Cumulative Risk Assessment Toolbox: Methods and Approaches for the Practitioner

Table 4

Additional resources for evaluating exposure.

Resource and access	Purpose and scope	Cumulative risk remarks
(4.1) Exposure Factors Handbook (EPA); http://cfpub.epa.gov/ncea/risk/; recordisplay.cfm?deid=236252; (this 2011 handbook updated the 1997 document; highlights are also available, at; http://cfpub.epa.gov/ncea/risk/; recordisplay.cfm?deid=221023); child-specific handbook: (published in 2008): http://cfpub.epa.gov/ncea/risk/; recordisplay.cfm?deid=199243	Provides extensive values and underlying bases for many factors that affect exposures. Examples include exposure duration, frequency, surface area, inhalation rate per activity level, and age/gender, as well as ingestion rates (including for incidental soil ingestion and by food type) based on age and gender. Because children can exhibit different exposure patterns to environmental toxicants than adults, the EPA published the Child-Specific Exposure Factors Handbook in 2008 to provide a summary of available statistical data on various factors assessing children's exposures.	Compendia of values for exposure parameters that can be reviewed to determine those most appropriate for a given site/setting, for adults and children. Can be used to assess multiple pathways and activities/intake rates for exposures to multiple chemicals.
(4.2) Sociodemographic Data Used for Identifying Potentially Highly Exposed Populations (EPA); http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=22562	Setting-specific social and demographic characteristics can cause various subgroups to incur higher exposures than the general population. Published in 1999, this report provides information to help identify those population subgroups; it includes information related to activity patterns (how time is spent), microenvironments (where time is spent), and other data such as gender, race, age, and economic status. Fact Finder searches and returns data from this document.	Can be used to guide the identification and characterization of subgroups within the general population who could be at risk for higher contaminant exposures and related effects, to be addressed in a CRA.
(4.3) NHEXAS, National Human Exposure Assessment Survey (EPA); http://www.epa.gov/heasd/edrb/nhexas.html; HEDS, Human Exposure Database System; http://www.epa.gov/heds/	The EPA Office of Research and Development conducted the NHEXAS survey in the 1990s to assess U.S. exposures to chemicals in concert with their activities.	This extensive set of exposure data linked to activity patterns can be used to support CRAs, including providing insights into potentially vulnerable subpopulations.
(4.4) 3MRA (Center for Exposure Assessment Modeling, CEAM) (EPA); http://www.epa.gov/ceampubl/mmedia/3mra/index.htm	Developed for screening-level exposure and risk assessments for multiple media, multiple pathways, and multiple receptors, for potential human and ecological health risks from chronic exposures to chemicals released from land-based waste management units containing listed waste streams. Site based, it was intended for national-scale application to generate risk- based standards (e.g., levels to exit from hazardous waste regulation); it evaluates human and ecological receptors and captures uncertainty and variability in risk estimates. (Ecological exposure and risk focus on population effects related to key species within habitats found in the proximity of sites.)	Can quantify exposure via multiple pathways after a simulated release. Human receptors include adult/child residents, home gardeners, beef and dairy farmers, and recreational fishers. Pathways include inhalation of outdoor air and indoor air while showering, ingestion of drinking water, and ingestion of farming products and fish.
(4.5) E-FAST, Exposure and Fate Assessment Screening Tool (EPA); http://www.epa.gov/oppt/exposure/pubs/efastdl.htm	Provides screening-level estimates for general population, consumer, and environmental exposures to concentrations of chemicals released to air, surface water, and landfills and released from consumer products. It estimates potential inhalation, dermal and ingestion doses, and the modeled concentrations and doses are designed to reasonably overestimate exposures for use in screening-level assessments.	Default exposure parameters are available, but the use of site-specific values is recommended. Can predict exposure concentrations for comparison to media-specific standards.
(4.6) FRAMES, Framework for Risk Analysis in Multimedia Environmental Systems (DOE Pacific Northwest National Laboratory, in support of EPA); http://www.epa.gov/athens/research/modeling/3mra.html	Integrated software system to conduct screening-level assessments of health and ecological risks for hazardous waste identification rule (HWIR) chemicals from land-based waste management units.	Can be applied to conduct health and ecological screening of multiple chemicals for disposal facilities.
