In a paper last year in Archives of Toxicology, “Toxicological comments to the discussion about REACH”, a group of distinguished European community toxicologists (Greim et al. 2006) expressed their opinions on discussions about the extent to which in vitro studies and considerations of structure activity relationships provide sufficient information to waive repeated exposure studies in animals. The authors argued that critical data needed for hazard identification and risk assessment can only be developed by conducting repeat dose studies in animals. They consider the data sets from these studies to be essential for risk assessment. In their abstract, they note that, “The evidence that available alternatives would support such replacement is weak. Progress to improve their value for risk assessment purposes is bound to be slow because the issues are very complex. As a group of European toxicologist we strongly support the need for more research support in these areas, but we believe that over claims for progress is damaging their development.”
We appreciate the concerns raised about too rapid replacement of these repeat studies without a clear path for how data sets from in vitro or SAR evaluations would supplant these more traditional toxicity studies. However, we disagree strongly with the conclusions of the commentary on the state of development of these methods for decision making. More importantly, we feel compelled to take exception with several points presented or inferences made in this paper. The points that require some discussion are: (1) current testing/risk assessment strategies represent an optimal approach for making decisions regarding human health risks of chemicals; (2) the goal of a replacement is to develop tests that provide perfect correspondence with the current in vivo toxicity testing approaches; (3) in vitro methods cannot provide information regarding dose–response necessary for risk assessments; and (4) approaches to introduce new methods for toxicity testing and risk assessment reflect consideration of cost reduction and decreased animal use rather than decisions taken on the basis of toxicological considerations. We briefly discuss each point below.