GLOSSARY OF TERMS

ACGIH	The American Conference of Governmental Industrial Hygienists is a voluntary membership organization of professional industrial hygiene personnel in governmental or educational institutions. The ACGIH develops and publishes recommended occupational exposure limits each year called Threshold Limit Values (TLV's) for hundreds of chemicals, physical agents, and Biological Exposure Indices (BEIs) to assess worker exposure.
Action Level	A concentration designated in 29 CFR Part 1910 for a specific substance, calculated as an eight (8)-hour time-weighted average, that initiates certain required activities such as exposure monitoring and medical surveillance.
acute effect	Symptom of exposure to a hazardous material that appears soon after a short-term exposure, coming quickly to a crisis.
acute exposure	A single, brief exposure to a large dose of a toxic substance.  Adverse health effects are evident soon after exposure.
acute toxicity	Adverse biological effects of a single dose of a toxic agent.
aerosol	A suspension of fine solid or liquid particles in air (e.g., paint spray, mist, fog).
anesthetic	A chemical that causes drowsiness.  Large doses of anesthetic chemicals can cause unconsciousness, coma, and death.
ANSI	American National Standards Institute.  This privately funded, voluntary organization develops standards for the safe design and operation of equipment and safe practices or procedures for industry.
asphyxiant	A chemical vapor or gas that replaces air and can, thereby, cause death by suffocation.  Asphyxiants are especially hazardous in confined spaces.
BEI - Biological Exposure Index	Guidance values established by the ACGIH for assessing biological monitoring results from speciments (such as urine or blood). A BEI is an index of an individual's uptake of a chemical specimen collected from healthy workers who have been exposed to chemicals to the same extent as workers with inhalation at the TLV.
boiling point	The temperature at which the vapor pressure of a liquid equals atmospheric pressure or at which the liquid changes to a vapor. The boiling point is usually expressed in degrees Fahrenheit. If a flammable material has a low boiling point, it indicates a special fire hazard.
carcinogen	A chemical or physical agent that is known or suspected to cause neoplasms (tumors) in humans and/or animals.
cardiac	Refers to the heart.
CAS Number	Identifies a particular chemical by a number assigned by the Chemical Abstracts Service, a service of the American Chemical Society that indexes and compiles abstracts of worldwide chemical literature called Chemical Abstracts.
cc	Cubic centimeter.  A metric-system volume measurement equal to a milliliter (ml).  One quart is about 946 cc (946 ml).
Ceiling Limit	The maximum allowable exposure limit for an airborne chemical, which is not to be exceeded even momentarily.  See also PEL and TLV.
central nervous system	The part of the body made up of the brain, spinal cord, and nerves.
chemical	As broadly applied to the chemical industry, an element or a compound produced by chemical reactions on a large scale for either direct industrial and consumer use or for reaction with other chemicals.
chemical family	Chemicals with similar structural characteristics are grouped into a chemical family (e.g., ketones, alcohols, hydrocarbons).
Chemical Hygiene Plan	A written program developed and implemented by the employer which sets forth procedures, equipment, personal protective equipment and work practices that are capable of protecting employees from the health hazards presented by hazardous chemicals used in the particular workplace.
Chemical Hygiene Officer	A person designated by the employer who is qualified by training or experience, to provide technical guidance in the development and implementation of the provisions of the Chemical Hygiene & Safety Plan.
Chemical Hygiene and Safety Plan (CHSP)	The written web-based program developed by LBNL to comply with the Federal OSHA "Lab Standard". The CHSP addresses all elements of the OSHA-mandated Chemical Hygiene Plan and provides further information specific to LBNL.
chemical reaction	A change in the arrangement of atoms or molecules to yield substances of different composition and properties. (see REACTIVITY)
chronic exposure	Repeated exposure or contact with a toxic substance over a long period.  Adverse biological effects from chronic exposure develop slowly, last a long time, and frequently recur.
chronic effect	Symptom of exposure to a hazardous material that develops slowly after many exposures or that recurs often.
chronic toxicity	Adverse biological effect of repeated doses or long-term exposure to a toxic agent.
