Risk*Assistant

Risk Assistant Helps assess human health risks posed by hazardous waste (prototype) C Micro J. Young/Hampshire Res. Inst J. Segna/EPA/OHEE ... 

EPA risk assessment practice, (and the Risk Assistant software) reflects this distinction between generic and site-specific information in the prediction of the risks associated with an agent at a specific site. The results of authoritative Hazard Identifications and Dose-Response Assessments are not expected to be re-evaluated by the risk assessors evaluating specific sites these assessors are expected to concentrate on site-specific Exposure Evaluation and Risk Characterization. 

Such exposure information, rather than predicted or measured environmental concentrations, is needed to predict the risks associated with an agent. (Risk Assistant was explicitly designed to provide risk assessors with assistance in this previously neglected area.)... 

The training of professional personnel in the risk assessment process is an ongoing activity at EPA. However, classroom training is only a partial answer to EPA s risk assessment dilemma. It lessens, but has not eliminated, the pressure of EPA to review technical reports with less experienced professional personnel. The development of a computer software system, Risk Assistant, to assist environmental personnel in conducting risk assessments and reviewing assessments generated by contractors, represents a complementary approach to increasing the technical quality and consistency of risk assessments. 

Components of Risk Assistant. There are three main components of the Risk Assistant software system, each of which reflects a different approach to using the information contained in the system. Each segment makes use of the same family of program modules, but selects different subsets of these modules to address particular questions. 

Case Description. Obviously, any site-specific risk assessment requires information on the relevant characteristics of the site. The Case Description module allows the user of Risk Assistant to enter or modify both the descriptive information regarding a site of potential chemical release and the sampling and analytical data (including quantitation limits) associated with that site. It also allows the user to select subsets of data associated with a site for use in any of the other Risk Assistant analyses. 

Exposure Assessment. As noted above, the Risk Assistant software is intended to build on EPA s existing information base on environmental fate and transport modelling, extending it to risk-relevant exposure calculations. Accordingly, it does not incorporate mathematical models of the environmental transport and fate of chemicals, but takes as its starting point user-specified data on environmental concentrations of chemicals to which people might be exposed. The Additional Analyses discussed below, however, do include tools to assist the risk assessor in selecting appropriate transport models. 

EPA has recently released the first volume containing the results of an effort to obtain the most reliable possible values for a variety of exposure parameters. This document, The Exposure Factors Handbook (4), covers 12 commonly considered exposure scenarios. The exposure assessment module of Risk Assistant incorporates the algorithms for calculating exposures under each of these scenarios, for all environmental media for which the scenario is applicable. The user can select any or all of the exposure scenarios that are relevant to the environmental media that are contaminated at a site. Where more than one contaminated medium could influence a scenario, the user has the option of selecting the most appropriate medium. 

As a further aid to the risk assessor, Risk Assistant incorporates a database of the "average" and "reasonable worst-case" values for the parameters applicable to each of the exposure scenarios. The "average" value is automatically provided as a default. However, such "average" values may not be appropriate for particular locations or populations, and the user has the ability to substitute the "reasonable worst case" parameter value, or any other appropriate value for the specific population under consideration, for each parameter in each scenario. Such an approach provides for risk assessments that are responsive to the context of specific sites, yet retain a fundamental consistency of approach. 

Risk Characterization. Once a quantitative exposure assessment has been made, Risk Assistant allows the user to automatically calculate lifetime excess cancer risk and/or a hazard index for toxic non-carcinogenic effects of chronic exposure for any agent included in the toxicity databases which currently include about 300 compounds. The appropriate hazard values (slope-potency factors and reference doses) for the relevant routes of exposure are automatically retrieved from the databases. The uncertainty calculations in the exposure assessment can also be retrieved to assess the range of risks associated with a given exposure situation. 

Risk Assistant yields a separate risk estimate for each chemical under consideration, and for each route of exposure to the chemical (oral, inhalation, or dermal). The user can readily combine these estimates to obtain an overall estimate of the risks associated with... 

Expert systems planned for Risk Assistant will incorporate the logical structure and information from each of these two documents, and use a series of questions regarding the site and the goals of the modeling exercise to guide the user in selecting an appropriate transport model. Anticipated future developments of these systems will provide more extensive information to the user on the reasoning employed to match models to a user s analytical needs and resources. 

An expert system planned for Risk Assistant addresses the probability that various exposure pathways will be of concern at a hazardous waste site. This module guides users in considering factors that may increase or decrease the likelihood that a chemical will be released from a unit such as a landfill or surface impoundment to any environmental media. If release cannot be ruled out, factors affecting transport to an area of potential exposure are considered. If the presence of contamination in an area of potential exposure cannot be discounted, potential exposure scenarios are reviewed. The end result is a listing of potential exposure pathways that the user may have to consider for the site. 

