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Guidance for Microbial Risk Assessment
Risk Assessment Forum
Although EPA has guidance for chemical risk assessment, Agency-wide guidance for assessing the risks to human health from microorganisms has not been developed. Microbial risk assessment differs significantly from chemical risk assessment. For example, microorganisms can proliferate in the host; they have different die-off rates in the environment; there are risks of secondary transmission; hosts may or may not acquire partial or complete immunity, and animal responses may be very different from human responses to the same microbe. There are a number of microbial risk assessment procedures and protocols used within the Agency (OW, ORD, OPPTS, and OSWER), as well as other federal Agencies (e.g., USDA and FDA) and the international community (e.g., the UN Food and Agriculture Organization and World Health Organization). EPA's Risk Assessment Forum, in cooperation with other Federal agencies, are working to leverage their resources, experience, and expertise to generate tools, methods and guidelines for performing microbial risk assessment.
The purpose of this inter-agency activity is to develop guidance on common approaches, where practical, to perform microbial risk assessment (MRA). The goal is to produce a flexible set of tools, methods, and approaches that can be selected from for use in varied situations. Issues specific to microbial risk, e.g., secondary transmission, development of immunity, and estimation of dose-response, will be addressed. As contributory documents are generated, they will be posted to this website, along with the draft and final Microbial Risk Assessment Guidance.
Activities and Reports:
Inter-Agency MRA Workgroup: The InterAgency Microbiological Risk Assessment Guidance development workgroup is comprised of U.S. federal agencies that have a role in or use MRA procedures to conduct their work. The document when completed and reviewed by experts will serve as a noncompulsory guidance document for agencies and their contractors to use in conducting MRA.
MRA Framework: The first step in development of risk assessment guidance is often the creation of an organizing framework. EPA's Office of Water working with the International Life Sciences Institute, ILSI, developed a framework. This framework is currently in use by EPA and others and is available here (29pp, 720KB, About PDF) 
The EPA Risk Assessment Forum panel identified the need to look at all available frameworks and conduct a comparison. A paper on the topic was commissioned and is available below.
Thesaurus The Office of Water also developed, with assistance of a contractor, a comprehensive Thesaurus for microbial risks.
Frameworks Comparison: The Microbial Risk Assessment Frameworks, Principles and Approaches* (147pp, 1.2MB, About PDF) document was produced under a contract to the EPA by Dr. Rebecca Parkin, George Washington University School of Public Health and Health Services, and Environmental Research Group.
Approaches for conducting MRA are rapidly evolving for decision-making about microbial pathogen-related health risks. The purposes of this paper was to identify the similarities and differences of current MRA frameworks, describe key scientific challenges, compare diverse applications of the frameworks, and provide insight for development of guidance for conducting MRA. Online searches and contacts with experts were used to identify current frameworks and completed MRAs. The scope of the search was worldwide, but the comparison of applications was limited to government-sponsored MRAs.
*Note: If you need alternative accommodations to view this PDF, which is not compliant with accessibility standards, please contact the Risk Assessment Forum staff at (202)564-6483.
Workshop on Challenges to Integrating Immunotoxicological and Microbial Risk Assessment for Susceptible Populations and Life Stages, and Real World Application of Microbial Risk Assessment Methods (30pp, 225KB, About PDF) . Future workshops are planned.
The EPA Risk Assessment Forum (RAF) convened a workshop of Agency, interagency and invited experts to address the intersection of human life stages, immunotoxicity impacts, and microbial disease susceptibility. The genesis for this workshop was the recognition that it is difficult to quantify the uncertainty surrounding microbial risks for sensitive groups, populations and lifestages. To complicate risk assessment even further, persons exposed to microbial pathogens are often exposed to chemical stressors, or even immunotoxins. The net effects of these additional stressors, or the effects based on immature immune system, are very real issues to the risk assessors at the EPA. There is also relatively little data on how these factors influence the dose-response to the pathogen(s) of interest. Therefore it was logical to seek out some of the experts in the several fields related to this issue, to determine what the state of the scientific knowledge was in this area.
The workshop was held on February 12-13, 2007 at the Crystal City Marriott in Arlington, Virginia. A wrap-up session was held on March 20, 2007 in Washington, D.C., to identify lessons learned and next steps.
Symposia at annual meetings of professional organizations. This workgroup has conducted two at the annual meeting of the Society for Risk Analysis.
The issues papers, workshop report, and thesaurus were developed by contractors to the U.S. Environmental Protection Agency. (Some individual EPA experts contributed specific discussions on topic(s) for which he or she has scientific expertise or knowledge of current Agency practice). The views expressed are those of the authors and do not necessarily reflect the views or policies of the EPA and should not be construed as implying EPA consent or endorsement.