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.
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Oil Drilling Environmental Health ConcernsLast Updated on 2014-11-29 21:42:39This article, written by Charles W. Schmidt 1, appeared first in Environmental Health Perspectives—the peer-reviewed, open access journal of the National Institute of Environmental Health Sciences
The article is a verbatim version of the original and is not available for edits or additions by Encyclopedia of Earth editors or authors. Companion articles on the same topic that are editable may exist within the Encyclopedia of Earth.
As Royal Dutch Shell and other oil companies prepare to drill offshore in the Alaskan Outer Continental Shelf (OCS), a new report commissioned by the Washington, DC–based Pew Environment Group concludes current response capabilities aren’t adequate to contain and clean up a major spill in the area.1 Marilyn Heiman, who directs the group’s U.S. Arctic program, says drilling on the Alaskan OCS requires a science-based... More »
PollutionLast Updated on 2014-11-09 17:40:04Pollution 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 »
HerbicideLast Updated on 2014-10-26 16:45:24A herbicide is any of a number of chemical substances intended to kill vegetation. Since the vast majority of herbicides are non-selective in their lethal action, there may be widespread adverse ecological consequences from their use. These outcomes include not only organism death, but may involve mutagenic, developmental and carcinogenic effects to animals and plants.
Herbicides are in broad use for agriculture, golf courses, utility corridors, residential and other land uses. The earliest herbicides were inorganic chemical substances, although modern herbicides are dominated by organic compounds. Presently, there is massive application of chemical herbicides; in the USA alone 480 million kilograms are applied annually.
Widespread herbicide use beginning in the 1940s is responsible for numerous species extinctions, including birds, amphibians, fish and arthropods. In many cases,... More »
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 »
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