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Lithography: The process of printing from a plane surface (as a smooth stone or metal plate) on which the image to be printed is ink-receptive and the blank area ink-repellent; the process of producing patterns on semiconductor crystals for use as integrated circuits.²
Metabolic acidosis: Decreased pH and bicarbonate content of the body fluids caused either by the accumulation of excess acids stronger than carbonic acid or by abnormal losses of fixed base from the body, as in diarrhea or renal disease.&sup8;
Methemoglobinemia: The disease state characterized by inadequate tissue oxygenation caused by excessive levels of blood methemoglobin. Methemoglobin is a hemoglobin molecule with a central iron atom in an oxidized (ferric) state. Methemoglobin cannot combine with and carry oxygen to the tissues, and thus, a high level of red blood cells in the methemoglobin state can lead to hypoxia, a deficiency of tissue oxygen.¹
Microbial: Of or related to microorganisms, small organisms that can only be seen with the aid of a microscope. The term microbe (microorganism) includes viruses, bacteria, yeast, molds, protozoa, and small algae. Microbes are important for degradation or decomposition of organic compounds in the environment.¹
Migration: Movement of a substance from one material to another with which it is in intimate contact. For example, an ingredient of a food package may migrate into the packaged product.³
Miscibility: The ability of a liquid or gas to dissolve uniformly in another liquid or gas.³
Molluscide: An agent for destroying mollusks (as snails).²
Monomer: A molecule or compound usually containing carbon and of relatively low molecular weight and simple structure, which is capable of conversion to polymers, synthetic resins or elastomers by combination with itself or other similar molecules or compounds.³
Mutagen: Any agent that has the capability of causing a permanent change in the genes of a cell.¹
Mutagenic: Capable of causing a change, or mutation, generally in genetic material (DNA) or in living cells. Some chemical agents as well as ionizing radiation can act as mutagens.¹,³
Nitrosamine: Any of a series of organic compounds in which NNO is attached to alkyl or aryl group, e.g., diphenylnitrosamine (C6H5)2NNO or dimethylnitrosamine (CH3)2NNO. Such compounds are formed by reaction between an amine and NOx or nitrites. They occur in many food products, whiskey, herbicides, and cosmetics, as well as in industrial environments such as tanneries, rubber factories, and iron foundries. They are also formed within the body by reaction of amine-containing drugs with the nitrites resulting from bacterial conversion of nitrates. Nitrosamines have been found to be strong carcinogens in laboratory animals.³
No Observed Adverse Effect Level (NOAEL): The dose of a chemical at which there is no increase in the frequency or severity of adverse effects noted in an exposed population.&sup4;
Organic solvent: A liquid hydrocarbon such as methyl ethyl ketone or toluene used to dissolve paints, varnishes, grease, oil, or other hydrocarbons.¹
Oxidizing agent: Any material that attracts electrons, thereby oxidizing another atom or molecule. The oxidizing agent itself is reduced; that is, it gains electrons. The material donating the electron is the reducing agent. Chlorine and oxygen are good oxidizing agents.¹
Partition: The distribution of a chemical between environmental compartments; air-water, water-soil, air-soil. A partition coefficient describes the steady state distribution of a chemical between two phases.
Parts Per Million (ppm): A unit of measure commonly employed to express the number of parts (e.g., grams) of a chemical contained within a million parts of gas (air), liquid (water), or solid (soil).¹
Parts per billion (ppb): A unit of measure commonly employed to express the number of parts (e.g., grams) of a chemical contained within a billion parts of gas (air), liquid (water), or solid (soil).1 This is a mass to volume measurement. In air, gases or vapors more commonly expressed as volume to volume measurements.
Peptide: any of various amides that are derived from two or more amino acids by combination of the amino group of one acid with the carboxyl group of another and are usually obtained by partial hydrolysis of proteins
Permeability: the quality or state of being permeable; that is, having pores or openings that allow liquids or gases to pass through.²
Permissible Exposure Limit (PEL): Occupational exposure limits established and enforced by the United States Occupational Safety and Health Administration. A legally allowable workplace exposure to a chemical or physical agent in the United States.¹
Peroxide: A compound (as hydrogen peroxide) in which oxygen is visualized as joined to oxygen.²
Photochemical: Describing a chemical reaction that is driven by sunlight.¹
Photochromic: Capable of changing color on exposure to radiant energy (as light).²
Photoconductive: Having, involving or operating by a method of electrical conductivity that is affected by exposure to light or other electromagnetic radiation.²
Photodegradation: The breakdown of complex materials into simpler materials by light.