combustible	Able to catch on fire and burn. According to the DOT and NFPA, combustible liquids are those having a flash point at or above 100o F (37.8oC), or liquids that will bum. They do not ignite as easily as flammable liquids. However, combustible liquids can be ignited under certain circumstances, and must be handled with caution."  Non liquid substances that will burn, such as wood and paper, are called "ordinary combustibles."  (See flammables)
combustible gas	A combustible gas is: A gas or mixture of gases having, in a container, an absolute pressure exceeding 40 psi at 70oF (21.1oC); or A gas or mixture of gases having, in a container, an absolute pressure exceeding 104 psi at 130oF (54.4oC) regardless of the pressure at 70oF (21.1oC): or A liquid having a vapor pressure exceeding 40 psi at 100oF (37.8oC) as determined by ASTM D-323-72.
combustible liquid	Any liquid having a flashpoint at or above 100oF but below 200oF.
compressed gas	A gas or mixture of gases in a container having an absolute pressure of 40 psi or greater at room temperature.
concentration	The relative amount of a given substance present when mixed with another substance(s).  Concentration is often expressed as parts per million (ppm), percent, or weight per unit volume, e.g., milligrams/cubic meter (mg/m3).
corrosive	A chemical that causes visible destruction of, or irreversible changes in living tissue by chemical action at the site of contact, or that has a severe corrosion rate on structural materials.
decomposition	The breakdown of a material into simpler compounds by chemical reaction, decay, heat, or other process.
density	The mass of a substance per unit volume.  The density of a liquid is usually compared to water, which has a unit density of 1; the density of a gas is usually compared to air.  Substances that float on water have densities of less than 1; substances that sink in water have densities greater than 1.
dermal	Refers to the skin.
dermatitis	An inflammation of the skin, which can be caused by irritation (chemical, physical, or mechanical) or allergic reaction.
designated area	An area that may be used for work with Particularly Hazardous Substances including "select carcinogens," reproductive toxins or substances which have a high degree of acute toxicity. A designated area may be the entire room, an area within a room or a device such as a fume hood or glove box.
dilution ventilation	See GENERAL VENTILATION.
dose	The amount of a substance received during exposure. See mg/kg.
DOT	The United States Department of Transportation is the federal agency that regulates the labeling and transportation of hazardous materials.
dyspnea	Shortness of breath; difficult or labored breathing.
EPA number	The number assigned to chemicals regulated by the United States Environmental Protection Agency (EPA).
epidemiology	The branch of medical science that deals with the incidence, distribution, and control of disease in a population.
erythema	A reddening of the skin.
EH&S	LBNL Environment, Health and Safety Division.
evaporation rate	The rate at which a material is converted to vapor (evaporates) at a given temperature and pressure when compared to the evaporation rate of a reference material (e.g. butyl acetate). Health and fire hazard evaluations of materials involve consideration of evaporation rates as one aspect of the evaluation.
explosive	A chemical that causes a sudden, almost instantaneous release of pressure, gas, and heat when subjected to sudden shock, pressure, or high temperature.
oF	Degrees, Fahrenheit; a temperature scale.
flammable	A flammable substance is one that will ignite and burn rapidly under normal ambient conditions; for example, liquids with a flash point below 100oF and solids that ignite readily. Note the Uniform Fire Code uses a cut off of 140oF, which qualifies more liquids as "flammable."
flashpoint	The minimum temperature at which a liquid gives off a vapor in sufficient concentration to ignite.
formula	The molecular composition of a chemical compound written in scientific symbols.  Water is H2O; hydrochloric acid is HCl.
fume hood	A ventilation device comprised of an enclosure on five sides with a moveable sash on the remaining side. Fume hoods are constructed and maintained to draw air from the open side in order to prevent or minimize the escape of air contaminants into the work area. This device allows chemical manipulations to be conducted in the enclosure without insertion of any portion of the employee's body other than hands and arms.
g/kg	Grams per kilogram.  A measurement used in experimental testing to indicate the dose of a test substance, in grams, given for each kilogram of the test subject's body weight.
general ventilation	Also known as general exhaust ventilation and dilution ventilation. Fresh air mixes with contaminants in the workroom air and is then exhausted. (See LOCAL EXHAUST VENTILATION).
hazard warning	The words, pictures, and symbols, or combination thereof, that appear on a label and indicate the hazards of the substance in the container.
hazardous chemical	A chemical or mixture of chemicals that can produce adverse physical effects (e.g., fire, explosion) or health effects (e.g., dermatitis, cancer).
health hazards	Substances for which there is evidence, from at least one scientific study, that acute or chronic health effects may occur in exposed persons.  These chemicals include carcinogens, toxic agents, reproductive toxins (mutagens and teratogens), irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, agents which act on the hematopoietic system, and agents that damage the lungs, skin, eyes, or mucous membranes.
g/Kg	See GRAMS PER KILOGRAM.
gram (g)	A metric unit of weight. One ounce equals 28.4 grams.
