TOXIC COMPOUNDSDOE-HDBK-1015/2-93Hazards of Chemicals and GasesCH-05Rev. 0Page 10Absorption through the skin can occur upon exposure to some toxic agents.Some liquids and vapors are known to pass through the skin in concentrationshigh enough such that respiratory protection is not adequate. For example,hydrogen cyanide (HCN) is known to pass through the unbroken skin.Consideration should be given to the type of work clothes being worn; if theybecome saturated with solvents, they will act as a reservoir to bathe the bodycontinually with the harmful material.Most volatile (easily vaporized) organic compounds are eliminated from the body in a matterof hours or, at most, days. Many of the poisonous elements, however, can be stored for longperiods of time in various parts of the body. Chronic (long term) toxicity damage is unlikelyto have an even distribution throughout the body. In toxicity studies with radioactive isotopes,the organ which suffers the most severe damage and appears to contribute most to the toxiceffect on the body as a whole, is called the critical organ. The particular organ that shows thelargest amount of damage is the one that is chosen for estimating the effect.Industrial poisoning may be classified as either acute or chronic. The classification is based onthe rate of intake of harmful materials, rate of onset of symptoms, and the duration ofsymptoms.Acute poisoning is characterized by rapid absorption of the material and sudden, severeexposure. For example, inhaling high levels of carbon monoxide or swallowing a large quantityof cyanide compound will produce acute poisoning. Generally, acute poisoning results froma single dose which is rapidly absorbed and damages one or more of the vital physiologicalprocesses. The development of cancer long after recovery from acute radiation damage iscalled a delayed acute effect.Chronic poisoning is characterized by absorption of a harmful material in small doses over along period of time; each dose, if taken alone, would barely be effective. In chronic poisoning,the harmful materials remain in the tissues, continually injuring a body process. The symptomsin chronic poisoning are usually different from the symptoms seen in acute poisoning by thesame toxic agent.The Occupational Safety and Health Act of 1970 requires that the Health and Human Servicespublish at least annually, a list of all known toxic substances by generic family, or other usefulgrouping, and the concentrations at which such toxicity is known to occur. Under the OSHAAct, the Secretary of Labor must issue regulations requiring employers to monitor employeeexposure to toxic materials and to keep records of any such exposure.The purpose of The Toxic Substances List is to identify "all known toxic substances" inaccordance with definitions that may be used by all sections of our society to describe toxicity.An excerpt of this list is illustrated in Figure 1. It must be emphatically stated that the presenceof a substance on the list does not automatically mean that it is to be avoided. A listing doesmean, however, that the substance has the documented potential of being hazardous if misused,and, therefore, care must be exercised to prevent tragic consequences.
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