ABC | DEF | GHI | JKL | MNO | PQR | STU | VWXYZ
The following glossary presents brief explanations of acronyms define and common terms frequently used by chemical manufacturers in their MSDS.
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M N O
m
Meter is a unit of length in the metric system. One meter is about 39 inches.
m3
Cubic meter is a metric measure of volume, approximately 35.3 cubic feet or 1.3 cubic
yards.
Malaise
A feeling of general discomfort, distress, or uneasiness, an out-of-sorts feeling.
Mechanical Exhaust
A powered device, such as a motor-driven fan or air steam venturi tube, for exhausting
contaminants from a workplace, vessel, or enclosure.
Mechanical Filter Respirator
A respirator used to protect against airborne particulate matter like dusts, mists, metal
fume, and smoke. Mechanical filter respirators do not provide protection against gases,
vapors, or oxygen deficient atmospheres.
Melting Point
The temperature at which a solid substance changes to a liquid state.
Metabolism
Physical and chemical processes taking place among the ions, atoms, and molecules of the
body.
Meter
A unit of length, equivalent to 39.37 inches.
mg
Milligram is a metric unit of weight that is one-thousandth of a gram, i.e. 1000
milligrams equals one gram.
mg/kg
Milligrams of substance per kilogram of body weight is an expression of toxicological
dose.
mg/m3
Milligrams per cubic meter is a unit for expressing concentrations of dusts, gases, or
mists in air.
Micron (Micrometer)
A unit of length equal to one-millionth of a meter; approximately 0.000039 of an inch.
Mist
Suspended liquid droplets generated by condensation from the gaseous to the liquid state,
or by breaking up a liquid into a dispersed state, such as splashing, foaming, or
atomizing. Mist is formed when a finely divided liquid is suspended in air.
Mixture
Any combination of two or more chemicals.
ml
Milliliter is a metric unit of capacity, equal in volume to 1 cubic centimeter (cc), or
approximately one-sixteenth of a cubic inch. One-thousandth of a liter.
mmHg
Millimeters (mm) of mercury (Hg) is a unit of measurement for low pressures or partial
vacuums.
Molecular Weight
Weight (mass) of a molecule based on the sum of the atomic weights of the atoms that make
up the molecule.
MSDS
Material Safety Data Sheet, a document containing information and instructions on the
chemical and physical characteristics of a substance, its hazards and risks, safe handling
requirements and the actions to be taken in the event of fire, spill or exposure.
Mutagen
A substance or agent capable of altering the genetic material in a living cell. See also
Reproductive Toxin.
MW
See Molecular Weight.
Narcosis
A state of stupor, unconsciousness, or arrested activity produced by the influence of
narcotics or other chemicals.
Nausea
Tendency to vomit, feeling of sickness at the stomach.
NFPA
National Fire Protection Association is an international membership organization which
promotes and improves fire protection and prevention and establishes safeguards against
loss of life and property by fire. Best known on the industrial scene for the National
Fire Codes—16 volumes of codes, standards, recommended practices and manuals
developed and periodically updated by NFPA technical committees. Among these is NFPA 704M,
the code for showing hazards of materials as they might be encountered under fire or
related emergency conditions, using the familiar diamond-shaped label or placard with
appropriate numbers or symbols.
Neurotoxin
A material that affects the nerve cells and may produce emotional or behavioral
abnormalities.
Neutralize
In acid-base chemistry, the process of bringing the pH to between 5 and 8, either by
adding an acid to a base or by adding a base to an acid.
NIOSH
National Institute for Occupational Safety and Health, U.S. Public Health Service, U.S.
Department of Health and Human Services (DHHS), among other activities, tests and
certifies respiratory protective devices and air sampling detector tubes, recommends
occupational exposure limits for various substances, and assists OSHA and MSHA in
occupational safety and health investigations and research.
Nonflammable
Not easily ignited, or if ignited, not burning rapidly.
Non-Sparking Tools
Tools made from beryllium-copper or aluminum-bronze that greatly reduce the possibility of
igniting dusts, gases, or flammable vapors. Although these tools may emit some sparks when
striking metal, the sparks have a low heat content and are not likely to ignite most
flammable liquids.
NTP
National Toxicology Program. The NTP publishes an Annual Report on Carcinogens.
Odor
A description of the smell of the substance.
