A Critique of the Use of Hormesis in Risk Assessment

A critique of the use of hormesis in risk assessment. Kitchin, KT; and Drane, Wanzer Summary: There are severe problems and limitations with the use of hormesis as the principal dose-response default assumption in risk assessment. These problems and limitations include: (a) unknown prevalence of hormetic dose-response curves, (b) random chance occurrence of hormesis and the shortage of data on the repeatability of hormesis, (c) unknown degree of generalizabiIity of hormesis, (d) there are dose response curves that are not hormetic, therefore hormesis cannot be universally generalized, (e) problems of post hoc rather than a priori hypothesis testing, (f) a possible large problem of `false positive' hormetic data sets which have not been extensively replicated, (g) the `mechanism of hormesis' is not understood at a rigorous scientific level, (h) in some cases hormesis may merely be the overall sum of many different mechanisms and many different dose-response curves - some beneficial and some toxic. For all of these reasons, hormesis should not now be used as the principal dose-response default assumption in risk assessment. At this point, it appears that hormesis is a long way away from common scientific acceptance and wide utility in biomedicine and use as the principal default assumption in a risk assessment process charged with ensuring public health protection.