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Routes of entry and modes of action.

Stokinger HE
Occupational diseases: a guide to their recognition, revised edition. Key MM, Henschel AF, Butler J, Ligs RN, Tabershaw IR, eds. Cincinnati, OH: National Institute for Occupational Safety and Health, 1977 Jun; :11-42
Substances found in the workplace can enter the human body through inhalation, skin contact and ingestion; each of these routes is described. Through inhalation gases, fumes, vapors and particulates enter the body. The toxic action of some gases and vapors arises due to their adsorption onto solid particles, allowing the gases to penetrate further into the body than they would be able to on their own. In the case of particulates there are four major factors influencing the site of the ultimate toxicologic response: the anatomy and dimensions of the respiratory system, the breathing rate and depth, the physical properties of the particles, and the biochemical reactivity of the particulates. Once a substance contacts the skin of a worker, four actions are possible: an effective barrier can be maintained against penetration, primary irritation can arise due to reaction of the substance and the skin surface, penetration of the skin and conjugation of the substance with tissue protein, and penetration of the skin resulting in the substance entering the blood stream and acting as a potential systemic poison. The ingestion of industrial substances is usually of lesser significance in that the number of substances that can be ingested are fewer, the frequency and degree of contact are very limited, and toxicity by mouth is generally of a lower order than by inhalation. The modes of action by which toxic substances exert their effects are reviewed. The following topics (and subtopics) are presented: physical actions (irritants, inert gases, adsorption, radioactivity); chemical processes (direct combination, indirect combination, chelation); toxic mechanisms (metabolic, detoxication); enzymes (classes of enzymes, secondary enzymatic mechanisms); and enzymology and its uses.
NIOSH-Author; Inhalants; Gas-adsorption; Toxic-vapors; Physical-reactions; Chemical-properties; Enzymatic-effects; Skin-exposure; Skin-absorption; Airborne-particles; Occupational-exposure
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Key MM; Henschel AF; Butler J; Ligo RN; Tabershaw IR
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Occupational diseases: a guide to their recognition, revised edition
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division