The authors had complete control over the design, conduct, interpretation, and reporting of the analyses included in this letter. The contents are solely the responsibility of the authors and do not necessarily reflect the official opinions or policies of the authors’ employers or clients.

None of the authors received specific financial support or honorarium as compensation for developing this letter. Several authors are members of the Evidence-Based Toxicology Collaboration (EBTC), and M.L. Stephens and S. Hoffmann serve as the secretariats for the North American and European EBTC Steering Committees, respectively, for which they are compensated for their time. The EBTC’s overall aims are to improve toxicological decision making, facilitate the modernization of the toxicological toolbox, and reinvigorate the safety sciences (see http://www.ebtox.com). S. Hoffmann, J.R. Fowle III, and J. Goodman are consultants and have worked on a range of toxicity and risk assessment issues for a wide variety of clients. R.A. Becker and N.B. Beck are employed by the American Chemistry Council, a trade association of chemical manufacturers. A. Boobis, D. Fergusson, M. Lalu, and M. Leist are employed by institutes of higher education. In the past 3 years, A. Boobis and M. Leist have worked on a range of toxicity and risk assessment issues for a number of clients; this has included some consultancies.

All authors contributed equally and are listed in alphabetical order.