Reducing risks for society without undermining the advancement of science or preventing innovation is a constant challenge for policy makers, who must find the appropriate balance. In spite of being referred to in more than 15 international agreements there is no single definition of the precautionary principle. The report suggests that the precautionary principle should allow, or in some cases justify, regulatory action in the absence of complete scientific evidence about a particular risk scenario. Action however should always be dependant on reasonable, albeit not complete, evidence of considerable potential risks.