New statement published on nonmalignant diseases related to asbestos exposure

Oct 4 2004

In its first official statement since 1986 on the topic, the American Thoracic Society (ATS) has published a document entitled “Diagnosis and Initial Management of Nonmalignant Diseases Related to Asbestos.” The revised statement, updated and reviewed by an 11-person committee of experts, appears in the second issue for September 2004 of the ATS peer-reviewed American Journal of Respiratory and Critical Care Medicine.

According to the authors, the new statement is designed to provide guidance to clinicians in their diagnosis of nonmalignant asbestos-related disease. The conditions covered, which are associated with breathing the mineral dust, include: asbestosis, a chronic, progressive lung disease often marked by scarring (fibrosis) of the lung tissue; pleural plaques and more diffuse forms of pleural thickening; benign or nonmalignant pleural effusions (the abnormal collection of fluid in the pleural space); and airway obstruction. (The pleura is the delicate membrane covering the lungs and the inner walls of the chest.)

The National Research Council defines the word asbestos as a “commercial-industrial term rather than a mineralogical term. It refers to well-developed and hair-like long-fibered varieties of certain minerals that satisfy particular industrial needs.”

In the late 19th century, industry recognized that commercial asbestos had high tensile strength, flexibility, resistance to chemical and thermal degradation, and high electrical resistance. Because of these qualities, asbestos was widely used in the past for insulation, brake linings, flooring, cement, paint, textiles, and various other products.

The statement points out: “World production and use of asbestos climbed steadily since its introduction in the late nineteenth century and fell rapidly after documentations of its hazards in the 1970s and 1980s. In Western industrialized countries, the widespread use of asbestos in industry and in the built environment in the first seven decades of the twentieth century has resulted in an epidemic of asbestos-related illness that now continues into the twenty-first century, despite decline in global production and use. Its use has now been banned in many Western countries.”

When asbestos-related disease is suspected, the document advises physicians to take a comprehensive occupational and environmental history. The history should emphasize occupational and environmental exposure 15 years or more prior the current office visit.

Representative occupations with potential for exposure include, but are not limited to, the following: workers involved in the manufacture of asbestos products; asbestos mining and milling; the construction trades (including insulators, sheet metal workers, electricians, plumbers, pipefitters, and carpenters); power plant workers; boilermakers; and shipyard workers.

The report estimates that asbestos is still a hazard for 1.3 million workers in the construction industry in the United States and for workers involved in the maintenance of buildings and equipment. Although the majority of products containing asbestos are older versions, new products that may contain the industrial mineral include brake pads, roofing materials, vinyl tile, and imported cement pipe and sheeting.

Asbestos fibers, when inhaled, settle deep in the lungs, causing scarring. Asbestosis, one of the primary diagnoses, is usually associated with exposure to the fibers over 10 to 20 years, although short intense exposure of several months to 1 year, can also cause the problem. The most common respiratory symptom associated with asbestosis is dyspnea (breathlessness) on exertion. A cough is also frequently present.

According to the experts, a chest radiograph (X-ray) is an extremely useful tool to aid in the diagnosis of asbestos-related pleural disease (fluid in the pleural space). The International Labor Organization (ILO) provides a classification score that correlates strongly with risk of death and diminished ventilatory capacity. When questions arise, high resolution computed tomography (HCRT) can offer a more sensitive analysis than that provided by a conventional chest X-ray.

In addition, the diagnosing physician should perform a lung function test and sometimes a broncho-alveolar lavage procedure (a test used to collect specimens from the smaller airways that cannot be seen though the bronchoscope.)

The report notes: “The specificity of the diagnosis of asbestosis increases with the number of consistent findings on chest film, the number of clinical features present (e.g. symptoms, signs and pulmonary function changes) and the significance and strength of the history of exposure.”

“The diagnosis of asbestos-related disease absolutely requires evidence of exposure and ruling out of other causes. If the diagnosis is suspected, the physician should always evaluate the patient for functional impairment,” said Dr. Tee L. Guidotti, Chair of the Review Committee, who is with George Washington University Medical Center, Washington, D.C.

After a patient has been identified as having asbestos-related disease or significant exposure, physicians are advised to inform the person of the risk of disease progression, the chance of possible malignancy, and the interaction between smoking and asbestos exposure in enhancing the possibility of lung cancer, as well as chronic airway obstruction. The physician should advise the patient to quit smoking, receive immunizations for pneumococcal pneumonia and flu, be screened for colon cancer, and receive a chest X-ray and a pulmonary function test every 3 to 5 years.

The statement adds: “The diagnosis of asbestosis, in particular, imposes a duty to inform the patient that he or she has a disease that is work-related, to report the disease, and to inform the patient that he or she may have legal or adjudication options for compensation. . .Impairment evaluation is largely unchanged from 1986 and remains an essential part of the clinical assessment.”

Although there is a strong statistical association between asbestos-related disease and malignancy, the report points out that the majority of patients do not develop cancer.

According to the document, once exposure to asbestos has occurred, no prophylactic medication or treatment is currently available to prevent the development or progression of asbestosis or other asbestos-related diseases. Treatment is often designed to ease symptoms.

The expert committee believes that the information presented in this new document should “provide a reliable basis for clinical diagnosis for some years to come.”

http://www.thoracic.org