Glossary and Appendix


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2,3,7,8-TCDD - Tetrachlorinated dibenzo-p-dioxin, a dioxin congener consisting of four chlorine atoms at the 2, 3, 7, and 8 respective positions on the benzene rings.

Acute exposure - Exposure over a relatively short time period.

Aerobic - Occurring only in he presence of free uncombined molecular oxygen, either as a gas in the atmosphere or dissolved in water.

Aerosol - The suspension of very fine, generally micrometer-size, solid and liquid particles in the atmosphere.

Ambient - Referring to surrounding, external, or unconfined conditions.

Anaerobic - Occurring in environmental conditions devoid of oxygen.

Angina - Sense of suffocation or suffocating pain

Aryl hydrocarbon receptor (Ah) - Cytoplasmic protein that TCDD has been shown to bind with and induce changes in the expression of specific genes and translation of their products and hence alter the biological effects.

Atherothrombosis - Formation of blood clots in arteries.

Atmosphere - The gaseous envelope surrounding Earth; a reservoir in Earth's surface system.

Autoimmune - autoimmune disorders are suspected of being caused by inflammation and destruction of tissues by the body's own antibodies

Bioaccumulate - The storage of chemicals in an organism in higher concentrations then are normally found in the environment.

Bioconcentrate - Build-up of chemical elements or substances in organisms in successively higher trophic levels.

Biomagnification factor - Used to describe the accumulation of chemicals in organisms, primarily aquatic, that live in contaminated environments.

Biota - Living organisms, such as animals, plants, fungi, etc.

B-lymphocytes - These lymphocytes produce circulating antibodies, and therefore are responsible for humoral immunity. B cells work chiefly by secreting soluble substances called antibodies into the body's fluids, or humors. (This is known as humoral immunity.)

Cell mediated immunity - See T-lymphocytes.

Chemotaxis - Movement of a cell in response to the stimulus of a gradient of chemical concentration

Chronic exposure - Exposure over a relatively long time period contaminant sink.

Cirrhosis - A condition in which liver responds to injury or death of some of its cells by producing interlacing fibrous tissues.

Degradation - The process by which a chemical is reduced to a less complex form.

Dry deposition - The deposition of material from the atmosphere onto Earth's surface in the form of solid particles. Such particles also may be "washed out" of the atmosphere by rain.

Ecosystem - The biotic community and its abiotic environment functioning as a system.

Environmental impact assessment - Identifies and predicts the impacts from development proposals on both the biophysical environment and on human health and well-being.

Exchange flux - The rate of flow from a source to a sink or receiver.

Fate model - Calculates how a chemical will partition itself between environmental `compartments`such as air, water, water sediment and soil and the exchange fluxes between these compartments.

Geosynthetics - The generic term for all synthetic materials used in geotechnical engirneering applications.

Geotextile - A permeable geosynthetic comprised solely of textiles. Current manufacturing techniques produce non-woven fabrics, knitted (nontubular) fabrics and woven fabrics.

Geomembrane - An essentially impermeable geosynthetic composed of one or more synthetic sheets
Cirrhosis: A condition in which liver responds to injury or death of some of its cells by producing interlacing fibrous tissues.

Glutathione - Glutathione (GSH) is a naturally occurring protein of three amino acids - glycine, glutamate (glutamic acid), and cysteine.

Half-life - The time it takes one half of a given material (such as a radioactive isotope or a pesticide) to decay or disappear.

Henry's Law constant - A measure of the tendency for a chemical to volatilize.

Hepatic - Related to the liver

Humoral - Circulating in the bloodstream. Humoral mediated immunity requires circulating antibodies. See also B-lymphocytes.

Immunoglobulins - A group of structurally related proteins that act as antibodies. There are five classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM. The most important classes are IgG, IgA and IgM.

Intracellular - Within the cell

LD 50 - The dose of a toxic compound that causes in 50% of a group of experimental animals to which the compound is administered.

LOD - Level Of Detection.

Myocardial infarction - Heart attack caused by lack of blood flow in a coronary artery due to a blood clot.

Natural killer - A type of lymphocyte that is able to kill certain types of cancer cells.

Neoplastic - New and abnormal; a new and abnormal growth is called neoplasm

Neutrophil - White blood cells with a lifespan around twelve hours; these cells arrive at the site of an infection or injury to engulf bacterial bodies.

Organochlorides - An organic compound composed of mostly carbon, hydrogen and chlorine.

Pathogen - A microorganism (e.g. bacterium, viruse) that parasitizes a host and produces a disease

PCDD/Fs - Polychlorinated dibenzo-p-dioxins and dibenzofurans, often referred to as dioxins. These compounds consist of two benzene rings enclosing a dioxin or a furan ring. Chlorination refers to the position of chlorine atoms on the benzene rings. Poly means many and prefixes such as di (2), tri (3), tetra (4), penta (5), hexa (6), hepta (7), octa (8) indicate the numbers of chlorine atoms present. Thus Tetrachlorinated dibenzo-p-dioxin (TCDD) is an example of a PCDD congener.

Pentachlorobenzenethiol (PCBT) - A substance derived from the metabolism of HCB

Photolytic degradation - Pertaining to chemical reactions triggered by radiant energy that convert a complex compound to more simple products.

Point source (of pollution) - Easily discernible source of pollution, such as a factory.

Pollution - A substance that adversely alters he physical, chemical, or biological quality of the earth's living systems or that accumulates in the cells or tissues of living organisms in amounts that threaten their health or survival.

Population - A group of individuals of the same species living in a given area at a given time.

Porphyria - A metabolic disorder in which the patient has an excessive amount of porphyrins. This disorder can be due to hereditary factors or can be caused by exposure to exogenous chemical substances such as HCB.

Porphyrin - A pigment that forms a constituent in various proteins

ppb - Parts per billion

Sediment - fragments of rock, soil and organic material transported and deposited in bodies of water by wind, water or other natural phenomena. The term can refer to any size of particles but is often used to indicate only fragments smaller than 6 mm.

Sedimentary core - Technique used to determine past levels of environmental contamination by examining soils layed down through time.

T ½ - See Half-life.

TDI - Tolerable Daily Intake. Refers to a daily intake of TCDD that is not likely to lead to any adverse effects. Its derivation was based on rat studies at the no-observed-adverse-effects-level (NOAEL) of 1ng/kg body wt/day. A safety factor of 10 was applied to allow for differences in susceptibility between rats and humans.

TEF - Toxic Equivalency Factor. TEFs are consensus values based on available data on relative potency values on a specific compound and are protective in nature. Relative potency values express the potency of a specific compound in comparison to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) the most potent dioxin congener, with a relative potency of 1.

TEQ - A certain amount of toxic equivalents calculated from multiplying the TEF value of a compound by the concentration of a specific matrix used to determine the total dioxin activity.

T-lymphocytes - They interact directly with their targets, attacking body cells that have been affected by viruses or warped malignancy. (This is cellular immunity.)

Trophic level - Functional classification of organisms in an ecosystem according to feeding relationships from first-level autotrophs through succeeding levels of herbivores and carnivores.

Volatilization - The conversion of a substance into the gas or vapor state and its emission into the environment.

Wet deposition - The deposition on Earth's surface of solid particles and dissolved chemical compound in rain.


Groundwater Contamination
Risks Of Volatilization
Health Effects
Ecological Effects
Glossary and Appendix
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Introduction | Groundwater Contamination

Risks Of Volatilization | Health Effects| Ecological Effects

Glossary | References | Our Group