Lethal dose (LD50) & lethal Concentration (LC50)
LD50 (Lethal Dose 50 percent) :
- The term LD50 is expressed, as the single exposure dose of the poison per unit weight of the organism required to kill 50 % of the test population, where the population is genetically homogeneous. It is applied in a particular way under stated experimental conditions.
- It is usually expressed in terms of mg poison per kilogram body weight of the experimental animals. Under certain conditions, the term micrograms per insect (μg/insect) may be used when chemical is applied topically to the insect.
- The LD50 can be found for any route of entry or administration but dermal (applied to the skin) and oral (given by mouth) administration methods are the most common.
- It is a frequently used to measure of acute toxicity of an insecticide on an organism.
- It is also important to know that the actual LD50 value may be different for a given chemical depending on the route of exposure e.g., oral, dermal, inhalation. For example, some LD50 in rat for dichlorvos, an insecticide commonly used in household pesticide strips, are listed below:
1. Oral LD50(rat): 56 mg /kg
2. Dermal LD50(rat): 75 mg/kg
3.Intraperitoneal LD50(rat): 15 mg/kg
4.Inhalation LC50(rat): 1.7 ppm (15 mg/m3), 4-hour exposure
5.In general, the smaller the LD50 value, the more toxic is the chemical. The opposite is also true, larger the LD50 value, the lower the toxicity.
LC50 ( Lethal Concentration 50 percent) :
- LC50 is the concentration of the chemical in the external medium (usually air or water surrounding experimental animals), which causes 50 % mortality of the test population, where the population is genetically homogeneous.
- This value is used when the exact dose given to the individual is dificult to be determined.
- LC50 is expressed as the percent of active ingredient of the chemical in the medium or as parts per million (ppm).
