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In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a given substance. The value of LD50 for a substance is the dose required to kill half the members of a tested population after a specified test duration. LD50 figures are frequently used as a general indicator of a substance's acute toxicity. A lower LD50 is indicative of higher toxicity.
Toxicology is a scientific discipline, overlapping with biology, chemistry, pharmacology, and medicine, that involves the study of the adverse effects of chemical substances on living organisms and the practice of diagnosing and treating exposures to toxins and toxicants. The relationship between dose and its effects on the exposed organism is of high significance in toxicology. Factors that influence chemical toxicity include the dosage, duration of exposure, route of exposure, species, age, sex, and environment. Toxicologists are experts on poisons and poisoning. There is a movement for evidence-based toxicology as part of the larger movement towards evidence-based practices. Toxicology is currently contributing to the field of cancer research, since some toxins can be used as drugs for killing tumor cells. One prime example of this is ribosome-inactivating proteins, tested in the treatment of leukemia.
A poison is any chemical substance that is harmful or lethal to living organisms. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broad sense.
Arsenic poisoning is a medical condition that occurs due to elevated levels of arsenic in the body. If arsenic poisoning occurs over a brief period of time, symptoms may include vomiting, abdominal pain, encephalopathy, and watery diarrhea that contains blood. Long-term exposure can result in thickening of the skin, darker skin, abdominal pain, diarrhea, heart disease, numbness, and cancer.
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (cytotoxicity) or an organ such as the liver (hepatotoxicity). Sometimes the word is more or less synonymous with poisoning in everyday usage.
Chronic toxicity, the development of adverse effects as a result of long term exposure to a contaminant or other stressor, is an important aspect of aquatic toxicology. Adverse effects associated with chronic toxicity can be directly lethal but are more commonly sublethal, including changes in growth, reproduction, or behavior. Chronic toxicity is in contrast to acute toxicity, which occurs over a shorter period of time to higher concentrations. Various toxicity tests can be performed to assess the chronic toxicity of different contaminants, and usually last at least 10% of an organism's lifespan. Results of aquatic chronic toxicity tests can be used to determine water quality guidelines and regulations for protection of aquatic organisms.
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 at which a given percentage of subjects will die. The lethal concentration is a lethal dose measurement used for gases or particulates. The LD may be based on the standard person concept, a theoretical individual that has perfectly "normal" characteristics, and thus not apply to all sub-populations.
Aquatic toxicology is the study of the effects of manufactured chemicals and other anthropogenic and natural materials and activities on aquatic organisms at various levels of organization, from subcellular through individual organisms to communities and ecosystems. Aquatic toxicology is a multidisciplinary field which integrates toxicology, aquatic ecology and aquatic chemistry.
Persistent organic pollutants (POPs) are organic compounds that are resistant to degradation through chemical, biological, and photolytic processes. They are toxic and adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released.
Palytoxin, PTX or PLTX is an intense vasoconstrictor, and is considered to be one of the most poisonous non-protein substances known, second only to maitotoxin in terms of toxicity in mice.
Ecotoxicology is the study of the effects of toxic chemicals on biological organisms, especially at the population, community, ecosystem, and biosphere levels. Ecotoxicology is a multidisciplinary field, which integrates toxicology and ecology.
Orellanine or orellanin is a mycotoxin found in a group of mushrooms known as the Orellani within the family Cortinariaceae. Structurally, it is a bipyridine N-oxide compound somewhat related to the herbicide diquat.
Ecotoxicity, the subject of study in the field of ecotoxicology, refers to the biological, chemical or physical stressors that affect ecosystems. Such stressors can occur in the natural environment at densities, concentrations, or levels high enough to disrupt natural biochemical and physiological behavior and interactions. This ultimately affects all living organisms that comprise an ecosystem.
Environmental toxicology is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms. Ecotoxicology is a subdiscipline of environmental toxicology concerned with studying the harmful effects of toxicants at the population and ecosystem levels.
Fenpropathrin, or fenopropathrin, is a widely used pyrethroid insecticide in agriculture and household. Fenpropathrin is an ingestion and contact synthetic pyrethroid. Its mode of action is similar to other natural (pyrethrum) and synthetic pyrethroids where in they interfere with the kinetics of voltage gated sodium channels causing paralysis and death of the pest. Fenpropathrin was the first of the light-stable synthetic pyrethroids to be synthesized in 1971, but it was not commercialized until 1980. Like other pyrethroids with an α-cyano group, fenpropathrin also belongs to the termed type II pyrethroids. Type II pyrethroids are a more potent toxicant than type I in depolarizing insect nerves. Application rates of fenpropathrin in agriculture according to US environmental protection agency (EPA) varies by crop but is not to exceed 0.4 lb ai/acre.
Poisoning is the harmful effect which occurs when toxic substances are introduced into the body. The term "poisoning" is a derivative of poison, a term describing any chemical substance that may harm or kill a living organism upon ingestion. Poisoning can be brought on by swallowing, inhaling, injecting or absorbing toxins through the skin. Toxicology is the practice and study of symptoms, mechanisms, diagnoses, and treatments correlated to poisoning.
The acute to chronic ratio (ACR) uses acute toxicity data to gauge the chronic toxicity (MATC) of a chemical of interest to an organism. The science behind determining a safe concentration to the environment is imperfect, statistically limited, and resource intensive. There is an unfilled demand for the rapid assessment of different chemical toxicity to many different organisms. The ACR is a proposed solution to this demand.
A bioassay is an analytical method to determine the potency or effect of a substance by its effect on living animals or plants, or on living cells or tissues. A bioassay can be either quantal or quantitative, direct or indirect. If the measured response is binary, the assay is quantal; if not, it is quantitative.
Naphthalene poisoning is a form of poisoning that occurs when naphthalene is ingested. Severe poisoning can result in haemolytic anaemia. Naphthalene was introduced in 1841 by Rossbach as an antiseptic to counteract typhoid fever. Although naphthalene was widely used industrially, only nine cases of poisoning have been reported since 1947 as of 1956, suggesting underdiagnosis of the condition. As a result, the condition has limited coverage within medical journals.
References
- ↑ Maryoung LA, Lavado R, Schlenk D (2014). "Impacts of hypersaline acclimation on the acute toxicity of the organophosphate chlorpyrifos to salmonids". Aquatic Toxicology . 152: 284–290. Bibcode:2014AqTox.152..284M. doi:10.1016/j.aquatox.2014.04.017. PMID 24799192.
- 1 2 Verma V, Yu QJ, Connell DW (2014). "Evaluation of effects of long term exposure on lethal toxicity with mammals". Environmental Pollution. 185: 234–239. Bibcode:2014EPoll.185..234V. doi:10.1016/j.envpol.2013.11.001. PMID 24291612.
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