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Lowest-observed-adverse-effect Level
The lowest-observed-adverse-effect level (LOAEL), or the lowest-observed-adverse-effect concentration (LOAEC), is the lowest concentration or amount of a substance found by experiment or observation that causes an adverse alteration of morphology, function, capacity, growth, development, or lifespan of a target organism distinguished from normal organisms of the same species under defined conditions of exposure. Federal agencies use set approval standards below this level. The United States Environmental Protection Agency defines LOAEL as the 'lowest level of a chemical stressor evaluated in a toxicity test that shows harmful effects on a plant or animal. While LOAELs and LOAECs are similar, they are not interchangeable. A LOAEL refers to a dose of chemical that is ingested, while a LOAEC refers to direct exposure to a chemical (e.g., through gills or the skin). See also *No-observed-adverse-effect level *Reference dose A reference dose is the United States Environmental Protectio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morphology (biology)
Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features. This includes aspects of the outward appearance (shape, structure, colour, pattern, size), i.e. external morphology (or eidonomy), as well as the form and structure of the internal parts like bones and organs, i.e. internal morphology (or anatomy). This is in contrast to physiology, which deals primarily with function. Morphology is a branch of life science dealing with the study of gross structure of an organism or taxon and its component parts. History The etymology of the word "morphology" is from the Ancient Greek (), meaning "form", and (), meaning "word, study, research". While the concept of form in biology, opposed to function, dates back to Aristotle (see Aristotle's biology), the field of morphology was developed by Johann Wolfgang von Goethe (1790) and independently by the German anatomist and physiologist Karl Friedrich Burdach ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on December 2, 1970, after Nixon signed an executive order. The order establishing the EPA was ratified by committee hearings in the House and Senate. The agency is led by its administrator, who is appointed by the president and approved by the Senate. The current administrator is Michael S. Regan. The EPA is not a Cabinet department, but the administrator is normally given cabinet rank. The EPA has its headquarters in Washington, D.C., regional offices for each of the agency's ten regions and 27 laboratories. The agency conducts environmental assessment, research, and education. It has the responsibility of maintaining and enforcing national standards under a variety of environmental laws, in consultation with state, tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
No-observed-adverse-effect Level
The no-observed-adverse-effect level (NOAEL) denotes the level of exposure of an organism, found by experiment or observation, at which there is no biologically or statistically significant increase in the frequency or severity of any adverse effects of the tested protocol. In drug development, the NOAEL of a new drug is assessed in laboratory animals, such as mice, prior to initiation of human trials in order to establish a safe clinical starting dose in humans. The OECD publishes guidelines for Preclinical Safety Assessments, in order to help scientists discover the NOAEL. Synopsis Some adverse effects in the exposed population when compared to its appropriate control might include alteration of morphology, functional capacity, growth, development or life span. The NOAEL is determined or proposed by qualified personnel, often a pharmacologist or a toxicologist. The NOAEL could be defined as "the highest experimental point that is without adverse effect," meaning that under lab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reference Dose
A reference dose is the United States Environmental Protection Agency's maximum acceptable oral dose of a toxic substance.Reference doses are most commonly determined for pesticides. The EPA defines an oral reference dose (abbreviated RfD) as: estimate, with uncertainty spanning perhaps an order of magnitude, of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. Regulatory status Unlike National Ambient Air Quality Standards, RfDs are not enforceable standards. Instead, the EPA uses RfDs as risk assessment benchmarks and tries to set other regulations so that people are not exposed to chemicals in amounts that exceed RfDs. According to the EPA, " aggregate daily exposure to a hemicalat or below the RfD (expressed as 100 percent or less of the RfD) is generally considered acceptable by EPA." For example, the EPA set an acute RfD for children of 0.0015 mg/kg/d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concentration Indicators
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', and ''volume concentration''. The concentration can refer to any kind of chemical mixture, but most frequently refers to solutes and solvents in solutions. The molar (amount) concentration has variants, such as normal concentration and osmotic concentration. Etymology The term concentration comes from the word concentrate, from the French , from con– + center, meaning “to put at the center”. Qualitative description Often in informal, non-technical language, concentration is described in a qualitative way, through the use of adjectives such as "dilute" for solutions of relatively low concentration and "concentrated" for solutions of relatively high concentration. To concentrate a solution, one must add more solute (for example, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
