Definitions  are provided for many common terms used in Safety Data Sheets, labels  and other documents related to hazard communication. You may encounter other  terms, not listed here, that are unfamiliar to you. If you do not know or  understand a term, ask your supervisor for help.

GLOSSARY OF COMMON HAZARD COMMUNICATION TERMS


Acrylic:
A  family of synthetic resins made by polymerizing esters of acrylic  acids.

Action level:
A term used by OSHA and NIOSH (see  entries) to express the level of toxicant that requires medical surveillance,  usually one half of the permissible exposure limit.

Activated  charcoal:
Charcoal is an amorphous form of carbon formed by burning wood,  nutshells, animal bones, and other carbonaceous materials. Charcoal becomes  activated by heating it with steam to 800-900 degrees C. During this treatment,  an aporous, submicroscopic internal structure is formed that gives it an  extensive internal surface area. Activated charcoal is commonly used as a gas or  vapor adsorbent in air-purifying respirators and as a solid sorbent in air  sampling.

Additives:
An inclusive name for a wide range of  chemical substances that are added in low percentage to stabilize certain end  products, such as antioxidants in rubber.

Aden-  (prefix):
Pertaining to a gland. Adenoma is a tumor of gland-like  tissue.

Adenoma:
An epithelial tumor, usually benign, with a  gland-like structure (the cells lining gland-like depressions or cavities in the  stroma).

Administrative controls:
Methods of controlling  employee exposures by job rotation, work assignment, time periods away from the  hazard, or training in specific work practices designed to reduce the  exposure.

Adsorption:
The condensation of gases, liquids, or  dissolved substances on the surfaces of solids.

AIHA:
American  Industrial Hygiene Association.

Air:
The mixture of gases that  surrounds the earth; its major components are as follows: 78.08 percent  nitrogen, 20.95 percent oxygen, 0.03 percent carbon dioxide, and 0.93 percent  argon. Water vapor (humidity) varies. See standard air.

Air  monitoring:
The sampling for and measuring of pollutants in the  atmosphere.

Air mover:
Any device that is capable of causing  air to be moved from one space to another. Such devices are generally used to  exhaust, force, or draw gases through specific assemblies.

Air quality  criteria:
The amounts of pollution and lengths of exposure at which  specific adverse effects to health and welfare take  place.

Air-purifying respirator:
Respirators that use filters  or sorbents to remove harmful substances from the air.

Air-supplied  respirator:
Respirator that provides a supply of breathable air from a  clean source outside of the contaminated work area.

Alloy:
A  mixture of metals (and sometimes a non-metal), as in  brass.

Alveoli:
Tiny air sacs of the lungs, formed at the ends  of bronchioles; through the thin walls of the alveoli, the blood takes in oxygen  and gives up carbon dioxide in respiration.

Alveolus:
A general  term used in anatomical nomenclature to designate a small sac-like  dilation.

Anaerobic bacteria:
Any bacteria that can survive in  a partial or complete absence of  air.

Anaphylaxis:
Hypersensitivity resulting from sensitization  following prior contact with a chemical or protein.

Andro-  (prefix):
Man, male. An androgen is an agent that produces masculinizing  effects.

Anemia:
Deficiency in the hemoglobin and erythrocyte  content of the blood. Term refers to a number of pathological states that may be  attributed to a large variety of causes and appear in many different  forms.

Angi-, angio- (prefix):
Blood or lymph vessel. Angiitis  is the inflammation of a blood vessel.

ANSI:
American National  Standards Institute: a voluntary membership organization (run with private  funding) that develops consensus standards nationally for a wide variety of  devices and procedures.

Anthracosilicosis:
A complex form of  pneumoconiosis; a chronic disease caused by breathing air containing dust that  has free silica as one of its components and that is generated in the various  processes in mining and preparing anthracite (hard) coal, and, to a lesser  degree, bituminous coal.

Anthracosis:
A disease of the lungs  caused by prolonged inhalation of dust that contains particles of carbon and  coal.

Antibiotic:
A substance produced by a microorganism that  in dilute solutions kills other organisms, or retards or completely represses  their growth, normally in doses that do not harm higher orders of  life.

Antibody:
Any of the body globulins that combine  specifically with antigens to neutralize toxins, agglutinate bacteria, or cells,  and precipitate soluble antigens. It is found naturally in the body or produced  by the body in response to the introduction into its tissues of a foreign  substance.

Antigen:
A substance that when introduced into the  body stimulates antibody production.

Antioxidant:
A compound  that retards deterioration by oxidation. Antioxidants for human food and animal  feeds, sometimes referred to as freshness preservers, retard rancidity of fats  and lessen loss of fat-soluble vitamins (A, D, E, K). Antioxidants also are  added to rubber, motor lubricants, and other materials to inhibit  deterioration:

Argyria:
A slate-gray or bluish discoloration of  the skin and deep tissues caused by the deposit of insoluble albuminate of  silver, occurring after the medicinal administration for a long period of a  soluble silver salt; formerly fairly common after the use of insufflations of  silver-containing materials into the nose and sinuses. Also seen with  occupational exposure to silver-containing  chemicals.

