David G. Kern

Flock Worker's Lung: Chronic Interstitial Lung Disease in the Nylon Flocking Industry

Chronic interstitial lung disease is diagnosed infrequently in the general population at an incidence of 29 cases per 100 000 person-years [1]. Sarcoidosis, connective tissue disease, pulmonary hemorrhage syndromes, and environmental agents account for 40% of cases; most other cases are categorized as cases of idiopathic pulmonary fibrosis [1]. Biopsy shows that most patients with idiopathic pulmonary fibrosis have usual interstitial pneumonia, heralding a grim prognosis, and that the remainder have desquamative interstitial pneumonia [2] or nonspecific interstitial pneumonia [3]. Only 10% of cases of idiopathic pulmonary fibrosis are biopsy-confirmed [1, 4]. Consequently, clinicians must consider alternative diagnoses, including the three well-established occupational interstitial lung diseases: mineral pneumoconioses, hypersensitivity pneumonitis, and bronchiolitis obliterans organizing pneumonia after acute inhalation injury. Additional environmental causes of interstitial lung disease may be recognized if temporal-spatial clusters of respiratory disease are evaluated. In November 1994 and February 1996, two young male textile workers from a plant in Rhode Island were referred by their pulmonologists to our academic occupational medicine clinic for evaluation of interstitial lung disease. Because the two cases constituted a sentinel occupational health event [5, 6], we alerted the National Institute for Occupational Safety and Health (NIOSH), the union representing the plants workers, and the companys management. On learning of an earlier outbreak of five cases of nongranulomatous interstitial lung disease at the companys plant in Canada [7] and two additional biopsy-confirmed cases there in 1995, we began an investigation at the Rhode Island facility. This report details the results of that investigation, including the clinicopathologic and epidemiologic features of a previously unrecognized occupational lung disease in the nylon flocking industry [8, 9]. Background In the flocking industry, short fibers (flock) are cut from cables of parallel synthetic monofilaments (tow) and applied (flocked) to an adhesive-coated substrate. At the index company, nylon tow, previously impregnated with a titanium dioxide delusterant, is usually dyed before it is bath-finished, cut, dried, screened, and bagged as flock. On the flock coating line, a water-based acrylic adhesive is applied to a moving bolt of cotton-polyester fabric before the bolt passes into the flocking room. There, on the basis of its electrostatic charge and vibration by beater bars, flock is embedded into the adhesive. After heat curing, the flocked fabric may be subjected to finishing, embossing, and printing. In the United States, an estimated 2500 workers employed at 12 flock manufacturing companies and 100 flocking companies make products for the upholstery, automobile, carpet, apparel, and novelty industries. Substances to which workers were exposed at both the Rhode Island and the Canadian plants included bioaerosols; nylon fiber; a flock finish of tannic acid, ammonium ether of potato starch, and an alcohol-ammonium sulfate mixture; an acrylic adhesive containing carbon black; nonfibrous zeolite; heat transfer oil; and thermal degradation products. In 1989, the companys Canadian plant reportedly began processing the thinnest (9 microns) nylon fiber in use; in 1991, this operation was relocated to Rhode Island. Use of the thinner fiber reportedly caused the plant to be blanketed in fine white powder. Except for a few case reports [10, 11], neither the literature nor industrial experience suggests that exposures in the flocking industry cause interstitial lung disease. The nylon manufacturers Material Safety Data Sheet notes that: As shipped, Nylon Polyamide Fiber products do not pose a hazard. Under normal conditions of use, Nylon Polyamide Fiber does not generate respirable fibers or dust. Nylon manufacturers have never conducted inhalation toxicity studies because of the assumption that nylon fiber is too thick to generate respirable fibers (diameter 3 microns) capable of alveolar deposition [12]. During the current investigation, however, NIOSH personnel identified airborne, respirable-size nylon fragments at the Rhode Island plant [8, 9]. Methods Case Finding and Case Definition To identify all outbreak-associated cases of interstitial lung disease at the Rhode Island plant, all currently employed production workers with persistent respiratory symptoms and former employees identified by word of mouth were invited for evaluation. Employees reporting symptoms were evaluated by pulmonary function testing and chest radiography. Spirometry was conducted as recommended by the American Thoracic Society [13], lung volumes were measured by using plethysmography, and diffusing capacity was measured by the single breath method; reference values were those of Crapo and colleagues [14-16], and the severity scale was that of the American Medical Association [17]. All employees with symptoms suggesting pulmonary dysfunction were studied by high-resolution computed tomography (CT) (HiSpeed Advantage Helical Scanner, GE Medical Systems, Milwaukee, Wisconsin). Those with unexplained restrictive lung function, impairment of diffusing capacity, or high-resolution CT findings consistent with interstitial lung disease were referred for bronchoalveolar lavage, biopsy (transbronchial or wedge), or both. Using a four-point ordinal scale, a pulmonary pathologist scored all specimens, including those of the five Canadian patients, with respect to 18 histopathologic features. Flock workers lung was defined by persistent respiratory symptoms, previous work in the flocking industry, and histologic evidence of interstitial lung disease that had no better explanation. In the absence of a tissue specimen, the triad of an abnormal distribution of cell types on bronchoalveolar lavage, restrictive lung function, and high-resolution CT findings of diffuse ground-glass opacity or micronodularity served as a surrogate for the histologic criterion. Blood samples for measurement of complete blood count, leukocyte differential, rheumatoid factor, and antinuclear antibody were obtained from employees who had bronchoalveolar lavage or biopsy. The Johns Hopkins University Dermatology, Allergy, and Clinical Immunology Reference Laboratory (Baltimore, Maryland) analyzed serum specimens for precipitating antibody to pigeon serum, Aspergillus fumigatus (antigens 1, 2, and 6), Aspergillus flavus, Aspergillus niger, Aureobasidium pullulans, and thermophilic actinomycetes; for specific IgE antibodies to a mixture of 8 to 10 common aeroallergens (Phadiatop, Pharmacia & Upjohn, Inc., Kalamazoo, Michigan); and for potato-specific IgE. Cohort Investigation The study cohort comprised all current and former production workers, employed at the Rhode Island facility on or after 15 June 1990, who worked for at least 18 months before 15 September 1996 (n = 165). The cohort was based on the companys annual vacation lists from 15 June 1990 through 15 June 1996, which tabulate all hourly workers employed continuously during the previous 6 months. Cohort membership was restricted to those who had worked for at least 18 months because employees working for shorter periods might not appear on vacation list. The company provided employment histories for salaried production workers who satisfied the criteria for cohort membership. Job histories were recorded for cohort members with accessible personnel files. The files of former employees were scrutinized for evidence of lung disease. After they had worked for 18 months, cohort members contributed person-years at risk for time worked subsequently from 15 June 1990 to 15 September 1996. Crude incidence rates of flock workers lung and all interstitial lung disease were calculated. General population estimates for age- and sex-specific incidence rates of pulmonary fibrosis-idiopathic pulmonary fibrosis and for sex-specific incidence rates of all interstitial lung disease were obtained from an interstitial lung disease registry maintained for Bernalillo County, New Mexico [1]. This registry provides the only such published incidence data for a general population in the United States. The racial and ethnic distributions of Bernalillo County and the study cohort were similar [1, 9]. By using the registrys estimates [1] and weights based on the age and sex distribution of the study cohort, standardized incidence ratios for pulmonary fibrosis-idiopathic pulmonary fibrosis and for all interstitial lung disease were calculated. To calculate the former, we counted cases of flock workers lung as cases of pulmonary fibrosis-idiopathic pulmonary fibrosis because they probably would have been assigned to this broader diagnostic category if the occupational association had been overlooked. We used exact Poisson calculations to derive 95% CIs for the estimated standardized incidence ratios [18, 19]. Computations were done by using SAS software (SAS Institute, Inc., Cary, North Carolina). Results Case Finding We clinically evaluated 39 of the 148 current production workers and 3 former employees. We also reviewed questionnaire responses, spirometry results, and chest radiographs of an additional 78 production workers who authorized us to review their NIOSH-generated screening records [9] (Figure 1). We found 7 men and 1 woman (mean age SD, 43 12 years) with flock workers lung; their demographic and clinical features are shown in Table 1 and Table 4, Table 2 and Table 5 and Table 3 and Table 6. Two reported stable dry cough and dyspnea; 6 reported gradually worsening dry cough and dyspnea; and 3 reported intermittent atypical chest pain. Median latency was 6 years from date of hire to symptom onset and 15 months from symptom onset to diagnosis. Only 2 persons reported work-related symptoms. No specific job category was associated with illness. Crackles were auscultate

