Listed here are the most common terms you will see when reading material safety data sheets or other reference materials concerned with chemical toxicity.
ACGIH—American Conference of Governmental Industrial Hygienists, a professional society which recommends exposure limits (TLVs) for toxic substances.
Acid—A substance which dissolves in water or certain other solvents, and releases hydrogen ions. For example, hydrogen chloride in solution is an acid, also referred to as hydrochloric acid or muriatic acid. (See pH .)
Acute—Acute exposures and acute effects involve short term high concentrations and immediate results of some kind (illness, irritation, or death). The effect of a chemical is considered acute when it appears with little time lag, such as within minutes or hours.
Alkaline—Also called basic or caustic. Having the ability to neutralize an acid and form a salt. Such a substance is also called an alkali.
ANSI—American National Standards Institute, a private organization that recommends work practices and engineering designs pertaining to safety and health.
Asphyxiant (simple)—A vapor or gas that has little or no toxic effects but can cause loss of consciousness or death by displacing air in the lungs and depriving an organism of oxygen. Examples are carbon dioxide and nitrogen.
Asthma—A disease that causes constriction of the bronchial tubes in the lungs as a result of irritation, allergy, or other stimulus.
Boiling point—The temperature at which a liquid boils and changes rapidly to a vapor state at a given pressure. Often expressed in degrees Fahrenheit at sea level pressure.
Carcinogen—A chemical capable of causing cancer. Such a material is often called carcinogenic.
C.A.S.—The Chemical Abstracts Service Registry Number is a numerical designation that uniquely identifies a specific chemical compound.
Caustic—Something that strongly irritates, corrodes, or destroys living tissue. (See alkaline).
Ceiling limit—The maximum concentration of a material in air that should not be exceeded, even instantaneously. (See PEL and TLV ).
Cell—The structured unit of which tissues are made. There are many types (such as nerve cells, muscle cells, and blood cells), with each type performing a special function.
Chemical family—A group of single elements or compounds with a common general name, such as “ketones.”
Chronic effect—An adverse effect with symptoms that develop slowly over time and persist or recur.
Circulatory system—The heart and blood vessels.
Combustible—Able to burn. Commonly defined to mean solids that ignite and burn slowly and liquids with a flash point above 100 degrees Fahrenheit (37.8 degrees Centigrade).
Concentration—The relative amount of one substance mixed into another substance.
Corrosive—A liquid or solid that causes visible destruction in human skin tissue at the site of contact.
Cubic centimeter (cc)—A metric unit of volume. One cc is equivalent to about 20 drops drop of water. One cc is also referred to as a milliliter (ml).
Cubic meter—A metric unit of volume. One cubic meter equals 35.5 cubic feet or 1.3 cubic yards. One cubic meter also equals 1000 liters or one million cubic centimeters.
Decomposition—Breakdown of a chemical by heat, chemical reaction, or other forces into simpler parts, compounds, or elements.
Dermal—Pertaining to the skin.
Dose—The amount of chemical to which an organism is exposed. Often expressed in milligrams per kilogram (mg/kg) or part per million (ppm).
Duration—Length of time exposed to a substance.
Edema—Swelling of body tissues due to water or fluid accumulation.
Evaporation—The process by which a liquid is changed into a vapor state and mixed into the surrounding air.
Evaporation rate—The ratio of the time required to evaporate a measured volume of a liquid chemical to the time required to evaporate the same volume of a reference liquid (usually ethyl ether). In general, the higher the ratio, the lower the boiling point.
Excursion limit—The average maximum concentration allowed over a short period of time (5 to 30 minutes depending upon the chemical). (See PEL.)
Flammable—Ignites easily and burns rapidly. The National Fire Protection Agency and the U.S. Dept. of Transportation define a flammable liquid as having a flash point of less than 100 degrees Fahrenheit (37.8 degrees Centigrade).
Flash point—The lowest temperature at which a liquid gives off enough vapors to ignite and produce a flame when an ignition source is present.
Gram (g)—A metric unit of weight. One U.S. ounce equals 28.4 grams. One U.S. pound equals 454 grams.
Hazard—The probability that a person will be harmed due to working with a toxic substance under given conditions of use.
IDLH—Immediately dangerous to life or health. A term used to describe certain very hazardous environments, usually with high concentrations of toxic chemicals, insufficient oxygen, or both.
Ignition temperature—The lowest temperature at which a substance will catch on fire and burn.
Incompatibles—Materials that could cause hazardous reactions from direct contact with each other.
Inflammable—Same as flammable.
Ingestion—Taking in a substance through the mouth.
Inhalation—Breathing in air or other substance.
Irritant—A substance that can cause an inflammatory response or reaction of the eye, skin, or respiratory system.
Kilogram (kg)—A metric unit of mass. Equals 1000 grams. Also equals 2.2 U.S. pounds.
Latency—The time lag between exposure and the first manifestation of health damage.
Latent effect—An effect that occurs a considerable time after exposure to a toxic substance.
Lethal concentration—A concentration of a chemical in air that will kill a test animal inhaling it.
Lethal dose—50% (LD50)—The dose of a chemical that will kill 50 percent of the test animals receiving it. The chemical may be given by mouth (oral), applied to the skin (dermal) or injected (parenteral). A given chemical will generally show different LD50 values depending on the route of administration.
Liter—A metric unit of volume. One U.S. quart is about 0.94 liter. One liter equals 1000 cubic centimeters (1000 cc)
Local effect—An effect that a toxic substance causes at the original point of contact, such as eye damage.
Local exhaust ventilation—A system for capturing and exhausting contaminants from the air at the point of origin, as in welding, grinding, sanding, or laboratory experiments.
