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AcetylcholineA substance that transmits nerve impulses (neurotransmitter).
AcetylcholinesteraseAn enzyme that occurs especially in some nerve endings and in the blood and promotes the breakdown of acetylcholine. Nerve agents inhibit the action of this enzyme.
AcidAny of various typically water-soluble and sour compounds that in solution are capable of reacting with a base to form a salt, that redden litmus, that have a pH less than 7, and that are hydrogen-containing molecules or ions able to give up a proton to a base or are substances able to accept an unshared pair of electrons from a base.
AcidosisAn abnormal increase in the acidity of the body's fluids, caused either by accumulation of acids or by depletion of bicarbonates.
AcridUnpleasantly sharp, pungent, or bitter to the taste or smell.
AcuityAcuteness of vision or perception.
AcuteHaving a sudden onset, sharp rise, and short course.
Acute Exposure Guideline Level (AEGL)Guideline intended to describe the risk to humans resulting from once-in-a-lifetime, or rare, exposure to airborne chemicals. Acute exposures are defined as single, non-repetitive exposures for not more than 8 hours.
There are three AEGL values:
AEGL-1: Discomfort, non-disabling.
AEGL-2: Irreversible or other serious, long-lasting effects or impaired ability to escape.
AEGL-3: Life-threatening effects or death.
AerosolA suspension of fine solid or liquid particles in gas.
AfebrileFree from fever.
AgentA factor such as a microorganism, chemical substance, or form of radiation that can result in illness or injury.
AgonistA chemical substance (such as a drug) that is capable of combining with a receptor on a cell and initiating the same reaction or activity typically produced by the binding of a substance that normally occurs in the body (i.e., is endogenous).
Air-purifying respirator (APR)An air-filtering device that covers the nose and mouth and removes contaminants from the surrounding air by passing it through a filter, cartridge, or canister. A variety of filter cartridges are designed to capture specific particles and/or gases. Filters must be replaced once absorption capacity is depleted.
AlopeciaLoss of hair; baldness.
AmbientSurrounding or encompassing, e.g., the ambient environment.
AmpuleA small glass vial that is sealed after filling; often used as a container for a solution to be given by hypodermic injection.
AnalgesicA drug that alleviates pain without causing loss of consciousness; a pain-reliever.
AnemiaAn abnormal deficiency in the oxygen-carrying component of the blood, measured in unit volume concentrations of hemoglobin, red blood cell volume, or red blood cell number.
AnestheticAn agent that causes loss of sensation with or without the loss of consciousness.
AnionA negatively charged ion, especially the ion that migrates to an anode in electrolysis.
AnoxiaDeficiency of oxygen, especially one so severe as to result in permanent damage.
AntagonistA chemical that acts within the body to reduce the physiological activity of another chemical substance (as an opiate), especially one that opposes the action on the nervous system of a drug or a substance occurring naturally in the body by combining with and blocking its nervous receptor.
AntibodyAny of a large number of proteins that are produced normally by specialized cells after stimulation by an antigen (e.g., a bacterium, virus, parasite, etc.) and act specifically against the antigen in an immune response. Also called immunoglobulin.
AntiemeticA drug that prevents or alleviates nausea and vomiting.
Antimitotic agentAn agent that prevents or interferes with cell division (mitosis).
AnxiolyticAn anti-anxiety drug.
AplasiaIncomplete or faulty development of an organ or tissue.
ApneaTemporary absence or cessation of breathing.
APRSee definition for Air-purifying respirator
Aqueous solubilityThe amount of a substance (solute) that can be dissolved in a given amount of water(solvent). Aqueous solubility is based on the chemical's respective Log Kow values:
Log Kow ≤ 1, soluble
Log Kow 1-5, slightly soluble
Log Kow > 5, insoluble
ArsenicA highly poisonous metallic element existing in three forms, yellow, black, and gray, of which the brittle, crystalline gray is the most common. Arsenic and its compounds are used in insecticides, weed killers, solid-state doping agents, and various alloys.
ArthralgiaPain in a joint or joints.
Ascending peripheral neuropathyNumbness that begins in the limbs.
Ascorbic acidVitamin C.
AsphyxiantA substance capable of inducing asphyxia, which is a lack of oxygen or an excess of carbon dioxide in the body, usually caused by the interruption of breathing and resulting in unconsciousness.
AsthmaA chronic respiratory disease, often arising from allergies, that is characterized by sudden recurring attacks of labored breathing, chest constriction, and coughing.
AsymptomaticExhibiting no symptoms of disease.
AtaxiaInability to coordinate muscular movement.
AtelectasisTotal or partial collapse of the lung.
AtrophyA wasting or decrease in size of a body organ, tissue, or part owing to disease, injury, or lack of use.

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BALBritish Anti-Lewisite, an antidote for Lewisite exposure.
BarbiturateAny of a class of drug used especially as sedatives, hypnotics, and antispasmodics.
BenzodiazepineAny of a class of drug used as antianxiety agents, muscle relaxants, sedatives, hypnotics, and sometimes as anticonvulsants.
Beta particleA subatomic particle that is ejected from the nucleus of unstable atoms. Beta particles can travel through several layers of human skin, and exposure to large sources of beta radiation can cause burns or skin reddening. Beta particles that enter the body can damage cells, which can lead to cell death or, later in life, to cancer.
Beta radiationSee definition of Beta particle.
Beta-adrenergicPertaining to a certain type of receptor, the beta-receptor, postulated to exist on the surface of certain cells and reacting to adrenaline or adrenaline-like agents.
Biological agentA living organism that can cause disease, sickness, and mortality in humans.
BiotoxinA substance produced by a living organism, such as a plant or fish, that has toxic effects.
BlanchingWhitening of the skin.
BlepharospasmSpasmodic blinking.
Blister agent (vesicant)A substance that causes blistering of the skin and mucous membranes. Exposure is through liquid or vapor contact with any tissue (i.e., eyes, skin, lungs).
BradycardiaSlow heart rate, usually fewer than 60 beats per minute in an adult human.
BronchiThe large airways leading to the lungs. Singular = bronchus.
BronchioleOne of the small airways leading to the lungs.
BronchitisChronic or acute inflammation of the large airways.
BronchoconstrictionNarrowing of the large airways.
BronchodilationExpansion of the large airways.
BronchodilatorA drug which enlarges the large airways.
BronchopneumoniaInflammation of small areas of the lung.
BronchospasmSpasmodic narrowing of the large airways.
BullaA large blister or vesicle. Plural = bullae.

