Iron, by catalyzing the generation of the hydroxyl radical via the Haber-Weiss reaction, may participate in oxidant tissue injury. To determine whether iron might contribute to cigarette smoke-induced lung injury, we estimated the iron content of the lower respiratory tract by measuring intracellular iron content of pulmonary macrophages and extracellular iron content of bronchoalveolar lavage fluid from cigarette smokers and nonsmokers. Bronchoalveolar lavage was performed by using methods that allow for recovery of samples enriched for bronchial and alveolar contents. The intracellular iron content of the alveolar macrophages was determined by staining cytocentrifuged, air-dried pulmonary macrophages with a modified Prussian blue stain and assigning a score of 0 to 3 (0 = no stain, 3 = dense staining throughout the cytoplasm) to 100 macrophages. The extracellular iron level of bronchoalveolar lavage fluid was determined by using modifications of the Ferrozine method of Carter. Macrophage intracellular iron content was measured in a group of cigarette smokers with chronic bronchitis (n = 17), in smokers without chronic bronchitis (n = 15), and in normal volunteers (n = 15). Extracellular iron concentration was determined in a subset of the subjects with chronic bronchitis (n = 12) and in a separate group of normal volunteers (n = 5). The intracellular iron score was elevated in the bronchial sample lavage fluid in both the smokers with chronic bronchitis (45.3 +/- 13.9) and the asymptomatic smokers (26.6 +/- 8.0) compared with the normal individuals (8.1 +/- 1.7, p less than 0.03, both comparisons), but did not differ between the two groups of cigarette-smoking subjects (p = 0.68).(ABSTRACT TRUNCATED AT 250 WORDS)