(4.7) TRACI, Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (EPA); http://www.epa.gov/nrmrl/std/traci/traci.html	TRACI is an impact assessment tool for evaluating multiple chemical-impact and resource-use categories to analyze various study designs. Impacts that can be modeled include ozone depletion, global warming, acidification, eutrophication, photochemical smog, cancer risk and noncancer health effects, human health criteria, ecotoxicity, fossil fuel use, land use, and water use. The program includes quantitative data on human carcinogenicity and noncarcinogenicity (based on human toxicity potentials), acidification, smog formation, and eutrophication. The model uses a probabilistic approach to determine spatial scale(s) for other impact categories such as acidification, smog formation, eutrophication, and land use.	Can be used to model and compare exposures to multiple chemicals and health risks associated with different projects. For example, it can graphically analyze the reduction in risk projected from one implementation design versus another. This tool is also relevant to risk characterization (Table 6).
(4.8) SCRAM, Support Center for Regulatory Atmospheric Modeling (EPA), includes links for air quality models, applications, and tools; http://www.epa.gov/ttn/scram/	Provides descriptions and documentation for different types of air quality models, information on modeling tools, and support for existing models. Also provides links to relevant workshops, conferences, reports, journal articles, and websites with further information about atmospheric and air quality models and monitors.	Good source of models, guidance, and other information useful for CRAs that involve air quality monitoring.
(4.9) Technology Transfer Network (TTN), CHIEF, Clearinghouse for Inventories and Emissions Factors (EPA); http://www.epa.gov/ttn/chief/	EPA resource of tools to support air pathway analyses. The TTN maintains a Clearinghouse for Inventories and Emission Factors (CHIEF) that links to a number of helpful technical documents on methods and data for constructing emissions inventories, including the Handbook for Criteria Pollutant Inventory Development: A Beginner’s Guide for Point and Area Sources, Handbook for Air Toxics Emission Inventory Development, Volume I: Stationary Sources, and Compilation of Air Pollutant Emission Factors.	Source for many tools used to assess emissions and dispersion of contaminants released to air. For some cases (notably for metals, including radionuclides), unit particulate emissions can be used to scale to source concentrations in order to estimate airborne and deposited contaminant concentrations.
(4.10) HARP, Hotspots Analysis and Reporting Program Tool (California Air Resources Board, CARB); http://www.arb.ca.gov/toxics/; harp/downloads.htm#2	Software package for facility emissions inventory databases; prioritize facilities for management; model atmospheric dispersion of chemicals from one or multiple facilities using EPA models; calculate cancer and noncancer (acute and chronic) health impacts using Cal/EPA guidance; use point estimates or data distributions of exposures to calculate inhalation and multipathway risks; perform stochastic health risk analyses; calculate potential health effects for individual receptors, population exposures, cumulative impacts for one or multiple facilities and one or multiple pollutants, and potential health effects using ground-level concentrations; present results as tables and isopleth maps.	Designed to address multiple sources, pollutants, concentrations, and exposure pathways to estimate cumulative health effects. Also relevant to risk characterization (Table 6), results can be printed, added to reports, or input to a GIS.
(4.11) CalTOX Model; http://www.dtsc.ca.gov/AssessingRisk/caltox.cfm	Spreadsheet-based model that relates the concentration of a chemical in soil to the risk of an adverse health effect for a person living or working on or near a site. Defaults are available, but site-specific values are recommended. It estimates the chemical concentration in the exposure media of breathing zone air, drinking water, food, and soil that people inhale, ingest, and dermally contact, and uses the standard equations found in RAGS (EPA 1989) to estimate exposure and risk.	Can be used to assess multiple exposures; it has tended to be more for research than practical applications. It can predict exposure concentrations that can be compared to media-specific standards and used to estimate single-chemical risks, which could then be overlain for CRAs.
