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Abiotic: Non-living components of the environment, including chemicals in the air, water and soil, and the level and variability of solar radiation and other aspects of the climate. ¹

Acid: A chemical that releases hydrogen ions (H+) in solution and produces hydronium ions (H30+). Such solutions have a sour taste, neutralize bases and conduct electricity.¹

Acrylate: 1) Any of several monomers used for the manufacture of thermosetting acrylic surface coating resins, e.g., 2-hydroxyethyl acrylate (HEA) and hydroxypropyl acrylate (HPA); (2) Polymer of acrylic acid or its esters, used in surface coatings, emulsion paints, paper and leather finishes, etc.³

Acute: Characterized by sharpness or severity (acute pain); Having a sudden onset, sharp rise, and short course (acute disease); Lasting a short time (acute experiments). ²

Acute exposure: In toxicology, doses administered or received over a period of 24 hours or less.¹

Additivity : The interaction of two or more chemical substances on a biological system whose combined effect is equal to the sum of the effects of each substance.¹

Adiabatic: Descriptive of a system or process in which no gain or loss of heat is allowed to occur.³

Aldehyde: A type of organic molecule containing a carbonyl group in which a carbon atom is bonded to an oxygen atom with a double covalent bond and to a hydrogen atom with a single covalent bond. Aldehydes can be reduced to form alcohols and oxidized to acids. Two common aldehydes are formaldehyde and acetylaldehyde. The basic chemical formula for aldehydes is as follows. The R- group represents any type of organic side chain. ¹

Algaecide: Chemical, usually added to water to kill or control algae.¹

Alkali : A chemical substance that can neutralize an acid. Also refers to soluble salts in soil, surface water, or groundwater.¹

Alkaline: Of, relating to, or having the properties of an alkali; esp: having a pH of more than 7.³

Alloy: A solid or liquid mixture of two or more metals; or of one or more metals with certain non-metallic elements, as in carbon steels.³

Ambient conditions : Describing a natural outside environment. The term ambient air, for example, commonly excludes indoor and workplace environments.¹

Ames Test: A test of the ability of a chemical to cause mutations and thereby act as a carcinogen. The process involves the use of a histidine-dependent strain of the bacterial species Salmonella typhimurium. The organism used is actually a mutant strain that requires the presence of the amino acid histidine for growth. The chemical being screened is usually mixed with an extract of rat liver, which provides enzymes that convert the chemical being tested from an inactive to an active form. The suspension of bacteria and the suspected mutagen are allowed to stand for an appropriate period of time. The mixture is then spread on the surface of an agar medium that contains all the ingredients needed for growth of the test strain of Salmonella except histidine. If a mutation occurs that converts the test strain back to the wild type, which does not need to find histidine in the environment in order to grow, colonies will develop on the surface of the agar medium. If mutations do not occur, nothing will grow on the medium, and the test will be considered negative. Because carcinogens are also mutagens, the test is used as a screening technique to test for carcinogenicity. The test is inexpensive and produces overnight results, but misses perhaps up to 40% of carcinogens. Also, the appearance of mutants does not prove that the chemical tested is a carcinogen. The procedure was developed by Bruce Ames at the University of California, Berkeley.¹

Amines: A family of compounds related to ammonia (NH3).¹

Anhydride: A chemical compound derived from an acid by elimination of a molecule of water. Thus, sulfur trioxide (SO3) is the anhydride of sulfuric acid (H2SO4), carbon dioxide (CO2) is the anhydride of carbonic acid (H2CO3), and phthalic acid [C6H4(CO2H)2] minus water gives phthalic anhydride [C6H4(CO2)O]. Not to be confused with anhydrous.³

Antagonistic effect: The interaction of two or more chemical substances on a biological system whose combined effect is less than the sum of the effects of the substances.¹

Antimalarial: Serving to prevent, check or cure malaria.²

Aquatic: Related to environments that contain liquid water.¹

Auto-ignition temperature : he lowest temperature at which a gas or vapor that is mixed with air will ignite without the presence of a flame or spark.¹