Primary Care Internal Medicine: A Challenging Career Choice for the 1990s

A career in primary care internal medicine can be challenging and rewarding, yet during the last decade fewer medical students have selected training in internal medicine. We wish to inform medical students, their advisors, and other physicians about the field of primary care internal medicine. We define the discipline, compare it with traditional internal medicine and with family practice, and describe features of strong primary care internal medicine training programs. We discuss common misconceptions and concerns about training programs and the career and give examples of career paths chosen by graduates of primary care programs. We encourage students to consider the option of primary care internal medicine when making career decisions and provide faculty advisors unfamiliar with primary care internal medicine training programs with a reference resource.

Exposure Assessment and Respirator Selection in the Cleaning of Crude Oil Process Vessels

Abstract The processes in the oil production industry are generally closed systems. The workers who clean and maintain process vessels, however, are exposed to the hazards of crude oil and confined spaces. Although respiratory protection is often used by these workers, exposures have not been documented and respirator selection procedures using detector tubes to measure benzene concentrations have not been validated. This study evaluates the effectiveness of this approach to respirator selection by examining actual exposures of a group of vessel workers and assessing the adequacy of protection that was provided. Personal breathing zone samples and area samples were collected by active adsorptive sampling during the cleaning of oil separators. Area air samples were also collected prior to entry into the vessels in conjunction with detector tube sampling conducted by safety personnel. Adsorptive air sampling indicated that exposure concentrations ranged from nondetectable to 5.8 ppm, averaged over the durat...

A retrospective cohort study of lung cancer incidence in nylon flock workers, 1998-2008.

Abstract During an investigation of a novel interstitial lung disease in a cohort of nylon flock workers, a former worker was found to have developed bilateral synchronous pulmonary adenocarcinomas three decades after he quit smoking, suggesting that exposures in this industry might pose excessive risk of lung cancer. We conducted a retrospective cohort study of lung cancer incidence in the original study cohort (n = 162) from August 15, 1998, to August 14, 2008. The Rhode Island Cancer Registry identified cohort members with lung cancer and provided age-gender-era-specific rates of lung cancer in Rhode Island. Five cases of lung cancer occurred among cohort members versus 1.61 cases expected for a standardized incidence ratio of 3.1 (95%CI, 1.01–7.23). The observed threefold increase in lung cancer incidence could not be readily ascribed to chance, study bias, or uncontrolled confounding. Workers in this industry should be notified of their potentially increased risk of lung cancer.

The Natural History of Flock Worker’s Lung

journal.publications.chestnet.org companies/organizations whose products or services may be discussed in this article . Correspondence to: Enrique Diaz-Guzman, MD, University of Alabama at Birmingham, 619 19th St S, Jefferson Tower 1102, Birmingham, AL 35294-7410; e-mail: diaze@uab.edu