Byssinosis, commonly known as brown lung disease, is an occupational disease that afflicts textile mill workers. It is a chronic, asthma-like narrowing of the airways that results from breathing in dust or particles of cotton or other vegetable fibers such as flax, hemp, jute, or sisal.
Referred to as an occupational or industrial disease, byssinosis is a type of reactive airway disease characterized by bronchoconstriction or narrowing of the bronchial tubes. Although it has long been known as brown lung disease, this is a misnomer, since the lungs of afflicted workers do not turn brown. However, the small air passages in the lungs do become blocked, seriously impeding lung function. Long term exposure to dust from fibers can result in chronic lung disease, characterized by shortness of breath and/or wheezing.
Inhaling cotton dust was first identified as a source of respiratory disease more than 300 years ago. During the industrial revolution, byssinosis was a common affliction of young girls toiling in textile mills and factories. Nevertheless, byssinosis has been recognized as an occupational disease of textile workers for less than 50 years.
In the United States, byssinosis is almost completely limited to workers who handle raw, unprocessed cotton, especially workers who are exposed to open bales of cotton or who work in the card room or in cotton spinning. Only workers in mills that manufacture yarn, thread, or fabric are at significant risk of dying of byssinosis. Between 1990 and 1999, 48% of the 81 byssinosis-related fatalities reported in the United States had occupations in the yarn, thread, or fabric industries listed on the deceased's death certificate. Although byssinosis can develop after acute exposure to fiber dust, it most often occurs in workers with a history of chronic exposure. Adequate ventilation in affected workplaces greatly reduces the risk of byssinosis. Smoking increases the risk of byssinosis in textile workers, as does any other impairment of lung function or a history of respiratory allergies.
Over the years, more than 800,000 American workers in the cotton, flax, and rope-making industries have been exposed to airborne particles that can cause byssinosis. Nevertheless, byssinosis is classified as a rare disease. Illnesses and fatalities from byssinosis have decreased significantly in the United States in recent decades, in part because of improved workplace conditions and safety measures and in part due to the significant shift in textile manufacturing from the United States to developing countries. Between 1979 and 1992, more than 35,000 textile workers were disabled by byssinosis and 183 died of the disease. In contrast, between 1990 and 1999, only 81 American workers died of byssinosis-related causes. By 2004, byssinosis was the underlying cause of only about two deaths and a contributing cause to only a few additional deaths. Most byssinosis-related deaths have occurred among workers living in the textile producing regions of North Carolina and South Carolina.
As textile industries have moved from the United States to developing countries, byssinosis has become increasingly common in those regions. Cotton and synthetic textile manufacturing is the largest industry in India, employing about 35 million workers and accounting for 14% of the country's industrial output. The Indian Council of Medical Research has reported that 8.4% of textile workers have byssinosis. A study published in 2010 found that more than 25% of Indian textile workers had chronic respiratory problems, almost 12% of which were diagnosed as byssinosis.
It is known that breathing in the dust produced by raw cotton can cause byssinosis in sensitive individuals. Evidence suggests that some agent within the cotton bract causes the bronchoconstriction of byssinosis. However, the nature of the agent directly responsible for byssinosis remains unclear—specifically, whether the cause is the cotton dust itself or endotoxins produced by bacteria that live on the cotton dust. Cotton dust may contain a variety of substances that can affect the lungs, including fibers, other particles of plant matter, soil, bacteria, fungi, pesticides, and other contaminants. These substances can accumulate during the growing, harvesting, processing, or storage of the material.
Endotoxins from gram-negative bacteria have been indicated as the cause of byssinosis in some studies. However, symptoms similar to byssinosis do not occur in other settings in which workers are exposed to endotoxins. A Harvard University study published in 2010, followed 447 Chinese cotton textile workers from 1981 to 2006, estimating lung function and respiratory symptoms as a function of past exposure to cotton dust and also as a function of cumulative exposure to endotoxin. Past exposure to endotoxin was associated with reduced lung function among retired cotton workers, but past endotoxin exposure was not associated with byssinosis. In contrast, exposure to endotoxin within the previous five years was significantly associated with byssinosis, as well as with chronic bronchitis and chronic cough.
The symptoms of byssinosis are similar to asthma, including tightness in the chest, coughing, wheezing, and breathing difficulties (dyspnea). Byssinosis symptoms from acute exposure include rapid breathing (tachypnea) and wheezing. The chest tightness and dyspnea tend to lessen with repeated exposure to the dust. In general, symptoms appear on the first day of work following a weekend or vacation and diminish or disappear completely after work or by the end of the workweek. This temporal pattern of symptoms distinguishes byssinosis from asthma. However, in as many as 25% of workers with byssinosis, especially those experiencing repeated or severe exposure over a period of years, chest tightness and other symptoms tend to recur or persist, with no lessening during the course of the week. Sometimes the symptoms persist until the end of the workweek or for as long as the worker stays on the job. In the most severe cases, symptoms become permanent. Both high levels of dust and longer exposure appear to contribute to the severity of symptoms. Workers who also smoke cigarettes have the most severe impairment. In most cases, symptoms of byssinosis improve once a worker is no longer exposed to the dust.
