Toxic ignorance has become a major issue in the current debate on chemicals policy both in the EU and the US.1 The term refers to a lack of knowledge of the health and environmental properties, as well as the mechanisms of action, of Existing Chemicals. There can be little doubt  that this term also goes to the heart of the problem facing us today. However, the availability of such data – at any rate for individual substances – gives rise to a new problem, which is that such data must now be evaluated in  light of the actions that need to be taken.