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CachexiaPhysical wasting and malnutrition.
CamphorAn aromatic crystalline compound, obtained naturally from the wood or leaves of the camphor tree or synthesized and used as an insect repellent, in the manufacture of film, plastics, lacquers, and explosives, and in medicine chiefly in external preparations to relieve mild pain and itching.
CapillariesThe smallest blood vessels.
CarcinogenicCausing or producing cancer.
CarcinogenicityCancer-causing potential (of an agent or substance).
Cardiac arrestTemporary or permanent cessation of the heartbeat.
Cardiac arrhythmiaAlteration of the heart rhythm.
Cardiac dysrhythmiaAn abnormality in an otherwise normal rhythmic pattern of the heart.
Cardiac sensitizationIncreased responsiveness or susceptibility of the heart to stimulating hormones following exposure to a chemical, which can lead to irregular heart rhythms (arrhythmias), cardiac arrest, or death.
CardiopulmonaryOf, relating to, or involving both the heart and the lungs.
Cardiopulmonary failureHeart and respiratory failure.
CardioversionApplication of an electric shock to restore normal heartbeat.
CastA mass formed in cavities of diseased organs.
CatharticAn agent for purging the bowels, especially a laxative.
CausticCapable of burning, corroding, and dissolving, or eating away by chemical action.
CBRNChemical, Biological, Radiological, Nuclear
Central nervous system (CNS)The brain and spinal cord.
Cerebral edemaAccumulation of fluid in and resultant swelling of the brain.
Chelating agentAn agent that removes a heavy metal, such as lead or mercury, from the bloodstream.
Chemical agentA chemical substance that is intended for use in military operations to kill, seriously injure, or incapacitate people through its physiological effects.
Chemical protective clothing and equipmentAny item of clothing (e.g., gloves, boots, suits) used to isolate parts of the body from direct contact with potentially hazardous substances. Safe use of this type of protective clothing and equipment requires specific skills developed through training and experience. This type of special clothing may protect against one chemical, yet be readily permeated by chemicals for which it was not designed. Therefore, protective clothing should not be used unless it is compatible with the released material. This type of special clothing offers little or no protection against heat and/or cold.
ChemosisSwelling of the outer membranes of the eye.
Chemotherapeutic agentA chemical agent or drug used in the treatment of disease; chemotherapeutic agents are selectively toxic to the causative agent of the disease, such as a virus, bacterium, or other microorganism.
CholinesteraseAn enzyme found primarily at nerve endings that catalyzes the breakdown of acetylcholine.
ChoreaAny of various nervous disorders of infectious or organic origin marked by spasmodic movements of the limbs and facial muscles and by incoordination.
ChoreiformSpasmodic and uncoordinated. See also chorea.
ChronicMarked by long duration, by frequent recurrence over a long time, and often by slow progression to become more serious.
ClonicIntermittent (e.g., movements).
CNSCentral nervous system.
CNS depressionReduced level of consciousness.
CNS excitationIncreased level of consciousness.
CoagulopathyA disease or condition affecting the ability of the blood to clot (coagulate).
ComaState of profound unconsciousness.
CombustibleWill ignite, burn, or support combustion.
Combustible liquidA liquid that has a flash point greater than 60.5°C (141°F) and below 93°C (200°F). U.S. regulations permit a flammable liquid with a flash point between 38°C (100°F) and 60.5°C (141°F) to be re-classed as a combustible liquid.
ConcussionAn injury to an organ, especially the brain, produced by a violent blow and followed by a temporary or prolonged loss of function.
Conjuctival injectionAccumulation of blood in the membranes of the eye (see also "injected conjuctiva").
ConjunctivaThe mucous membrane that lines the inner surface of the eyelid and the exposed surface of the eyeball. Plural = conjunctivae.
ConjunctivitisInflammation of the membranes of the eye (conjuctiva).
Contact dermatitisInflammation of the skin caused by direct contact with an irritant.
ConvulsionAn intense, paroxysmal, involuntary muscular contraction. During convulsions, the patient's body shakes rapidly and uncontrollably and his/her muscles contract and relax repeatedly. The term "convulsion" is often used interchangeably with "seizure," although there are many types of seizure, some of which have subtle or mild symptoms instead of convulsions.
CopiousLarge in quantity; abundant.
CorneaThe transparent part of the coat of the eyeball that covers the iris and pupil and admits light to the interior.
Corneal epitheliumThe outer layer of the cornea (of the eye).
CorticosteroidAny of the steroid hormones produced by the adrenal cortex or their synthetic equivalents, such as cortisol and aldosterone.
Cranial nerve palsyA form of paralysis.
CrystallineBeing, relating to, or composed of crystals.
CyanosisBluish discoloration of the skin due to deficient oxygenation of the blood.
CylindruriaPresence of casts (masses) in the urine.
CytotoxicHaving a harmful effect on cells; cell-killing or cell-harming.

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DecontaminationThe removal of a dangerous material from any person, object, or area to the extent necessary to prevent potential adverse health effects.
DecontaminationThe destruction, physical removal, or reduction of a toxic substance to an acceptable level.
Decubitus ulcersBed sores.
DefecationThe discharge of feces.
DeliquescentTending to dissolve and become liquid by the absorption of moisture from the air.
DementiaMarked decline in mental function.
DepersonalizationA feeling of loss of identity.
DerealizationA feeling of altered reality.
DermalOf or relating to the skin (dermis).
DermatitisInflammation of the skin.
DermatosisA skin disease, especially one that is not accompanied by inflammation. (Plural = dermatoses.)
DetoxificationThe metabolic process by which the toxic qualities of a poison or toxin are reduced by the body.
DetoxifyTo treat (an individual), usually under a medically supervised program designed to rid the body of toxic substances.
Deviations (conjugate or dissociated)Abnormal movements of one or both eyes.
DiaphoresisSweating, especially when profuse and medically induced.
DiatomaceousConsisting of diatoms or their skeletons; diatomaceous earth is a light, crumbly silica-containing material used in filtration.
DikeA barrier blocking a passage, especially for protection.
DiplopiaDouble vision.
Disseminated intravascular coagulationWidespread formation of clots in the blood vessels.
DiureticTending to increase the discharge of urine.
DNAA nucleic acid that carries the genetic information in the cell and is capable of self-replication and synthesis of RNA.
DonTo put on (clothing).
DysarthriaDifficulty in articulating words, resulting in slurred speech.
DysphagiaDifficulty in swallowing.
DysphasiaDifficulty in using or understanding language.
DysphoniaDefective use of the voice; slurred speech.
DyspneaDifficulty in breathing, or shortness of breath.
DysrhythmiaAbnormal or disordered heart rhythm.