Odor Threshold
The lowest concentration of a substance's vapor, in air, that can be smelled.
Olfactory
Relating to the sense of smell.
Oral
Used in or taken into the body through the mouth.
Oral Toxicity
Adverse effects resulting from taking a substance into the body by mouth.
Organic Peroxide
An organic compound that is an oxidizer and contains the bivalent -O-O- structure and may
be considered a structural derivative of hydrogen peroxide where one or both of the
hydrogen atoms has been replaced by an organic radical.
OSHA
Occupational Safety and Health Administration, U.S. Department of Labor.
Overexposure
Exposure to a hazardous material beyond the allowable exposure limits.
Oxidizer
A substance that readily yields oxygen to or accepts electrons from another substance. By
yielding oxygen or accepting electrons, an oxidizer can easily cause or enhance the
combustion of other materials. Examples of oxidizers include bleach, which contains sodium
hypochlorite, concentrated hydrogen peroxide (greater than 30%), and ammonium nitrate.
P Q R
Pathologic
Pertaining to or caused by disease.
Pathology
Scientific study of alterations produced by disease.
PEL
Permissible Exposure Limit is an occupational exposure limit established by OSHA's
regulatory authority. It may be a time-weighted average (TWA) limit or a maximum
concentration exposure limit.
Percent Volatile
Percent volatile by volume is the percentage of a liquid or solid (by volume) that will
evaporate at a temperature of 70°F. Examples: butane, gasoline, and paint thinner
(mineral spirits) are 100 percent volatile; their individual evaporation rates vary, but
in time, each will evaporate completely.
pH
The symbol relating the hydrogen ion (H+) concentration to that of a given standard
solution. A pH of 7 is neutral. Numbers increasing from 7 to 14 indicate greater
alkalinity. Numbers decreasing from 7 to 0 indicate greater acidity.
Physical Hazard
Used to describe a chemical that is explosive, flammable, an organic peroxide, an
oxidizer, pyrophoric, unstable, or water reactive.
Placenta
A structure attached to the wall of the uterus to nourish the fetus during pregnancy.
Polymerization
A chemical reaction in which one or more small molecules combine to form larger molecules.
A hazardous polymerization is such a reaction that takes place at a rate that releases
large amounts of energy. If hazardous polymerization can occur with a given material, the
MSDS usually will list conditions that could start the reaction and, if the material
contains a polymerization inhibitor, the length of time during which the inhibitor will be
effective.
ppb
Parts per billion. The concentration of a particular chemical in solution. For every one
part of the chemical. there are a billion parts of solution. Used to express very low
concentrations.
ppm
Parts per million. The concentration of a particular chemical in solution. For every one
part of the chemical, there are a million parts of solution. Used to express very low
concentrations. One inch in sixteen miles is a common example of the magnitude of parts
per million.
Prenatal
Preceding birth.
psi
Pounds per square inch is the pressure a material exerts on the walls of a confining
vessel or enclosure. For technical accuracy, pressure must be expressed as psig (pounds
per square inch gauge) or psia (pounds per square inch absolute; that is, gauge pressure
plus sea level atmospheric pressure, or psig plus approximately 14.7 pounds per square
inch). See also mmHg.
Pulmonary
Relating to, or associated with, the lungs.
Pulmonary Edema
Fluid in the lungs.
Pyrophoric
A chemical substance that will ignite spontaneously in air at or below a temperature of
130°F (54.4°C).
Reaction
A chemical transformation or change. The interaction of two or more substances to form new
substances.
Reactivity
Chemical reaction with the release of energy. Undesirable effects—such as pressure
buildup, temperature increase, formation of noxious, toxic or corrosive
byproducts—may occur because of the reactivity of a substance to heating, burning,
direct contact with other materials, or other conditions in use or in storage.
RCRA
Resource Conservation and Recovery Act is environmental legislation aimed at controlling
the generation, treatment, storage, transportation and disposal of hazardous wastes. It is
administered by EPA.
Reducing Agent
In a reduction reaction, which always occurs simultaneously with an oxidation reaction,
the reducing agent is the chemical or substance which combines with oxygen, or loses
electrons to the reaction. See Oxidation.
REL
The NIOSH REL (Recommended Exposure Limit) is the highest allowable airborne concentration
which is not expected to injure workers. It may be expressed as a ceiling limit or as a
time-weighted average (TWA).