Asbestos:
A hydrated magnesium silicate in fibrous  form.

Asbestosis:
A disease of the lungs caused by inhalation  of fine airborne asbestos fibers.

ASHRAE:
American Society of  Heating, Refrigeration, and Air Conditioning  Engineers.

Asphyxia:
Suffocation from lack of oxygen. Chemical  asphyxia is produced by a substance such as carbon monoxide that combines with  hemoglobin to reduce the blood's capacity to transport oxygen. Simple asphyxia  is the result of exposure to a substance, such as methane, that displaces  oxygen.

Assigned Protection Factor (APF):
The level of  respiratory protection expected from a respirator that its properly functioning,  has been properly fitted, and is worn by a worker trained in its use. APFs can  be used to help provide an estimate of the maximum concentrations of a  contaminant in which a particular respirator can be  used.

Asthma:
Constriction of the bronchial tubes in response  to irritation, allergy, or other stimulus.

Atmospheric  pressure:
The pressure exerted in all directions by the atmosphere. At  sea level, mean atmospheric pressure is 29.92 in. Hg, 14.7 psi, or 407 in.  wg.

Atrophy:
Arrested development or wasting away of cells and  tissue.

Baritosis:
An inert pneumoconiosis produced by the  inhalation of insoluble barium compounds.

Base:
A compound that  reacts with an acid to form a salt; another term for alkali. It turns litmus  paper blue.

Bauxite pneumoconiosis:
Shaver's disease. Found in  workers exposed to fumes containing aluminum oxide and minute silica particles  arising from smelting bauxite in the manufacture of  corundum.

BEI:
See Biological exposures  indices.

Benign:
Not malignant. A benign tumor is one that does  not metastasize or invade tissue. Benign tumors may still be lethal because of  pressure on vital organs.

Berylliosis:
Chronic beryllium  intoxication.

Biological Exposure Indices (BEI):
Advisory  biological limit values adopted by the ACGIH for some substances. Indices are  based on urine, blood, or expired air samples. A BEI may be a value for the  substance itself or it may refer to a level of a metabolite. BEIs represent the  value of the biological determinant that is most likely to be the value of that  determinant obtained from a worker exposed at the 8-hour TLV-TWA for the  substance in question.

Biological oxygen demand (BOD):
Quantity  of oxygen required for the biological and chemical oxidation of waterborne  substances under test conditions.

Biopsy:
Careful removal of  small bits of living tissue from the body for further study and examination,  usually under the microscope.

Black liquor:
A liquor composed  of alkaline and organic matter resulting from digestion of wood pulp and cooking  acid during the manufacture of paper.

Bone marrow:
A soft  tissue that constitutes the central filling of many bones and that produces  blood corpuscles.

Bradycardia:
Abnormal slowness of the  heartbeat, as evidenced by the slowing of the pulse rate to 50 or  less.

Braze:
To solder with any relatively infusible  alloy.

Breathing zone:
Imaginary globe of two foot radius  surrounding the head.

Breathing zone sample:
An air-sample  collected in the breathing zone of workers to assess their exposure to airborne  contaminants.

Bronchial tubes:
Branches or subdivisions of the  trachea (windpipe). A bronchiole is a branch of a bronchus, which is a branch of  the windpipe.

Bronchiectasis:
A chronic dilation of the bronchi  or bronchioles marked by fetid breath and paroxysmal coughing, with the  expectoration of mucopurulent matter. It may affect the tube uniformly, or may  occur in irregular pockets, or the dilated tubes may have terminal bulbous  enlargements.

Bronchiole:
The slenderest of the many tubes that  carry air into and out of the lungs.

Bronchiolitis:
See  Bronchopneumonia.

Brochoalveolitis:
Bronchopneumonia.

Bronchopneumonia:
A  name given to an inflammation of the lungs that usually begins in the terminal  bronchioles. These become clogged with a mucopurulent exudate forming  consolidated patches in adjacent lobules. The disease is essentially secondary  in character, following infections of the upper respiratory tract, specific  infectious fevers, and debilitating diseases.

Buffer:
Any  substance in a fluid that tends to resist the change in ph when acid or alkali  is added.

Bursa:
A synovial lined sac that facilitates the  motion of tendons; usually near a joint.

Bursitis:
Inflammation  of a bursa.

Byssinosis:
Disease occurring to those who  experience prolonged exposure to heavy air concentrations of cotton or flax  dust.

Cancer:
A cellular tumor the natural course of which is  fatal and usually associated with formation of secondary  tumors.

Carbon black:
Essentially a pure carbon, best known as  common soot. Commercial carbon black is produced by making soot under controlled  conditions. It is sometimes times called furnace black, acetylene black, or  thermal black.