(4.12) DEPM, Dietary Exposure Potential Model (EPA); http://www.epa.gov/nerlcwww/depm.html	Estimates dietary exposures to multiple chemicals based on data from several national, government-sponsored food intake surveys and chemical residue monitoring programs. Includes recipes developed specifically for exposure analyses that link consumption survey data for prepared foods to chemical residue information, which is normally reported for raw food ingredients, to estimate daily dietary exposure. The summary databases are aggregated in a way that allows the analyst to select appropriate demographic factors, such as age/gender groups, geographical regions, ethnic groups, and economic status. Includes modules for evaluating exposures from residues, soil, and tap water.	Can be used to assess exposures to multiple chemicals from ingesting food and tap water; it could potentially provide context for ambient exposures in the area of a site.
(4.13) All-Ages Lead Model (EPA); http://cfpub.epa.gov/ncea/cfm/; recordisplay.cfm?deid=139314; supporting technical data and related methods and models are at; http://www.epa.gov/superfund/; health/contaminants/lead/products.htm; related documents including interim soil lead guidance for CERCLA sites and RCRA corrective action facilities are also available: http://www.epa.gov/superfund/; lead/products/oswerdir.pdf	EPA model used to predict lead concentrations in body tissues and organs for a hypothetical individual based on a simulated lifetime of lead exposure, extrapolated to a population of similarly exposed individuals. Rather than external dose, most health effects data for lead are based on blood lead concentration which is an integrated measure of internal dose, reflecting total exposure from all sources (e.g., both site-related and background sources for Superfund sites). Both the EPA and Cal/EPA Department of Toxic Substances Control (DTSC) have developed models to estimate blood lead concentrations from exposures to lead from various media, including soil, water, air, and food. In addition to its tool for assessing exposures to children (IEUBK, integrated exposure uptake and biokinetic model), the EPA also developed a further set of models for evaluating lead exposures and risks for nonresidential adults (the all-ages model).	Useful for evaluating the impact of multiple sources of lead by multiple routes. Results could potentially be combined with risks estimated for certain other contaminants if interactions with lead are known to occur (e.g., see ATSDR interaction profiles, (5.4) in Table 5).
(4.14) NIOSH NORA Mixed Exposures program; http://www.cdc.gov/niosh/nora/	Provides technical and support information on projects involving mixed exposures in the workplace. National Occupational Research Agenda (NORA) program identified a number of research areas for NIOSH that addressed mixed occupational exposures, with an aim of protecting individuals in the workplace from exposures to multiple chemicals. The website for the mixed exposures team provides links to related studies, as well as information on how to join a listserv group to discuss topics related to mixed exposures.	Information resource for mixtures in the workplace; scientific knowledge developed through this effort can offer insights for assessing the combined effects of chemicals at contaminated sites, occupational settings, and other scenarios involving multiple chemicals.
(4.15) National Cancer Registry (CDC); http://www.cdc.gov/cancer/dcpc/data/; (this website includes links to various state registries); U.S. census data; http://www.census.gov	A number of health registry databases contain information on various diseases, conditions, and other health-related data, including cancer, asthma, birth defects, and blood lead levels. Organizations such as the CDC and others maintain these databases to allow these data to be evaluated in concert with modeled or measured chemical exposure data to correlate potential influences of multiple exposures and to calibrate risk models. For example, the CDC national registry of cancer cases includes cancer type and target tissue, as well as demographic and location information. Many state and local government health departments and other health organizations also maintain disease and condition registries to monitor trends over time; determine patterns in various populations; guide planning and evaluation of control programs; help set priorities for allocating health resources; advance clinical, epidemiologic, and health services research; provide information for a national database of cancer incidence. Other government resources can also be used to indicate vulnerable population groups who might be at increased risk, such as data from the U.S. Census Bureau.	Data could be used to indicate key community health concerns or for an exploratory investigation of a certain disease or condition that might increase the vulnerability of certain people who could be exposed to a given chemical. However, the links to diseases from environmental exposures or directly to environmental pollutants as causal or contributing factors are not usually clear. This tool is also directly relevant to risk characterization (Table 6).