The Geographic Microdata from EPA's 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.
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What are toxicity-weighted concentrations? Toxicity-weighted concentrations are RSEI-modeled concentrations of chemicals released to the environment, multiplied by chemical- and exposure route-specific toxicity weights. Unlike RSEI hazard-based values and much like risk-related RSEI Score values, these RSEI results include environmental fate and transport modeling using physicochemical property and chemical transformation data. However, unlike RSEI Score, no numerical estimates of the potentially exposed populations are considered or characterized in producing these toxicity-weighted concentration results.
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What is a RSEI Score? RSEI Score is a screening-level scoring metric that is intended to be the primary descriptor of relative risk-related impacts to human health for use in comparative and trend analysis. RSEI Scores are calculated as unitless values that account for the size of a chemical release, the fate and transport of a chemical within the environment, the size and location(s) of potentially exposed populations, and a chemical's route-specific relative toxicity. A RSEI Score is calculated as chemical toxicity weight multiplied by the estimated dose, multiplied by the potentially exposed population.
How do the RSEI Scores in the Microdata Dashboard relate to the RSEI Scores in EasyRSEI? The RSEI Scores in the Microdata Dashboard are expressed at the Census block group level, while the RSEI Scores presented elsewhere in EasyRSEI are expressed at different aggregation levels. The RSEI Score for any release in EasyRSEI is the sum of the scores for all the block groups affected by the release. The RSEI Score for any facility in EasyRSEI is the sum of all the releases reported by the facility, including releases resulting from off-site transfers, which may be geographically far from the TRI reporting facility. The RSEI Score for any county, state, or EPA Region in EasyRSEI is the sum of the scores for all the facilities with a reported address in that geography. In contrast, the RSEI Score for a county, state or EPA Region in the Microdata Dashboard is the sum of block group RSEI Scores for all the block groups in that geography. Note that over all reported data (nationally), the RSEI Scores will be the same in both EasyRSEI and in the Microdata Dashboard.
Do block groups with high toxicity-weighted concentrations also have high RSEI Scores? In the RSEI Microdata Dashboard, both toxicity-weighted concentrations and RSEI Scores are expressed at the Census block group level, although they are expressed in different scales. In many cases, they have the same relative proportions: block groups with relatively high toxicity-weighted concentrations also have high RSEI Scores. However, the two measures are calculated differently and in some cases, they may diverge:
- RSEI Score may be relatively higher if the population is large (you can check the population value in the “Ranked Table” at the top right of the Dashboard). RSEI Score includes the number of people potentially exposed whereas the toxicity-weighted concentration does not.
- RSEI Score may be relatively higher even if the population is the same, or lower, if there are people living close to the facility who are facing high concentrations (often from fugitive releases). The RSEI Score is calculated for each 810 meter by 810 meter grid cell, which can be substantially smaller than a Census block group (especially in rural areas), then summed. For toxicity-weighted concentrations, the concentration is averaged over all of the grid cells in the block group. A small number of grid cells with very high concentrations but nonzero population may get averaged out in a block group encompassing many grid cells, while resulting in a relatively high score. This is more likely in rural areas where block groups are larger.
- Toxicity-weighted concentration may be relatively higher for a Census block group if the population is very low.
Learn more about RSEI Scores and toxicity-weighted concentration
