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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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  • Can I get access to the Emissions Inventory System if I am not a data provider to EPA?

    The Emission Inventory System (EIS) is a secured database for EPA and State/Local and Tribal Air Agencies only. The EIS is used to develop the National Emission Inventory (NEI). While you cannot have access to EIS, you can have access to the current and past NEIs through EPA’s NEI website…

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  • How do I get access to the Emissions Inventory System?

    Access to the Emissions Inventory System (EIS) is available to state, local, tribal agencies, their representatives (such as contractors), to multijurisdictional organizations (MJOs), and to EPA staff. The EIS is not available to the public. Instructions for access to the EIS is available in the Emissions Inventory System (EIS) User’s…

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  • How are people potentially exposed to nitrate?

    For many situations, the potential for children’s exposure from drinking water is medium to low. The potential can be higher when private wells become contaminated with nitrates from feed lot and agricultural runoff, and contaminated groundwater. Some geographic areas are at higher risk of drinking water contamination of private wells…

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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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  • 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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  • How do I reset my password for the Emissions Inventory System?

    Instructions for resetting your password are available in the Emissions Inventory System (EIS) User’s Manual and How To’s section on “How Do I Update My Password?” Follow the instructions to reset your password.

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