Databases. The Database component of Risk Assistant allows the user to look up information directly in any of the databases, without using the analytical programs. These databases are automatically called up as necessary during Risk Assistant analyses, but a user may simply want to report specific information about a chemical or chemicals. The databases contained in the system are described below. 

Regulatory and Advisory Standards. In some cases, rather than performing a detailed risk assessment for a specific situation, a user may wish to rely upon the risk assessments that underlie various published regulatory and advisory standards. In other cases (such as at Superfund sites), the user would want to know the relationship between observed concentrations and regulatory/advisory standards even if she or he intended to perform an independent risk assessment. Risk Assistant contains databases of standards and advisory values developed by the Federal government, State governments, and other bodies, such as ... 

State water quality standards will frequently be "applicable" or "relevant and appropriate" requirements for a Superfund site. For most states and chemicals, the particular standards that apply to a water body depend upon the designation of the water body as a member of a particular class, with the set of classes varying among states. Risk Assistant contains an automated procedure to help the user in selecting the most appropriate water body classifications for her or his particular site. 

User Interface. The object of software systems for risk assessment is to make the process of generating or reviewing risk assessments easier for system users. Software that is not easy to learn or use, or that requires constant reference to manuals or other support documents, will do little to help risk assessors faced with a demanding workload. Accordingly, a key emphasis in the development of Risk Assistant is that the software be usable by persons with little or no computer experience, without the need for training, and that the majority of a user s questions can be answered in the software, without the need to refer to manuals. The development of technical manuals is an important part of the Risk Assistant effort, but the user should not need to refer to these manuals frequently. 

To avoid the need for users to rely on manuals, several features have been added to the user interface for Risk Assistant (i.e., the menus by which the user enters and retrieves information). These are described briefly below. In addition, an effort has been made reduce the amount of typing required of the user to a bare minimum and to make the keystrokes that activate the system as obvious as possible. 

Help Screens. Each menu in Risk Assistant has one or more associated HELP screens, accessible by pressing a function key. The HELP screen explains how to select an item from a menu, change a default value, or enter data. 

Reference Screens. Whenever Risk Assistant provides a default value, a REFERENCE screen can be called up to provide a citation for the literature source from which the value was taken. 

Notepad. Each menu in Risk Assistant has an associated Notepad screen. By pressing a function key, the user can call up the notepad for the menu, and use it to explain important features of his or her assessment, or the reasons underlying the selection of particular values. 

Novice User Pathway The user of Risk Assistant has the option, at any point, of using the system in either an "experienced user", or a "novice user" mode. A function key toggles between the two modes. In the "novice user" mode, each key menu is preceded by one or more screens explaining its place in the risk assessment process and indicating how to make an appropriate response. 

Authoritative Databases. Efforts to ensure the accuracy of the information in Risk Assistant databases involve both the selection of data sources and Quality Assurance procedures for data entry. As noted below, an effort was made to locate the most authoritative source for each database. Database entries are repeatedly checked against original sources. Finally, the user is supplied with a citation of the original literature source, and so is able to confirm database contents if necessary. 

Integrated Risk Information System (IRIS) - Wherever possible, Risk Assistant obtains information on chemical hazards from the EPA s Integrated Risk Information System (IRIS). All information on chemical hazards contained in IRIS is subject to rigorous peer review and represents and Agency-wide standard value 10). 

Specialized Databases. Some potential users of Risk Assistant may have developed independent estimates of toxic risk associated with chemicals, particularly for chemicals not included in EPA toxic hazard databases. Such users (such as State governments), who typically will have access to considerable toxicological expertise may wish to use these hazard values in Risk Assistant analyses. Such specialized hazard databases can readily be incorporated into the system. 

Referenced Calculations. Exposure assessment involves numerous calculations, covering both cross-media transfers of chemicals and the derivation of exposures from concentrations and scenario-specific parameters. In general terms, such calculations can be viewed as the limiting case (in simplicity) of either theoretical or empirical models. All calculations in Risk Assistant for deriving exposures from concentrations in an appropriate medium (e.g. inhalation exposures from air concentrations) are obtained from the Exposure Factors Handbook (4). Equations for evaluating cross-media transfer for particular exposure scenarios (e.g. volatilization from domestic water to household air) are obtained from literature sources. For such equations, the original reference is provided for the user. 

Expert Systems as "Automated Documents." Sometimes a user needs to make a decision based upon the consideration of categorical or qualitative information, rather than calculations involving numerical parameters. Expert Systems comprise several types of computer programs that address this type of information. Risk Assistant will contain a variety of small expert systems that assist users in different aspects of the risk assessment process. 

