Session VI: Estimating Likelihood and Exposure, Part II

Abstract

Exposure or likelihood of occurrence of an identified hazard is a key factor used by regulators in determining the magnitude of risk. One example of exposure is the amount of gene flow between transgenic crops and their non-transgenic counterparts or their compatible wild relatives. Gene flow itself is not a hazard, but instead represents the exposure of the environment to transgenes and the potentially novel traits that they produce. In assessing the risk presented by transgenes, the amount of gene flow may vary geographically, and depends upon several factors, including climatic conditions, existing pollinators, and day length. The variability in levels of gene flow makes it sensible to make a worst-case assumption when estimating exposure from gene flow; that is, to assume that gene flow and introgression will occur to other compatible populations, particularly wild relatives. Consequently, the most important fact to establish is whether or not gene flow can occur. Determining the precise amount of gene flow and its geographic variation