SECOND REPORT OF THE COCENE WORKING GROUP ON RISK ASSESSMENT 
7 
Tnc natural environment is actually a succession of individual environments, and 
when the loss of survival each of these is taken into account and multiplied 
together, the 10 ^ figure is clearly obtained. 
2) The original emphasis for the testing contracts was concerned with the 
possibility of converting EK2 systems to EK3. Since the revised Guidelines do 
not specify EK3 containment in any experiments, it was concluded that what was 
needed was information on survival of cloned fragments in EK1 experiments (such 
as in x! 666) • Such experiments would, of course, be for risk assessment rather 
than in preparation for certification of vectors. 
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