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ECGSee "electrocardiogram"
EctropionAbnormal turning out of the eyelid.
EczematoidResembling eczema, an inflammatory condition of the skin characterized by redness, itching, and oozing blister-like lesions, which become scaly, crusted, or hardened.
EdemaAn abnormal, excessive accumulation of thin, watery fluid in tissue spaces or a body cavity.
EffluentSomething that flows out, especially a discharge of waste into the environment.
Electrocardiogram (ECG)A recording of the electrical activity of the heart.
ElectrolyteAny of the ions (as of sodium, potassium, calcium, or bicarbonate) that in a biological fluid regulate or affect most metabolic processes (as the flow of nutrients into and waste products out of cells).
EmesisThe act of vomiting.
EmphysemaA disease of the lungs characterized by air-filled expansions in lung tissues.
EncephalopathyA disease of the brain.
EndophthalmitisInflammation of the interior of the eyeball.
EndoscopicA medical procedure that uses an instrument (endoscope) to examine visually the interior of a bodily canal or a hollow organ such as the colon, bladder, or stomach.
EndotrachealWithin or passing through the trachea (windpipe), e.g., an endotracheal tube.
Endotracheal intubationInsertion of a tube within the trachea.
EnteritisInflammation of the intestinal tract, especially of the small intestine.
EpigastricAbdominal, specifically, over or above the stomach.
EpitheliumThe covering of internal and external surfaces of the body, including the lining of vessels and other small cavities.
ERPGEmergency Response Planning Guidelines developed by the American Industrial Hygiene Association (AIHA).
ERPG-1The maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hour without experiencing more than mild, transient adverse health effects or without perceiving a clearly defined objectionable odor.
ERPG-2The maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms that could impair an individual’s ability to take protective action.
ERPG-3The maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hour without experiencing or developing life-threatening health effects.
ErythemaRedness of the skin.
ErythrocyteRed blood cell.
EthanolA colorless, volatile, flammable liquid that is the intoxicating agent in liquors and is also used as a solvent.
EuphoriaA disproportionate feeling of well-being.
EvolveTo give off or emit (e.g., a gas).
ExothermicReleasing heat.

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Face shieldA supplementary protective device worn to shield the wearer's face from certain hazards. Face shields are secondary protectors only and must be worn with safety glasses or goggles.
FasciculationMuscular twitching.
FatalCausing death.
FebrileShowing symptoms indicating fever; feverish.
FibrosisAn increase in fibrous tissue situated within but not restricted to or characteristic of a particular organ or tissue.
FlaccidLacking firmness, resilience, or muscle tone.
Flaccid paralysisParalysis with reduced muscle tone and reflexes.
FlammableCapable of being ignited and rapidly consumed by fire.
Flammable liquidA liquid that has a flash point of 60.5°C (141°F) or lower.
Flash pointLowest temperature at which a liquid or solid gives off vapor in such a concentration that, when the vapor combines with air near the surface of the liquid or solid, a flammable mixture is formed. Hence, the lower the flash point, the more flammable the material.
FogSee Water spray.
FomepizoleA drug that is a competitive inhibitor of an enzyme (alcohol dehydrogenase) that catalyzes the breakdown of methanol and ethylene glycol into their toxic metabolites, and is used to treat poisoning by those substances.
FrictionRubbing of one body against another.


Gamma radiationA packet of energy, called a photon, that is emitted from the nucleus of an unstable atom. Gamma radiation is high-energy electromagnetic radiation that can penetrate most substances (lead is the best barrier against gamma radiation). Because of its high energy, gamma radiation can penetrate the human body from the outside and damage cells, which could lead to cancer later in life.
Gas maskA face covering device used to protect the wearer from injurious gases and other noxious materials by filtering and purifying inhaled air. It usually consists of a face cover with two eyepieces and a mouthpiece that contacts a canister containing a filter; the filter absorbs noxious gases as they pass through the canister to the mouth. The face cover also has a one-way outlet valve for exhaled air.
GastricPertaining to the stomach.
Gastric hypomotilitySlowing of muscular movement of the stomach.
Gastric lavageA procedure to empty the contents of the stomach, usually for analysis or removal of irritating elements such as poisons. Also called stomach pumping or gastric suction.
GastritisInflammation of the lining of the stomach.
GastroenteritisInflammation of the lining of the stomach and intestines.
Gastrointestinal (GI)Relating to or affecting both the stomach and the intestines.
General population limit (GPL)An airborne exposure limit designed to protect the general public.
GerminalOf, relating to, or having the nature of a germ cell (sperm, egg, or their precursors).
GlottisThe vocal apparatus of the larynx, consisting of the vocal cords and the opening between them.
GogglesA wraparound, protective device that fits the face, surrounding the eyes in order to shield them from impact, splash and vapor hazards. Goggles are available non-vented or with direct or indirect vents.
GonadAn organ in an animal that produce gametes, e.g., a testis or ovary.
GoutA metabolic disease marked by a painful inflammation of the joints, deposits of uric acid salts in and around the joints, and usually an excessive amount of uric acid in the blood.
GPLSee: General population limit.
Green ZoneAn area where contamination with chemical, biological, radiological, or nuclear (CBRN) agents is unlikely. This zone covers the area beyond the expected significant dispersal range of the initial event and secondary contamination range caused by traffic and emergency responders.

