Society For Risk Analysis Annual Meeting 2012

Advancing Analysis

Session Schedule & Abstracts

* Disclaimer: All presentations represent the views of the authors, and not the organizations that support their research. Please apply the standard disclaimer that any opinions, findings, and conclusions or recommendations in abstracts, posters, and presentations at the meeting are those of the authors and do not necessarily reflect the views of any other organization or agency. Meeting attendees and authors should be aware that this disclaimer is intended to apply to all abstracts contained in this document. Authors who wish to emphasize this disclaimer should do so in their presentation or poster. In an effort to make the abstracts as concise as possible and easy for meeting participants to read, the abstracts have been formatted such that they exclude references to papers, affiliations, and/or funding sources. Authors who wish to provide attendees with this information should do so in their presentation or poster.

Common abbreviations

Symposium: Innovative QRA Models for Food Safety: Complex Models to Answer Complex Questions

Room: Pacific Concourse H   1:30 - 3 PM

Chair(s): Jane Van Doren, Regis Pouillot

Sponsored by MRASG

Risk assessment supports risk-based decision making in food safety. The type of risk assessment required to answer specific risk manager questions depends on the question as well as the complexity of food processes, food-pathogen interactions and food safety systems. In situations when complex interactions between parameters are expected, complex models, complex mathematical methods, and/or innovative computer solutions are required. This symposium will present four examples of these risk assessment activities currently developed by US federal agencies and their partners. As an example, the development of a discrete event model was needed to track cross-contamination with time in deli departments. Such models converge slowly and its development needed the use of innovative, specific computational tools. Similarly, a comparative risk assessment from consumption of raw- vs. pasteurized-milk cheeses that accounted for bacterial growth in varying environmental conditions as well as the spatial distribution of contaminants found that these factors dramatically impacted the efficacy of predefined risk management options. Assessment of risk in these kinds of complex situations reveals unexpected results that might be hidden in simpler frameworks. These examples illustrate how innovative models help risk managers to develop and test innovative risk management options.

T3-F.1  13:30  Cross-contamination modeling of L. monocytogenes in retail environments. Gallagher D*, Pouillot R, Bauer N, Dennis S, Kause J; Virginia Tech, FDA, USDA, FDA, USDA

Abstract: A stochastic discrete event model was developed to simulate worker behavior in retail delis to evaluate the potential for and control of L. monocytogenes cross contamination. The concentrations of L. monocytogenes in retail sales were then modeled through consumer handling to produce a risk of listeriosis. The model tracks L. monocytogenes cross contamination across different sites and foods in the deli area as the workers perform their normal duties of serving customers, cleaning equipment, changing gloves, etc. The model thus serves as a “virtual deli” where the different worker behaviors or food characteristics can be evaluated for their public health impact. The Monte Carlo model was written in R with parallel processing, and run on a high performance computing system typically with 200 to 1000 computer cores. A run consisted of one million customer servings for each of 100 stores. The model had extensive data requirements. Industry data, literature reviews and the results from several research projects specifically designed to support the risk assessment were used to populate the model. A range of over 25 specific risk reduction strategies were evaluated for different retail store situations, e.g. clean stores, stores with niches, etc. Consistent beneficial risk reduction strategies at the retail level included sanitation, temperature control, and niche control. Consistent beneficial production plant strategies included lower bacterial levels in product and the use of growth inhibitors. The complex model is therefore able to meet the needs of USDA and FDA risk managers who will use the results to evaluate proposed new or modified regulations.

T3-F.2  13:50  Quantitative assessment of the risk of listeriosis from soft-ripened cheese consumption in the United States and Canada. Pouillot R*, Nguyen L, Dennis S; Fda/Cfsan, Health Canada - Santé Canada

Abstract: A risk assessment model developed to estimate the risk of listeriosis associated with soft-ripened cheese produced and consumed in both the United States and in Canada, has all of the usual features of quantitative microbial risk assessment and several enhancements. The model considers farm and processing plant sources of L. monocytogenes contamination, growth under changing conditions during ‘traditional’ and ‘stabilized process’ cheese-making, and growth in a solid medium. The baseline model considers the manufacture of cheese made from pasteurized milk, using a ‘stabilized cheese’ process, where the source of contamination is from environmental L. monocytogenes in the processing plant. An alternative model for raw milk cheese considers environmental contamination on farm and in the processing plant and contamination from mastitic cows. The results inform FDA and Health Canada about the impact of strategies designed to reduce listeriosis such as: i) changes to current regulations for 60-day aging; ii) mitigations that lead to some log reduction in bulk milk contamination; and, iii) testing programs for milk and/or finished product cheeses.

