In toxicology, the median lethal dose, LD₅₀ (abbreviation for “Lethal Dose, 50%”), or LCt₅₀ (Lethal Concentration & Time) of a toxic substance or radiation is the dose required to kill half the members of a tested population. Toxicology (from the Greek words toxicos and logos) is the study of the adverse effects of Chemicals on living organisms Forensic toxicology is the use of Toxicology and other disciplines such as Analytical chemistry, Pharmacology and Clinical chemistry to aid medicolegal Toxinology is the specialized area of Toxicology that deals specifically with animal plant and microbial toxins but is also considered a science in its own right The history of Poison stretches from before 4500 BC to the Present day. S00-T14 - Injury (S00-S09 Head ( Superficial Injury of head ( Superficial injury of 17 Injury and poisoning (800-999 fracture of skull (800-804 ( Fracture of Vault of skull ( Fracture of Base of skull In the context of Biology, poisons are substances that can cause damage, Illness, or Death to Organisms usually by This article is about the class of Biotoxins For other uses see Venom (disambiguation and Venomous (disambiguation. A toxicant is a chemical compound that has an effect on organisms An antidote or counterdose is a substance which can counteract a form of Poisoning. Acceptable daily intake or ADI is a measure of the amount of a specific substance (usually a Food additive, or a residue of a veterinary drug or pesticide in Acute toxicity describes the adverse effects of a substance which result either from a single exposure or from multiple exposures in a short space of time (usually less than 24 hours Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at ftudruinsubstance is lost Biomagnification, also known as bioamplification, or biological magnification is the increase in concentration of a substance such as the Pesticide Fixed Dose Procedure (FDP proposed in 1984 is a method to assess a substance's acute oral Toxicity. In Toxicology, the median lethal dose, LD50 (abbreviation for “Lethal Dose 50%” or LCt50 (Lethal Concentration & Time of a A lethal dose (LD is an indication of the Lethality of a given substance or type of Radiation. Toxic capacity can mean the Toxicity of a substance possibly in relation to a specific Organism and toxic capacity can mean the capacity of an organism Toxicity Class refers to a classification system for Pesticides created by a national or international government-related or -sponsored organization A toxin ( Greek:, toxikon, lit (poison for use on arrows is a Poisonous substance produced by living cells or organisms that is active at very low This article is about the class of Biotoxins For other uses see Venom (disambiguation and Venomous (disambiguation. A neurotoxin is a Toxin that acts specifically on nerve cells ( Neurons, usually by interacting with Membrane proteins such as Ion channels Necrosis (in Greek Νεκρός = "dead" is the name given to unnatural Death of cells and living tissue. Hemotoxins, haemotoxins or hematotoxins are Toxins that destroy Red blood cells (that is cause Hemolysis) disrupt Blood Mycotoxin (from the Greek μύκης (mykes mukos "fungus" is a Toxin produced by an organism of the Fungus kingdom which includes Mushrooms Aflatoxins are naturally occurring Mycotoxins that are produced by many species of Aspergillus, a Fungus, most notably Aspergillus Phototoxins are Toxins that can cause allergic reactions in particularly susceptible individuals and which can cause dangerous Photosensitivity in a much broader range This is a list of toxins poisons and chemical weapons from works of fiction (usually in Fantasy and Science fiction) The Bradford sweets poisoning was the accidental Arsenic poisoning of more than 200 people in Bradford, England in 1858 an estimated 20 people died when sometimes referred to as, is a neurological syndrome caused by severe Mercury poisoning. is a Neurological syndrome caused by severe Mercury poisoning. Alexander Litvinenko was a former officer of Russian Federal Security Service, who escaped prosecution in Russia and received a Political asylum in The Bhopal disaster was an Industrial disaster that occurred in the city of Bhopal, Madhya Pradesh, India, resulting in the immediate deaths The 2007 pet food recalls comprise the contamination and wide recall of many brands of cat and dog foods beginning in March 2007 and the ensuing developments This is a list of Poisonings in chronological order of victim Toxic metals are Metals that form Poisonous soluble compounds and have no biological role i Lead poisoning (also known as saturnism, plumbism, or painter's colic) is a medical condition caused by increased levels of the metal Lead in Mercury poisoning (also known as mercurialism, hydrargyria, Hunter-Russell syndrome, or acrodynia when affecting children is a Disease Cadmium has no constructive purpose in the Human body It and its compounds are extremely Toxic even in low concentrations and will Bioaccumulate in Antimony (IPA (Received Pronunciation, /ˈæntɪmoʊni/ (US is a Chemical element with the symbol Sb (stibium meaning "mark" and Arsenic Poisoning kills by Allosteric inhibition of essential metabolic Enzymes, leading to death from multi-system Beryllium (bəˈrɪliəm is a Chemical element with the symbol Be and Atomic number 4 Iron poisoning is caused by a large excess of Iron intake It has been primarily been associated with young children who consumed large quantities of iron supplement pills Thallium (ˈθæliəm is a Chemical element with the symbol Tl and Atomic number 81 In high concentrations soluble Fluoride Salts are somewhat Toxic. Oxygen toxicity or oxygen toxicity syndrome (also known as the " Paul Bert effect" or the "Lorrain Smith effect" describes harmful effects caused There are four syndromes called shellfish poisoning, which share some common features and are primarily associated with bivalve molluscs (such as Mussels Paralytic shellfish poisoning (PSP is one of the four recognized syndromes of Shellfish poisoning (the others being Neurotoxic shellfish poisoning, diarrhetic Diarrhetic shellfish poisoning (DSP is one of the four recognised symptom types of Shellfish poisoning, the others being Paralytic shellfish poisoning, Neurotoxic Amnesic shellfish poisoning (ASP is a human illness caused by consumption of the marine biotoxin called Domoic acid. Ciguatera is a Foodborne illness poisoning in humans caused by eating Marine species whose flesh is contaminated with a toxin known as Ciguatoxin, Scombroid food poisoning is a foodborne Illness that results from eating spoiled (decayed Fish. Tetrodotoxin (anhydrotetrodotoxin 4-epitetrodotoxin tetrodonic acid TTX is a potent Neurotoxin with no known antidote which blocks Action potentials in Nerves Pesticide Poisonings occur when chemicals intended to control a pest affect non-target organisms such as Humans Wildlife, or Bees Since Many Organophosphates are potent Neurotoxins functioning by inhibiting the action of Acetylcholinesterase (AChE in nerve cells. Foodborne illness (also foodborne disease) is any Illness resulting from the consumption of food Historically most cases of nicotine poisoning have been the result of its use as an Insecticide; however such use is less frequent now than previously Carbon monoxide poisoning occurs after the inhalation of Carbon monoxide gas Vitamin poisoning, or hypervitaminosis, refers to a condition of high storage levels of Vitamins which can lead to Toxic Symptoms The medical The term drug overdose (or simply overdose or OD) describes the Ingestion or application of a Drug or other substance in quantities See also List of deadly fungi Mushroom poisoning, also known as mycetism, refers to deleterious effects from ingestion of Toxic substances present This is a list of Plants containing Poisonous parts that pose a serious risk of illness, injury or Death to Humans or Animals. Hazard symbols are easily recognizable symbols designed to warn about hazardous materials or locations The term carcinogen refers to any substance Radionuclide or radiation that is an agent directly involved in the promotion of Cancer or in the fatation of its propagation In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) This is a list of Extremely Hazardous Substances as defined by Section 302 of the U Biological warfare (BW — known as a germ warfare, biological weapons and bioweaponry — is the use of any Pathogen ( Bacterium Toxicology (from the Greek words toxicos and logos) is the study of the adverse effects of Chemicals on living organisms A dose is a quantity of something ( Chemical, physical or Biological) that may impact an organism biologically the greater the quantity the larger the dose LD₅₀ figures are frequently used as a general indicator of a substance's acute toxicity. The test was created by J. W. Trevan in 1927^[1]. It is being phased out in some jurisdictions in favor of tests such as the Fixed Dose Procedure. Fixed Dose Procedure (FDP proposed in 1984 is a method to assess a substance's acute oral Toxicity. ^[2], however the concept, and calculation of the median lethal dose for comparison purposes, continues in wide use.

