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In toxicology, the median lethal dose, LD 50 (abbreviation for "lethal dose, 50%"), LC 50 (lethal concentration, 50%) or LCt 50 is a toxic unit that measures the lethal dose of a given substance. [1] The value of LD 50 for a substance is the dose required to kill half the members of a tested population after a specified test duration.
In toxicology, the lethal dose (LD) is an indication of the lethal toxicity of a given substance or type of radiation.Because resistance varies from one individual to another, the "lethal dose" represents a dose (usually recorded as dose per kilogram of subject body weight) at which a given percentage of subjects will die.
Oral LD 50: Up to and including 50 mg/kg From 50 to 500 mg/kg From 500 to 5000 mg/kg Greater than 5000 mg/kg Inhalation LC50 Up to and including 0.2 mg/L From 0.2 to 2 mg/L From 2. to 20 mg/L Greater than 20 mg/L Dermal LD50 Up to and including 200 mg/kg From 200 to 2000 mg/kg From 2000 to 20,000 mg/kg Greater than 20,000 mg/kg Eye Effects
The system is based on LD50 determination in rats, thus an oral solid agent with an LD50 at 5 mg or less/kg bodyweight is Class Ia, at 5–50 mg/kg is Class Ib, LD50 at 50–2000 mg/kg is Class II, and at LD50 at the concentration more than 2000 mg/kg is classified as Class III. Values may differ for liquid oral agents and dermal agents. [1]
The median lethal dose of a substance is defined as the dose that leads to death in 50% of the tested population. It is a significant parameter in toxicology study and indicates the acute toxicity of a particular substance. LD50 is usually expressed in the weight of the chemical administered in milligram per unit of body weight (mg/kg). [29]
It is calculated using the LD50 or LC50. [1] The Occupational Safety and Health Administration (OSHA) regulation (1910.134(b)) defines the term as "an atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere."
Many gases have toxic properties, which are often assessed using the LC 50 (median lethal concentration) measure. In the United States, many of these gases have been assigned an NFPA 704 health rating of 4 (may be fatal) or 3 (may cause serious or permanent injury), and/or exposure limits (TLV, TWA/PEL, STEL, or REL) determined by the ACGIH professional association.
The median toxic dose encompasses the category of toxicity that is greater than half maximum effective concentration (ED 50) but less than the median lethal dose (LD 50). However, for some highly potent toxins (ex. lofentanil , botulinum toxin ) the difference between the ED 50 and TD 50 is so minute that the values assigned to them may be ...