Risk Characterization Choices And Risk Exaggeration:

            The characterization of the risk associated with a specified dose of a chemical is influenced by several factors.  Regulatory agencies choose values for these factors designed to result in upper-bound characterizations of human health risks as opposed to true values of risk.  These choices are usually driven by regulatory policy and not science.  One of the major choices made by regulatory agencies is to assume that high-dose behavior in the most sensitive gender, strain, and species of experimental animals is predictive of low-dose behavior in humans.

            Some choices frequently made by regulatory agencies to increase the cancer slope factor (CSF) or cancer potency are as follows:

            i)          choosing the data set (study, species, gender, tissue site, and severity of response) 
that results in the largest CSF,

            ii)         choosing the method of fitting the relationship between the observed response
frequencies and the corresponding dose levels (dose-response modeling) that results
in the largest CSF,

            iii)        choosing the method of extrapolating from high experimental doses to lower doses (high-to-low-dose extrapolation) that results in the largest CSF,

            iv)        choosing the method of extrapolating from animals to humans (interspecies extrapolation) that results in the largest CSF, and

            v)         choosing the measure of risk (extra risk instead of added risk) that results in the largest CSF.