Flock worker's lung disease presents a useful paradigm for identifying new occupational causes of lung disease. It is an unusual interstitial lung disease characterized by lymphocytic bronchiolitis and peribronchiolitis in workers exposed to flock fibers in manufacturing velvet-like fabrics, fuzzy greeting cards and wall papers, and automotive gaskets and glove box surfaces. Flock is made by cutting short synthetic fibers from bundles of parallel monofilaments of nylon or other polymers for application to adhesive-coated substrates. Unlike respirable mineral fibers such as asbestos, synthetic flock is visible, as illustrated in its typical applications. Since 1975, published case reports have raised suspicion of a respiratory hazard associated with various synthetic fi bers, including polyester, nylon, and acrylic dust. With regard to synthetic flock, early reports in 1974 and 1981 of workplace evaluations by National Institute of Occupational Safety and Health (NIOSH) investigators attributed respiratory symptoms among workers to irritant properties of nonrespirable flock fibers on the upper airways but did not pursue the possibility of lung disease associated with flock work. Systematic workplace investigation of lung disease in workers that flock with synthetic fibers awaited the recognition of case clusters of interstitial disease in small workforces, first in Kingston, Ontario, Canada, and then in Rhode Island, as detailed in the background of the follow-up study by Turcotte
et al published in this issue of CHEST. Subsequently, additional cases or subclinical morbidity have been found in relation to nylon flock in two Massachusetts plants, to polyethylene flock in Spain, to polypropylene flock in Turkey, and to rayon flock in Kansas.