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Half-lifeThe time required for half of the atoms of a radioactive substance to decay or disintegrate.
HalonAny of several halocarbons used as fire-extinguishing agents.
HematemesisVomiting blood.
HematologicOf or relating to the blood.
HematopoieticRelating to the formation of blood or blood cells in the body.
HematuriaThe presence of blood in the urine.
HemodialysisA medical procedure to remove wastes or toxins from the blood and adjust fluid and electrolyte imbalances.
HemoglobinuriaThe presence of hemoglobin (the oxygen-carrying pigment in the blood) in the urine.
HemolysisLysis (destruction) of red blood cells (see also "intravascular hemolysis").
Hemolytic anemiaAnemia caused by the destruction of blood cells.
HemoptysisSpitting up of blood.
HemorrhageExcessive bleeding.
HemorrhagicPertaining to a hemorrhage.
Hemorrhagic gastritisInflammation of the lining of the stomach with bleeding.
Hemorrhagic gastroenteritisInflammation of the lining of the stomach and intestines with severe bleeding.
HEPAHigh Efficiency Particulate Air filters
HEPA PAPRHigh Efficiency Particulate Air Powered Air-Purifying Respirator
Hepatic encephalopathyCentral nervous system disease, which is a result of liver failure.
HepatomegalyAbnormal enlargement of the liver.
High Efficiency Particulate Air (HEPA) filtersUsed in ventilation systems, HEPA filters remove 99.7% of particles 0.3 microns and smaller, which include dust, mold spores, dust mites, pet dander, allergens, and many biological agents such as anthrax spores. They do not purify the air for most chemical agents.
HydrolysisDecomposition of a chemical compound by reaction with water, such as the dissociation of a dissolved salt or the catalytic conversion of starch to glucose.
HydrolyzeTo subject to or undergo hydrolysis.
HygroscopicReadily taking up and retaining water or moisture.
HyperemiaAbnormal accumulation of blood.
HyperkalemiaHigh blood levels of potassium.
HyperkeratosisThickening of the outer layer of the skin.
HyperpigmentationDarkening of a body part or tissue.
HyperpneaIncrease in the rate and depth of breathing.
HyperreflexiaOveractive body reflexes.
HypertensionAbnormally elevated blood pressure.
HyperthermiaExceptionally high body temperature.
HyperventilationExcessive rate and depth of respiration.
HypocalcemiaLow blood levels of calcium.
HypoglycemiaLow blood levels of sugar (glucose).
HypokalemiaLow blood levels of potassium.
HypomagnesemiaLow blood levels of magnesium
HyporeflexiaUnderactive body reflexes.
HypotensionAbnormally low blood pressure.
HypothermiaAbnormally low body temperature.
HypovolemiaA decrease in the volume of circulating blood.
Hypovolemic shockA life-threatening condition in which the heart is unable to supply enough blood to the body because of inadequate blood volume or blood loss. May occur subsequent to serious dehydration.
HypoxemiaOxygen deficiency in the blood.
HypoxiaDecreased oxygen supply to the tissues.

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IDLHSee: Immediately dangerous to life and health.
IleusObstruction of the intestines.
Immediately Dangerous to Life or HealthAs defined by NIOSH, an immediately dangerous to life or health condition is a situation "that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment." NIOSH also states that the purpose of establishing an IDLH is to "ensure that the worker can escape from a given contaminated environment in the event of failure of the respiratory protection equipment."
ImmiscibleNot mixing readily with water.
Incapacitating agentAn agent that produces temporary physiological and/or mental effects via action on the central nervous system. Effects may persist for hours or days, but victims usually do not require medical treatment, although treatment may speed recovery.
InebriationDrunkenness (intoxication).
InertNot readily reactive with other elements; forming few or no chemical compounds.
InflammationA local response to cellular injury that is marked by redness, heat, pain, swelling, cellular and blood vessel changes, and often loss of function and that serves as a mechanism initiating the elimination of noxious agents and of damaged tissue.
InflammatoryAccompanied with, or tending to cause, inflammation.
InhalationThe act of drawing in breath.
InhibitorAn agent that slows or interferes with a chemical reaction; a substance that reduces the activity of another substance (as an enzyme).
Initial isolation and protective action distancesTwo types of recommended safe distances listed in the U.S. Department of Transportation ERG 2000 for toxic inhalation hazard (TIH) substances, which are poisonous by inhalation and/or water-reactive materials, which produce toxic gases upon contact with water. The "Initial Isolation Distance" is a distance within which all persons should be considered for evacuation in all directions from the actual spill/leak source. The "Protective Action Distance" represents a downwind distance from the spill/leak source within which Protective Actions, those steps taken to preserve the health and safety of emergency responders and the public, could be implemented.
Injected conjuctivaAccumulation of blood in the membranes of the eye (see also "conjuctival injection").
InspiratoryOf, relating to, or used for the drawing air into the lungs.
IntracranialOccurring or situated within the skull (cranium).
Intracranial hypertensionElevated pressure of the fluid surrounding the brain and spinal cord (cerebrospinal fluid, or CSF).
IntravascularWithin blood vessels or a blood vessel.
Intravascular hemolysisLysis (destruction) or red blood cells (see also "hemolysis").
IntubationInsertion of a tube into a hollow organ or body passage; to intubate.
IonAn atom or a group of atoms that has acquired a net electric charge by gaining or losing one or more electrons.
IpecacA medicinal preparation made from the dried roots and rhizomes of a shrub, sometimes used to induce vomiting, particularly in cases of poisoning and drug overdose.
IritisInflammation of the iris of the eye.
IrrigationContinuous washing.


JaundiceYellowish pigmentation of the skin and tissues.


KeratitisCorrosion of the cornea of the eye.


