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Dose
Discussion
➤ used to characterize the total amount of material to which an organism is exposed;
➤ defines the amount of chemical given in relation to body weight.
➤ usually implies the exposure dose, the total amount of chemical administered to an organism or incorporated into a test system.
➤ may not be directly proportional to the toxic effects since toxicity depends on the amount of chemical absorbed.
correctly describes only the actual amount of chemical absorbed when the chemical is administered orally or by injection.
➤ Under these circumstances, the administered dose is identical to the absorbed dose; other routes of application such as dermal application or inhalation do not define the amount of agent absorbed.
Different chemicals have a wide spectrum of doses needed to induce toxic effects or death.
➤ To characterize the acute toxicity of different chemicals, LD 50 values are frequently used as a basis for comparisons.
➤ Certain chemicals are very toxic and produce death after administration of microgram doses, while others are tolerated without serious toxicity in gram doses.
Table 2. LD 50 values (rats) for some chemicals