T3-F.3  14:10  Mitigation of foodborne illnesses by implementation of pathogen controls at beef slaughter establishments. Johnson RA*, Schlosser WD, Bauer NE; United States Department of Agriculture Food Safety and Inspection Service

Abstract: Enteric pathogens, such as E. coli O157:H7, are present on hides and in the gastrointestinal tracts of cattle and can contaminate beef carcasses during hide removal and evisceration. Cattle slaughter establishments employ numerous interventions to control this contamination. FSIS developed a risk assessment to evaluate the impact of interventions at several critical points throughout the slaughter process. The risk assessment estimates the number of E. coli O157:H7 illnesses from beef consumption that could be prevented annually if the number or type of interventions was improved. Using FSIS data on cattle slaughter establishment practices, we identified 11 interventions applied on hides or on pre- or post-evisceration carcasses and determined the number of establishments that currently utilize each intervention individually or in combination. The risk assessment includes a slaughter process model that simulates the transfer of contamination from hides and gastrointestinal tracts to the carcass during dehiding and evisceration. We then estimated the contamination in grinder lots of ground beef under current conditions as well as for scenarios that involve different types of interventions. We utilized a streamlined approach that attributes a proportional decrease in illnesses to a given decrease in contamination of ground beef as a result of slaughter practices, obviating the need to model pre-harvest or consumer practices common in a traditional farm-to-fork risk assessment. The risk assessment showed that the overall effect of adding interventions is dependent on the effectiveness associated with the particular intervention, how much beef is already processed under the given intervention, and how many other interventions are already applied in a given establishment. Interventions applied post-evisceration had a greater impact on reducing illnesses because they have the opportunity to remove contamination from both the hide and the gastrointestinal system.

T3-F.4  14:30  The Joint United States-Canadian Norovirus in Shellfish Quantitative Risk Assessment: Capturing Variability and Taming Uncertainty. Van Doren JM*, Holtzman J, Buenaventura E, Burkhardt III W, Calci KR, Catford A, Edwards R, Hajen W, Pouillot R, Smith M; U.S. Food and Drug Administration, Health Canada, Canadian Food Inspection Agency, Environment Canada

Abstract: Many foodborne norovirus outbreaks can be traced to transmission from infected food handlers. However, most shellfish-related outbreaks have been traced to contamination of the water in the shellfish growing area. Although shellfish harvested for interstate commerce are grown in approved areas meeting water quality standards, viral contamination from inadequately treated municipal wastewater outfalls or sporadic sources of contamination (i.e. overboard discharge) can take place. Bioaccumulation of pathogenic microbiological contaminants by filter-feeding bivalve shellfish including oysters, clams, and mussels, can increase the risk of illness when consumed. Members of the United States and Canadian governments from the U.S. Food and Drug Administration, Health Canada, Canadian Food Inspection Agency, and Environment Canada are jointly developing a quantitative risk assessment to evaluate the impact of preventive controls in reducing the number of shellfish-related Norovirus illnesses. The risk assessment must synthesize the risks from controllable and uncontrollable influences informed by wastewater treatment plant flow and treatment efficiency, dilution, environmental inactivation, shellfish bioaccumulation, post-harvest treatment, and consumption patterns. The risk assessment must properly describe how the risk depends on the influences and how the influences vary so that managers understand how the risk changes under various risk management strategies. The risk assessment also needs to inform risk managers about the uncertainty associated with risk outputs. This presentation will highlight some of the innovative approaches taken in the design and development of this risk assessment.

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