PRINCIPLES OF TOXICOLOGY

16 GENERAL PRINCIPLES OF TOXICOLOGY
Figure 1.2 The no effect region is the range of doses that falls below the threshold dose. The threshold is the
highest dose which elicits no effect (or the dose below which a response is not observed).
Figure 1.3 (a) The dose-response curve can have a variety of shapes, including line 1, which is linear; line 2,
which is sublinear; and line 3, which is supralinear. (b) U-shaped curve representing a dose-response relationship
for a chemical with beneficial, as well as adverse effects. At very low doses, a beneficial effect occurs, which is
lost with increasing dose. Even higher doses produce a toxic effect. Other variations on the shape of the
dose-response curve are possible, depending upon how toxic and beneficial effects are portrayed.