Tobbacco Worker’s Lung

Definition

Tobacco worker’s lung is a condition marked by lung inflammation and subsequent scarring in the air sacs due to inhaling molds present in tobacco. It is not a lung infection but rather an immune reaction within the lungs to these molds. It is a type of hypersensitivity pneumonitis or extrinsic allergic alveolitis. The condition is also known as tobacco farmer’s lung but also occurs among tobaccos factory worker. Even though tobacco is commonly encountered in daily life, especially among tobacco users, this lung condition is almost entirely seen only in tobacco factory and farm workers. It is a result of a prolonged exposure to large amounts of tobacco dust with the airborne mold that the condition arises. Such large amounts is not encountered in daily life. Cigarette smoking may exacerbate tobacco worker’s lung but is not the cause of the condition.

Incidence

The prevalence of tobacco worker’s lung is difficult to estimate as there is no reputable data. Often tobacco worker’s remain undiagnosed until the late stages. Furthermore the major tobacco producers are within developing nations in Asia and South America where reliable data may be difficult to acquire. Despite this lack of documented evidence, there have been findings to suggest that the condition is more frequently seen among males. However, this is more likely due to the fact that tobacco worker’s have traditionally been men. There is no evidence to indicate a high risk group as the condition is not seen among children or the elderly. It is important to note that child labor is used in certain countries for the harvesting and processing of tobacco. Therefore children may be also at risk.

Pathophysiology

Tobacco worker’s lung is a type of lung disease known as hypersensitivity pneumonitis. It simply means that there is inflammation of the lung due to an immune-mediated reaction. It is not an infection, commonly referred to as pneumonia, or a lung disease caused by certain types of dusts such as coal, which is known as pneumonoconiosis. Tobacco worker’s lung is very similar to another hypersensitivity pneumonitis known as farmer’s lung. In both these conditions, farmer’s lung and tobacco worker’s lung, there is an immune reaction to certain fungi but not an infection. The names of these condition illustrates the people who are at the higher risk of being exposed to these fungi.

Once the fungi enter the lungs, the antigens (protein substances) of the fungi is identified as being foreign. The body’s immune system is then triggered to take action. Although the body produces antibodies against the antigens, it is not clear if the antibodies direct the immune response. Certain types of immune cells known as macrophages and polymorphonuclear leukocytes are stimulated into action by the antigens. These cells release chemical substances that cause injury to the lung tissue. The injury further stimulates the immune response leading to the release of chemicals that causes inflammation.

Symptoms

Tobacco worker’s lung, as with any type of hypersensitivity pneumonitis, can be acute, subacute or chronic. The presentation may differ to some extent in each form.

Acute

Acute tobacco worker’s lung symptoms arise suddenly and are intense. It closely resembles the flu (seasonal influenza) and often it is never diagnosed as hypersensitivity pneumonitis. The symptoms in the acute form starts about 4 to 6 hours after a person is exposed to the tobacco molds and eases within 12 hours after discontinuing exposure to the tobacco dust and mold.

  • Coughing
  • Fever
  • Headache
  • Muscle pains
  • Malaise

Chronic

The chronic form of tobacco worker’s lung develops gradually. A person may have repeated acute attacks or chronic tobacco worker’s lung can develop over time without any acute attacks. In due course, chronic inflammation of the lung eventually leads to scarring of the lung tissue (pulmonary fibrosis). This is irreversible and affects lung function permanently. Therefore the symptoms persist and gradually worsens if a person does not discontinue exposure to the tobacco dust and molds. Even if exposure is discontinued, the symptoms may improve to some degree but not resolve completely.

  • Chronic cough
  • Shortness of breath with physical activity (exertional dyspnea)
  • Fatigue
  • Weight loss

Causes

Tobacco is produced from drying the leaves of the tobacco plant, Nicotiana tabacum. Various different species of molds may form on tobacco especially in humid climates. It can affect both the fresh leaves on the plant or the dried leaves that are to be processed into tobacco products. Therefore tobacco worker’s lung affect both farm workers handling tobacco in the fields and factory workers handling the dried product. The main fungi that causes tobacco worker’s lung includes :

  • Aspergillus species
  • Scopulariopsis brevicaulis
  • Rhizopus nigricans

Tobacco worker’s lung affects both adult males and females. Females tend to be at a greater risk although most patients are male, possibly due to the fact that more tobacco workers are male. It is important to note that unlike some other occupational diseases, there is no notable risk to the family members of these workers. Using mask may help to significantly reduce the risk of develop tobacco worker’s lung.

Diagnosis

The condition should be suspected by the signs and symptoms coupled with a history of working in the tobacco industry. Various tests can be used to confirm lung inflammation, pulmonary function and changes to lung structure but this is not specific for tobacco worker’s lung. These investigations include :

  • Blood tests
  • Chest x-ray
  • Computed tomography (CT) scan
  • Spirometry, lung volume and diffusion capacity testing
  • Lung biopsy

Treatment

There is no specific treatment for tobacco worker’s lung. Ideally the condition should be prevented and masks may be helpful in this regard. Once chronic tobacco worker’s lung develops, patient’s should avoid further tobacco exposure. While this does not cure the condition, it can help improve the symptoms to some degree. As with most types of hypersensitivity pneumonitis, systemic corticosteroids like prednisone may be used. While this may offer some relief, more so in acute cases, corticosteroids are not very effective chronic tobacco worker’s lung. The scarring of the lung tissue (pulmonary fibrosis) seen in chronic cases is irreversible and corticosteroids therefore offer little relief.

References :

www.merckmanuals.com/professional/pulmonary_disorders/interstitial_lung_diseases/hypersensitivity_pneumonitis.html

emedicine.medscape.com/article/302379-overview