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GLOSSARY 77 Glossary A acetylcholinesterase True cholinesterase (ChE). Acetylcholinesterase hydrolyzes acetylcholine within the central nervous system and peripheral neuroeffector functions. acute effect An effect that results from a brief exposure or shortly after an acute exposure (see below). acute exposure A short-term exposure that lasts from minutes to hours (usually 1â24 hr). aerosol Liquid or solid particles suspended in air. C ChE50 The vapor exposure producing significant cholinesterase (ChE) inhibition in 50% of the given population. cholinesterase An enzyme capable of catalyzing the hydrolysis of acetylcholine. chronic effect An effect of gradual onset and duration of months and years. chronic exposure An exposure (usually at low concentrations) of long duration, such as months or years. Ct Concentration Ã time. Note that Ct is not necessarily a constant. For example, a 2-min exposure to a concentration of 100 mg/m3 (Ct = 200 mg-min/m3) does not necessarily produce the same toxicological effects as a 50-min
GLOSSARY 78 exposure to a concentration of 4 mg/m3 (Ct = 200 mg-min/m3). D depiliation Removal of hair. dose The amount of a substance that enters or interacts with organisms. An administered dose is the amount of substance administered to an animal or human, usually measured in milligrams per kilogram of body weight; milligrams per square meter of body-surface area; or parts per million of the diet, drinking water, or ambient air. An effective dose is the amount of the substance reaching the target organ. E ECt50 The vapor exposure causing a specifically defined effect in 50% of the given population. Within the context of this report, the route of exposure can be either inhalation or percutaneous. ED50 The dose of liquid agent causing a specifically defined effect in 50% of the given population. In this report, ED50 refers to a percutaneous liquid exposure. exposure duration The length of time that a receptor population is exposed to a contaminant. exposure route The route by which a contaminant enters the body (dermal, inhalation, or oral). I ICt50 The vapor exposure causing incapacitation (see below) in 50% of the given population. Within the context of this report, the route of exposure can be either inhalation or percutaneous. ID50 The dose of liquid agent causing a defined degree of incapacitation in 50% of the given population. Within this context, ID50 refers to a percutaneous liquid exposure. Unless otherwise specified, all ID50s are for bare skin. incapacitation An effect considered moderate to severe, unless otherwise specified. It might include prostration and convulsions. L LCt50 The vapor exposure causing lethality in 50% of the given population. Within the context of this report, the route of exposure can be either inhalation or percutaneous. LD50 The dosage of liquid agent causing lethality in 50% of the given population. Within this context, LD50 refers to a percutaneous liquid exposure. Unless otherwise specified, all LD50s are for percutaneous liquid contamination of bare skin. M microgram (Âµg) One millionth of a gram.
GLOSSARY 79 mild effects For the organophosphate nerve agents, mild effects are miosis and rhinorrhea. For HD, mild effects are slight ocular irritation. milligram (mg) One thousandth of a gram. minute volume The volume of air expelled from the lungs in a minute, which is assumed to be 15 liters unless otherwise stated. miosis A decrease in pupil size. N no-observed- The highest dose of a substance that can be administered adverse-effect level without observation of adverse effects in laboratory animals. (NOAEL) P percutaneous vapor Percutaneous vapor exposures are defined as vapor exposures exposure to intact bare skin. Vapor inhalation is prevented by use of an appropriate protective mask and does not contribute to overall toxicity. Percutaneous vapor exposures can result from vapor dissemination of chemical agents or from liquid contamination of clothing with subsequent vapor penetration. potency The degree to which an agent can cause strong or toxic effects. R rhinorrhea Running nose. S severe effects For the organophosphate nerve agents, severe effects are systemic, such as vomiting, involuntary urination, or defecation, prostration, incapacitation, tremors, collapse, and convulsions. Exposures that produce these effects might not be substantially different from exposures that produce lethality. For HD, severe nonlethal effects consist of skin burns, such as severe redness (erythema) and blistering (vesication). T threshold The lowest dose of a substance at which a specified measurable effect is observed and below which it is not observed. In this report, threshold effects refer to minimal or negligible effects. toxic Harmful to living organisms. toxicity The adverse effects of chemicals on living organisms. toxicology The study of adverse effects of chemicals on living organisms. toxic substance A substance that destroys life or injures health when introduced into or absorbed by a living organism. U uncertainty factors Factors used to divide a no-observed-adverse-effect level (NOAEL) or lowest-observed-adverse-effect level (LOAEL) to obtain a safe exposure level.