LabilityThe state of constantly undergoing or likely to undergo change; unstable.
LacrimationExcessive tear production.
LacrimatorA tear-producing chemical.
LaryngealRelating to, affecting, or near the larynx (voice box).
LaryngitisInflammation of the voice box.
LaryngospasmInvoluntary contraction of the vocal cords that impedes airflow to the lungs.
LatentExisting in hidden or dormant form; not currently showing signs of activity or existence.
Latent periodSymptom-free period.
LavageWashing out a hollow organ (such as the stomach) by flushing with water.
LesionAn abnormal change in structure of an organ or part due to injury or disease, especially such a change that is circumscribed and well-defined.
LethalCapable of causing death
LethargyAbnormal drowsiness (see also somnolence).
LeukocyteWhite blood cell.
LeukocytosisAbnormal increase in the number of circulating white blood cells.
LeukopeniaA reduced white blood cell count.
LipidsSubstances, such as fats, that are some of the principal structural constituents of the cells of living organisms.
Lobular emphysemaSmall areas of lung disease (see also "emphysema")
LocalizedRestricted to a definite part of the body; not general or systemic.
LorazepamA drug used therapeutically to control seizures.
Lung damaging agentA substance that causes physical injury to the respiratory tract, including the lungs. In extreme cases, membranes swell and lungs become filled with fluid; death results from lack of oxygen.
LymphocytosisAbnormal increase in the number of lymphocytes (a kind of white blood cell).

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MalaiseVague feeling of generalized weakness.
MandibleThe lower jaw.
Mechanical ventilationArtificial ventilation of the lungs (as by positive end-expiratory pressure) using means external to the body.
Mees' linesWhite lines in the nails.
MelanosisAbnormal darkening of the skin or tissues.
MelenaThe passage of bloody stools.
Metabolic acidosisAccumulation of acid in the blood and tissues.
MetabolismThe process by which a substance is broken down in the body.
MetaplasiaAbnormal replacement of cells.
MethemoglobinemiaExcessive accumulation of an inactive form of hemoglobin in the blood.
MiosisContracted or pinpoint pupils.
MiscibleCapable of mixing readily, usually with water.
MitosisThe process of cell division.
Motor dysfunctionDifficulty moving.
MucosaThe lining of certain body passages, such as the gastrointestinal tract or the airways (see also "mucous membrane").
Mucous membraneA membrane rich in mucous glands; specifically, a membrane lining body passages and cavities that communicate directly or indirectly with the exterior, which functions in protection, support, nutrient absorption, and secretion of mucus, enzymes, and salts; the membrane is always soft and smooth and kept lubricated by the secretions of the cells and numerous glands embedded in the membrane. Also called mucosa.
MucusA gummy, slippery secretion produced by mucous membranes, which it moistens and protects.
MyalgiaMuscle pain.
MydriasisDilated pupils.
MyelosuppressionSuppression of the bone marrow's production of blood cells and platelets.
MyocardialPertaining to the muscular tissue of the heart.
Myocardial depressionA decrease in the heart's ability to pump blood.
Myocardial failureHeart failure.
MyocardiumThe muscular tissue of the heart.
MyoclonicA sudden, involuntary twitching of muscles or parts of muscles, without any rhythm or pattern, occurring in various disorders of the nervous system.


n.o.s.Not otherwise specified, e.g., where the name of a specific chemical is not listed in the applicable regulations, a generic name such as "Corrosive liquid, n.o.s."is used on shipping papers.
NarcoticA drug (as opium) that in moderate doses dulls the senses, relieves pain, and induces profound sleep, but in excessive doses causes stupor, coma, or convulsions.
NecrosisDeath of living tissue; specifically, death of a portion of tissue differentially affected by local injury (as through loss of blood supply, corrosion, burning, or the local lesion of a disease).
NecroticAffected with, characterized by, or producing necrosis.
Necrotizing bronchiolitisDestruction of tissue and irritation of the airways.
NeoplasmAbnormal growth of tissue, such as cancer.
NeopreneA synthetic rubber produced by polymerization of chloroprene and used in weather-resistant products, adhesives, shoe soles, sportswear, paints, and rocket fuels.
Nerve agentAn agent that interferes with the function of the central nervous system. Exposure is primarily through contact with the liquid (via skin and eyes) and secondarily through inhalation of the vapor.
Nettle agentAn agent that causes severe irritation to the skin and mucous membranes, as well as pain; also called urticant. (Note that in this database, nettle agents are included in the Blister Agent category.)
NeuromyopathyA disease of the nerves and associated muscle tissue.
NeuropathyA disease or abnormality of the nervous system.
NeuropsychiatricIn medicine, pertaining to disorders with both neurological and psychiatric features.
NeutralizationThe state or quality of being neutralized. A reaction between an acid and a base that yields a salt and water.
NFPANational Fire Protection Association
NFPA 704Standard System for the Identification of the Hazards of Materials for Emergency Response. A standard providing a readily recognized, easily understood system for identifying specific hazards and their severity using spatial, visual, and numerical methods to describe in simple terms the relative hazards of a material. It addresses the health, flammability, instability, and related hazards that may be presented as short-term, acute exposures that are most likely to occur as a result of fire, spill, or similar emergency.
NFPA 704 FlammabilityThe red (upper) quadrant of the NFPA 704 symbol. The values are:
4 – Danger. Flammable gas or extremely flammable liquid.
3 – Warning. Flammable liquid, flash point below 100°F (38°C).
2 – Caution. Combustible liquid, flash point of 100° to 200°F (38° to 93°C).
1 – Combustible if heated.
0 – Not combustible.
NFPA 704 HealthThe blue (left-hand) quadrant of the NFPA 704 symbol. The values are:
4 – Danger. May be fatal on short exposure. Specialized protective equipment required.
3 – Warning. Corrosive or toxic. Avoid skin contact or inhalation.
2 – Warning. May be harmful if inhaled or absorbed
1 – Caution. May be irritating.
0 – No unusual hazard.
NFPA 704 ReactivityThe yellow (right-hand) quadrant of the NFPA 704 symbol. The values are:
4 – Danger. Explosive material at room temperature
3 – Danger. May be explosive if shocked, heated under confinement or mixed with water.
2 – Warning. Unstable or may react violently if mixed with water.
1 – Caution. May react if heated or mixed with water, but not violently.
0 – Stable. Not reactive when mixed with water.
NFPA 704 SpecialThe white (lower) quadrant of the NFPA 704 symbol. The values are:
W – Water Reactive.
OX – Oxidizing Agent.
NIOSHNational Institute for Occupational Safety and Health.
Non-polarNot polar; not having an electric charge.
Not established/determinedThis term is used when information is not available for a given agent.
Not RecommendedThis term is used when there is insufficient data for the agent.
NPONothing by mouth; from the Latin nil per os. May also be written n.p.o.
NPPTLNational Personal Protective Technology Laboratory
NucleophileA chemical compound or group that is attracted to nuclei and tends to donate or share electrons.
NystagmusInvoluntary movement (oscillation) of the eyeballs.

