Nonspecific airway hyperreactivity in nonsmoking bituminous coal miners demonstrated by quantitative methacholine inhalation challenge.

Because nonsmoking underground bituminous coal miners often have symptoms of chronic bronchitis and because a high proportion of patients with chronic bronchitis have nonspecific airway hyperreactivity, we hypothesized that coal miners would have a higher prevalence of nonspecific airway hyperreactivity than nonminer nonsmoking control subjects. By use of a quantitative methacholine provocative inhalation challenge test, we evaluated 22 underground bituminous coal miners and 41 nonminer age- and sex-matched control subjects from the same community. We found that a significantly higher proportion of miners had reactivity to inhalation of 100 mg/ml or less of methacholine, X2 = 6.19, p less than 0.02. The slope of phase III of the single-breath nitrogen washout test was higher in the reactive miners than in the nonreactive miners and reactive control subjects, even though the reactive miners had only been working underground 8 +/- 3 (SEM) years. Within the reactive miner subgroup, the higher the reactivity to methacholine, the more abnormal the slope of phase III of the single-breath nitrogen test, r = 0.79. Miners had more symptoms than controls; the presence of methacholine reactivity was not associated with increased symptoms. We conclude that the bituminous coal miners in our study had an increased prevalence of nonspecific airway hyperreactivity and that within the reactive miner subgroup there was evidence of early airways disease. We speculate that the nonspecific airway hyperreactivity may be related to, and also be an indicator of, lung injury in coal miners.