Doseâ"response models: how might we think about linearity and nonlinearity?

We add to the issues raised by Dr David Ropeikâ(TM)s article Risk Communication and Non-Linearity (forthcoming, BELLE Newsletter , 2008) regarding the thinking about the acceptance of linear and nonlinear (hormetic) doseâ"response models. We summarize some of the perceptual aspects discussed by Ropeik (2008) and comment on decision-making by the single decision-maker. It seems that the heuristics discussed by Ropeik (2008) are related to those private decision-makers who may not benefit from extensive technical, scientific, and legal advice sufficiently to make well-informed decisions and, perhaps more importantly, may not have the funds for that advice. Doseâ"response models are intangible, abstract quantities: unlike private goods and services, they are not priced by the market. We suggest a duality between the private and the public decision-maker that in the end may loose its crispness, because it can occur in the same person. Nonetheless, this duality is evident at the analysis phase of decision-making, relative to the decision phase, and thus, provides a convenient way to address the issues addressed by Ropeik (2008). In particular, for at least legal and common sense reasons, the public decision-maker must follow a scientific-analytical causal process â" as represented by models of doseâ"response â" to select and justify her choice of one over the other. Whether the final decision as to which model is to be used in regulatory law is a matter that goes beyond the analytical aspects of the choice and is governed by political and other aspects of governance. [PUBLICATION ABSTRACT]