Grams per Kilogram (g/Kg)	This indicates the dose of a substance given to test animals in toxicity studies. For example, a dose may be 2 grams (of substance) per kilogram of body weight (of the experimental animal).
hazardous material	Any substance or compound that has the capability of producing adverse effects on the health and safety of humans as a hazardous waste, as well reaction or change.
hematopoietic system	The blood-forming organs of the body, including bone marrow and the spleen.
hepatotoxin	A chemical that can cause liver damage (e.g., carbon tetrachloride).
IARC	International Agency for Research on Cancer.  IARC publishes "Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man," one of the publications used to determine the cancer risk of a chemical.
incompatible	The term applied to two substances to indicate that one material cannot be mixed with the other without the possibility of a dangerous reaction.
ignitable	A solid, liquid or compressed gas that has a flash point of less than 140oF.
ignition temperature	The lowest temperature at which a substance will ignite and continue to burn.  The lower the ignition temperature, the more likely the substance is to be a fire hazard.
ingestion	Taking a material into the body through the mouth and swallowing it.
inhalation	Breathing in of airborne substances that may be in the form of gases, fumes, mists, vapors, dusts, or aerosols.
inhibitor	A substance that is added to another to prevent the occurrence of an undesirable chemical reaction.
irritant	A substance that produces inflammation or aggravation of the tissue, including the skin, eyes, nose, or respiratory system.
lacrimation	Abnormal or excessive production of tears as a result of exposure of the eyes to an irritant.
LC50	The concentration of a substance in air that will kill half (50%) of the exposed test animals.  A measure of acute toxicity.
LD50	The dose of a substance that will kill half (50%) of the treated test animals when given as a single dose.  A measure of acute toxicity.
LEL or LFL	Lower Explosive Limit or Lower Flammable Limit. The lowest concentration of a substance that will produce a fire or flash when an ignition source (flame, spark, etc.) is present. It is expressed in percent of vapor or gas in the air by volume. Below the LEL or LFL, the air/contaminant mixture is theoretically too "lean" to burn. (See also UEL).
local exhaust ventilation	A ventilation method for removing contaminated air at the point where the contaminants are generated (e.g., a fume hood).
m3	Cubic meter. A volume measurement in the metric system. One m3 is about 35.3 cubic feet or 1.3 cubic yards.
mechanical exhaust	A powered device, e.g., a motor-driven fan, that removes contaminants from a work area or enclosure.
melting point	The temperature at which a solid changes to a liquid. A melting range may be given for mixtures.
mg/kg	Milligrams per kilogram.  A term used in experimental testing to indicate the dose of a test substance, in milligrams, that was given for each kilogram of body weight of the test animal.
mg/m3	Milligrams per cubic meter.  A way of expressing the concentration of dusts, gases, aerosols, or mists in the air.
milligram (mg)	A unit of weight in the metric system. One thousand milligrams equal one gram.
milliliter (ml)	A metric unit used to measure capacity. One milliliter equals one cubic centimeter. One thousand milliliters equal one liter.
mist	A suspension in air of finely divided particles of liquid.
mucous membranes	A protective lining of cells found, for example, in the mouth, throat, nose, and other parts of the respiratory system.
mutagen	A substance capable of causing damage to genes and chromosomes, particularly those of sperm or egg cells, resulting in mutations.
mutation	A genetic alteration that can be inherited, thus affecting future generations.
narcosis	A state of deep unconsciousness caused by the influence of a drug or other chemical.
nephrotoxin	A chemical that causes kidney damage (e.g., uranium).
neurotoxin	A chemical whose primary toxic effect is on the nervous system (e.g., carbon disulfide).
