Minimum Lethal Dose Definition

Search for “minimum toxic dose” in Oxford Reference » The choice of 50% lethality as the reference avoids the risk of ambiguity in extreme measurements and reduces the scope of the tests required. However, this also means that LD50 is not the lethal dose for all subjects; some can be killed by much less, while others survive at doses much higher than the LD50. Measures such as “LD1” and “LD99” (dose required to kill 1% and 99% of the tested population, respectively) are sometimes used for specific purposes. [3] A comparable measure is the LCt50, which refers to the lethal dose resulting from exposure, where C is the concentration and t is the time. It is often expressed in mg-min/m3. LCt50 is the dose that causes incapacity for work rather than death. These measures are commonly used to indicate the comparative effectiveness of chemical warfare agents, and doses are generally qualified based on respiratory rate (e.g., rest time = 10 L/min) for inhalation or the degree of penetration of clothing into the skin. The concept of Ct was first proposed by Fritz Haber and is sometimes referred to as Haber`s law, which assumes that 1-minute exposure of 100 mg/m3 is equivalent to 10 minutes of 10 mg/m3 (1 × 100 = 100, as well as 10 × 10 = 100). [ref.

needed] “Minimum Lethal Dose.” Merriam-Webster.com Medical Dictionary, Merriam-Webster, www.merriam-webster.com/medical/minimum%20lethal%20dose. Retrieved 11 October 2022. LD01 Lethal dose for 1% of the animal population In toxicology, lethal dose (LD) is an indication of the lethal toxicity of a particular substance or type of radiation. Because resistance varies from individual to individual, the “lethal dose” represents a dose (usually recorded as a dose per kilogram of body weight) at which a certain percentage of subjects die. Lethal concentration is a lethal dose measurement used for gases or particles. ML can be based on the concept of the standard person, a theoretical individual who has perfectly “normal” characteristics and therefore does not apply to all subpopulations. From: minimum toxic dose in A Dictionary of Psychology » Some chemicals, such as hydrocyanic acid, are rapidly detoxified by the human body and do not follow Haber`s Law. In these cases, the lethal concentration can simply be expressed as LC50 and qualified by an exposure time (e.g. 10 minutes). In safety data sheets for toxic substances, this form of the term is often used, even if the substance follows Haber`s law.

[ref. needed] Subscribe to America`s largest dictionary and get thousands of other definitions and an advanced search – ad-free! The LD50 is only one source of toxicity information. To obtain a more accurate picture of the immediate or acute toxicity of a chemical, additional information should be considered, such as the lowest dose causing a toxic effect (TDLO), the recovery rate of a toxic effect, and the possibility that exposure to certain mixtures may result in an increase in the toxic effect of a single chemical. The lowest lethal dose (LDLo) is the lowest amount of drug that can cause death in a particular species under controlled conditions. [5] [6] The dosage is per unit body weight (usually expressed in milligrams per kilogram) of a substance known to have caused death in a particular species. When specifying an LDLo, the species and method of administration (e.g., ingested, inhaled, intravenous) are usually indicated. LCLo is the lowest concentration of a chemical administered over a period of time that results in the death of a single animal. LCLo is usually for acute exposure (<24 hours). [8] [9] It is related to LC50, the average lethal concentration. LCLo is used for gases and aerosols.

[10] If immediate toxicity is similar in all different animals tested, the degree of immediate toxicity to humans is likely to be similar. If LD50 levels are different for different animal species, approximations and assumptions should be made when estimating the likely lethal dose to humans. Tables 1 and 2 contain a column for estimated lethal doses in humans. Special calculations are used to convert the LD50 values of animals into potentially lethal doses for humans. Safety factors of 10,000 or 1000 are typically included in these calculations to account for variability between individuals and their response to a chemical, as well as uncertainties in experimental test results. As a measure of toxicity, the lethal dose is somewhat unreliable, and results can vary considerably from one test facility to another due to factors such as the genetic characteristics of the sampled population, the animal species tested, environmental factors, and the method of administration. [11] The smallest dose of a drug that causes signs or symptoms of toxicity in an organism. Also called minimum toxic dosage. See also therapeutic index, therapeutic ratio, toxic dosage. Compare median effective dose, median lethal dose, median toxic dose, minimum effective dose, minimum lethal dose. Inhalation and dermal absorption are the most common ways in which chemicals enter the body in the workplace. Therefore, inhalation (LC50) and dermal application (dermal LD50) tests are the most relevant from an occupational exposure perspective.

Despite this, the most commonly conducted lethality study is the oral LD50. This difference occurs because administering chemicals to animals by mouth is much easier and less expensive than other techniques. However, the results of oral studies are important for drug trials, food poisoning and accidental household poisoning. Occupational oral poisoning can occur due to contamination of food or cigarettes by unwashed hands and accidental ingestion. Therefore, to compare the toxic efficacy or intensity of different chemicals, researchers need to measure the same effect. One way is to perform lethality tests (LD50 tests) by measuring the amount of a chemical needed to cause death. This type of test is also known as a “quantum” test because it measures an effect that “occurs” or “does not occur.” For gases and aerosols, lethal concentration (expressed in mg/m3 or ppm, parts per million) is the analogous concept, although this also depends on the duration of exposure, which must be included in the definition. The term incipient lethal stage is used to describe a time-independent LC50. [7] If the lethal effects of inhalation of a compound are to be tested, the chemical (usually a gas or vapour) is first mixed at a known concentration in a special air chamber where the test animals are housed.

This concentration is usually expressed in parts per million (ppm) or milligrams per cubic metre (mg/m3). In these experiments, the concentration that kills 50% of the animals is called LC50 (lethal concentration 50) and not LD50. If an LC50 is indicated, it should also indicate the type of animal tested and the duration of exposure, e.g. LC50 (rat) – 1000 ppm/4 hours or LC50 (mouse) – 5 mg/m3/2 hours. The mean lethal dose, LD50 (short for “lethal dose, 50%”), LC50 (lethal concentration, 50%) or LCt50 (lethal concentration and duration) of a toxin, radiation or pathogen is the dose required to kill half of the members of a tested population after a certain trial period. LD50 values are often used as a general indicator of the acute toxicity of a substance. A lower LD50 indicates increased toxicity. The test was developed by J.W. Trevan in 1927.

[1] The term “semilethal dose” is sometimes used with the same meaning, especially in translations of non-English texts, but can also refer to a sublethal dose; Because of this ambiguity, it is usually avoided.