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2005 National-Scale Air Toxics Assessment

2005 Assessment Results

README: Explanation of Data Elements in NATA Results Tables (PDF format).

The file, 2005 NATA Issues and Updates, provides a list of some of the known issues and updates that were not addressed during the review of the 2005 NATA. Reviewing this file will provide a better understanding of the results and help in determining how best to use them.

State-specific NATA Emissions (zipped MS Access format)

The NEI is EPA’s comprehensive, facility-specific emissions inventory database. It is used to support air quality modeling and other activities within the Air Toxics Program. For the 2005 NATA, the point source inventory used was developed by starting with the 2005 NEI. These data have undergone reviews by regional, state, local, and tribal agencies, and the resulting emission files accessed below were updated based on comments received during those reviews. The file, 2005 NATA Summary of Comments (MS Access Format – 2.5 MB), presents these comments. The final inventory, the 2005 NATA Inventory Version 3 (V3) is posted below. Following development of this inventory an additional series of changes resulting from further review and adjustments was made prior to preparing the final modeled ambient concentrations, exposures, and risks (Version 4 or "V4"). These post- version 3 inventory change are summarized in the file, 2005 NATA Inventory Adjustments (zipped file - 1173.31 KB).

The following PDF files may also be useful for understanding the 2005 NEI.

Compiling the 2005 NEI point source inventory. (PDF format - .24 MB)

Quality Assurance and Data Augmentation for Point Sources. (PDF format - .28 MB)

We revised the mobile onroad, nonroad, and airport files as well as the stationary point and nonpoint data. The county emissions summary reflects all revisions, and the stationary point source tables provide detailed emissions data. Most of the changes made as a result of the review were made to this source sector.

The final 2005 NATA inventory files accessed below (under Select a State) provide the pollutant-specific tons/year emissions and modeling data for the year 2005 for every state (including Puerto Rico, the Virgin Islands, and the District of Columbia) and for every county in each state. These tables also provide a breakdown of the emissions by source sector, i.e., stationary point and nonpoint, and mobile sources. These files provide the emissions for all air toxics assessed, with the exception of diesel PM. The diesel PM emissions are summarized for each state and accessed by clicking on the Summary of DPM Emissions (Zipped MSACCESS 2007 format - 26.3 KB).

The document, Air Toxics Pie Charts, provides the percent contribution of each emission source to the total emissions of each air toxic in the inventory. Note that while forest and wildfires are included in the emission inventory, these emissions were NOT modeled and thus, not included in the risk estimates in the 2005 NATA.

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.

State Files (each file is zipped MS Access format, 0.17 MB - 8.4 MB, and must be saved before opening)

2005 County-Level Modeled Ambient Concentrations, Exposures, and Risks (Microsoft Access or Excel 2003 format)

The following tables present the EPA's 2005 national-scale assessment estimates across the United States plus Puerto Rico, the Virgin Islands, and the District of Columbia using 2005 national air toxics emission inventory as input to the models ASPEN, AERMOD, CMAQ, and an inhalation exposure model (HAPEM5). 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).

These data are presented in different ways. The nationwide, county-level files (i.e., the Excel files listed below), present each endpoint risk or hazard quotient estimate by state and county. Additionally, the data are presented by source sector (i.e., stationary, mobile, background, and secondary pollutant). The Microsoft Access files present individual pollutant results for each state and county in the assessment. Conversely, the state summary files present the results by state and county for all pollutants.

While the files, 2005 NATA US Neurological Risk County and 2005 NATA US Respiratory Risk County, present the noncancer results specifically for those endpoints, the individual county-level pollutant files accessible below these, provide the noncancer information for other endpoints (e.g., reproductive system), when a dose-response value was available for that air toxic. Information on these additional endpoints, (e.g., the endpoint and critical concentration used for each), can be found in the file,Health Effects Information (PDF). For a more complete discussion and list of RfC concentrations used in this NATA, see section 5.0 and Appendix-H in the TMD.

There is also a change in the way these data are presented. The inventory typically identifies emissions as being emitted from “major” sources or “area” sources based on the definitions contained in the CAA (see Glossary definitions of area and major sources). For presentation of the results here, the NATA results are identified as “point” and “nonpoint” stationary sources rather than “major” and “area” sources. The point and nonpoint designations reflect the way each source of emissions was modeled. For example, larger sources as well as some smaller sources, i.e., area sources in the inventory, are included in the point source summaries if the location of their emissions was identified with latitude and longitude coordinates. Smaller, area source emissions where a specific location for the emission source was not known, were presented as nonpoint sources. Emissions from these nonpoint sources, which are generally inventoried on a county-wide basis, are allocated to a census tract for modeling using appropriate surrogates. This nonpoint source approach was used for mobile source emissions as well. For the airports modeled in NATA, the locations of these emissions were actually known and thus, were modeled at their actual locations. However, the risk results for airports are summarized under the nonroad, mobile source category.

County-level Pollutants (MS Access format, 0.2 MB - 1.5 MB)


State Summaries (MS Access format, 0.2 MB - 20 MB)

2005 Tract-Level Modeled Ambient Concentrations, Exposures, and Risks (Microsoft Access 2003 format)

In the following section, the focus of the presentation is at the census tract level. This was the smallest spatial resolution for the NATA. The initial group of zipped files contains MS Access files for each of the endpoints listed. As with the county-level files, these results also provide the contribution of each source sector to the total risk or hazard quotient. The tract-level results are also presented by pollutant and by state.

Note: Cancer risks presented in the above Onroad and Nonroad Mobile Risk files identify cancer risks that are not due to the diesel PM component of diesel engine emissions. These cancer risks are due to the other air toxics, such as benzene, which are found in the gaseous component.

Tract-level Pollutants (MS Access format, 1.4 MB - 28 MB)


State Summaries (MS Access format, 1.5 MB - 400 MB)

2005 Google Earth Risk Maps (KMZ Format)

The file, Instructions for Downloading and Using Google Earth Maps (PDF ), provides step-by-step instructions for accessing the data in these interactive Google Earth maps.

These maps show the geographic patterns of estimated cumulative cancer or noncancer risk due to inhalation of air toxics. EPA developed these maps to inform both national and more localized efforts to collect air toxics information and characterize emissions (e.g., prioritize pollutants/geographic areas of interest for more refined data collection such as monitoring). These files not only present the risk levels for each tract, but also the air toxics contributing to risk levels and their percent contribution. An additional overlay provides the names and locations for each source identified and the toxicity-weighted emissions contributing to 90% of the cancer risk or the emissions contributing to 90% of the total mass for that tract.

State Summaries (zipped KMZ format, 0.06 MB - 22 MB)

Note: These zipped files must be saved and the contents extracted before opening.


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