NFPA	National Fire Protection Association.  This organization provides information on fire protection and prevention.  The NFPA 704 "Standard of the Identification of the Fire Hazards of Materials" describes a hazard-warning, labeling system. This system rates the hazard of a material during a fire. These hazards are divided into health, flammability, and reactivity hazards and appear in a well-known diamond system using numerals from zero through four to indicate severity of the hazard. Zero indicates no special hazard and four indicates severe hazard.
NIOSH	National Institute for Occupational Safety and Health.  This agency of the Center for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services (DHHS) tests and certifies respiratory devices, recommends occupational exposure limits, and assists OSHA by conducting research and investigations.
NTP	National Toxicology Program.  Publishes "Annual Report on Carcinogens," listing substances either known or anticipated to be carcinogens.
odor threshold	The lowest concentration of a substance's vapor, in air, that a person can detect by smell.  Odor thresholds are highly variable, depending on the individual and the nature of the substance.
olfactory	Refers to the sense of smell.
oral	Refers to the mouth.
organic peroxide	A type of oxidizer that is very useful because of its reactive properties, considered by law (OSHA) to be a physical hazard.
OSHA	Occupational Safety and Health Administration.  This government agency develops and enforces occupational safety and health standards for most industry and business in the U.S.
oxidation	A reaction in which a substance combines with oxygen to cause chemical change (e.g., fire).  In a broader sense, oxidation is a reaction in which electrons are lost and is accompanied by reduction — a reaction in which electrons are gained.
oxidizer	A material that causes the ignition of combustible materials without an external source of ignition.  When mixed with combustible materials, an oxidizer increases the rate of burning of these materials when the mixtures are ignited.  Oxidizers can evolve oxygen, and can therefore support combustion in an oxygen-free atmosphere. They are usually unstable or reactive.
oxygen deficiency	An atmosphere having less than the normal percentage of oxygen found in normal air. Normal air contains 21% oxygen at sea level.
PEL	PERMISSIBLE EXPOSURE LIMIT (PEL)
Permissible exposure limit (PEL)	An exposure limit that is published and enforced by OSHA as a legal standard. PEL may be either a time-weighted-average (TWA) exposure limit (8 hour), a 15-minute short term exposure limit (STEL), or a ceiling (C). The PELs are found in Tables Z- 1, Z-2, or Z-3 of OSHA regulations 1910.1000. (See also TLV).
personal protective equipment	Any devices or clothing worn by the worker to protect against hazards in the environment. Examples are respirators, gloves, and chemical splash goggles.
pH	A measure of how acidic or basic (caustic) a substance is on a scale of 1 (very acidic) to 14 (very basic); pH 7 indicates that the substance is neutral.
physical hazard	A substance that is a combustible liquid, a compressed gas, an organic peroxide, or an oxidizer and is explosive, flammable, pyrophoric, unstable (reactive), or water-reactive.
polymerization	A chemical reaction in which individual molecules combine to form a single large molecule (a polymer).  Hazardous polymerization is an uncontrolled reaction releasing large amounts of energy (heat).
ppb	Parts per billion.  A measurement used to express very small concentrations of a given substance present in a mixture.  Often used as a unit to measure the parts (by volume) of a gas or vapor in a billion parts of air.
ppm	Parts per million.  A measurement used to express very small concentrations of a given substance present in a mixture.  Often used as a unit to measure the parts (by volume) of a gas or vapor in a million parts of air.
psi	Pounds per square inch, a unit of pressure measurement used with compressed gases, etc.
pulmonary	Refers to the lungs.
pyrophoric	A chemical that can ignite spontaneously in air at or below 130o F.
reactivity	A substance's susceptibility to undergoing a chemical reaction or change that may result in dangerous side effects, such as explosions, burning, and corrosive or toxic emissions. The conditions that cause the reaction, such as heat, other chemicals, and dropping, will usually be specified as "Conditions to Avoid" when a chemical's reactivity is discussed on a MSDS.
reproductive toxins	Chemicals that affect the reproductive capabilities including chromosomal damage (mutations) and effects on fetuses (teratogenesis).
respirator	A device which is designed to protect the wearer from inhaling harmful contaminants.
respiratory hazard	An airborne contaminant that, when it enters the body via inhalation has an adverse health effect.
respiratory protective equipment	Air-cleaning or air-supply respirators that protect against toxic materials in the air.
route of entry	The means by which a toxic substance enters the body.  For example, absorption through the skin, inhalation, ingestion.  May also be called mode of entry.