Photolysis: The breakdown of a material by sunlight.¹
Photooxidation: Oxidation under the influence of radiant energy (as light).²
Plasticizer: Chemical additives used to increase the flexibility of plastics.¹
Polyelectrolyte: Synthetic or natural polymer containing many positive or negative charges. This material is water soluble, promotes changes in the fluid properties of aqueous suspensions and slurries, is strongly reactive with particles or ions carrying the opposite charge, and is frequently resistant to biological decomposition.¹
Polymer: A macromolecule formed by the chemical union of five or more identical combining units called monomers. In most cases the number of monomers is quite large (3500 for pure cellulose) and often is not precisely known. In synthetic polymers this number can be controlled to a predetermined extent, e.g., by short-stopping agents. (Combinations of two, three, or four monomers are called, respectively, dimers, trimers, and tetramers and are known collectively as oligomers.)³
Polymeric mordant: A substance capable of binding a dye to a textile fiber.³ In the case of vinyl benzyl chloride, a polymeric mordant is a positively charged polymer used to coat paper to fix negatively charged inks to give permanence.
Polymerization: A chemical reaction, usually carried out with a catalyst, heat, or light, and often under high pressure, in which a large number of relatively simple molecules combine to form a chainlike macromolecule. The combining units are called monomers, e.g., styrene is the monomer for polystyrene. The linear chains can be combined (cross-linked) by addition of appropriate chemicals.³
Product Safety: Product safety and product risk characterization or product risk assessment are used interchangeably throughout this web site and refer to a multi-step, scientific process to assess the probability that exposure to a Dow product during any stage of its lifecycle will lead to an unacceptable impact on human health or the environment.
Product Stewardship: The process and activities of making health, safety and environmental protection an integral part of designing, manufacturing, marketing, distributing, using, recycling and disposing of our products.
Prolonged exposure: Prolonged toxicity tests involve the administration of the test chemical on multiple occasions. The test chemical may be administered once or more each day, irregularly as when it is incorporated in the diet, at specific times such as during pregnancy or in some cases regularly but only at weekly intervals. Also, in the prolonged tests the experiment is usually conducted for not less than ninety days in the rat or mouse.&sup5;
Reaction kinetics: The rate of change of a chemical reaction from initial to final states under non equilibrium conditions.²
Reagent: A substance used (as in detecting or measuring a component, in preparing a product, or in developing photographs) because of its chemical or biological activity.²
Responsible Care®: The chemical industry's award winning program to improve health, safety and environmental performance.
Risk: Probability that a given exposure to a substance will cause harm.
Risk Assessment: The estimation of the likelihood of adverse effects occurring, taking into consideration the exposure, the nature of the effects, and the target population. It involves four steps: Hazard Identification, Dose Response, Exposure Assessment and Risk Characterization.&sup4; Throughout the site, used interchangeably with "Product Safety Assessment."
Risk Characterization: A description of the nature and magnitude of health or environmental risk. The description combines results of exposure assessment and hazard identification and describes the uncertainty associated with each step.&sup4;
Risk Management: The management of potential adverse effects of exposure to a chemical, taking into account social values, legal requirements, and costs of control.&sup4;
Saponification: The chemical reaction in which an ester is heated with aqueous alkali such as sodium hydroxide to form an alcohol (usually glycerol) and the sodium salt of the acid corresponding to the ester. The process is usually carried out on fats (glyceryl esters of fatty acids). The sodium salt form is called a soap.³
Scavenger: Any substance added to a system or mixture to consume or inactivate traces of impurities.
Sensitizer: A substance capable of causing an allergic response affecting the skin or possibly respiratory system.
