Cassin M H, Lammerding A M, Todd E C, Ross W, McColl R S
Decisionalysis Risk Consulting, Ottawa, ON, Canada.
Int J Food Microbiol. 1998 May 5;41(1):21-44. doi: 10.1016/s0168-1605(98)00028-2.
Quantitative Risk Assessment (QRA) is a methodology used to organize and analyze scientific information to estimate the probability and severity of an adverse event. Applied to microbial food safety, the methodology can also help to identify those stages in the manufacture, distribution, handling, and consumption of foods that contribute to an increased risk of foodborne illness, and help focus resources and efforts to most effectively reduce the risk of foodborne pathogens. The term Process Risk Model (PRM) is introduced in this paper to describe the integration and application of QRA methodology with scenario analysis and predictive microbiology to provide an objective assessment of the hygienic characteristics of a manufacturing process. The methodology was applied to model the human health risk associated with Escherichia coli O157:H7 in ground beef hamburgers. The PRM incorporated two mathematical submodels; the first was intended to described the behaviour of the pathogen from the production of the food through processing, handling, 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 simulation was used to assess the effect of the uncertainty and variability in the model parameters on the predicted human health risk. The model 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 may be reasonable for the home-prepared hamburgers described by this model. The efficacy of three risk mitigation strategies were evaluated by modifying the values of the predictive factors and comparing the new predicted risk. The average probability of illness was predicted to be 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 reduction in the concentration of E. coli O157:H7 in the feces of cattle shedding the pathogen and one aimed at convincing consumers to cook hamburgers more thoroughly. The conclusions of this approach are only accurate to the extent that the model accurately represents the process. Currently, uncertainty and ignorance about the hygienic effects of the individual operations during production, processing, and handling limit the applicability of a PRM to specify HACCP criteria in a quantitative manner. However, with continuous improvement through stimulated research, a PRM should encompass all available information about the process, food, and pathogen and should be the most appropriate decision-support tool since it represents current knowledge.
定量风险评估（QRA）是一种用于整理和分析科学信息以估计不良事件发生概率和严重程度的方法。应用于微生物食品安全领域时，该方法还可帮助确定食品生产、分销、处理和消费过程中那些会增加食源性疾病风险的阶段，并有助于集中资源和精力，以最有效地降低食源性病原体的风险。本文引入了过程风险模型（PRM）这一术语，用于描述QRA方法与情景分析和预测微生物学的整合与应用，以便对生产过程的卫生特性进行客观评估。该方法被应用于对牛肉汉堡中大肠杆菌O157:H7相关的人类健康风险进行建模。PRM包含两个数学子模型；第一个旨在描述病原体从食品生产到加工、处理和消费的行为，以预测人类接触情况。然后，将接触估计值用作剂量反应模型的输入，以估计与食用该过程生产的食品相关的健康风险。蒙特卡洛模拟用于评估模型参数的不确定性和变异性对预测的人类健康风险的影响。该模型预测，每餐食用这种牛肉汉堡，极幼儿童患溶血性尿毒综合征的概率为3.7×10⁻⁶，死亡概率为1.9×10⁻⁷。对于所有的汉堡餐来说，这些估计值可能偏高，但对于该模型所描述的家庭自制汉堡来说可能是合理的。通过修改预测因子的值并比较新的预测风险，评估了三种风险缓解策略的效果。在一种假设的缓解策略下，即通过降低储存温度来减少零售储存期间的微生物生长，预计疾病的平均概率将降低80%。预计该策略比一种假设的干预措施更有效，后者估计可合理降低携带病原体的牛粪便中大肠杆菌O157:H7的浓度，还有一种策略是说服消费者将汉堡烹制得更熟。这种方法的结论仅在模型准确反映过程的程度上是准确的。目前，对于生产、加工和处理过程中各个操作的卫生效果存在不确定性和未知因素，这限制了PRM以定量方式指定危害分析与关键控制点（HACCP）标准的适用性。然而，通过积极的研究不断改进，PRM应涵盖有关过程、食品和病原体的所有可用信息，并且由于它代表了当前的知识，应该是最合适的决策支持工具。