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OcularOf or relating to the eye.
Off-gassingThe release of chemicals from non-metallic substances under ambient or greater pressure conditions.
OliguriaReduced excretion of urine.
OpacificationThe act or process of becoming opaque; clouding.
OpaqueImpenetrable by light; neither transparent nor translucent.
OphthalmicOf or relating to the eye; ocular.
OphthalmologistA physician who specializes in ophthalmology, the treatment of diseases and conditions of the eye.
OpiateA drug, hormone, or other chemical substance having sedative or narcotic effects similar to those from substances containing opium or its derivatives.
OpioidA synthetic substance with opiate-like qualities.
OpisthotonosA condition of spasm of the muscles of the back, which causes the body to arch backwards in hyperextension, e.g. during convulsions or seizures.
Optic neuritisInflammation of the optic nerve.
Optic neuropathyDegeneration of the optic nerve.
Organ congestionAccumulation of blood in the organs.
OrganophosphateAn organophosphorus compound.
OrganophosphorusOf, relating to, or being a phosphorus-containing organic pesticide (as malathion) that acts by inhibiting cholinesterase.
OropharyngealThe part of the pharynx between the soft palate and the epiglottis.
OSHAOccupational Safety and Health Administration.
OsteosclerosisAbnormal hardening of the bone or bone marrow.
OxidantA substance that oxidizes another substance; an oxidizing agent.
OxidationGenerally, the chemical reaction of a substance with oxygen (O2) or an oxygen-containing material, which adds oxygen atom(s) to the compound being oxidized. More rigorously, "the loss of electrons from an atom, compound or molecule." Oxidation reactions frequently generate heat (are exothermic).
OxidizerA substance that oxidizes another substance, especially one that supports the combustion of fuel; an oxidizing agent.
Oxidizing agentA substance that oxidizes another substance. Oxdizing agents can cause other materials to combust more readily (or upon contact) or make fires burn more strongly.


PallorDeficiency of color especially of the face; paleness.
PalpitationIrregular, rapid beating or pulsation of the heart.
PancreatitisInflammation of the pancreas.
PancytopeniaAn abnormal reduction in the number of red blood cells, white blood cells, and blood platelets in the blood.
ParalysisLoss or impairment of the ability to move a body part, usually as a result of damage to its nerve supply.
Parenteralintroduced otherwise than by way of the intestines, e.g., parenteral drug administration can be by intravenous, intramuscular, or subcutaneous injection
ParesthesiaSensation of prickling tingling or creeping on the skin, with no apparent physical cause.
ParkinsonismA condition causing tremor and weakness of the resting muscles and shuffling gait.
ParoxysmalSuddenly recurring or intensifying (e.g., pain or symptoms).
PELOSHA Permissible Exposure Limit.
PelletA small, solid or densely packed ball or mass.
PeripheralRelated to, located in, or constituting an outer boundary, surface, or periphery.
Peripheral Nervous SystemThe part of the nervous system that is outside the central nervous system and comprises the cranial nerves (except the optic nerve), the spinal nerves, and the autonomic nervous system.
Peripheral neuropathyDegeneration of certain nerves.
PerseverationContinual, involuntary repetition of behaviors.
PesticideA pesticide is any substance or mixture of substances intended to be used to control, repel, or kill any pest. Pests compete with humans for food, destroy property, spread disease, or are considered a nuisance. They include insects, mice and other animals, unwanted plants (weeds), fungi, or microorganisms like bacteria and viruses. (U.S. EPA)
PharyngitisInflammation of the throat (pharynx).
PhenytoinAn anticonvulsant drug used most commonly in the treatment of epilepsy. Also called diphenylhydantoin.
PhotophobiaA painful sensitivity to light.
PlateletA minute body found in the blood of mammals that functions to promote blood clotting; also called thrombocyte.
PneumoniaAn inflammatory lung disease (see also pneumonitis).
PneumonitisA disease characterized by inflammation of the lungs (see also pneumonia).
Pocket resuscitation maskA device that protects a rescuer from being contaminated by a victim when giving emergency mouth-to-mouth resuscitation. It consists of a curved plastic cup that rests over a victim’s mouth and has a short tube attached for the rescuer to blow into.
Poison or PoisonousThe words "poison" or "poisonous" are synonymous with the word "toxic".
PolarExhibiting polarity, i.e., having electric charges.
PolydipsiaExcessive thirst.
PolymerizedHaving undergone polymerization, a process in which two or more smaller molecules are joined to form larger molecules that contain repeating structural units.
PolyneuropathyA degenerative disease of the nerves.
Positive Pressure Self-Contained Breathing Apparatus (SCBA)An apparatus providing a constant, positive pressure flow of air within the face piece, even if one inhales deeply while doing heavy work. Use apparatus certified by NIOSH and the Department of Labor/Mine Safety and Health Administration in accordance with 42 CFR Part 84. Use it in accordance with the requirements for respiratory protection specified in OSHA 29 CFR 1910.134 (Respiratory Protection) and/or 29 CFR 1910.156 (f) (Fire Brigades Standard).
Powered Air-Purifying Respirator (PAPR)A motorized respirator system that uses a filter to clean surrounding air before deliveringto the wearer to breathe. It typically includes a blower/battery box worn on the belt, headpiece, and breathing tube.
ppmParts per million.
Prodromal syndromePremonitory or precursory symptoms.
ProptosisAbnormal bulging (forward projection) of the eyeball.
ProstrationComplete physical or mental exhaustion.
ProteinuriaThe presence of excess protein in the urine.
PruritusSevere itching.
PseudomembraneA false membrane or fibrous deposit formed in some disease processes.
psiaA unit of pressure, pounds per square inch absolute
psigA unit of pressure, pounds per square inch gauge
PsychicOf or relating to the mind; mental.
PsychosisA serious mental disorder.
PtosisDrooping of the upper eyelid.
PtyalismExcessive salivation.
PulmonaryRelated to or associated with the lungs.
Pulmonary aspirationThe inhalation of foreign materials such as stomach contents into the lungs.
Pulmonary edemaAccumulation of fluid in the lungs.
Pulmonary fibrosisAn increase in fibrous tissue in the lungs.
Pulmonary hemorrhageBleeding in the lungs.
Pulmonary hypertensionHigh blood pressure in the lungs.
Pulmonary thrombosisThe presence of blood clots in the lungs.
PungentAffecting the organs of taste or smell with a sharp acrid sensation.
PustularContaining pus.
PustuleA small elevation of the skin containing pus and having an inflamed base.
PVCA polymer of vinyl chloride used instead of rubber in electric cables.