Azo compounds: Relating to or containing the bivalent group N==N united at both ends to carbon.²


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Base : Chemicals that release hydroxide ions (OH-) in solution. Such solutions have a soapy feel, neutralize acids, and conduct electricity.¹

Benzylic group: a univalent radical C6, H5, CH2, derived from toluene.²

Bifunctional or dual functional monomer : A molecule or compound usually containing carbon and of relatively low molecular weight and simple structure, which is capable of conversion to polymers, and which has two chemically distinct components that allow the molecule to participate in different kinds of reactions.

Bioaccumulate: The ability of a chemical to increase in concentration in organisms that reside in contaminated environments. Chemicals likely to bioaccumulate are not readily decomposed in the environment or in the organism and are likely to be stored in fatty tissue.¹

Bioconcentration: The increase in the amount of a chemical in an organism resulting from the uptake, or absorption, of the substance exceeding the rate of metabolism or excretion.¹

Biodegradable: Describes a substance that can be metabolized into simpler components. The degradation or decomposition is usually performed by bacteria or microbes.¹

Biodegradation: The metabolic breakdown of materials into simpler components by living organisms.¹


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Carcinogen: A chemical substance or type of radiation that can cause cancer in exposed animals or humans. There is no single definition of the evidence necessary to classify a substance as a carcinogen. Four sources of evidence are used: EPIDEMIOLOGY, long term animal testing, short-term tests (such as the AMES TEST), and STRUCTURE-ACTIVITY RELATIONSHIPS. Separate guidelines and policies defining carcinogens have been used by the United States Environmental Protection Agency, the Occupational Safety and Health Administration, the Consumer Product Safety Commission, and the Food and Drug Administration. These agencies, and the International Agency for Research on Cancer, classify chemicals by the degree of evidence available as to their carcinogenicity…Carcinogens vary in their estimated ability to induce cancer.¹

Catalyst: A substance that enables a chemical reaction to proceed at a usually faster rate or under different conditions (as at a lower temperature) than otherwise possible.²

Cationic: Possessing a positive charge

Chelating agent: A chemical compound that has the ability to bind strongly with metal ions.¹

Chemical intermediate: A compound considered as a chemical stepping stone between the parent substance (or raw materials) and the final product(s).³

Choline: Member of the vitamin B complex. Essential in the diet of rats, rabbits, chickens, and dogs. In humans it is required for lecithin formation and can replace methionine in the diet. There is no evidence of disease in humans caused by choline deficiency. It is a dietary factor important in furnishing free methyl groups for transmethylation; has a lipotropic function.³

Chronic: Marked by long duration or frequent recurrence : not acute.²

Chronic exposure: In toxicology, doses that extend for long periods, from six months to a lifetime.¹

Chronic toxicity: Adverse health effects that are either the result of chronic exposure or are permanent or long-lasting, as in scarring of lung tissue, following a shorter exposure.¹

Closed cell foams : a nonabsorbent cellular plastic in which few of the cells are interconnected.

Coalescent: A material that assists in filmmaking by helping polymer particles flow together to form a continuous film.³

Combustible: Capable of combustion, an act or instance of burning.²

Copolymerize: A material produced by the polymerization of two or more dissimilar monomers, e.g., styrene-butadiene synthetic rubber.³

Coupling agent: A material used to protect fiberglass laminates from effects of water absorption.³


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Decompose: To break down into constituent parts or elements or into simpler compounds, to undergo chemical breakdown; decay, rot.²

Dehydrating agent: A substance that is capable of removing water from a material or drying a material.

Dietary intake: That which is ingested (eaten) or consumed through available foods.