Carbon monoxide:
A colorless, odorless, toxic  gas produced by any process that involves the incomplete combustion of  carbon-containing substances. It is emitted through the exhaust of  gasoline-powered vehicles.

Carboy:
A large glass bottle,  usually protected by a crate.

Carboxyhemoglobin:
The reversible  combination of carbon monoxide with  hemoglobin.

Carcinoma:
Malignant tumors derived from epithelial  tissues, that is, the outer skin, the membranes lining the body cavities, and  certain glands.

Cardiac:
(1) Pertaining to the heart; (2) a  cordial or restorative medicine; (3) a person with heart  disorder.

Cardiovascular:
Relating to the heart and to the  blood vessels or circulation.

Cas number:
Identifies a  particular chemical by the Chemical Abstract Service, a service of the American  Chemical Society that indexes and compiles abstracts of worldwide chemical  literature called Chemical Abstracts.

Catalyst:
A substance  that changes the speed of a chemical reaction but that undergoes no permanent  change itself. In respirator use, a substance that converts a toxic gas (or  vapor) into a less toxic gas (or vapor). Usually catalysts greatly increase the  reaction rate, as in conversion of petroleum to gasoline by cracking. In paint  manufacture, catalysts, which hasten film-forming, sometimes become part of the  final product. In most uses, however, they do not, and can often be used over  again.

Caustic:
Something that strongly irritates, burns,  corrodes, or destroys living tissue. See Alkali.

Chemical  cartridge:
The type of absorption unit used with a respirator for removal  of low concentrations of specific vapors and gases.

Chemical  reaction:
A change in the arrangement of atoms or molecules to yield  substances of different compositions and properties. Common types of reactions  are combination, decomposition, double decomposition, replacement, and double  replacement.

Chronic:
Persistent, prolonged,  repeated.

Combustible Liquid:
As defined by OSHA, it is any  liquid having a flash point as determined by a closed cup method, of equal to or  greater than 100 degrees F. Combustible liquids are divided into two  classes:
· "Class II liquids" include those with flashpoints at or above 100  degrees F. and below 140 degrees F., except any mixture having components with  flashpoints of 200 degrees F. or higher, the volume of which make up 99 percent  or more of the total volume of the mixture.
· "Class III liquids" include  those with flashpoints at or above 140 degrees F. Class III liquids are divided  into two subclasses:
· "Class IIIA liquids" include those with flashpoints at  or above 140 degrees F. and below 200 degrees F., except any mixture having  components with flashpoints of 200 degrees F., or higher, the total volume of  which make up 99 percent or more of the total volume of the mixture.
·  "Class IIIB liquids" include those with flashpoints at or above 200 degrees F.  This standard does not cover Class IIIB liquids. Where the term "Class III  liquids" is used in this section, it means only Class IIIA liquids.

Compound:
A substance composed of two or more elements joined  according to the laws of chemical combination. Each compound has its own  characteristic properties different from those of its constituent  elements.

Concentration:
The amount of a given substance in a  stated unit of measure. Common methods of stating concentration are percent by  weight or by volume, weight per unit volume, normality, and so  on.

Condensate:
The liquid resulting from the process of  condensation. In sampling, the term is generally applied to the material that is  removed from a gas sample by means of  cooling.

Condensation:
Act or process of reducing from one form  to another denser form such as steam to water.

Confined  space:
Any enclosed area not designed for human occupancy that has a  limited means of entry and egress and in which existing ventilation is not  sufficient to ensure that the space is free of a hazardous atmosphere, oxygen  deficiency, or other known or potential hazards. Examples are storage tanks,  boilers, sewers, and tank cars. A permit-required confined space, as defined by  the OSHA standard, is one that requires a permit process and implementation of a  comprehensive confined space entry program prior to entry.

Conjunctiva:
The delicate mucous membrane that lines the  eyelids and covers the exposed surface of the  eyeball.

Conjunctivitis:
Inflammation of the  conjuctiva.

Contact dermatitis:
Dermatitis caused by contact  with a substance - gaseous, liquid, or solid. May be caused by primary  irritation or an allergy.

Copolymers:
Mixed polymers or  heteropolymers. Products of the polymerization of two or more substances at the  same time.

Cornea:
Transparent membrane covering the anterior  portion of the eye.

Corrosion:
Physical change, usually  deterioration or destruction, brought about through chemical or electrochemical  action, as contrasted with erosion, caused by mechanical  action.

Cristobalite:
A crystalline form of free silica,  extremely hard and inert chemically, and very resistant to heat. Quartz in  refractory bricks and amorphous silica in diatomaceous earth are altered to  cristobalite when exposed to high temperatures  (calcined).

Cryogenics:
The field of science dealing with the  behavior of matter at very low temperatures.

Cubic centimeter  (cm3):
A volumetric measurement that is equal to one milliliter  (ml).

Culture (biology):
A population of microorganisms or  tissue cells cultivated in a medium.

Cyanosis:
Blue appearance  of the skin, especially on the face and extremities, indicating a lack of  sufficient oxygen in the arterial blood.

