RSEI Geographic Microdata (RSEI-GM)

On this page:

• What are RSEI Geographic Microdata?
• Geographic Microdata results
• Working with the Geographic Microdata grid cells
• Water Geographic Microdata
• Accessing RSEI Geographic Microdata

What are RSEI Geographic Microdata?

The Geographic Microdata from EPA's Risk-Screening Environmental Indicators (RSEI) model are unique datasets that provide detailed air and water modeling results at various levels of aggregation, spatial geographies, and time periods for data user needs. RSEI Geographic Microdata allow for a flexible ability to compare and analyze RSEI model outputs and results from a receptor-based perspective of potentially impacted geographic areas. These data include values related to each modeled chemical release to air and water and each potentially impacted geographic area located around the facilities that ultimately release the chemical into the environment. Users can examine the potential impacts that environmental releases of toxic chemicals from multiple facilities may have on a particular area, regardless of where the releases originate, and get a more realistic picture of the degree to which the area is potentially affected by TRI chemical releases. 

Underlying these results is the ability to locate facilities, environmental releases, and people geographically and attribute characteristics of the physical environment such as meteorology, hydrography, and topography on surrounding areas once they are located to estimate potential exposure and relative health impacts. The RSEI model describes the U.S. and its territories using a grid-based system and a surface water network. Facility- and chemical-specific data retrieved from Agency-reported informational data sources (such as site addresses and lat/long coordinates) are then geographically indexed to their corresponding grid cell in the grid system or stream segment (flowline) in the surface water network for modeling purposes. The RSEI air modeling and RSEI water modeling pages contain more information on how RSEI models these types of releases. 

Geographic Microdata results

The Geographic Microdata contain several metrics for RSEI data users. For each impacted grid cell, the Geographic Microdata files provide individual chemical concentration, toxicity-weighted concentration, RSEI Score, and population. The files also contain index fields that link to the RSEI chemical, facility, and off-site tables, so users can easily link to that information. For each impacted stream segment (flowline) downstream of a water discharge, the Geographic Microdata files provide individual chemical concentration, toxicity-weighted concentration, and other index fields that link to the surface water network and other RSEI tables. These disaggregated results are made available to users for purposes of analyzing which chemical releases are affecting geographical areas. Geographic Microdata results can also be presented in aggregated files that sum modeled chemical releases and their relative impacts over each geographic unit. 

While the variations in potential impacts in and around a given area can be provided at very granular levels, RSEI model results are screening-level estimates based on computer modeling, and cannot solely be used to determine actual on-the-ground exposures or risks at any given point. RSEI Geographic Microdata, like the other types of RSEI model results, should only be used for screening-level analyses, comparisons, and trends.

Working with the Geographic Microdata grid cells

The most detailed files for air are disaggregated grid cell files, meaning RSEI values are presented for each modeled chemical release and each impacted 810 meter by 810 meter grid cell. These disaggregated files are very large in size (up to 120 gigabyte (GB) per year for the entire United States) and can be difficult to download and manipulate from a technical perspective. To make data analysis easier for users, EPA also produces Microdata files at less granular levels, including Census block groups, Census tracts, and zone improvement plan (ZIP) codes, and produces aggregated files that sum up RSEI results into single values for each geographic unit.

Grid shapefile templates are provided on the RSEI ftp site and the RSEI grid and locational information page contains more background information on the RSEI grid-based system.

Water Geographic Microdata

RSEI Geographic Microdata for water are produced differently than the RSEI Geographic Microdata for air. Instead of the RSEI grid cell that is used in the air Microdata, the water Microdata use the flowline, or stream segment, as the basic unit of geographic analysis. RSEI has adopted the National Hydrography Dataset (NHD) system for indexing water stream segments (flowlines). The NHD provides a national framework for assigning flowline addresses to water-related entities such as facility dischargers, drinking water supplies, fish habitat areas, and wild and scenic rivers. Flowline addresses establish the locations of these entities relative to one another within the NHD surface water drainage network in a manner similar to street addresses. Once linked to the NHD by their flowline addresses, the upstream/downstream relationships of these water-related entities and any associated information about them can then be modeled and analyzed to produce RSEI results.

Accessing RSEI Geographic Microdata

Beginning with the 2018 Toxics Release Inventory (TRI) reporting year, RSEI Microdata datasets are typically produced on a two-year alternating schedule. In even TRI reporting years (2018, 2020, 2022, etc.), expanded Microdata datasets are produced that include RSEI model results for all TRI reporting years (1988-most recent reporting year) at different geographies (e.g., grid cell, Census block group, Census tract, and ZIP code) for different chemical sets (e.g., all chemicals, core chemicals/original industries). In odd TRI reporting years (2019, 2021, 2023, etc.), Microdata are only produced for the three most recent TRI reporting years.

Non-routine or ad hoc Microdata datasets may also be produced and will be made available to the public. The Geographic Microdata are posted in various formats on several different public websites for download. Details on getting the Geographic Microdata.