Dose-response assessment: Characterization of the relationship between the dose (exposure) of a chemical and the anticipated incidence of an adverse health or environmental effect in an exposed population.&sup4;


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Electrodeposition: To deposit (as a metal or rubber) by electrolysis, or by producing chemical changes by passing an electric current through a solution or suspension. ²,³

Electrolysis: The passage of an electric current through an electrolyte, causing the migration of the positively charged ions to the negative electrode (cathode) and the negatively charged ions to the positive electrode (anode).¹

Embryofetal death: Death which occurs during in utero development. Related terms include: embryolethality (death which occurs during the embryonic period); fetolethality (death which occurs during the fetal period, i.e., after completion of organogenesis).&sup7;

Embryotoxic: A non-specific term to indicate adverse effects on the developing embryo.

Emollient: A softening agent, especially for skin and mucous membranes

Environmental fate: The end result of the physical, chemical, and/or biological changes occurring in a chemical after its release into the environment.¹

Environmental partitioning: The distribution of a chemical among the environmental media (air, water, soil).&sup4;

Environmental pathways: The routes by which a chemical moves after release into the environment.&sup4;

Environmental transformation: A description of the processes or mechanisms which contribute to the degradation (chemical and biological) of a chemical in the environment. The nature of the environmental transformation is highly dependent on the environmental compartment (medium) in which the chemical resides (air, water, soil, sediment).

Environmental transport: The movement of a chemical after release into the environment.&sup4;

Epidemiology: The science that deals with the incidence and distribution of disease or other medical problems in a population.

Ester: Any of a class of often fragrant organic compounds that can be represented by the formula RCOOR´ and that are usually formed by the reaction between an acid and an alcohol with elimination of water.²

Excipient: An inert substance used as a diluent or vehicle for a drug.&sup6;

Exothermic: Decribes a process or chemical reaction that is accompanied by evolution of heat, for example, combustion reactions.³

Explosive Limits: The range of concentration of a flammable gas or vapor (% by volume in air) in which explosion can occur upon ignition in a confined area.³

Exposure: Contact between a chemical, physical, or biological agent and the outer surfaces of an organism. Exposure to an agent does not imply that it will be absorbed or that it will produce an effect.¹

Exposure assessment: The qualitative or quantitative determination or estimation of the magnitude, frequency, duration and route of exposure.&sup4;

Extract: To withdraw by physical or chemical process; also: to treat with a solvent so as to remove a soluble substance (extractability (n); extractable (adj)).²


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Fatty acid: A carboxylic acid derived from or contained in an animal or vegetable fat or oil. All fatty acids are composed of a chain of alkyl groups containing from 4 to 22 carbon atoms (usually an even number) and characterized by a terminal carboxyl group - COOH. The generic formula for mentioned acetic is CH3(CH2)xCOOH (the carbon atom count includes the carboxyl group). Fatty acids may be saturated or unsaturated (olefinic), and solid, semisolid, or liquid. They are classed among the lipids, together with soap and waxes.³

Feedstock: Gaseous or liquid petroleum-derived hydrocarbons or mixtures of hydrocarbons from which gasoline, fuel oil, and petrochemicals are produced by thermal or catalytic cracking… Feedstocks commonly used include ethane, propane, butane, butene, benzene, toluene, xylene, naphtha, and gas oils.³

Fetotoxic: Describing a chemical substance or other agent that has adverse effects on a developing fetus.¹ (fetotoxicity (n)).

Flammability: The ease with which a material (gas, liquid, or solid) will ignite either spontaneously (pyrophoric) or from exposure to a high-temperature environment (autoignition) or a spark or open flame. It also involves the rate of spreading of a flame once it has started. The more readily ignition occurs, the more flammable the material; less easily ignited materials are said to be combustible, but the line of demarcation is often indefinite and depends on the state of subdivision of the material, as well as its chemical nature.³

Flash point: The lowest temperature at which a flammable liquid produces a sufficient amount of vapor to ignite with a spark.¹

Flocculating: Causing suspended particles to aggregate in a way that causes some clumps or tufts; precipitate.²,³

Formate: a salt or ester of formic acid.²

Free radical: A molecular fragment having one or more unpaired electrons, usually short-lived and highly reactive.

