Changing Patterns in Asbestos-Induced Lung Disease

Study objectives: To determine patterns in asbestos-induced lung diseases found in older, less exposed workers. Design: Review of a database evaluating lung function, smoking status, form of asbestos-induced lung disease, and radiograph abnormalities. Setting: Outpatient clinic. Participants: A total of 3383 asbestos-exposed workers referred for independent medical evaluation, including control subjects who lacked asbestos-specific radiograph abnormalities (n = 243), subjects with low International Labor Organization (ILO) scores (n = 2,685), high ILO scores (n = 312), bronchogenic cancer (n = 63), and mesothelioma (n = 80). Of these, 3,327 workers have specific smoking status information and 3,312 workers have lung volume measures. Interventions: Chest radiographs were interpreted by a certified B-reader, and abnormalities were quantified according to the ILO scoring system. Spirometry and lung volume measurement were performed. Subjects completed a self-administered questionnaire that was reviewed at the time of examination. Control subjects were screened on two separate occasions at least 10 years apart to exclude subclinical or slowly progressive asbestos-induced lung disease. Measurements and results: The mean age of the population was 65.1 ± 9.9 years, and the latency was 41.4 ± 10.1 years (± SD). Most subjects (41.8%) had normal pulmonary function. Obstruction was the most common pulmonary function abnormality (25.4%), followed by restriction (19.3%) and a mixed pattern (6.0%). Most subjects (79.4%) had low ILO scores. Benign pleural abnormalities were the only findings in 54% of subjects with low ILO score. Subjects with high ILO scores were older, smoked more, and had a longer latency than subjects with low ILO scores and control subjects. Smokers were younger, had a shorter latency, and had paradoxically greater ILO scores than nonsmokers. Subjects with bronchogenic cancer and mesothelioma had longer latencies than control subjects and subjects with benign asbestos-induced lung disease. Conclusions: Asbestos-induced lung disease today is characterized by low ILO scores, long latencies, greater disease magnitude in smokers, and a normal or obstructive pattern of pulmonary function abnormality. Spirometric evaluation in the absence of lung volume measurements caused misclassification that resulted in overestimation of the presence of a restrictive pattern of pulmonary function.