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Thesaurus of Terms Used in Microbial Risk Assessment

Chapter One: Introduction

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The United States Environmental Protection Agency’s (EPA) Office of Water has developed this Thesaurus of Microbiological Risk Assessment (MRA) Terms because it is important for risk assessors, managers, and communicators to have available and to use common, understandable terms and definitions for the various facets of the MRA process. This Thesaurus is a collection of definitions of terms that may be relevant for microbial risk assessment (MRA). It should help risk assessors, managers, and communicators become aware of various definitions so that they can better communicate with each other and avoid misunderstandings. It should also help increase transparency and contribute to a common understanding of the MRA process and presentation of MRA results.

Currently, various program offices within EPA, as well as other Federal Agencies (e.g., Food and Drug Administration [FDA] and United States Department of Agriculture [USDA]) and International Agencies (e.g., World Health Organization [WHO] and Food and Agricultural Organization [FAO]), utilize terms often unique to the activities or MRA applications for that specific agency. Different Agencies may also have different operating definitions for the same term. This Thesaurus seeks to identify the terms that have the most potential to cause confusion due to varying uses for terms.

1.1 Background and Scope

Risk assessment is an important tool used by a variety of disciplines or fields of study. Because the different fields of risk assessment use their own methods and terms and also borrow from other scientific disciplines, much of the nomenclature is broadly used, but narrowly defined within a field. In addition, similar concepts may go by different names in different fields. For example, in ecological risk assessment a stressor interacts with a receptor, whereas in chemical risk assessment for human health scenarios, toxicants (or toxins) interact with humans through various exposure routes. In MRA, hazards interact with hosts either through “primary” and “secondary” exposures. Pointing out these differences is not meant to suggest that these differences are inappropriate, but to help designers and users of risk assessment understand that these differences exist so that as the science of risk assessment evolves, it is less likely that any given term is adopted for multiple uses.

The major fields of risk assessment that contributed terms and definitions to this Thesaurus include:

Because risk assessment is multi-disciplinary, terms and definitions from contributing disciplines are often adopted. Term preference is often determined by the risk assessor’s educational background and areas of expertise. Disciplines that contribute to risk assessment terminology include, but are not limited to: biology, chemistry, computer science, economics, epidemiology, law, mathematics/statistics, medicine (clinical), microbiology, pharmacology, philosophy, policy, toxicology and veterinary sciences. In addition, terms may be favored or disfavored by different government agencies. In many cases the terminology adopted by an agency comes from the legislations that enable that agency’s regulatory authorities. Risk assessors, managers, or communicators that are isolated in one agency’s working culture may not be familiar with how risk assessment terms are used in other agencies.

Terms are generally proposed and modified by mostly informal processes that involve communication between policy makers, risk assessors, industry, academia, the general public, and other stakeholders. One example of the process of creating a definition is when the definition of a term is presented in a draft guidance document and then commented on by stakeholders. In some cases, terms are included in statutes, so they have legal definitions within that context. One example is “safety factor” that is defined by statue for food additives, but has non-legal definitions in other contexts. More formal efforts for evaluating definitions are carried out by the Organisation for Economic Co-operation and Development (OECD) and the International Programme of Chemical Safety (IPCS), such as their joint project on the Harmonisation of Hazard/Risk Assessment Terminology (IPCS/OECD 2004) and the work of the IPCS Exposure Terminology Subcommittee (IPCS 2001).

This Thesaurus of terms and definitions has been compiled based upon existing risk assessment related documents prepared by various national and international entities having responsibilities for conducting, interpreting, or using risk assessments (especially related to microbiological risks). It is not intended to provide all terms and definitions that may be used for various science applications in all facets of microbiology, ecology, chemistry, biology, etc. The intent of this document is to capture those terms and defnintions which appear to have significant risk assessment applications as identified in existing documents. It should be noted that there also may be a few gaps in risk assessment related terms or definitions that were not provided by the various documents searched in the present effort.

This Thesaurus contains a few terms or definitions which are used in specific regulations; however, the bulk of relevant regulatory terms are not included because they have specific definitions that are context-dependent. Any terms identified here as regulatory definitions should not be considered as the definitive source and should be further examined in the referenced regulatory document. It is important for anyone using this Thesaurus to know that in certain regulatory uses of terms there may be a specific context for the definition and additional background information for its uses may be provided in that regulatory document that are not covered here. Because there is an authoritative source for the definitions of regulatory and statutory terms (they can be found in the Code of Federal Regualtions or the United States Code) they are not covered comprehensively in this Thesaurus.

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1.2 Sources Consulted

Numerous (mostly online) glossaries, lists of terms and definitions, and publications were consulted during the development of the Thesaurus. Throughout the Thesaurus, primary (and in some cases secondary) sources for each definition are indicated. The primary sources consulted are briefly described below. Complete references for all primary sources, including URLs (as available), are provided in the Reference section at the end of the Thesaurus.

EPA Sources

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Other U.S. Sources

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International Sources

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Water Quality Standards | Drinking Water | Research and Development

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