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QIDFour times per day or four daily doses; from the Latin quater in die. May also be written q.i.d.


RADSReactive Airways Dysfunction Syndrome.
RalesAn abnormal respiratory sound.
Red ZoneAreas where significant contamination with chemical, biological, radiological, or nuclear (CBRN) agents has been confirmed or is strongly suspected but area has not been characterized. The Area is presumed to be life threatening from both skin contact and inhalation.
RefractoryResistant to treatment or cure.
Refractory cardiogenic shockShock resulting from failure of the heart's ability to pump sufficient blood.
RELNIOSH Recommended Exposure Limit. The designation "(skin)" in this section "indicates the potential for dermal absorption; skin exposure should be prevented as necessary through the use of good work practices and gloves, coveralls, goggles, and other appropriate equipment," according to the NIOSH Pocket Guide to Chemical Hazards.
RenalOf, relating to, or in the region of the kidneys.
Renal failureKidney failure.
ResidualThe quantity left over at the end of a process.
RespirationThe act of breathing. The physical and chemical process by which an organism supplies its cells and tissues with the oxygen needed for metabolism and relieves them of the carbon dioxide formed in energy-producing reactions.
RespiratorA device ("approved") that has met the requirements of 42 CFR part 84, has been designed to protect the wearer from inhalation of harmful atmospheres, and has been approved by the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA).
Respiratory depressionReduced respiratory function.
Respiratory failureThe loss of lung function, either acute or chronic, that results in subnormal oxygenation of blood or abnormally increased carbon dioxide. The inability to breathe by a person’s own means.
ResuscitationRestoration of consciousness.
Retinal hemorrhageBleeding of the membrane in the rear of the eye.
RhabdomyolysisDestruction or degeneration of skeletal muscle tissue.
RhinorrheaRunny nose; excessive secretion of mucus from the nose.
RhonchiA coarse rattling sound somewhat like snoring, usually caused by secretion in a bronchial tube.
Riot Control/Tear agentA substance that causes intense irritation to the eyes and upper respiratory tract, including profuse tearing.
Risus sardonicusMuscle spasm resulting in distortion of the face into a grinning expression, such as during convulsions or seizures.
RTECsRegistry of Toxic Effects of Chemical Substances (RTECS).

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SCBASelf-Contained Breathing Apparatus.
SedationInduced state of relaxation, especially by the use of sedative drugs.
SeizureA sudden attack (as of a disease). A sudden change in behavior due to excessive electrical activity in the brain.
Self-Contained Breathing Apparatus (SCBA)A respiratory filter mask that contains its own air supply. It is composed of a face piece connected by a hose to a wearable, compressed, clean-air supply pack much like a scuba tank.
SepsisA toxic condition resulting from the spread of infection.
SequelaA secondary consequence or result; aftereffect. (Plural = sequelae.)
SerumThe clear yellowish fluid obtained upon separating whole blood into its solid and liquid components after it has been allowed to clot. Also called blood serum.
SevereSerious (for a health effect); of high intensity (for an exposure).
ShockA state of profound depression of the vital processes of the body that is characterized by paleness (pallor), rapid but weak pulse, rapid and shallow respiration, reduced total blood volume, and low blood pressure and that is caused usually by severe especially crushing injuries, hemorrhage, burns, or major surgery.
Short-Term Exposure Limit (STEL)An airborne exposure limit designed to address short-term upward deviations in exposure. Typically, exposures at the STEL should not be longer than 15 minutes and should not occur more than 4 times per day, and at least 60 minutes should elapse between successive exposures in this range.
SloughingSeparating or casting off dead tissue from living tissue, as in a wound.
SlurryA thin mixture of a liquid, especially water, and any of several finely divided insoluble substances.
Sodium hypochloriteThe active ingredient in household liquid chlorine bleach. It is ordinarily about 5% strength in a water-based solution of bleach.
SomaticPertaining to or characteristic of the body (physical).
SomnolenceA state of abnormal drowsiness (see also lethargy).
SorbentA substance that takes up and holds, e.g., liquids, by absorption or adsorption.
SpasmAbnormal and involuntary contraction of a muscle or of a hollow organ (such as an artery).
SpasmodicRelating to, characterized by, or resulting from spasm.
SpermatogenesisFormation and development of spermatozoa.
SputumMatter ejected from the lungs and air passages during cough.
StabilizerA substance that renders or maintains a solution, mixture, suspension, or state resistant to chemical change.
STBSuper Tropical Bleach slurry.
STELSee: Short-Term Exposure Limit.
StomatitisInflammatory disease of the mouth.
Street Clothing and Work UniformsThese garments, such as uniforms worn by police and emergency medical services personnel, provide almost no protection from the harmful effects of dangerous goods.
Stricture formationAbnormal narrowing of the digestive tract.
Structural Fire Fighters' Protective Clothing (SFPC)Turnout or bunker gear; the protective clothing normally worn by fire fighters during structural fire fighting operations. It includes a helmet, coat, pants, boots, gloves and a hood to cover parts of the head not protected by the helmet and face piece. This clothing must be used with full-face piece positive pressure self-contained breathing apparatus (SCBA).
StuporA state of diminished responsiveness and impaired consciousness.
SubacuteLess marked than acute in character; falling between acute and chronic in nature.
SubcutaneousLocated or placed just beneath the skin.
SublethalSlightly less than lethal; e.g., less than the amount of an agent required to cause death
SublimeTo pass directly from the solid to the vapor state and condense back to solid form.
SuffocationSensation of inability to get enough air.
SyncopeA brief loss of consciousness caused by a temporary deficiency of oxygen in the brain; a black out; fainting.
SynesthesiasMixed sensory perceptions (e.g., seeing sounds or feeling colours).
SyntheticProduced artificially; not of natural origin.
SystemicAffecting the body generally; not localized.
Systemic agentA substance with whole-body (systemic) or multi-organ-system effects. This category includes so-called “Blood Agents,” as well as other agents with systemic effects.
Systemic toxicityWhole-body toxicity.