Fugitive emissions: Any gas, liquid, solid, mist, dust, or other material that escapes from a product or process and is not routed to a pollution control device.¹

Fungicide: an agent that destroys fungi or inhibits their growth.²


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Genotoxic: Describing a chemical or physical agent capable of damaging the genes in a cell.¹ (genotoxicity (n)).


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Halide: a binary compound of a halogen with a more electropositive element or radical.²

Halogen: One of the electronegative elements of group VII A of the periodic table (fluorine, chlorine, bromine, iodine, astatine, listed in order of their activity, fluorine being the most active of all chemical elements).³

Hazard: A potentially dangerous inherent property of a substance.&sup4;

Hazard identification: Recognition of the potential of a substance to cause harm to human health or the environment.

Hemolysis: A breaking down of red blood cells with the liberation of hemoglobin.²

Homopolymer: A natural or synthetic polymer derived from a single monomer, such as a polymer of ethylene.³

Humectant: A substance having affinity for water with stabilizing action on the water content of a material. A humectant keeps within a narrow range the moisture content caused by humidity fluctuations.³

Hydrogen peroxide: An unstable compound H2O2 used as an oxidizing and bleaching agent, an antiseptic, and a propellant.²

Hydrogenation: Any reaction of hydrogen with an organic compound. It may occur either as direct addition of hydrogen to the double bonds of unsaturated molecules, resulting in a saturated product, or it may cause rupture of the bonds of organic compounds, with subsequent reaction of hydrogen with the molecular fragments.³

Hydrolysis: The chemical reaction of a substance with water, resulting in the splitting of the larger molecule into smaller parts; an important degradation mechanism for pollutants in water or on land.¹

Hydroperoxide: A compound containing an O2H group.²


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Impurity: The presence of one substance in another, often in such low concentration that it cannot be measured quantitatively by ordinary analytical methods. It is impossible to prepare an ideally pure substance. In certain metal crystal lattices, foreign substances can exist in as low a concentration as one-millionth of an atomic percent. For example, arsenic atoms are present in germanium crystals in this percentage; this fact is largely responsible for the semiconducting properties of germanium. Here the impurity is beneficial, but often it is detrimental, for example, in graphite used as a moderator in nuclear reactors, and in many metallic catalysts. In the air, trace amounts of sulfur dioxide and carbon monoxide are potentially dangerous impurities in concentration of 5 ppm of sulfur dioxide and 50 ppm of carbon monoxide.³

In vitro: In glass, outside an intact living organism. Refers to experiments that are conducted in Petri dishes, test tubes, and like apparatus. Chemical toxicity tests performed in the laboratory using cell or tissue cultures are in vitro tests.¹

In vivo: In a living organism. Experiments performed inside living organisms, such as chemical toxicity tests that involve the introduction of the tested substance into or on the body of an animal.¹

Inhibitor: A compound that retards or stops an undesired chemical reaction, such as corrosion, oxidation, or polymerization.³

Initiator: An agent used to start the polymerization of a monomer. Its action is similar to that of a catalyst, except that it is usually consumed in the reaction.³

Ion exchange resins: Synthetic resins containing an active group that gives the resin a property of combining with or exchanging ions (an atom or molecule that carries a positive or negative charge) between the resin and a solution. For example, water softening -- a form of cation exchange --, or the conversion of hard water to soft water, involves exchanging ions of calcium and magnesium present in the hard water with sodium ions present on the resin.¹,²,³

Isomer: One of two or more molecules having the same number and kind of atoms and hence the same molecular weight, but differing in respect to the arrangement or configuration of the atoms.³


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Ketone: A class of liquid organic compounds in which the carbonyl group, C=O, is attached to two alkyl groups; they are derived by oxidation of secondary alcohols. The simplest member of the series is acetone, CH3C(O)CH3, but many more complex ketones are known.³


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