Flock worker's lung
Synonyms and keywords:

# Overview
Flock Worker's Lung(FWL) is an unusual disease interstitial disease characterized by lymphocytic bronchiolitis and peribronchiolitis in workers exposed to flock fibers. Flock is made for the application to adhesive-coated substrates by cutting short synthetic fibers from bundles of parallel nylon monofilaments or other polymers. They are usually prepared from synthetic materials.
The disease was identified initially in 1998 when a group of workers at a flocking plant developed unknown cause interstitial lung disease. The first cases to be identified were initially described as desquamative pneumonia and were attributed not with flock fibers, but to unspecified toxin exposure. As subsequent cases appeared, the clinical results with exposure to the flock seemed to be best characterized as lymphocytic bronchiolitis. Typically it presents with progressive dyspnea, dry cough, and constitutional symptoms. Some patients also show work-related symptoms, especially early in the process.

# Historical Perspective
- Since 1975, distributed case reports have raised doubt of a respiratory danger related with different manufactured strands, including polyester, nylon, and acrylic dust.
- Early reports in 1974 and 1981 of working environment assessments by National Institute of Occupational Safety and Health (NIOSH) agents ascribed respiratory manifestations among laborers to  irritant properties of nonrespirable flock fibers on the upper airways but did not pursue the possibility of lung disease associated with flock work 
- During 1990 and 1991, five workers from a nylon flock handling plant in Ontario presented with cough and dyspnea.
- In 1995 and 1996, two workers from a similar nylon flock handling plant in Rhode Island presented independently to the same doctor with cough and dyspnea.
- The underlying diagnosis for the lung ailment in these two employees was initially thought to be work-related Hypersensitivity pneumonitis. With additional case finding investigation at the Rhode Island location, a total of eight cases among the approximately 150 workers at the plant were identified by January 1998 based upon a screening questionnaire (symptoms of cough and dyspnea), pulmonary function abnormalities (restrictive pattern with reduced diffusion capacity), radiographic findings and/or histological findings on tissue obtained by open lung or transbronchial lung biopsy. Based upon the aggregate histopathological results from biopsied cases, the disease process was not thought to be hypersensitivity pneumonitis.
- "Flock Workers's lung" officially came to known in 1998, when scientists from NIOSH distributed the aftereffects of an epidemiological examination of episodes in Ontario and Rhode Island..
- Previously, interstitial lung disease in flock workers was mistakenly ascribed to mycotoxins present in polluted adhesive.

# Classification
The disease currently still has not been stratified.

# Pathophysiology
- Flock consists of short fibers that are cut from long filaments and glued to a backing material such as cloth to provide a fuzzy, carpet-like surface texture. They are usually made from synthetic materials such as nylon, rayon, or polypropylene. The cutting process results in the formation of airborne particles or fibers in the respirable range. Inhalation of flock dust causes interstitial lung disease.
- Preliminary toxicological findings indicate that ultrafine respirable nylon fragments after a single intratracheal instillation trigger an acute inflammatory lung injury in rats. Yet flock finishing agents or other particulate matter components found in the soil of flock processing plants can not yet be removed.
- We have studied interstitial pneumonitis among nylon flock processors with a histopathological pattern  bronchiolar and peribronchiolar lymphocytic inflammation and lymphoid hyperplasia  that indicates an inflammatory and possibly immunological response to a respiratory toxicant. 
- In one study microscopic examination of polypropylene fiber-exposed lungs revealed a dose-dependent increase in cellularity (especially macrophage infiltration), but no fibrosis. In another study, the researchers found high serum IL-8 and TNF- levels in the polypropylene flocking workers. Furthermore, these levels showed a negative correlation with DL, CO levels. These results suggest that IL-8 and TNF- may act as key mediators for inflammatory lung injury in the pathogenesis of  flock worker's lung.

# Causes
- FWL  results from the inhalation of airborne nylon fibers at work. Nylon fibers are used in making products for upholstery, automobiles, carpet, and apparel.

# Differentiating Flock Worker's Lung from other Diseases
FWL presents like most Interstitial Lung Disease.
Differentiating FWL from other similar interstitial lung diseases can be done based on a history of exposure and work environment.

# Epidemiology and Demographics
- Cases have been reported in the United States, Canada, Turkey, and Spain.
- In a study flocking workers when compared to controls, whereas age, sex, tobacco use and working years were not found to be significantly associated with respiratory symptoms. 

