Examining the risks and benefits of considering both the traditional dose--response and hormesis in arriving at an acceptable exposure level.

In examining traditional dose-response and hormesis, we have considered the case examples of pulmonary hyperplasia following inhalation of carbon black and pulmonary hyperplasia after methyleneindolenine (3MEIN) exposures, development of irreversible pulmonary fibrosis, effect of continuous exercise and low-level lead exposures, and colorectal cancer. Adaptation can be used to estimate conventional dose responses. All cases discussed provided increased information about the reactions if hormetic features were included. In only the shigatoxin case was there clear irrefutable evidence that beneficial hormetic properties exist and must be considered; however, the one-in-six advantage is too great to ignore the potential benefits of hormesis. We recommend such hormetic properties be considered together with conventional dose responses to improve estimates of chemical risk.