in 1995?

    SO2 emissions reductions from utilities during this time are primarily attributed to the impacts of the acid rain program. As described on EPA’s Acid Rain Program web page, Phase 1 of this program began in 1995 and affected 263 units at 110 most coal-burning electric utility plants in 21 eastern…

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  • How complete are the data in the National Emissions Inventory?

    While the goal of the National Emissions Inventory (NEI) program is to include all emissions data, there are always challenges meeting this goal. The answer about completeness of coverage of sources depends on the emissions sector and pollutant. In general, the criteria air pollutants and precursors (CAPs) are expected to…

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  • Where is more information available about emissions estimation methods used by the EPA?

    For criteria air pollutants and precursors as well as for hazardous air pollutants, the methods are described in the technical support document (TSD) for the latest National Emissions Inventory (NEI) available from the main NEI page . For greenhouse gas emissions, you can find greenhouse gas inventory methods from the…

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  • Where are the NAICS/ SIC and SCC codes changes that have been implemented for the 2017NEI?

    Please refer to the NEI webpage for 2017 documentation , and follow the link for Appendix 2 - 2017 NEI Plan Code Changes. That Excel file describes anticipated changes for the SCCs and NAICS and includes a helpful read me. I'll just note in the next NEI/EIS email that SCC…

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  • Hunting season is underway, is it ok to eat wild game meat harvested from the local area?

    There is no evidence to indicate there are any human health risks resulting from the train derailment that would limit eating wild game. To learn about other advisories or notices unrelated to the incident, contact the agency listed on your hunting license.

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  • How are emissions trends compiled?

    For criteria air pollutants and precursors, the emissions trends are based on the triennial National Emissions Inventory data, with some interim year data included for non-triennial years. The methods and interim-year approaches are described on the “Development of Data” tab included with the data provided on the Air Pollutant Emissions…

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  • How do I determine what SCCs have changed between inventory years?

    These are available in the EIS (Reporting Code table) or public website: https://sor-scc-api.epa.gov/sccwebservices/sccsearch/ Filter on “last inventory year” to remove SCCs no longer active. If this column has a date in it, then the SCC has been retired as of that date. The “last updated date” (column J) indicates when…

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  • Are the GHGs in the National Emissions Inventory Complete?

    No, the 2020 National Emissions Inventory (NEI) does not comprehensively capture all sources and sinks of greenhouse gases (GHGs) in the United States. For this information, users should review the EPA’s annual Inventory of U.S. Greenhouse Gas Emissions and Sinks . However, the NEI does report GHG emissions for select…

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  • What are EPA’s plans for the 2020 National Emissions Inventory given the atypical situation from COVID-19 that is impacting emissions? What will it be used for?

    The EPA intends to prepare a 2020 National Emissions Inventory in collaboration with state, local, and tribal air agency partners. The Air Emissions Reporting Rule (AERR) requires states and delegated local and tribal agencies to report emissions from stationary sources and provide model inputs for onroad and nonroad sources (except…

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  • How often are the NEI data updated and how frequently are the data published?

    The full NEI is created for every third inventory year (e.g., 2008, 2011, 2014, and 2017). The data for each version has been updated two times each for the 2008, 2011, and 2014 NEI cycles. For the 2017 NEI and beyond, the EPA is trying to publish only a single…

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  • Why do mobile source NOx emissions jump higher between 2001 and 2002 on the emissions trends?

    The emissions model used for mobile sources changed from MOBILE6.2 to MOVES 2010 in December 2009. This change included a notable increase in NOx emissions. The EPA adjusted data back to 2002 to reflect the change in models. The higher emissions in 2002 are because of this method change and…

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  • What facilities are required to report to the NEI?

    The emissions reporting thresholds are in the Air Emissions Reporting Rule (AERR), 40 CFR Part 51, Subpart A, Appendix A, Table 1 , which require state/local air agencies to report emissions as point sources for facilities that meet or exceed these emissions thresholds. The AERR requires states/locals to report to…

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  • Why do the PM2.5 emissions for the electric utilities source category jump up between 1998 and 1999?

    The estimation method for PM emissions from fuel combustion sources was enhanced beginning with the 1999 National Emissions Inventory. Prior to 1999, the emissions measurement data methodology only included the filterable portion (which means the solid particle matter at elevated stack temperatures). Beginning with the 1999 NEI, both the filterable…

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