By 202380261
Threshold Dose
Discussion
➤ For many chemicals and effects, there will be a dose below where no effect or response is observed. This is known as the threshold dose.
➤ This concept implies that a no observed adverse effect level (NOAEL) can be determined and that this value can be used to determine the safe intake for food additives and contaminants such as pesticides.
➤ Noncarcinogenic substances are characterized by a threshold below which the body is able to cope with or recover from the exposure. A brief or low exposure leaves no consequence until the next exposure.
➤ Carcinogenic substances are different as they have no such threshold. All repeated exposures to a carcinogenic substance add up, and the risk is never zero. At low doses, the risk is proportional to the exposure.
e Figure 3. Dose response curves. LOAEL; lowest- observed-adverse-effect level, ED 50; median effective dose, LD 50 ; median lethal dose. Source:
Dose-response curves for carcinogens are assumed to have no threshold; that is, any exposure produces some chance of causing cancer.