The term semilethal dose is occasionally used with the same meaning, particularly in translations from non-English-language texts, but can also refer to a sublethal dose; because of this ambiguity, it is usually avoided.

Medical Subject Headings, Medical Subject Headings (MeSH) (ID D007928) defines LD₅₀ as:

The dose amount of poisonous or toxic substance or dose of ionizing radiation required to kill 50% of the tested population. Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books

Conventions

The LD₅₀ is usually expressed as the mass of substance administered per unit mass of test subject, such as grams of substance per kilogram of body mass. For other uses of the words gram or gramme see Gram (disambiguation. Stating it this way allows the relative toxicity of different substances to be compared, and normalizes for the variation in the size of the animals exposed (although toxicity does not always scale simply with body mass). Typically, the LD₅₀ of a substance is given in milligrams per kilogram of body weight. In the case of some neurotoxins such as batrachotoxin, one of the most deadly toxins known, the LD₅₀ may be more conveniently expressed as micrograms per kilogram (µg/kg)of body mass. A neurotoxin is a Toxin that acts specifically on nerve cells ( Neurons, usually by interacting with Membrane proteins such as Ion channels Batrachotoxins ( BTX) are extremely potent Cardiotoxic and Neurotoxic steroidal Alkaloids found in certain species of frogs (

The choice of 50% lethality as a benchmark avoids the potential for ambiguity of making measurements in the extremes, and reduces the amount of testing required. However, this also means that LD₅₀ is not the lethal dose for all subjects; some may be killed by much less, while others survive doses far higher than the LD₅₀. Measures such as 'LD1' and 'LD99' (dosage required to kill 1% or 99% respectively of the test population) are occasionally used for specific purposes. ^[3]

Lethal dosage often varies depending on the method of administration; for instance, many substances are less toxic when administered orally than when intravenously administered. Intravenous therapy or IV therapy is the giving of Liquid substances directly into a Vein. For this reason, LD₅₀ figures are often qualified with the mode of administration, e. g. "LD₅₀ i. v. "

The related quantities LD₅₀/30 or an LD₅₀/60 are used to refer to a dose that without treatment will be lethal to 50% of the population within (respectively) 30 or 60 days. These measures are used more commonly within Radiation Health Physics, as survival beyond 60 days usually results in recovery. Health physics is a field of science concerned with radiation physics and radiation biology with the goal of informing the safe use of ionizing radiation

A comparable measurement is LCt₅₀ which relates to lethal dosage from exposure, where C is concentration and t is time. It is often expressed in terms of mg-min/m³. ICt₅₀ is the dose which will cause incapacitation rather than death. These measures are commonly used to indicate the comparative efficacy of chemical warfare agents, and dosages are typically qualified by rates of breathing (e. Chemical warfare involves using the toxic properties of Chemical substances to kill injure or incapacitate an enemy. g. , resting = 10 l/min) for inhalation, or degree of clothing for skin penetration. The concept of Ct was first proposed by Fritz Haber, and is sometimes referred to as Haber's Law, which assumes that exposure to 1 minute of 100 mg/m³ is equivalent to 10 minutes of 10 mg/m³ (1 × 100 = 100, as does 10 × 10 = 100). Fritz Haber (9 December 1868 &ndash 29 January 1934 was a German chemist, who received the Nobel Prize in Chemistry in 1918 for his development for Haber's Law makes Equivalent any two groupings of Dose concentration and Exposure time that have Equivalent Mathematical products

Some chemicals, such as hydrogen cyanide are rapidly detoxified by the human body, and do not follow Haber's Law. Hydrogen cyanide is a Chemical compound with Chemical formula HCN So in these cases the lethal concentration may be given simply as LC₅₀ and qualified by a duration of exposure (e. g. 10 minutes). The Material Safety Data Sheets for toxic substances frequently use this form of the term even if the substance does follow Haber's Law. A material safety data sheet ( MSDS) is a form containing data regarding the properties of a particular substance

For disease-causing organisms, there is also a measure known as the median infective dose and dosage. The median infective dose (ID₅₀) is the number of organisms received by a person or test animal qualified by the route of administration (e. g. , 1,200 org/man per oral). Because of the difficulties in counting actual organisms in a dose, infective doses may be expressed in terms of biological assay, such as the number of LD₅₀'s to some test animal. In biological warfare infective dosage is the number of infective doses per minute for a cubic meter (e. Biological warfare (BW — known as a germ warfare, biological weapons and bioweaponry — is the use of any Pathogen ( Bacterium g. , ICt₅₀ is 100 medium doses - min/m³).

Animal rights concerns

Animal-rights and animal-welfare groups, such as Animal Rights International,^[4] have campaigned against LD₅₀ testing on animals in particular as, in the case of some substances, causing the animals to die slow, painful deaths. "Animal liberation" redirects here for other uses see Animal liberation (disambiguation. Animal welfare refers to the viewpoint that it is morally acceptable for humans to use nonhuman animals for food in animal research, as clothing and in entertainment Several countries, including the UK, have taken steps to ban the oral LD₅₀, and the Organization for Economic Co-operation and Development (OECD) abolished the requirement for the oral test in 2001 (see Test Guideline 401, Trends in Pharmacological Sciences Vol 22, February 22, 2001). The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Events 1495 - King Charles VIII of France enters Naples to claim the city's throne Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar.

Examples

See also

• Animal testing
• Reed-Muench method

Other measures of toxicity

• Certain safety factor
• Fixed Dose Procedure
• Lowest published toxic concentration (TCLo)
• Lowest published lethal dose (LDLo)
• IC₅₀ (50% inhibitory concentration)
• Draize test
• Indicative limit value
• No Observable Adverse Effect Level (NOAEL)
• Lowest Observable Adverse Effect Level (LOAEL)

Related measures

• TCID₅₀ Tissue Culture Infective Dosage
• EID₅₀ Egg Infective Dosage
• ELD₅₀ Egg Lethal Dosage
• Plaque forming units (pfu)

References

External links

• Canadian Centre for Occupational Health and Safety
• List of LD-50s for selected psychoactive substances