Reproductive Toxin
Substances that affect either male or female reproductive systems and may impair the
ability to have children. See also Mutagen.
Respiratory Protection
Devices that will protect the wearer's respiratory system from overexposure by inhalation
to airborne contaminants. Respiratory protection is used when a worker must work in an
area where he/she might be exposed to concentration in excess of the allowable exposure
limit.
Respiratory System
The breathing system that includes the lungs and the air passages (trachea or
"windpipe," larynx, mouth, and nose) to the air outside the body, plus the
associated nervous and circulatory supply.
Routes of Entry
The means by which material may gain access to the body, for example, inhalation,
ingestion, and skin contact.
S T U
Self-Contained Breathing Apparatus
A respiratory protection device that consists of a supply or a means of respirable air,
oxygen, or oxygen-generating material which is carried by the wearer.
Sensitizer
A chemical that causes a substantial proportion of exposed people or animals to develop an
allergic reaction in normal tissue after repeated exposure to the chemical.
Silicosis
A disease of the lungs (fibrosis) caused by the inhalation of silica dust.
Skn
Skin.
"Skin"
A notation sometimes used with PEL or TLV exposure data that indicates that the stated
substance may be absorbed by the skin, mucous membranes, and eyes, either by airborne or
by direct contact.
Skin Absorption
Ability of some hazardous chemicals to pass directly through the skin and enter the
bloodstream.
Skin Toxicity
See Dermal Toxicity.
Solubility in Water
A term expressing the percentage of a material (by weight) that will dissolve in water at
ambient temperature.
Solvent
A substance, usually a liquid, in which other substances are dissolved. The most common
solvent is water.
Specific Chemical Identity
The chemical name, Chemical Abstracts Service (CAS) Registry Number, or any precise
chemical designation of a substance.
Specific Gravity
The weight of a material compared to the weight of an equal volume of water is an
expression of the density (or heaviness) of a material. Insoluble materials with specific
gravity of less than 1.0 will float on water. Insoluble materials with specific gravity
greater than 1.0 will sink in water. Some flammable liquids have specific gravities
greater than 1.0 and will sink in water. Most flammable liquids have specific gravities
less than 1.0 and, if not soluble, will float on water, which is an important
consideration for fire suppression.
Spill or Leak Procedures
The methods, equipment, and precautions that should be used to control or clean up a leak
or spill.
Splash-Proof Goggles
Eye protection that fits snugly against the face, and may have indirect ventilation ports.
Spontaneously Combustible
Capable of catching fire without an ignition source. Can occur due to oxidation in air or
by internal heat buildup.
Stability
The ability of a material to remain unchanged. For MSDS purposes, a material is stable if
it remains in the same form under expected and reasonable conditions of storage or use.
Conditions that may cause instability (dangerous change) are stated; for example,
temperatures above 150°F; shock from dropping.
STEL
Short-Term Exposure Limit (ACGIH terminology). See TLV.
Subcutaneous
Beneath the layers of the skin.
Supplied-Air Respirators
Air line respirators or self-contained breathing apparatus.
Sys
System or systemic.
Systemic Poison
A poison that spreads throughout the body, affecting all body systems and organs. Its
adverse effect is not localized in one spot or area.
Systemic Toxicity
Adverse effects caused by a substance that affects the body in a general rather than local
manner.
Synonym
Another name or names by which a material is known. Methyl alcohol, for example, is also
known as methanol or wood alcohol.
Target Organ Toxin
A toxic substance that attacks a specific organ of the body. For example, overexposure to
carbon tetrachloride can cause liver damage.
TCL
Toxic concentration low, the lowest concentration of a gas or vapor capable of producing a
defined toxic effect in a specified test species over a specified time.
TDL
Toxic dose low, lowest administered dose of a material capable of producing a defined
toxic effect in a specified test species.
Temp
Temperature.
Ter
See Teratogen.
Teratogen
A substance or agent, exposure to which by a pregnant female can result in malformations
in the fetus.
Tfx
Toxic effects(s).
TLV
Threshold Limit Value is a term used by ACGIH to express the airborne concentration of
material to which nearly all persons can be exposed day after day without adverse effects.
ACGIH expresses TLVs in three ways:
TLV-TWA: The allowable Time-Weighted Average concentration for a normal 8-hour workday or 40-hour workweek.
