Persistent asthma after repeated exposure to high concentrations of gases in pulpmills.

This is a clinicopathologic study of three subjects with irritant-induced asthma. They were pulpmill workers who had a history of multiple "gassing" episodes that occurred over a period of years. Persistent symptoms of asthma and nonspecific bronchial hyperresponsiveness and/or variable airflow obstruction occurred after at least one episode of "gassing," resulting in symptoms severe enough to require emergency room treatment. One of the three subjects had normal spirometry values before he entered the pulpmill. Bronchial biopsy done on these subjects showed changes compatible with asthma, including thickened basement membrane in two and cellular infiltration with activated eosinophils and mononuclear cells in all three. The results of immunohistology of bronchial mucosal biopsy of these subjects were compared with those of patients with allergic asthma and patients with Western red cedar-induced asthma. Subjects with irritant-induced asthma had a greater density of activated eosinophils and fewer T-lymphocytes, suggesting that cell-mediated immune mechanisms are not involved in the pathogenesis of this condition.