Cytotoxin:
A  substance, developed in the blood serum, having a toxic effect upon  cells.

Dangerous to life or health, immediately (IDLH):
Used to  describe very hazardous atmospheres where employee exposure can cause serious  injury or death within a short time or serous delayed  effects.

Decontaminate:
To make safe by eliminating poisonous  or otherwise harmful substances, such as noxious chemicals or radioactive  material.

Density:
The ratio of mass to  volume.

Dilution:
The process of increasing the proportion of  solvent or diluent (liquid) to solute or particulate matter  (solid).

Dispersion:
The general term describing systems  consisting of particulate matter suspended in air or other fluid; also, the  mixing and dilution of contaminant in the ambient  environment.

Diuretic:
Anything that promotes excretion of  urine.

DNA:
Deoxyribonucleic acid. The genetic material within  the cell.

Dose:
(1) Used to express the amount of a chemical or  of ionizing radiation entry absorbed in a unit volume or an organ or individual.  Dose rate is the dose delivered per unit of time. Dose rate is the dose  delivered per unit of time. (see also Roentgen, Rad, Rem.) (2) Used to express  amount of exposure to a chemical substance.

Dyspnea:
Shortness  of breath, difficult or labored breathing. More strictly, the sensation of  shortness of breath.

Dysuria:
Difficulty or pain in  urination.

Ecology:
The science of the relationships between  living organisms and their environments.

Eczema:
A skin disease  or disorder. Dermatitis.

Effluent:
Generally something that  flows out or forth, like a stream flowing out into a lake. In terms of  pollution, an outflow of a sewer, storage tank, canal, or other  channel.

Elastomer:
In a chemical industry sense, a synthetic  polymer with rubber-like characteristics; a synthetic or natural rubber or a  soft, rubbery plastic with some degree of elasticity at room  temperature.

Element:
Solid, liquid, or gaseous matter that  cannot be further decomposed into simpler substances by chemical means. The  atoms of an element may differ physically but do not differ chemically. All  atoms of an element contain a definite number of protons and thus have the same  atomic number.

Embryo:
The name for the early stage of  development of an organism. In humans, the period from conception to the end of  the second month.

Emission factor:
Statistical average of the  amount of a specific pollutant emitted from each type of polluting source in  relation to a unit quality of material handled, processed, or  burned.

Emission standards:
The maximum amount of pollutant  permitted to be discharged from a single polluting source.

Emphysema:
A lung disease in which the walls of the air sacs  (alveoli) have been stretched too thin and have broken  down.

Emulsion:
A suspension, each in the other, of two or more  unlike liquids that usually do not dissolve in each  other.

Enamel:
A paint-like oily substance that produces a  glossy finish to a surface to which it is applied, often containing various  synthetic resins. It is lead free, in contrast to the ceramic enamel, that is,  porcelain enamel, which contains lead.

Endemic:
(1) Present in  a community of among a group of people; usually refers to a disease prevailing  continually in a region. (2) The continuing prevalence of a disease, as  distinguished from an epidemic.

Endocrine:
Secreting without  the means of a duct or tube. The term is applied to certain glands that produce  secretions that enter the bloodstream or the lymph directly and are then carried  to the particular gland or tissue whose function they  regulate.

Endothermic:
Characterized by or formed with  absorption of heat.

Endotoxin:
A toxin that is part of the wall  of a microorganism and is released when that organism  dies.

Engineering controls:
Methods of controlling employee  exposures by modifying the source or reducing the quantity of contaminants  released into the work  environment.

Enteric:
Intestinal.

Enterotoxin:
A  toxin specific for cells of the intestine; gives rise to symptoms of food  poisoning.

Enzymes:
Delicate chemical substances, mostly  proteins, that enter into and bring about chemical reactions in living  organisms.

Epicondylitis:
Inflammation of certain bony  prominences in the area of the elbow, for example, tennis  elbow.

Epidermis:
The superficial scarfskin or upper (outer)  layer of skin.

Epilation:
Temporary or permanent loss of body  hair.

Epithelioma:
Carcinoma of the epithelial cells of the  skin and other epithelial surfaces.

Erythema:
Reddening of the  skin.

Eschar:
The crust formed after injury by a caustic  chemical or heat.

Esters:
Organic compounds that may be formed  by interaction between an alcohol and an acid, or by other means. Esters are  nonionic compounds, including solvents and natural fats.

Exhalation  valve:
A device that allows exhaled air to leave a respirator and  prevents outside air from entering through the valve.

Exhaust  ventilation:
The removal of air, usually by mechanical means, from any  space. The flow of air between two points is because of a pressure difference  between the two points. This pressure difference causes air to flow from the  high-pressure to the low-pressure zone.

Exothermic,  Exothermal:
Characterized by or formed with evolution of  heat.

Exposure:
Contact with a chemical, biological, or  physical hazard.

