Fig. 2.
With time, better knowledge allows appreciation that lower exposures must be ensured in order to avoid adverse health effects, and it is also realized that very small doses are tolerated without any risk of adverse effects. However, only with near-perfect knowledge will the two curves meet. It is the purpose of modern toxicology to responsibly interpret science so that adverse effects are avoided, although with due recognition that some low-level exposures must be allowed. Redrawn from (63).