Generation of Risk Assessments. Much of the risk assessment workload faced by EPA regional personnel and state personnel does not involve the development of detailed risk assessments that attempt to be as accurate as possible in characterizing particular situations. These professionals need to use relatively simple risk assessments to set risk management priorities. They need to be able to decide which situations require immediate attention, which can be deferred for later action because they pose little risk even under worst-case conditions, and which require more detailed evaluation. Risk Assist-ant can help to make such decisions in a consistent manner, while maintaining sensitivity to important features of particular situations. ... 

More Detailed Analyses. When dealing with a more limited number of sites (dozens, rather than hundreds), Risk Assistant allows the user to take specific site conditions into account while maintaining a consistent approach to risk assessment. The assessments can be... 

Summary of Site Information. The case description section of Risk Assistant provides a sufficient level of descriptive detail to enable a user to form a clear conceptual model of the site and to present relevant information concisely. It also enables a summary evaluation of the adequacy of the data base on a site. 

Assistance in Modeling. Risk Assistant does not perform transport modeling, because other EPA-developed systems already provide these capabilities. It does, however, assist the user in selecting the appropriate transport models for a site, if modeling proves to be appropriate. An effort is underway to facilitate the automatic transfer of information between Risk Assistant and EPA modeling software, such as PC-GEMS (3). 

Calculation of Exposure. A great advantage of Risk Assistant is that it allows users to consider a wide range of factors that will influence quantitative exposure estimates (e.g., specific exposure factors for different populations, pathways, and scenarios) with a minimum of effort. Thus, a user can rapidly produce alternative exposure evaluations, including best estimates, reasonable worst-case exposure estimates, and worst case exposure estimates. Moreover, the system provides the user with information on the degree of uncertainty contributed by various assumptions used in the analysis, which can guide the user s future data collection efforts so that they result in maximum reduction of uncertainty. 

Calculation of Lifetime Excess Cancer Risk and Hazard Indices for Chronic Exposure. For each exposure estimate, it is extremely easy to generate corresponding risk estimates. Thus, the user can quickly specify the full range of risks that may reasonably be attributed to a site. If reasonable worst-case or worst-case assumptions indicate minimal risk, it may be possible to defer the action until more pressing problems are addressed. Alternately, the Risk Assistant analyses may indicate current or potential risks that should be immediately ameliorated. When a wide range of risks may apply to a site, it may be important to conduct additional studies to reduce the uncertainties associated with a site. 

Reviews of Risk Assessment Generated by Others. In many cases, it will be important for EPA and state staff to review risk assessments generated by third parties (e.g., contractors or potentially responsible parties). Risk Assistant facilitates such reviews, by providing... 

When a risk assessment under review deviates from the use of standard factors, there may in many cases be a valid reason for so doing the assessment may reflect particular conditions at or near a specific site. The ability to annotate findings in Risk Assistant provides a ready means for reviewers to indicate the importance and/or validity of deviations from standard procedures. 

Sampling/Analysis Checklist. This module of Risk Assistant, developed specifically for the review of Superfund risk assessments, prompts the user to consider key issues in quality assurance and quality control for sampling conducted at a waste site. It provides a concise summary of whether the standards developed under EPA s Superfund program have been met. 

Quantitation and Detection Limits Reviews. Because the quality of laboratory analyses of chemical contamination is critical to the validity of any conclusions about risk, EPA initiated the Contract Laboratory Program (CLP) to ensure consistent, high quality analyses. By comparing reported quantitation limits for samples at a site to quantitation limits specified by CLP, Risk Assistant will provide a report on a key feature of analytical quality sensitivity. 

Comparison of Toxic Hazard Values with Standard Values. For the derivation of valid risk estimates, it is crucial that current hazard estimates from authoritative sources are employed in risk calculations. Risk Assistant enables a reviewer to easily compare the values used in a particular assessment with standard values from IRIS or HEAST. 

Communication. In addition to its use for analyses, Risk Assistant produces several standard types of reports that allow users to synthesize and summarize information on risk in a consistent format. Any assumptions that are used in an analysis are noted in these reports. These reports enable a user to effectively communicate key site information with other personnel, including risk management decision-rmakers and outside risk assessment consultants. 

Record Keeping. Risk Assistant will store and retrieve data entered for every exposure and risk assessment that has been performed and will automatically transfer data from one program to another, eliminating the need for repetitive data entry. It is easy to retrieve and review information from past assessments and to conduct multiple assessments on the same set of data with differing assumptions. Risk Assistant s electronic notepad stores any annotations concerning an assessment. 

Reference. Risk Assistant is a ready reference source that reduces the necessity of flipping through numerous reference books or searching several external databases. 

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