Strengths and Limitations of the RSEI Model
Strengths of the RSEI Model
- The model provides important hazard-based and risk-related perspectives regarding the impacts of TRI releases on chronic human health.
- The model quickly organizes and evaluates data in a complex manner. For example, the air exposure model is combined with US Census data to directly estimate the size of exposed populations and subpopulations and the magnitude of their exposure, rather than assuming that all individuals surrounding a facility are equally exposed.
- The model allows for greatly increased speed in performing screening analyses, thereby conserving resources for conducting more precise, site-specific risk evaluations. In addition, its use as a priority-setting tool allows resources to be focused in areas that will provide the greatest potential risk reduction.
- The model can perform single- and multi-media analyses.
- Custom-designed selections can be based upon a wide range of variables.
- This adaptable method can model any chemical if toxicity characteristics, appropriate physicochemical properties, release levels and release location are known or can be estimated.
- The model considers both cancer and non-cancer human health endpoints.
- The RSEI method has been subject to repeated expert peer review and review by EPA's Science Advisory Board (SAB).
- The model's methodology and assumptions are transparent. Complete and detailed documentation of the RSEI model is available.
- RSEI uses standard EPA hazard information and exposure models.
Limitations of the RSEI Model
- RSEI results do not provide users with quantitative risk estimates (e.g., excess cases of cancer).
- RSEI results do not evaluate individual risk.
- The model does not account for all sources of TRI chemicals; it only accounts for those sources that are required to report to TRI. It also does not provide scores for all TRI chemicals, although chemicals without toxicity weights account for a very small percentage of total releases and of total risk-related impacts.
- TRI does not account for all toxic chemicals.
- The model assumes that air concentrations of TRI chemicals are the same for indoor and outdoor exposures, and that populations are continuously exposed.
- Dermal and food ingestion pathways (other than fish consumption), and some other indirect exposure pathways are not evaluated.
- Acute health effects associated with short-term, periodic exposures to higher levels of these same chemicals are not addressed.
- Ecological effects are not addressed.
- RSEI results have greater uncertainty when examining disaggregated results at the local or facility level.
Unlike a formal risk assessment, RSEI does not describe a specific level of risk related to any particular disease; rather it highlights situations that may lead to potential chronic human health risks. Moreover, results of all screening-level tools — including RSEI — should be supplemented with additional analyses.