Hazards of Chemicals and GasesDOE-HDBK-1015/2-93TOXIC COMPOUNDSRev. 0CH-05Page 9Hazardis the possibility that a material will cause injury when a specific quantity is used underspecific conditions. Several key elements are considered when evaluating a health hazard.Toxicity of the materials usedPhysical properties of these materialsAbsorption probabilities of these materials by individualsExtent and intensity of exposure to these materialsControl measures usedToxicity is relative. It refers to a harmful effect on some biologic mechanism. The term toxicityis commonly used in comparing one chemical agent with another, but such comparison ismeaningless if the biologic mechanism, and the conditions under which the harmful effectsoccur, are not specified.Although the toxic effects of many chemical agents used in industry are well known, the toxiceffects of many other commonly used chemical agents are not as well defined. The toxicity ofa material is not a physical constant (such as boiling point, melting point, or temperature);therefore, only a general statement can be made concerning the harmful nature of a givenchemical agent.Many chemical agents are nonselective in their action on tissue or cells; they may exert aharmful effect on all living matter. Other chemical agents may act only on specific cells.Another agent may be harmful only to certain species; other species may have built-in protectivedevices.The degree to which a substance will affect living cells can be measured only after recognizablechanges have occurred following absorption. Some changes (impaired judgment, delayedreaction time) may be produced at levels too low to cause actual cell damage. Toxicity isdependent upon the dose, rate, method, and site of absorption, and many other factors includinggeneral state of health, individual differences, tolerance, diet, and temperature.In general, industrial poisonings usually result from inhalation, ingestion, and absorption.The inhalation and absorption of toxic agents by the lungs is dependent upon thesolubility in body fluids, the diffusion through the lungs, the volume ofinhalation, the volume of blood in the lungs, and the concentration gradient ofvapors between the inhaled air and the blood.Ingestion of the toxic agent can occur to some extent; however, there wouldgenerally be considerable inhalation of the material where such conditions exist.
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