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How to Use—and Not Use—RSEI

How should RSEI be used?


RSEI should be used for screening-level activities, such as:

Note that detailed, local results involve the most uncertainty as a result of small sample size. All RSEI results should be followed up with additional analysis if detailed conclusions are desired.

How should RSEI not be used?


RSEI does not provide a risk assessment so it is inappropriate to use it to:

What risk factors does RSEI consider?


RSEI incorporates a number of components of risk assessment including the amount of chemical released, the fate and transport of the chemical, the route and extent of human exposure to the chemical, the number of people affected, and the toxicity of the chemical.

What health endpoints does RSEI consider?


RSEI considers both cancer and non-cancer chronic human health endpoints. Acute human health effects and ecological effects are not addressed. RSEI does not address all potential exposure pathways of TRI-reported releases and does not address all sources of toxic chemical exposure.

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What are some of the limitations of RSEI?


As with any model, RSEI is subject to the limitations of the underlying data sources and models that it incorporates, in addition its own limitations:

What types of simplifying assumptions does RSEI use?


Screening-level calculations, like those in RSEI, frequently require simplifying assumptions. These assumptions are used to fill data gaps or reduce the complexity of the calculation. Some examples of simplifying assumptions used by RSEI:

When analyses using simplifying assumptions of this nature are applied in a small sample situation, such as local analyses (e.g., a facility-level analysis), the error associated with these assumptions is likely to be more significant than in the larger sample situation of a larger geographic area. In that case, assumptions of this nature tend to better reflect the population.

Learn more about how RSEI works

How has RSEI been appropriately used?


EPA Offices at Headquarters and in the Regions, and outside analysts have used RSEI to investigate:

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What is a RSEI score?


RSEI starts with TRI releases. For each exposure pathway from each chemical release, the model generates an "Indicator Element." This Indicator Element is a risk-related score that is a unitless value proportional to the potential risk-related impact of the release. This score is the product of the estimated dose of a chemical multiplied by the chemical's assigned toxicity weight multiplied by the exposed population. Indicator Elements are specific to each exposure pathway, chemical, release medium, facility, and year. Indicator Elements are summed to provide the outputs requested by the user.

What does a high RSEI score mean?


High scores identify areas for further investigation. They do not conclusively demonstrate sources of risk. If a facility receives a high RSEI score one cannot identify that facility as the predominant source of chronic human risk. RSEI points to releases that may be a problem that warrant further investigation. However, RSEI scores are directly comparable to each other. A RSEI score 10 times higher than another RSEI score suggests that the potential for risk is 10 times higher. Relatively small releases may lead to high risk scores if the toxicity weight is particularly high or if the estimated exposed population is large. Conversely, large releases may lead to low risk scores if the toxicity weight is low or if the estimated exposed population is small.

What are examples of further investigation warranted by high RSEI scores?


Because of the simplifying assumptions in the RSEI model, high RSEI scores can only identify potential problems. Further investigation is warranted in order to conclude that a particular facility is a source of high chronic human risk. There are a number of ways to investigate how RSEI assumptions may affect risk-related results. For each facility and release, users are able to review the specific parameters used to generate the estimates. Users may want to research those parameters to determine if they represent the best estimate for a specific facility. Examples of steps one might take include:

Technical questions about RSEI should be directed to the RSEI team

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