2011 NATA: Assessment Results

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About the 2011 Assessment

This page provides the inventory inputs, ambient and exposure concentrations, and results for the 2011 National-scale Air Toxics Assessments.  There are also links to supporting files and web pages. EPA suggests that the results of this assessment be used cautiously, as the overall quality and uncertainties of the assessment will vary from location to location as well as from pollutant to pollutant.  In many cases more localized assessments, including monitoring and modeling, may be needed to better characterize local-level risk.

The following files will assist in navigating the results of this assessment:

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2011 NATA Emissions

The National Emissions Inventory (NEI) is EPA’s comprehensive emissions inventory. It is used to support air quality modeling and other activities within the Air Toxics Program. The starting point for the 2011 NATA inventory was the 2011 NEI. These data were modified based on comments provided by regional, state, local, and tribal agencies during the NATA review.  The resulting emission files, accessed below, reflect the emissions used in NATA.

The county level emissions summary reflects all revisions made as a result of review comments. The stationary point source tables – Facility and Process Level Summaries – provide the detailed emissions data. Most of the changes made as a result of the review were made to the stationary point source information. 

NOTE: Emission inventories submitted by State, Local, and Tribal agencies may vary in the level of detail and completeness. For this reason, NATA risk estimates should not be compared across these agencies in different geographic regions without considering differences in their respective inventories.

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2011 Modeled Ambient Concentrations, Exposures and Risks

The following tables present the EPA’s 2011 NATA ambient concentration, exposure concentration, and risk estimates across the United States plus Puerto Rico, the Virgin Islands, and the District of Columbia. The 2011 NEI, after review by State, Local, and Tribal agencies, was used as input to the AERMOD and CMAQ models to generate ambient concentrations.  The ambient concentrations were used as input to the inhalation exposure model (HAPEM7) to generate exposure concentrations. Exposure modeling is an important step in this assessment because it takes into account that people move from one location to another (e.g., from outside environments to inside environments).  Exposure concentrations were then used with health-benchmark information to estimate risks or hazards.  More information on the 2011 NATA methods can be found on the Assessment Methods[3] page or in the Technical Support Document[4].

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