Flock worker's lung: Chronic interstitial lung disease in the nylon flocking industry

Background: Two young men working at a nylon flocking plant in Rhode Island developed interstitial lung disease of unknown cause. Similar clusters at the same company's Canadian plant were reported previously. Objective: To define the extent, clinicopathologic features, and potential causes of the apparent disease outbreak. Design: Case-finding survey and retrospective cohort study. Setting: Academic occupational medicine program. Patients: All workers employed at the Rhode Island plant on or after 15 June 1990. Measurements: Symptomatic employees had chest radiography, pulmonary function tests, high-resolution computed tomography, and serologic testing. Those with unexplained radiographic or pulmonary function abnormalities underwent bronchoalveolar lavage, lung biopsy, or both. The case definition of "flock worker's lung" required histologic evidence of interstitial lung disease (or lavage evidence of lung inflammation) not explained by another condition. Results: Eight cases of flock worker's lung were identified at the Rhode Isla nd plant. Th ree cases were characterized by a high proportion of eosinophils (25% to 40%) in ravage fluid. Six of the seven patients who had biopsy had histologic findings of nonspecific interstitial pneumonia, and the seventh had bronchiolitis obliterans organizing pneumonia. All seven of these patients had peribronchovascular interstitial lymphoid nodules, usually with germinal centers, and most had lymphocytic bronchiolitis and interstitial fibrosis. All improved after leaving work. Review of the Canadian tissue specimens showed many similar histologic findings. Among the 165-member study cohort, a 48-fold or greater increase was seen in the sex-adjusted incidence rate of all interstitial lung disease. Conclusions: Work in the nylon flocking industry poses substantial risk for a previously unrecognized occupational interstitial lung disease. Nylon fiber is the suspected cause of this condition.