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T waveThe third and last common wave in an electrocardiogram. It reflects the electrical activity produced when the ventricles are recharging for the next contraction (repolarizing)./td>
TachycardiaA rapid heart rate, especially one above 100 beats per minute in an adult.
TachypneaRapid breathing.
TEELDepartment of Energey Temporary Emergency Exposure Limit
TEEL-0The threshold concentration below which most people will experience no appreciable risk of health effects.
TEEL-1The maximum concentration in air below which it is believed nearly all individuals could be exposed without experiencing other than mild transient adverse health effects or perceiving a clearly defined objectionable odor.
TEEL-2The maximum concentration in air below which it is believed nearly all individuals could be exposed without experiencing or developing irreversible or other serious health effects or symptoms that could impair their abilities to take protective action.
TEEL-3The maximum concentration in air below which it is believed nearly all individuals could be exposed without experiencing or developing life-threatening health effects.
TepidLukewarm (referring to liquids)
TetanyAn abnormal phase of prolonged muscular contractions.
ThrombocyteA type of blood cell, also called platelet.
ThrombocytopeniaAn abnormal decrease in the number of platelets in circulating blood.
ThrombosisThe formation or presence of blood clots.
Time-weighted average (TWA)An average value of exposure over the course of an 8-hour (typically) work shift
TinnitusA sound in one ear or both ears, such as buzzing, ringing, or whistling.
Totally-Encapsulating Chemical Protective (TECP) SuitA full body garment which is constructed of protective clothing materials; covers the wearer's torso, head, arms, legs and respirator; may cover the wearer's hands and feet with tightly attached gloves and boots; completely encloses the wearer and respirator by itself or in combination with the wearer's gloves and boots.
ToxicPoisonous, injurious to health or dangerous to life.
Toxic Inhalation Hazard (TIH)Term used in the U.S. Department of Transportation ERG 2000 guidebook to describe gases and volatile liquids that are toxic when inhaled.
ToxicityThe quality, state, or relative degree of being toxic or poisonous.
ToxinA poisonous substance formed during the metabolism and growth of certain living microorganisms and some plants and animals. It is usually very unstable, notably toxic when introduced into the tissues, and typically capable of inducing antibody formation.
TransdermalThrough or by way of the skin, such as a skin patch.
TransfusionThe transfer of whole blood or blood products from one individual to another.
TransientExisting temporarily; passing away in time.
TriageA process for sorting injured people into groups based on their need for or likely benefit from immediate medical treatment. Triage is used in hospital emergency rooms, on battlefields, and at disaster sites when limited medical resources must be allocated.
TrismusMuscle spasm which causes the jaw to be rigidly clamped, such as during convulsions or seizures.
TWASee: Time-weighted average.


UlcerA break in skin or mucous membrane with loss of surface tissue, disintegration and death of tissue, and often pus.
UlcerationTissue damage (e.g., of the cornea, airway lining, stomach or intestine lining).
UnknownThis term is used when information for a section has not been identified for the agent.
UrticantAn agent that causes severe irritation to the skin and mucous membranes, as well as pain; also called nettle agent.


VaporThe state of a substance that exists below its critical temperature and that may be liquefied by application of sufficient pressure.
Vapor densityWeight of a volume of pure vapor or gas (with no air present) compared to the weight of an equal volume of dry air at the same temperature and pressure. A vapor density less than 1 (one) indicates that the vapor is lighter than air and will tend to rise. A vapor density greater than 1 (one) indicates that the vapor is heavier than air and may travel along the ground.
Vapor pressurePressure at which a liquid and its vapor are in equilibrium at a given temperature. Liquids with high vapor pressures evaporate rapidly.
VaporizeTo convert into vapor, as by the application of heat, whether naturally or artificially.
Vascular collapseCollapse of the blood vessels.
VasoconstrictionNarrowing of the interior diameter of blood vessels.
VasodilationWidening of the interior diameter of blood vessels.
VasopressorOf, relating to, or causing constriction of blood vessels, and thereby an increase in blood pressure.
VentilationThe circulation and exchange of gases in the lungs that is basic to respiration.
VermiculiteA lightweight, highly absorbent material made from mica.
VertigoA sensation that one’s self or one’s surroundings are whirling dizzily.
VesicantAn agent that produces blisters on exposed tissue.
VesicationFormation of blisters; blistering.
VolatileEvaporating readily at normal temperatures and pressures.
Vomiting agentAn agent that causes exposed persons to vomit.
VomitusVomited matter.


Water spray (fog)Method or way to apply or distribute water. The water is finely divided to provide for high heat absorption. Water spray patterns can range from about 10 to 90 degrees. Water spray streams can be used to extinguish or control the burning of a fire or to provide exposure protection for personnel, equipment, buildings, etc. (From U.S. DOT ERG 2000)
WhealA small elevation or swelling on the skin that usually itches or burns.
Worker population limit (WPL)An airborne exposure limit designed to protect workers. It is expressed as a time-weighted average (TWA) for exposure over an 8-hour work shift.
WPLSee: Worker population limit.


XerostomiaAbnormal dryness of the mouth.


Yellow ZoneAreas where contamination with chemical, biological, radiological, or nuclear (CBRN) agents is possible but active release has ended and initial monitoring exists.


µgMicrogram; one-millionth of a gram.
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