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depending on the extent of the knowledge available, the complexity of the problem, and the time available to conduct the assessment. In quantitative risk assessments, risk is expressed as a numerical estimate of the chance of illness or death after exposure to a specific hazard. This estimate represents the cumulative probabilities of certain events happening and the uncertainty associated with those events. A qualitative risk assessment, on the other hand, uses verbal descriptors of the risk and uncertainties, and often involves the aggregation of expert opinions.

Of the four approaches, the quantitative risk assessment-based approach is the most scientifically rigorous and provides insight into the level of risk associated with specific exposures and the degree of uncertainty inherent in the risk estimate. An example of the use of a risk estimate and associated uncertainty is the current standard for hypoallergenic infant formulas, where there is 95% certainty that 90% of the sensitive population will not react (American Academy of Pediatrics, 2000). The risk assessment-based approach is preferred when a biological threshold cannot be justified scientifically. Several recent papers have discussed the application of the risk assessment-based approach to food allergens (Bindslev-Jensen et al., 2002; Moneret-Vautrin and Kanny, 2004; Cordle, 2004; Wensing et al., 2002a).

The issues that need to be considered when using a risk assessment-based approach include:

  • What is the biological endpoint or biomarker of concern?

  • Is the response measurable?

  • What is the population (or sub-population) of interest?

  • What are the exposure levels?

  • What data and assumptions are needed for the assessment, and how do gaps in the

existing data affect the level of uncertainty?

Other issues that should be considered in regard to understanding the relationship between the exposure level and nature of the response include:

  • How sensitive and accurate are the available analytical methods?

  • How do changes in individual sensitivities over time and within populations contribute to the overall uncertainty?

  • What are the limitations of the clinical studies (e.g., small number of volunteers, not testing the most sensitive subpopulation) that are used to determine the dose- response relationship and how do these limitations contribute to the overall uncertainty?

  • Which dose-response models (e.g., threshold, non-threshold) are appropriate?

It is not clear whether the data and modeling techniques available at the present time are sufficient to allow use of the risk assessment-based approach to establish thresholds for food allergens and for gluten. As an example of the complexity of this approach, the following describes the process of developing a dose-response model that can be used in a quantitative risk assessment:

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