Diagnosis of byssinosis requires a detailed medical and occupational history to determine whether symptoms are related to workplace exposure and the timing of exposures. The physical exam focuses on the lungs, and a chest x ray and lung function tests are performed. A computed tomography (CT) scan of the chest may also be performed. Hypersensitivity of the bronchial air passages to the drug methacholine, typically used to diagnose asthma, is often observed with byssinosis as well.
The most important aspect of byssinosis treatment is removing patients from the source of the dust, such as transferring them to less-contaminated work areas or changing jobs. Affected workers should quit smoking immediately. Early-stage treatment involves attempting to reverse the narrowing of the airways. Antihistamines may reduce chest tightness. Asthma medications, such as bronchodilators (either tablets or an inhaler), can relax breathing passages and improve the flow of air. A nebulizer that releases a very fine spray of medication deep into the lungs may be used to treat chronic byssinosis. Corticosteroids may be used to treat severe cases. Patients with low blood oxygen levels may require home oxygen therapy. Physical exercise programs, breathing exercises, education programs and support groups can also be helpful.
In the United States, the Occupational Health & Safety Administration (OSHA), within the U.S. Department of Labor, sets cotton dust standards for the textile industry. Twenty-five states, as well as Puerto Rico and the Virgin Islands, have OSHA-approved plans and their own standards and enforcement protocols. Federal standards permit a maximum of 1 mg of cotton dust per cubic meter of air. The allowable concentrations are lower for specific types of cotton mill occupations. Between 1978, when the OSHA cotton dust rule was implemented, and 2000, the incidence of byssinosis among textile workers fell from 12% to less than 1%.
The cotton processing industry is required to maintain ongoing surveillance measures for byssinosis.
These include reporting symptoms and regular spirometry—using an instrument called a spirometer to measure the amount of air entering and exiting textile workers' lungs. In developing countries, where most textile processing and manufacturing occurs, regulations and surveillance may be far more relaxed. Byssinosis remains an important occupational health problem in these areas.
Byssinosis does not usually lead to permanently disabling lung disease and is rarely fatal. Prolonged exposure was once believed to cause byssinosis, but this has been disproven. Continued exposure to cotton or other fiber dust in patients with byssinosis can worsen symptoms, causing more frequent wheezing and possibly leading to chronic bronchitis and further lung damage. In the United States, people with byssinosis may be eligible for worker's compensation.
Eliminating exposure to textile dust is the surest way to prevent byssinosis. Improved ventilation and machinery, the use of exhaust hoods, and wetting procedures have all proven to be effective measures for reducing workplace dust levels and preventing byssinosis. Protective equipment required for certain procedures also prevents exposure to excessive levels of other contaminants. The use of face masks by textile workers, and refraining from smoking, further reduce the risk of byssinosis. Surveillance measures in the textile industry, including reporting of symptoms and spirometry, aid in the early detection of byssinosis.
See also Asthma ; Bronchitis ; Smoking .
“Byssinosis.” American Lung Association. http://www.lung.org/lung-disease/byssinosis (accessed October 13, 2012).
“Cotton Dust.” Occupational Health & Safety Administration. July 11, 2007. http://www.osha.gov/SLTC/cottondust/index.html (accessed October 13, 2012).
Dugdale III, David C. “Byssinosis.” MedlinePlus. June 10, 2011. http://www.nlm.nih.gov/medlineplus/ency/article/001089.htm (accessed October 13, 2012).
American Lung Association, 1301 Pennsylvania Ave. NW, Ste. 800, Washington, DC, 20004, (202) 785-3355, Fax: (202) 452-1805, (800) LUNGUSA (586-4872), email@example.com, http://www.lung.org .
The American Lung Association is the leading organization working to improve lung health and prevent lung disease through education, advocacy, and research.
Occupational Safety & Health Administration, 200 Constitution Ave., Washington, DC, 20210, (800) 321-OSHA (6742), http://www.osha.gov .
OSHA is the organization within the U.S. Department of Labor that is responsible for workplace safety and health, including cotton dust exposure.
U.S. Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, 30333, (800) CDC-INFO (232-4636), firstname.lastname@example.org, http://www.cdc.gov .
The CDC monitors health in the United States and worldwide and maintains a comprehensive informational website.
Margaret Alic, PhD