At worst, it is useless, or leads to inappropriate action. This may involve extrapolation of limited test data. Several orders of magnitude of uncertainty may be involved, see Table 4.4. If the risk is determined to be nontrivial, we move onto the next stages. For illustration, the text provides the example of trichloroethylene ingestion exposure via drinking water.
Lifetime risk is estimated versus the concentration of the trichloroethylene in drinking water.
Math models are used to extrapolate high dose data to the range of low concentrations of concern to public health. This is shown in Fig. A dose manifestation diagram is illustrated in Fig. 4.4 of the text. This is for global warming.