# Risk Factors
- In textile workers, the lung of the flock worker is seen chronically exposed to short nylon fibers usually flocked onto textile products. Flock is created by cutting guillotine or rotary cutting. It has been believed that rotary cutting is more dangerous than guillotine cutting..
- Working in manufacturing and maintenance, on a flocking scale, and more days and hours a week, cleaning with compressed air, and increased current and accumulated exposure to respiratory dust were found to be strongly correlated with disease symptoms.
- Multivariate research found that becoming a worker flocking with polypropylene was a predictive factor for pulmonary function disability.
- An analysis showed that the risk of respiratory symptoms increased by almost 4 times in polypropylene flocking workers when compared to controls.

# Natural History, Complications and Prognosis
FWL's natural history reflects the following trends
- Total Symptom Resolution;
- Abnormalities to both the radiographic and pulmonary functions;
- Permanent yet manageable signs and restrictive pulmonary function deficits;
- And progressive pulmonary deterioration, causing death from respiratory failure and secondary hypertension. The presence and development of FWL is correlated with low baseline diffusing potential of the lung for carbon monoxide. 
- In general, after steroid therapy and leaving the place of operation, improvement occurred over a period of months or years, with some experiencing recurrent dyspnea, activity restriction or chronic supplemental oxygen needs.
- There was also 3 times increase in lung cancer incidence. 

# Diagnosis

## Diagnostic Criteria
A case of flock worker's lung  is  defined as:
- A histological diagnosis of non-specific interstitial pneumonia, with or without interstitial fibrosis, characterized by bronchiolocentric nodular and diffuse interstitial lymphoid infiltration and non-uniform alveolar filling by macrophages;
- Other histologic manifestations of Interstitial Lung Disease (ILD)  not attributable to another disease; or
- A grossly abnormal distribution of cell types on bronchoalveolar lavage (BAL) with restrictive lung function and HRCT findings of either diffuse ground-glass opacity or micronodularity, in the absence of a tissue specimen.

## History and Symptoms
- The nylon flock exposed workers most commonly presented with chronic respiratory symptoms over several years, but subacute presentations also occurred. For example, in a Canadian outbreak, 5 of 88 exposed workers developed the disease after exposure occurring over several days
- Restrictive ventilatory defects are most common, but obstructive defects have been reported. 
A study showed 20 individual from different geographic locations  having FWL shared symptoms of
- dyspnea and cough, with and without sputum production.
- These symptoms were present for months to years before clinical presentation, which, for some cases, seemed precipitated by an acute exacerbation in the preceding few days. Symptom onsets for the patients occurred over a 15-yr period, with no apparent concentration of onsets for any plant location.
- Few nonrespiratory symptoms were noted. Weight loss was noted in two patients and two workers had arthralgia or myalgias. Eight of the 20 patients were noted to have asthma, increased bronchial responsiveness to methacholine, or increased bronchodilator responsiveness.

## Physical Examination
- Physical examination in one study showed that both patients with FWL and control groups were evaluated as normal.
- Others have reported
- inspiratory crackles on auscultation 
- Pulmonary function test results revealing a restrictive pattern 

## Laboratory Findings
- There are no specific laboratory findings associated with FWL.

## Imaging Findings
- High-resolution CT scan remained a highly sensitive diagnostic test. Pulmonary function tests and plain chest X-ray were less sensitive.
- The most common findings in FWL on CT scan  were ground-glass opacities and micronodules, with a peripheral predominance in some.

## Other Diagnostic Studies
- Transbronchial biopsy may prove helpful in the consideration of alternate diagnoses, but wedge biopsy by thoracotomy or thoracoscopy is necessary to adequately examine the characteristic lesion of this interstitial lung disease in relation to the pulmonary lobular architecture. 

# Treatment

## Medical Therapy
- Cessation of nylon exposure and corticosteroid therapy, for exacerbation of respiratory problems, has been observed to lead symptomatic improvement but overall lung functions are still seen to decline in certain cases.

## Prevention
- Several observations affirmed that the exposure preceded the disease and that the disease improved with exposure cessation  to the implicated work environments.
- NIOSH has made recommendations to companies that manufacture flock and make flock containing products that aim to reduce workers exposure to flock dust. These include: engineering controls and alternative methods to cleaning the workplace with compressed air, which re-aerosolizes settled dust, improved cutter maintenance, and implementation of medical surveillance programs have reduced the number of reported cases.