Table 6: Selected resources for characterizing risk and uncertainty and presenting results.

Resource and accessPurpose and scopeCumulative risk remarks

(6.1) SADA (Spatial Analysis and Decision Assistance);
Integrated software with flexible land use scenarios and exposure pathways. Emphasizes spatial distribution of contaminant data; modules cover visualization, geospatial analysis, statistical analysis, sampling design, and decision analysis. Outputs can be tabular or graphical. Can address both health and ecological risk to support integrated decisions. Useful for cumulative risk assessments; can combine pathways to assess overall exposures and summed risks and HIs for receptors of interest. Input data can reflect site-specific conditions; interactions are not considered.

(6.2) RAIMI, Regional Air Impact Modeling Initiative (EPA);
Risk-based prioritization tool developed by Region 6 to support regional risk-based prioritization at the community level from exposures to multiple airborne contaminants from multiple sources via multiple exposure pathways. Designed to support cross-program analyses. Includes Risk-MAP, to estimate health risks from exposures to chemical emissions over large areas. Assesses multiple contaminants and multiple sources for EPA programs, for air contaminants. Designed to consider source-specific and contaminant-specific contributions to cumulative exposures associated with the air pathway.

(6.3) Environmental Load Profile (EPA);
Compares indicators of well-being with derived benchmarks. This screening-level tool was developed by EPA Region 2 to represent the environmental burden in a community in support of EJ evaluations, with links to census data via a GIS layer to support the demographic component of such assessments.Similar to RAIMI but as a screening tool, focuses on inputs for Toxics Release Inventory (TRI) emissions, air toxics, and facility density. More detailed analyses of a community burden would be conducted at the local level.

(6.4) Cumulative Adjustment of Protective Concentration Levels (PCLs), TCEQ (Texas Commission on Environmental Quality);
PCLs are a set of toxicity-based screening criteria developed for use in risk assessments. Individual PCLs were derived to evaluate risks from individual chemicals, and TCEQ developed an equation to adjust these downward when evaluating multiple chemicals, when at least 10 carcinogenic or noncarcinogenic chemicals of concern (COCs) are identified for a given pathway. These adjustments reduce PCLs for individual chemicals based on the ratio of the measured concentration of each to its PCL. If the sum of these ratios exceeds a predetermined target, adjusted PCL values may be necessary for some COCs to ensure that state risk reduction rule mandates are met (e.g., to not exceed a risk of 10−4 or an HI of 10). COCs to be adjusted are determined from a decision process outlined in the guidance.Can be used for screening calculations based on the sum of ratios approach (similar to NIOSH, IRSST, and others, including the approach used to assess radionuclides), under the default assumption of additivity.

(6.5) HEM-3, Human Exposure Model-3 (EPA);
Designed to predict risks associated with chemicals released to ambient air, used primarily to assess risk for major point sources of air toxics. Generates results for one facility at a time focusing on the inhalation pathway. Contains an atmospheric dispersion model and U.S. census information at the census block level. Each source must be located by latitude and longitude, and its release parameters must be described. This tool is generally used to estimate concentrations within 50 km of a source. It provides ambient air concentrations as surrogates for lifetime exposure, for use with unit risk estimates and inhalation RfCs to produce estimates of cancer risk and noncancer HI, respectively.Presents risk and noncancer estimates. To support a CRA, estimates for individual sources could be overlain to suggest insights for multiple sources.

(6.6) Probabilistic tools (Monte Carlo analysis resources), such as those described at:;
Statistical methods for addressing uncertainty and variability in estimating health risks by developing multiple descriptors to calculate a quantity repeatedly with randomly selected scenarios for each calculation. These are most useful for single-point risk estimates, and they can be used as a presentation tool because graphics show the range of scenarios and outputs.Combining approximations for multiple sources of potential risk (e.g., from environment and lifestyle) is complicated. These tools could be used to combine results for individual exposures that consider variability and uncertainty.

(6.7) Software and User’s Manual for the Integrated Exposure Uptake Biokinetic Model for Lead in Children (IEUBK) (also Adult Lead Model, other data) (EPA);;
The IEUBK model consists of four modules (exposure, uptake, biokinetic, and probability distribution) to estimate blood
lead levels in children exposed to lead by various routes. A distribution of lead concentrations from the geometric mean can be used to estimate the risk that lead levels in blood for a child or group of children will exceed a target level. The tool is included here (in addition to the related entry in Table 4) because it can also be used to assess the uncertainty in the risk estimate.
Can estimate blood lead levels based on exposures to multiple sources via multiple routes using a complex set of variables that include adjustable exposure, uptake, and biokinetic
parameters. (See related entry in Table 4.)

(6.8) Policy for Risk Characterization (EPA);
Emphasizes transparency in decision making, clarity in communication, and consistency in assumptions and policies. Encourages plans that reflect these values and consistency and calls for programs to fall within a “zone of reasonableness.” Encourages an open process as well as program- and region-specific policies, procedures, and implementation for CRAs.

(6.9) Elements to Consider When Drafting EPA Risk Characterizations;
Outlines the basic principles of risk characterization and presents an outline for developing chemical risk assessments that includes hazard identification, dose response, exposure, conclusions, and context. Provides insights for applying risk characterization principles for CRAs, with suggestions for topics to consider when conducting an assessment.

(6.10) Handbook on Risk Characterization (EPA);
Describes the importance of conducting the risk characterization process in a transparent manner, with products that are clear, consistent, and reasonable (TCCR). Appendices of this handbook include the EPA 1995 risk characterization policy and illustrative case studies. The basic principles outlined in this report are useful for CRAs and can be helpful to risk assessment practitioners, managers, and the general public.