Facepiece:
That portion of a respirator that  coves the wearer's nose and mouth in a half-mask facepiece, or the nose, mouth,  and eyes in a full facepiece. It is designed to make a gas-tight or dust-tight  fit with the face and includes the headbands, exhalation valves, and connections  for air-purifying device, or respirable gas source, or both.

Federal  Register:
Publication of U.S. government documents officially promulgated  under the law, documents whose validity depends upon such publication. It is  published on each day following a government working day. It is, in effect, the  daily supplement to the Code of Federal Regulations  (CFR).

Fibrillation:
Very rapid irregular contractions of the  muscle fibers of the heart resulting in a lack of synchronism of the  heartbeat.

Filter, HEPA:
High efficiency particulate air  filter. A disposable, extended-medium, dry-type filter with a particle removal  efficiency of no less than 99.97 percent for 0.3 um  particles.

Flammable Liquid:
As defined by OSHA, it is any  liquid having a flashpoint below 100 F (37.8 C), except any mixture having  components with flashpoints of 100 degrees F. or higher, the total of which make  up 99 percent or more of the total volume of the mixture. Flammable liquids are  known as Class I liquids. Class I liquids are divided into three classes:
·  Class IA includes liquids having flashpoints below 73 degrees F. and a boiling  point below 100 degrees F.
· Class IB includes liquids having flashpoints  below 73 degrees F. and a boiling point at or above 100 degrees F.
· Class  IC includes liquids having flashpoints at or above 73 degrees F. and below 100  degrees F.

Fume fever:
Metal fume fever is an acute condition  caused by a brief high exposure to the freshly generated fumes of metals, such  as zinc or magnesium, or their oxides.

Gastritis:
Inflammation  of the stomach.

General ventilation:
System of ventilation  consisting of either natural or mechanically induced fresh air movements to mix  with and dilute contaminants in the workroom air. This is not the recommended  type of ventilation to control contaminates that are toxic.

Genetic  effects:
Mutations or other changes produced by irradiation of the germ  plasm.

Gland:
Any body organ that manufactures some liquid  product and secretes it from its cells.

Grams per kilogram  (g/kg):
This indicates the dose of a substance given to test animals in  toxicity studies.

Gravity, specific:
The ratio of the mass of a  unit volume of a substance to the mass of the same volume of a standard  substance at a standard temperature. Water at 39.2 F (4 C) is the standard  substance usually referred to. For gases, dry air, at the same temperature and  pressure as the gas, is often taken as the standard  substance.

Halogenated hydrocarbon:
A chemical material that  has carbon plus one or more of these elements: chlorine, fluorine, bromine, and  iodine.

Hemoptysis:
Bleeding from the lungs, spitting blood, or  blood-stained sputum.

Hemorrhage:
Bleeding; especially profuse  bleeding, as from a ruptured or cut blood vessel (artery or  vein).

HEPA filter:
High-efficiency particulate air filter. A  disposable, extended-medium, dry-type filter with a particle removal efficiency  of no less than 99.97 percent for 0.3 um  particles.

Hepatitis:
Inflammation of the  liver.

Hepatotoxin:
Chemicals that produce liver  damage.

HVAC system:
Heating, ventilating, and air conditioning  system.

Hydration:
The process of converting raw material into  pulp by prolonged beating in water; to combine with water or the elements of  water.

Hypertension:
Abnormally high tension; especially high  blood pressure.

Hypothermia:
A systemic effect of cold stress;  condition of reduced body temperature.

IDLH:
Immediately  dangerous to life or health.

Immiscible:
Not miscible. Any  liquid that does not mix another liquid, in which case the result is two  separate layers or cloudiness or turbidity.

Incompatible:
A  term applied to liquid and solid systems to indicate that one material cannot be  mixed with another specified material without the possibility of a dangerous  reaction.

Inert (chemical):
Not having active  properties.

Inert gas:
A gas that does not normally combine  chemically with the base metal or filler metal.

Ingestion:
(1)  The process of taking substances into the stomach, such as food, drink, or  medicine. (2) With regard to certain cells, the act of engulfing or taking up  bacteria and other foreign matter.

Inhalation valve:
A device  that allows respirable air to enter the facepiece and prevents exhaled air from  leaving the facepiece through the intake  opening.

Innocuous:
Harmless.

Inorganic:
Used  to designate compounds that generally do not contain carbon, whose source is  matter other than vegetable or animal. Examples are sulfuric acid and salt.  Exceptions are carbon monoxide and carbon dioxide.

Intermediate:
A chemical formed as a middle step in a series of chemical reactions,  especially in the manufacture of organic dyes and pigments. In many cases, it  may be isolated and used to form a variety of desired products. In other cases,  the intermediate may be unstable or used up at  once.

Intoxication:
Either drunkenness or  poisoning.

Intraperitoneal:
Inside the space formed by the  membrane that lines the interior wall of the abdomen and covers the abdominal  organs.

Intrinsically safe:
Said of an instrument that is  designed and certified to be operated safely in flammable or explosive  atmospheres.

