Toxicology is the study of the impacts of chemicals (as drugs, food additives and environmental contaminants) on both humans and the environment. The Industrial Revolution of the mid-19th century released many naturally-occurring chemicals into the environment in unprecedented amounts and resulted in the production of thousands of new substances. Results from toxicity studies support drug, food and industrial chemical regulation, remediation, and production. Although past practices focused on exposures of high doses to single chemicals practitioners of the science have recognized the importance of evaluating the impacts of low doses, and chemical mixtures as more sensitive biochemical and genomic methods are incorporated into chemical evaluation and regulation.
SciDev.Net has produced a special Spotlight on "Nuclear Power After Fukushima" on 29 September 2011. SciDev.Net Spotlights are collections of feature, news and opinion...
BacteriaLast Updated on 2014-10-12 18:54:28
Bacteria are any of a very large group of single-celled microorganisms that display a wide range of metabolic types, geometric shapes and environmental habitats—and niches—of occurrence. Normally only several micrometers in length, bacteria assume the form of spheres, rods, spirals and other shapes. Bacteria are found in a very broad gamut of habitats; for example, bacterial extremophiles that thrive in such places as hot springs, arctic environments, radioactive waste, deep sea oil seeps, deep Earth crustal environments, hypersaline ponds and within other living organisms. There are approximately 50 million bacterial organisms in a single gram of typical surface soil. The worldwide bacterial biomass exceeds that of all plants and animals on Earth. However, the majority of bacteria have not yet been characterised,
Bacteria are members of the prokaryote... More »
FluorineLast Updated on 2014-09-13 19:14:38Fluorine is a highly reactive chemical element with atomic symbol F. Having the atomic number nine, fluorine is the lightest halogen. Fluorine is a yellow-green gas which does not occur as a free, unreacted element in the natural environment. Under conditions of standard temperature and pressure, elemental fluorine forms a diatomic molecule with chemical formula F2. Chemically, fluorine is one of the strongest known oxidizing agents, and even more reactive and hazardous than chlorine. Its very high electron affinity causes fluorine to react directly with almost all other elements except for several of the Noble gases.
Previous Element: Oxygen
Next Element: Neon
Phase at Room Temp.
Density... More »
RicinLast Updated on 2014-06-30 13:49:34
The Director's Emergency Operations Center at the Centers for Disease Control and Prevention (CDC) has assembled basic information about the toxin ricin. You can find more detailed information on the CDC's Ricin Homepage.
Ricin is a poison found naturally in castor beans. If castor beans are chewed and swallowed, the released ricin can cause injury. Ricin can be made from the waste material left over from processing castor beans.
It can be in the form of a powder, a mist, or a pellet, or it can be dissolved in water or weak acid.
It is a stable substance under normal conditions, but can be inactivated by heat above 80 degrees Centigrade (176 degrees Fahrenheit).
Castor beans are processed throughout the world to make castor oil. Ricin is part of the waste “mash” produced when castor oil is made.
Ricin has been used experimentally in medicine to... More »
SeleniumLast Updated on 2014-06-29 16:59:07
Selenium is a gray, metallic element. Its atomic number is 34 and its symbol is Se. The Swedish scientist Jons Jacob Berzelius discovered selenium in 1817. In studying the sulfuric acid produced in a particular Swedish factory, he discovered an impurity which he eventually identified as selenium. Selenium occurs in three distinct forms: as a non-crystalline, gray metal; it can form as a deep red to black powder; and it can form as red crystals. It is stable in air and in water. Selenium is actually an important trace element to mammals and some plants. Too much selenium in a mammal’s diet is poisonous and has been shown to cause deformities. When there is not enough selenium, a mammal can also have health problems. For example, sheep that graze in areas with too little selenium in the soil eventually have a problem known as “white muscle disease.” Lack of selenium... More »
PollutionLast Updated on 2014-06-28 18:51:13Pollution is environmental contamination that results in harm or death to living organisms. Most pollution is in the form of chemical additions to air, water or soil; however, in modern times starting in the mid-twentieth century noise and light have been considered as pollution sources. Most pollution is man-made, with natural fluctuations in atmospheric composition, surface water bodies and soil considered temporal gyrations in the Earth's natural history. The chief driver of pollution is the massive growth in human population, which induces the proximate causes of intensive agriculture and extraordinary industrial output. The United Nations and the Blacksmith Institute are two prominent organisations that tabulate locales of the greatest pollution intensity; while their listings do not correspond precisely, the overlap countries that both entities agree are the worst polluted... More »
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