Methodology


Risk-Screening Environmental Indicators(RSEI)

a screening-level tool from pounds-based, hazard-based, and risk-related perspectives

To assess and compare the hazard or potential impact of industrial chemical release from each facilities in the world, we use US EPA’s Risk-Screening Environmental Indicators (RSEI) methodology (v.2.3.4). The reason why we use RSEI is because

- This 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 complex data.
- And this methodology 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.

This adaptable method can model any chemical if toxicity characteristics, appropriate physicochemical properties, release levels and release location are known or can be estimated. Moreover, it considers both cancer and non-cancer chronic human health endpoints.
This methodology uses risk concepts to quickly and easily screen large amounts of Toxics Release Inventory (TRI). RSEI is particularly useful for examining trends to measure change, ranking and prioritizing chemicals and industry sectors for strategic planning, conducting risk-related targeting, and supporting community-based projects.

The RSEI approach augments estimates of volumes released with toxicity and exposure considerations, but does not address all of the potential factors that a full risk assessment would include. The model uses information on facilities’ chemical releases and transfers from these facilities to off-site facilities to model risk-related impacts. These releases are reported by facilities to the Pollutant Released and transfer Registers (PRTR).

This model is based on current US EPA methodologies for assessing toxicity. The method EPA has chosen for assigning toxicity weights to chemicals is clear and reproducible, based upon easily accessible and publicly available information, and uses expert EPA-wide judgments to the greatest extent possible. RSEI reflects the toxicities of chemicals relative to one another using a continuous system of numerical weights. Toxicity weights for chemicals increase as the toxicological potential to cause chronic human health effects increases. Toxicity-adjusted releases are called “hazard-based results” and provide an alternative perspective to pounds-based or full risk-related results, and are especially valuable when necessary data for risk-related modeling are not available.
Algorithms for Assigning Toxicity Weights
Oral Pathway Inhalation Pathway
Non-Carcinogens: Oral Slope Factor(risk per mg/kg-day)/1.0 * 10-6 3.5 / Rfc (mg/m3)
Carcinogens(WOE categories A and B): Oral Slope Factor (risk per mg/kg-day)/ 1.0 * 10-6 Inhalation Unit Risk(risk per mg/m3)/2.8 * 10-7
Carcinogens(WOE category C): Oral Slope Factor (risk per mg/kg-day)/(1.0 * 10-6*10) Inhalation Unit Risk (risk per mg/m3)/(2.8 * 10-7*10)
The toxicity scoring method separately evaluates exposure routes (inhalation and oral) and classes of effects (cancer and non-cancer). For each exposure route, chemicals are scored based on their single most sensitive adverse effect; if a chemical exhibits both cancer and non-cancer effects, the higher of the two weights is assigned as the final weight for that route. The algorithms used to assign toxicity weights are shown the upper table.