Jaundice:
Icterus. A serious symptom of disease  that causes the skin, the whites of the eyes, and even the mucous membranes to  turn yellow.

Keratitis:
Inflammation of the  cornea.

Lacquer:
A colloidal dispersion or solution of  nitrocellulose or similar film-forming compounds, resins, and plasticizers in  solvents and diluents used as a protective and decorative coating for various  surfaces.

Laryngitis:
Inflammation of the  larynx.

Latex:
Originally, a milky extract from the rubber  tree, containing about 35 percent rubber hydrocarbon, with the remainder being  water, proteins, and sugars. Also applied to water emulsions of synthetic  rubbers or resins.
In emulsion paints, the film-forming resin is in the form  of latex.

Lethal:
Capable of causing  death.

Leukemia:
A group of malignant blood diseases  distinguished by overproduction of white blood  cells.

Leukocytosis:
An abnormal increase in the number of  white blood cells.

Liquefied petroleum gas:
A compressed or  liquefied gas usually composed of propane, some butane, and lesser quantities of  other light hydrocarbons and impurities; obtained as a by-product in petroleum  refining. Used chiefly as a fuel and in chemical synthesis.

Lower  explosive limit (LEL):
The lower limit of flammability of gas or vapor at  ordinary ambient temperatures expressed by a percentage of the gas or vapor in  air by volume. This limit is assumed constant for temperatures up to 250 F (120  C); above this, it should be decreased by a factor of 0.7, because of  explosibility increases with higher temperatures.

Lymph  node:
Small oval bodies with a gland-like structure scattered throughout  the body in the course of the lymph vessels. Also known as lymphatic nodes,  lymph glands, and lymphatic glands.

Malaise:
A vague feeling of  bodily discomfort.

Malignant:
As applied to a tumor, cancerous  and capable of undergoing metastasis (invasion of surrounding  tissue).

Safety Data Sheet (SDS):
As part of hazard  communication standards (right-to-know laws), federal and state OSHA programs  require manufacturers and importers of chemicals to prepare compendia of  information on their products. Categories of information that must be provided  on MSDSs include physical properties, recommended exposure limits, personal  protective equipment, spill-handling procedures, first aid, health effects, and  toxicological data.

Maximum permissible concentration  (MPC):
Concentrations set by the National Committee on Radiation  Protection (NCRP); recommended maximum average concentrations of radionuclides  to which a worker may be exposed assuming that he works 8 hours a day, 5 days a  week, and 50 weeks a year.

Melanoderma:
Abnormal darkening of  the skin.

Melting point:
The transition point between the solid  and liquid states. Expressed as the temperature at which this change  occurs.

Membrane:
A thin, pliable layer of animal tissue that  covers a surface, lines the interior of a cavity or organ, or divides a  space.

Metal fume fever:
A flu-like condition caused by  inhaling heated metal fumes.

Mica:
A large group of silicates  of varying composition that are similar in physical properties. All have  excellent cleavage and can be split into very thin sheets. Used in electrical  insulation.

Mineral spirits:
A petroleum fraction with a  boiling range between 300 and 400 F (149 and 240 C).

Monomer:
A  compound of relatively low molecular weight that, under certain conditions,  either alone or with another monomer, forms various types and lengths of  molecular chains called polymers or copolymers of high molecular weight.  Styrene, for example, is a monomer that polymerizes readily to form polystyrene.  See polymer.

MPE:
Maximum permissible  exposure.

MPL:
May be either maximum permissible level, limit,  or dose; refers to the tolerable dose rate for humans exposed to nuclear  radiation.

MSHA:
The Mine Safety and Health Administration; a  federal agency that regulates safety and health in the mining  industry.

MSDS:
Material safety data  sheet.

Musculoskeletal system:
The combined system of muscles  and bones that comprise the internal biomechanical  environment.

Mutation:
A transformation of the gene that may  result in the alteration of characteristics of offspring.

NA or  N.A.:
An abbreviation for "Not  Applicable".

Narcosis:
Stupor or unconsciousness produced by  chemical substances.

Narcotics:
Chemical agents that completely  or partially induce sleep.

Necrosis:
Death of body  tissue.

Nephrotoxins:
Chemicals that produce kidney  damage.

Nephritis:
Inflammation of the  kidneys.

Neuritis:
Inflammation of a  nerve.

Neurotoxin:
Chemicals that produce their primary effect  on the nervous system.

NFPA:
The National Fire Protection  Association; a voluntary membership organization whose aim is to promote and  improve fire protection and prevention. The NFPA publishes the National Fires  Codes.

NIOSH:
The National Institute for Occupational Safety  and Health; a federal agency that conducts research on health and safety  concerns, tests and certifies respirators, and trains occupational health and  safety professionals.

Nuisance dust:
Dust with a long history  of little adverse effect on the lungs; does not produce significant organic  disease or toxic effect when exposures are kept at reasonable  levels.

Odor threshold:
The minimum concentration of a  substance at which a majority of test subjects can detect and identify the  characteristic odor of a substance.