Melting point—The temperature at which a solid substance changes into the liquid state.
Milligram (mg)—A metric unit of mass. One gram equals 1000 mg. One U.S. ounce equals 28,400 mg.
Milligrams per cubic meter—mg/m3 A measure of concentration, often used to express PELs and TLVs.
mm Hg—Millimeters (mm) of the metal mercury (Hg). A measurement for pressure. At sea level, the earth’s atmosphere exerts 760 mmHg of pressure.
MSDS—material safety data sheet. A form listing the properties and hazards of a substance. The manufacture must supply a MSDS form upon request.
MSHA—Mine Safety and Health Administration, an agency in the U. S. Dept. of Labor that regulates safety and health in the mining industry. Also tests and certifies respirators. (See NIOSH).
Mutagen—A chemical or physical agent that affects the genetic material in cells in such a way that it may cause an undesirable mutation to occur in some later generation. Such an agent is called mutagenic. Many mutagens are also carcinogens .
Nervous system—The nerves, brain, and associated mechanisms in the body that control its processes.
NFPA—National Fire Protection Association. NFPA has developed a scale for rating the severity of fire, reactivity, and health hazards. References to these ratings frequently appear on MSDSs.
NIOSH—National Institute for Occupational Safety and Health. NIOSH is a federal agency that conducts research on occupational safety and health questions and recommends new standards to federal OSHA. NIOSH, along with MSHA, tests and certifies respirators.
Oral—Pertaining to the mouth.
OSHA—Occupational Safety and Health Administration, an agency in the U.S. Dept. of Labor, which regulates safety and health conditions in most of the nation’s private sector workplaces.
Oxidizer—Materials that release oxygen or act like oxygen; materials that attract electrons.
Oxygen deficiency—An atmosphere having less than the normal amount (21%) of oxygen. When oxygen concentration in air falls dangerously low to 19.5% or less, many people become dizzy, experience a buzzing in the ears, have a rapid heartbeat, become confused, or lose consciousness.
PEL—permissible exposure limit. For federal purposes PELs refer to three different types of exposure limits to a hazardous substance: a ceiling limit, a short term (15 minute) limit, and an eight-hour time-weighted average (TWA) limit. These limits are enforceable by law.
pH—A unit for expressing how acidic or how alkaline a solution or chemical is, on a scale of 1 to 14. A pH of 1 indicates a strongly acidic solution; pH 7 indicates a neutral solution; and pH 14 indicates a strongly alkaline solution.
Polymerization—A chemical reaction in which small molecules combine to form much larger molecules. A hazardous polymerization is a reaction that occurs at a fast rate, releasing large amounts of energy.
ppb—Parts per billion. A measure of concentration. 1000 times fewer than a ppm.
ppm—Parts per million. A measure of concentration (usually parts of a substance per million parts of air). PELs and TLV s are often expressed in ppm. For example, 1 inch in 16 miles = 1 ppm.
psi—Pounds per square inch. A unit of pressure. At sea level, the earth’s atmosphere exerts 14.7 psi.
Reaction—A chemical transformation or change.
Reactivity—A substance’s ability to undergo a chemical reaction or change that may result in dangerous side effects, such as an explosion, burning, and corrosive or toxic emissions.
Reducer—Materials that burn, chemically react with, and give up electrons (see oxidizer).
Reduction—A reaction in which oxygen is lost from a substance, or a chemical change in which an atom gains one or more electrons. A reduction reaction always occurs simultaneously with an oxidation reaction; that is, one substance gains oxygen (is oxidized) while another substance loses oxygen (is reduced).
Reproductive toxin—A chemical that can interfere with the reproductive system.
Respirator—A device worn to protect against inhalation of hazardous substances.
Respiratory system—The breathing system. Includes lungs, air passages, larynx, mouth, nose, and the associated nerves and blood vessels.
Route of entry—The means by which a hazardous substance enters the body. Common routes are skin contact, eye contact, inhalation, and ingestion.
Sensitizer—A substance that on first exposure causes little or no reaction in a person, but which on repeated exposure may cause an intense response, not necessarily limited to the site of initial contact.
Solubility—The degree to which a chemical can dissolve in a solvent, such as water.
Solution—A mixture in which the components are uniformly dispersed. All solutions are composed of a solvent (water or other fluid) and the dissolved substance (called the solute).
Solvent—A substance (most commonly water but often an organic compound) that dissolves another substance. (See Solution)
Specific gravity—The ratio of the mass of a volume of material to the mass of an equal volume of water, at a given temperature.
STEL—Short-term exposure limit. The maximum average concentration allowed for a continuous 15-minute exposure period. (See TLV)
Susceptibility—Increased risk of harm from toxic substances due to personal traits such as diet, smoking, drinking, allergy, and pregnancy.
Systemic effect—Spread throughout the body, affecting all body systems and organs, not localized in one spot or area.
Teratogen—A chemical or physical agent that affects a developing embryo fetus and can cause birth defects in offspring. Such an agent is called teratogenic .
TLV—Threshold limit value. An exposure limit recommended by the ACGIH. There are three types of ACGIH TLVs:
Toxic—The ability of a substance or material to cause disease, injury, or death.
Toxicology – The study of poisons. The basic assumption of toxicology is that there is a relationship between the dose (amount), the concentration at the affected site, and the resulting effects (response).
Trade name—The trademark name or commercial name used by the manufacturer or supplier for a material.
TWA—Time-weighted average. The average concentration of a chemical in air over the total exposure time, usually eight hours. (See PEL and TLV.)
Vapor pressure—The pressure exerted by a saturated vapor above its own liquid in a closed container at given conditions of temperature and pressure. The lower the boiling point of a substance, the higher its vapor pressure.