Shock sensitive: Susceptibility of a chemical to rapidly decompose or explode when struck, vibrated or otherwise agitated.&sup9;
Short-term exposure limit (STEL): An occupational air concentration standard using 15-minute averaging times within an 8-hour workday. A STEL is set for a material that can cause adverse health effects if workers are exposed to higher concentrations for short periods. Materials not requiring a STEL can have short-term peaks without adverse effect, and only their overall 8-hour average must be below a certain limit.¹
Shortstop (shortstopping agent): A material used in a polymerization reaction to cut off the reaction at a predetermined point.
Skin sensitizer: A substance capable of causing an allergic response affecting the skin or possibly respiratory system.
Solvent: The dissolving medium, or liquid portion, of a solution. Water is frequently referred to as the universal solvent. The term also applies to organic materials (e.g., benzene, acetone, or gasoline) used to clean (dissolve) oils or grease from machinery, fabrics, or other surfaces, or to extract hydrocarbons from some source material.¹
Stearate: a salt or ester of stearic acid.²
Structure-Activity Relationship: The connection between the molecular structure of a chemical and its toxicity. Although only poorly predictive, an untested chemical similar in composition and spatial arrangement to a material known to be a human toxicant would be suspected to exhibit similar toxic effects based on a SAR analysis.¹
Surfactant: A substance that alters the properties, and especially lowers the attractive force exerted between molecules below a liquid surface upon those at the surface/air interface. The reduction in the attractive forces allows the liquid to flow. Derived from surface-active agent. Examples include detergents, wetting agents and emulsifiers.²,³
Synergy: Two or more agents working in a way that the total effect is greater than the predicted sum of the agents working together.¹
Teratogenic: Of, relating to, or causing developmental malformations² (or birth defects).
Threshold Limit Value (TLV®): Occupational exposure limit set by the American Conference of Governmental Industrial Hygienists. An airborne concentration of a gas or particle to which most workers can be exposed on a daily basis for a working lifetime without adverse effect.¹
Time-weighted average (TWA): A method employed to calculate the exposure of workers to airborne materials, which considers the duration of exposure to various airborne concentrations, usually during an 8-hour day.¹
Toxicant: Any chemical that has the potential of causing acute or chronic adverse effects in animals, plants, or humans.¹
Toxicity: The ability of a chemical substance to cause acute or chronic health effects in animals, plants or humans.¹
Transport: The movement of a chemical between environmental compartments, by air, water or migratory species.4
Uncertainty Factor: An adjustment to experimental toxicity data to help set acceptable levels of human exposure or dose. The uncertainty factor takes into consideration:
- Known differences between laboratory animals and humans and the uncertainty introduced by extrapolating from animal data to humans;
- Variation in susceptibility among humans;
- Strength of evidence that the chemical presents a real hazard to human health;
- Type and severity of the potential adverse effect;
- Potency of the toxic agent;
- Quality of the experimental data, and known differences between experimental conditions and realistic exposures.4
Validated: Officially sanctioned; supported or corroborated on a sound or authoritative basis; conforming to accepted principles.² Reproducible by other scientists.
Vapor Pressure: The pressure (usually expressed in millimeters of mercury) characteristic at any given temperature of a vapor in equilibrium with its liquid or solid form.
Vermiculite: Any of various micaceous minerals that are hydrous silicates resulting usually from expansion of the granules of mica at high temperatures to give a lightweight highly water-absorbent material, generally used as fillers.²
Viscous: Viscid; having an adhesive quality: sticky. Having or characterized by viscosity: the property of a fluid or semifluid that enables it to develop and maintain an amount of shearing stress dependent upon the velocity of flow and then to offer continued resistance to flow.²
Volatile: Describing a substance that evaporates or vaporizes rapidly at room temperatures.¹ For example, water is highly volatile.
Volatile Organic Compounds (VOCs): A category of volatile organic compounds with relatively high vapor pressures, a major category of air contaminants. Most VOCs are carbon-hydrogen compounds (hydrocarbons), but they also may be aldehydes, ketones, chlorinated hydrocarbons, and others. Thousands of individual compounds exist, including the unburnt hydrocarbon compounds emitted from automobiles or industrial processes and the organic solvents lost to evaporation from household, commercial, or industrial cleaning and painting operations, and other activities. Some VOCs participate in the atmospheric reactions that lead to photochemical air pollution, and excessive exposure to certain individual compounds is associated with skin irritation, central nervous system depression, and/or an increased risk or cancer.¹