Olefins:
A class of  unsaturated hydrocarbons characterized by relatively great chemical activity.  Obtained from petroleum and natural gas. Examples are butene, ethylene, and  propylene. Generalized formula:  CnH2n.

Oncogenic:
Tumor-generating.

Opacity:
The  condition of being nontransparent; a  cataract.

Organic:
Chemicals that contain carbon. To date,  nearly one million organic compounds have been synthesized or isolated. See also  Inorganic.

Os-, oste-, osteo- (prefix):
Pertaining to bone. The  Latin os- is most often associated with anatomical structures, whereas the Greek  osteo- usually refers to conditions involving bone. Osteogenesis means formation  of bone.

Overexposure:
Exposure beyond the specified limits.

Paraffins, Paraffin series:
(from parum affinis - small  affinity.) Straight- or branched-chain hydrocarbon components of crude oil and  natural gas whose molecules are saturated (that is, carbon atoms attached to  each other by single bonds) and therefore very stable. Examples are methane and  ethane. Generalized formula: CnH2n+2.

Particle  concentration:
Concentration expressed in terms of number of particles  per unit volume of air or other gas. When expressing particle concentrations,  the method of determining the concentration should be  stated.

Particulate matter:
A suspension of fine solid or  liquid particles in air, such as dust, fog, fume, mist, smoke, or sprays.  Particulate matter suspended in air is commonly known as an  aerosol.

Pathogen:
Any microorganism capable of causing  disease.

Percutaneous:
Performed through the unbroken skin, as  by absorption of an ointment through the  skin.

Permeation:
Process by which a chemical moves through a  protective clothing material on a molecular level.

Personal protective  equipment:
Devices worn by the worker to protect against hazards in the  environment. Respirators, gloves, and hearing protectors are  examples.

Pesticides:
General term for chemicals used to kill  such pests as rats, insects, fungi, bacteria, weeds, and so on, that prey on  humans or agricultural products. Among these are insecticides, herbicides,  rodenticides, miticides, fumigants, and repellants.

pH:
The  degree of acidity or alkalinity of a solution, with neutrality indicated as  7.

Pharmaceuticals:
Drugs and related chemicals reaching the  public primarily through drug suppliers. In government reports, this category  includes not only such medicinals as aspirin and antibiotics but also such  nutriments as vitamins and amino acids for both human and animal  use.

Phenolic resins:
A class of resins produced as the  condensation product of phenol or substituted phenol and formaldehyde or other  aldehydes.

Pigment:
A finely divided, insoluble substance that  imparts color to a material.

Plasticizers:
Organic chemicals  used in modifying plastics, synthetic rubber, and similar materials to  facilitate compounding and processing, and to impart flexibility to the end  product.

Pneumo- (Greek), pulmo- (Latin) (prefix):
Pertaining  to the lungs.

Pneumoconiosis:
Dusty lungs; a result of the  continued inhalation of various kinds of dust or other  particles.

Pneumonitis:
Inflammation of the  lungs.

Polar solvents:
Solvents (such as alcohols and ketones)  that contain oxygen and that have high dielectric  constants.

Polystyrene resins:
Synthetic resins formed by  polymerization of styrene.

Pressure, vapor:
The pressure  exerted by a vapor. If a vapor is kept in confinement at a constant temperature  over its liquid so that it can accumulate above the liquid, the vapor pressure  approaches a fixed limit called the maximum, or saturated, vapor pressure,  dependent only on the temperature and the liquid.

Process safety  management (PSM):
Encompassing safety concept for the chemical processing  industry that is mandated and regulated in OSHA's process safety management  standard. In PSM, potential hazards are systematically analyzed for each step of  a chemical process.

Propagation of flame:
The spread of flame  through the entire volume of a flammable vapor-air mixture for a single source  of ignition. A vapor-air mixture below the lower flammable limit may burn at the  point of ignition without propagating from the ignition  source.

Protection factor (PF):
In respiratory protective  equipment, the ratio of the ambient airborne concentration of the contaminant to  the concentration inside the facepiece.

Pulmonary:
Pertaining  to the lungs.

Pupil:
The variable aperture in the iris through  which light travels toward the interior regions of the eye. The pupil size  varies from 2 mm to 8 mm.

Qualitative fit testing:
A method of  assessing the effectiveness of a particular size and brand of respirator based  on an individual's subjective response to a test atmosphere. The most common  test agents are isoamyl acetate (banana oil), irritant smoke, and sodium  saccharin. Proper respirator fit is indicated by the individual reporting no  indication of the test agent inside the facepiece during the performance of a  full range of facial movements.

Quantitative fit testing:
A  method of assessing the effectiveness of a particular size and brand of  respirator on an individual. Instrumentation is used to measure both the test  atmosphere (a gas, vapor or aerosol, such as DOP) and the concentration of the  test contaminants inside the facepeice of the respirator. The quantitative fit  factor thus obtained is used to determine if a suitable fit has been obtained by  referring to a table or to the software of the instrumentation. Quantitative fit  factors obtained in this way do not correlate well with Assigned Protection  Factors, which are based on actual measurements of levels of contaminant inside  the facepiece during actual work.

