QUANTITATIVE RISK ASSESSMENT FOR ESCHERICHIA-COLI O157-H7 IN-GROUND BEEF HAMBURGERS

Quantitative Risk Assessment (QRA) is a methodology used to organize a nd analyze scientific information to estimate the probability and seve rity of an adverse event. Applied to microbial food safety, the method ology can also help to identify those stages in the manufacture, distr ibution, handling, and consumption of foods that contribute to an incr eased risk of foodborne illness, and help focus resources and efforts to most effectively reduce the risk of foodborne pathogens. The term P rocess Risk Model (PRM) is introduced in this paper to describe the in tegration and application of QRA methodology with scenario analysis an d predictive microbiology to provide an objective assessment of the hy gienic characteristics of a manufacturing process. The methodology was applied to model the human health risk associated with Escherichia co li 0157:H7 in ground beef hamburgers. The PRM incorporated two mathema tical submodels; the first was intended to described the behaviour of the pathogen from the production of the food through processing, handl ing, and consumption to predict human exposure. The exposure estimate was then used as input to a dose-response model to estimate the health risk associated with consuming food from the process. Monte Carlo sim ulation was used to assess the effect of the uncertainty and variabili ty in the model parameters on the predicted human health risk. The mod el predicted a probability of Hemolytic Uremic Syndrome of 3.7 x 10(-6 ) and a probability of mortality of 1.9 x 10(-7) per meal for the very young. These estimates are likely high for all hamburger meals, but m ay be reasonable for the home-prepared hamburgers described by this mo del. The efficacy of three risk mitigation strategies were evaluated b y modifying the values of the predictive factors and comparing the new predicted risk. The average probability of illness was predicted to b e reduced by 80% under a hypothetical mitigation strategy directed at reducing microbial growth during retail storage through a reduction in storage temperature. This strategy was predicted to be more effective than a hypothetical intervention which estimated a plausible reductio n in the concentration of E. coli 0157:H7 in the feces of cattle shedd ing the pathogen and one aimed at convincing consumers to cook hamburg ers more thoroughly. The conclusions of this approach are only accurat e to the extent that the model accurately represents the process. Curr ently, uncertainty and ignorance about the hygienic effects of the ind ividual operations during production, processing, and handling limit t he applicability of a PRM to specify HACCP criteria in a quantitative manner. However, with continuous improvement through stimulated resear ch, a PRM should encompass all available information about the process , food, and pathogen and should be the most appropriate decision-suppo rt tool since it represents current knowledge. (C) 1998 Elsevier Scien ce B.V.