Respiratory System and Toxic Substances

Option C

The respiratory system carries the greatest risk of exposure by industrial hazardous substances. Absorption is very high once inhalation has occurred. Gases, fumes, vapors, aerosolized liquids and dust particles are rapidly absorbed and/or deposited on lung tissue.


The absorption and resultant action of toxic substances depends on the level of penetration reached by these agents within the pulmonary tree and the defensive mechanisms found at that level. The upper portion of the respiratory system, including the nose and upper pharynx, is susceptible to absorption, while filtering many coarse particles from the air. This is the case with the snorting of cocaine.

Irritants in this area produce sneezing, which clears many of the larger particles (>5 microns). The mid portion of the respiratory tree, including the trachea and bronchial tubes, are lined with cilia. These hair-like structures along with mucous membrane secretions trap smaller irritant particles (2-5 microns) and induce a cough that moves them upward to where they are swallowed or expectorated. The lower portion of the respiratory tree, the alveoli, is exposed to some of the smallest irritants (>2 microns). Particles deposited in this region are phagosotized in an attempt at removal. Occasionally the end result is the development of scar tissue and fibrosis leading to progressive loss of pulmonary function. This is typical of the reaction to by-products of the burning of coal. Chemical agents that irritate the respiratory system may induce a significant inflammatory response leading to constriction of the airways and decreased respiratory volume, commonly manifested as reactive airway disease (asthma). If the reaction is severe pulmonary edema can ensue. Among many well-known agents, chlorine, phosgene, bromine, ammonia gases and hydrogen chloride can induce these types of reaction.

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