The inhalation of sensitizing agents or irritants results in the occurrence of occupational asthma, according to the authors. Various sensitizing agents discussed include grain, flour, coffee beans, castor beans, colophony, tea fluff, tobacco, woods, dusts from shellfish and laboratory animals and from mites, silkworms, and other insects, metal dusts, organic compounds, drugs, and enzymes. Specific irritants which cause chemical asthma include strong alkalis, acids, and oxidizing agents such as ammonia (7664417), chlorine (7782505), hydrogen-chloride (7647010), phosgene (75445), hydrogen-fluoride (7664393), oxides of nitrogen or sulfur, and zinc-chloride (7646857). Workers at risk include those involved in food processing, wood and furniture industry, animal breeding, engineering works, chemical industry, construction workers, fur processing industry, pharmaceuticals, health facilities, and the production of detergents. The greatest risk occurs among workers involved in handling grains and cereals, woodworkers, printers, manufacturers of polyurethane foams, insulation workers, and meat wrappers exposed to fumes of polyvinyl-chloride. Characteristic respiratory disorders caused by these agents include acute reversible obstruction of the airways due to bronchoconstriction, airway edema, or inflammation, and mucus excretion induced by exposure to agents inherent in the work process. Clinical effects include dyspnea, chest tightness, wheezing, and pulmonary function impairment of the obstructive type. Atopic subjects and those with chronic inflammatory diseases of the respiratory tract are particularly susceptible.