Single Exposure vs Multiple Exposure

All currently known human or animal feeding trials have used single (bolus) exposures and monitored for subsequent adverse outcomes. In actual exposure scenarios, multiple exposures, for example at different meals or from different routes (food, water, contact, etc.). may occur. To appfy dose-response models based on bolus doses to these latter scenarios it is necessary to make an assumption about how multiple exposures and doses may combine to produce an effect. At present, the default assumption used is one of statistical independence of multiple exposures (Haas, 1996). If p\,pi-,-- ■ Pn represent risks from individual doses (such as individual days), the risk of one or more adverse outcomes from the joint exposure (pt) is written as:

It is likely, however, that with further developments in the field of microbial dose-response assessment the framework for estimating joint risks from multiple exposures will evolve.

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