TLV-STEL: The Short-Term Exposure Limit, or maximum concentration for a continuous 15-minute exposure period (maximum of four such periods per day, with at least 60 minutes between exposure periods, and provided the daily TLV-TWA is not exceeded).
TLV-C: The Ceiling exposure limit. The concentration that should not be exceeded even instantaneously.
Torr
A unit of pressure, equal to 1/760 atmosphere.
Toxic
A chemical falling within any of the following categories:
a. A chemical that has a median lethal dose (LD50) of more than 50 milligrams per kilogram but not more than 500 milligrams per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
b. A chemical that has a median lethal dose (LD50) of more than 200 milligrams per kilogram but not more than 1,000 milligrams per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between two and three kilograms each.
c. A chemical that has a median lethal concentration (LC50) in air of more than 200 parts per million but not more than 2,000 parts per million by volume of gas or vapor, or more than two milligrams per liter but not more than 20 milligrams per liter of mist, fume, or dust, when administered by continuous inhalation for one hour (or less if death occurs within one hour) to albino rats weighing between 200 and 300 grams each. See also Highly Toxic.
Toxic Substance
Any substance that can cause acute or chronic injury to the human body, or which is
suspected of being able to cause diseases or injury under some conditions.
Toxicity
The degree of poisoning that can occur from exposure to a chemical.
Trade name
The trademark name or commercial trade name for a material or product.
Transplacental
A chemical that is capable of causing physical defects in the developing embryo because it
can easily cross the placental barrier between mother and fetus.
TSCA
Toxic Substances Control Act. Federal Environmental Legislation administered by EPA that
regulates the manufacture, handling, and use of materials classified as "toxic
substances."
TWA
Time-Weighted Average exposure is the airborne concentration of a material to which a
person is exposed, averaged over the total exposure time-generally the total workday (8
hours). Also see TLV.
UEL, or UFL
Upper explosive limit or upper flammable limit of a vapor or gas; the highest
concentration (highest percentage of the substance in air) that will produce a flash of
fire when an ignition source (heat, arc, or flame) is present. At higher concentrations,
the mixture is too "rich" to burn. See also LEL.
ug
Microgram, one millionth of a gram.
Unstable
Tending toward decomposition or other unwanted chemical change during normal handling or
storage.
Unstable Reactive
A chemical that, in the pure state, or as produced or transported, will vigorously
polymerize, decompose, condense, or become self-reactive under conditions of shock,
pressure, or temperature.
VWXYZ
Vapor
The gaseous form of a solid or liquid substance as it evaporates.
Vapor Density
The weight of a vapor or gas compared to the weight of an equal volume of air is an
expression of the density of the vapor or gas. Materials lighter than air have vapor
densities less than 1.0. Some examples are acetylene, methane, hydrogen. Materials heavier
than air, such as propane, hydrogen sulfide, ethane, butane, chlorine, and sulfur dioxide,
have vapor densities greater than 1.0. All vapors and gases will mix with air, but the
lighter materials will tend to rise and dissipate unless confined. Heavier vapors and
gases are likely to concentrate in low places-along or under floors, in sumps, sewers, and
manholes, in trenches and ditches where they may create fire or health hazards.
Vapor Pressure
The pressure exerted by a saturated vapor above its own liquid in a closed container.
Vapor pressures reported on MSDS are in milliliters of mercury (mmHg) at 68°F (20°C),
unless stated overwise. Some important facts to remember are that vapor pressure increases
with temperature, and the lower the boiling point of a chemical, the higher its vapor
pressure.
Examples of vapor pressures at 20°C in mm Hg:
| Acetone | 184 |
| Mercury | 0.002 |
| Methylene Chloride | 350 |
| Phenol | 0.36 |
Ventilation
See General Exhaust, Local Exhaust, and Mechanical Exhaust.
Vermiculite
Substance used as sorbent for spill control and cleanup.
Viscosity
The tendency of a fluid to resist internal flow without regard to its density.
Volatility
A measure of how quickly a substance forms a vapor at ordinary temperatures. Chemicals
with higher vapor pressures and lower boiling points will have higher volatilities and
will evaporate quicker.
Water-Reactive
A chemical that reacts with water to release a gas that is either flammable or toxic.