Toxicity 33
Toxicity 33 : The toxicity of a substance is the capacity to cause injury to a living organism (WHO, 1978a). A highly toxic substance will cause damage to an organism if administered in very small amounts and a substance of low toxicity will not produce an effect unless the amount is very large. However, toxicity cannot be defined in quantitative terms without reference to the quantity of substance administered or absorbed, the way in which this quantity is administered (e.g., inhalation, ingestion, injection) and distributed in time (e.g., single or repeated doses), the type and severity of injury, and the time needed to produce the injury. Acute Toxicity: Adverse effects occurring within a short time of administration of a single dose of a chemical, or immediately following short or continuous exposure, or multiple doses over 24 hours or less. Subacute Toxicity: Adverse effects occurring as a result of repeated daily dosing of a chemical, or exposure of the chemical, for part of an organism's lifespan (usually not exceeding 10%). With experimental animals, the period of exposure may range from a few days to 6 months. Chronic Toxicity: Adverse effects occurring as a result of repeated dosing with a chemical on a daily basis, or exposure of the chemical, for large part of an organism's lifespan (usually more than 50%). With experimental animals, this usually means a period of exposure of more than 3 months. Chronic exposure studies over 2 years using rats or mice are used to assess the carcinogenic potential of chemicals
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