secondary container	A container into which personnel transfer material from the vendor supplied container.
select carcinogen	means any substance that meets one of the following criteria: (i) It is regulated by OSHA as a carcinogen; or (ii) It is listed under the category, "known to be carcinogens," in the Annual Report on Carcinogens published by the National Toxicology Program (NTP) (latest edition); or (iii) It is listed under Group 1 ("carcinogenic to humans") by the International Agency for Research on Cancer Monographs (IARC) (latest editions); or (iv) It is listed in either Group 2A or 2B by IARC or under the category, "reasonably anticipated to be carcinogens" by NTP, and causes statistically significant tumor incidence in experimental animals.
sensitizer	A substance that may cause no reaction in a person during initial exposures, but subsequent exposures will cause an allergic response to the substance.
Short Term Exposure Limit	Represented as STEL or TLV-STEL, this is the maximum concentration to which workers can be exposed for a short period of time (15 minutes) for only four times throughout the day with at least one hour between exposures. Also the daily TLV-TWA must not be exceeded. "SKIN" - This designation sometimes appears alongside a TLV or PEL. It refers to the possibility of absorption of the particular chemical through the skin and eyes. Thus, protection of large surface areas of skin should be considered to prevent skin absorption so that the TLV is not invalidated.
solubility in water	Indicates the amount, in %, of a substance that will dissolve in water.  Solubility information is important for determining spill-cleanup and firefighting procedures.
solvent	A liquid that dissolves other substances.  Some common solvents are water, alcohol, and mineral spirits.
STEL	Short Term Exposure Limit:  The maximum concentration allowed in a continuous, 15-minute exposure.  There may be no more than 4 such exposures each day with at least 1 hour between exposures.  The daily TWA cannot be exceeded, however.
suspect carcinogen	A substance that might cause cancer in humans but has not yet been proven to do so.
synonym	Another name by which a chemical is known.  For example, synonyms for methyl alcohol are methanol and wood alcohol.
systemic	Spread throughout the body; affecting many or all body systems or organs; not localized in one spot or area.
systemic poison	A substance that has a toxic effect upon several organ systems of the body.
target organ effects	Effects on specific organs of the body caused by exposure to a hazardous chemical.
teratogen	An agent or substance that may cause physical defects in the developing embryo or fetus when a pregnant female is exposed to that substance.
Threshold Limit Value - TLV	Airborne concentrations of substances devised by the ACGIH that represent conditions under which it is believed that nearly all workers may be exposed day after day with no adverse effect. TLV's are advisory exposure guidelines, not legal standards, that are based on evidence from industrial experience, animal studies, or human studies when they exist. There are three different types of TLV's: Time Weighted Average (TLV-TWA), Short Term Exposure Limit (TLV-STEL) and Ceiling (TLV-C). (See also PEL.)
TLV-C	Threshold Limit Value-Ceiling:  The maximum concentration of a toxic substance for which exposure is allowed.  This limit is not to be exceeded, even momentarily.  The TWA must still be observed.
TWA	Time Weighted Average:  The exposure limit averaged over a normal 8-hour workday or 40-hour workweek.
toxic substance	A substance that causes harmful biological effects after either short-term or long-term exposure.
toxicity	A relative measure of the adverse biological effects that can result from exposure to a harmful substance.
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 manufacturers or distributors involved.
UEL or UFL	Upper Explosive Limit or Upper Flammable Limit: The concentration of a substance above which an ignition source (flame, spark, etc.) will not create a flame or explosion. Above this level the air/contaminant mixture is too "rich" to burn. (See also LEL/LFL.)
unstable	A chemical is unstable if it tends to decompose or undergo other undesirable chemical changes during normal handling or storage.
vapor	The gas given off by a liquid or solid at room temperature.
ventilation	Circulation and exchange of air and the method by which this is accomplished.
vertigo	A state of dizziness, and possibly disorientation.
viscosity	A term used to describe the rate at which a liquid flows or pours.  A very viscous liquid, like molasses, flows slowly.
volatile	A term used for a liquid that evaporates at room temperature.  Very volatile liquids, such as gasoline, form vapors (evaporate) quickly and are a breathing hazard.
water-reactive	A chemical that reacts with water to release a flammable or toxic gas.

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