Reagent:
Any substance used  in a chemical reaction to produce, measure, examine, or detect another  substance.

REL:
Recommended exposure limit. An exposure limit,  generally a time-weighted average, to a substance; developed by NIOSH based on  toxicological and industrial hygiene data.

Renal:
Having to do  with the kidneys.

Resin:
A sold or semisolid amorphous  (noncrystalline) organic compound or mixture of such compounds with no definite  melting point and no tendency to crystallize. May be of vegetable (gum arabic),  animal (shellac), or synthetic (celluloid) origin. Some resins may be molded,  cast, or extruded. Others are used as adhesives, in the treatment of textiles  and paper, or as protective coatings.

Respirable-size  particulates:
Particulates in a size range that permits them to penetrate  deep into the lungs upon inhalation.

Respirator:
A device to  protect the wearer from inhalation of harmful  contaminants.

Rhinitis:
Inflammation of the mucous membrane  lining in the nasal passages.

Route of entry:
A path by which  chemicals can enter the body. There are three main routes of entry: inhalation,  ingestion, and skin absorption.

RTECS:
Registry of Toxic  Effects of Chemical Substances.

Salivation:
An excessive  discharge of saliva; ptyalism.

Sampling:
The withdrawal or  isolation of a fractional part of a whole. In air analysis, the separation of a  portion of an ambient atmosphere with subsequent analysis to determine  concentration.

Scleroderma:
Hardening of the  skin.

SCBA:
Self-contained breathing  apparatus.

SDS:
Safety Data Sheet

Siderosis:
The deposition of iron pigments in the  lung - can be associated with disease.

Silicates:
Compounds of  silicon, oxygen, and one or more metals with or without hydrogen. These dusts  cause nonspecific dust reactions, but generally do not interfere with pulmonary  function or result in disability.

Silicosis:
A disease of the  lungs caused by the inhalation of silica dust.

Slurry:
A thick,  creamy liquid resulting from the mixing and grinding of limestone, clay, water,  and other raw materials.

Solution:
Mixture in which the  components lose their individual properties and are uniformly dispersed. All  solutions are composed of a solvent (water or other fluid) and a solute (the  dissolved substance). A true solution is homogeneous, as salt in  water.

Solvent:
A substance that dissolves another substance.  Usually refers to organic solvents.

Soot:
Agglomerations of  carbon particles impregnated with tar; formed in the incomplete combustion of  carbonaceous material.

Specific gravity:
The ratio of the mass  of a unit volume of a substance to the mass of the same volume of a standard  substance at a standard temperature. Water at 39.2 F (4 C) is usually the  standard for liquids; for gases, dry air (at the same temperature and pressure  as the gas) is often taken as the standard substance. See  Density.

Specific weight:
The weight per unit volume of a  substance; same as density.

Sterilization:
The process of  making sterile; the killing of all forms of  life.

Stupor:
Partial unconsciousness or nearly complete  unconsiousness.

Suspect carcinogen:
A material believed to be  capable of causing cancer, based on limited scientific  evidence.

Synergistic:
Pertaining to an action of two or more  substances, organs, or organisms to achieve an effect greater than the additive  effects of the separate elements.

Systemic:
Spread throughout  the body; affecting all body systems and organs, not localized in one spot or  area.

Threshold:
The level where the first effects occur; also,  the point at which a person begins to notice a tone becoming  audible.

Toxin:
A poisonous substance derived from an  organism.

Trade name:
The commercial name or trademark by which  a chemical is known. One chemical may have a variety of trade names depending on  the manufacturing or distributors  involved.

Turbid:
Cloudy.

Vapor  pressure:
Pressure (measured in pounds per square inch absolute-psia)  exerted by a vapor. If a vapor is kept in confinement over its liquid so that  the vapor can accumulate above the liquid (the temperature being held constant),  the vapor pressure approaches a fixed limit called the maximum (or saturated)  vapor pressure, dependent only on the temperature and the  liquid.

Ventilation:
One of the principal methods to control  health hazards, may be defined as causing fresh air to circulate to replace foul  air simultaneously removed.

Ventilation, dilution:
Airflow  designed to dilute contaminants to acceptable levels. Also called general  ventilation.

Ventilation, local exhaust:
Ventilation near the  point of generation of a contaminant.

Ventilation,  mechanical:
Air movement caused by a fan or other air-moving  device.

Ventilation, natural:
Air movement caused by wind,  temperature difference, or other nonmechanical  factors.

Viscosity:
The property of a fluid the resists  internal flow by releasing counteracting  forces.

Volatility:
The tendency or ability of a liquid to  vaporize. Such liquids as alcohol and gasoline, because of their well-known  tendency to evaporate rapidly, are called volatile liquids.