Pneumoconiosis (Pulmonary Fibrosis)
The diagnosis of asbestosis depends on a history of exposure to asbestos dust, a latency of at least 10 years, and evidence of diffuse fibrosis and pleural plaques by chest x-ray or CT scan. The likelihood of the diagnosis is increased by the presence of a restrictive pattern on pulmonary function testing. The risk of developing asbestosis is directly related to the cumulative dose. Bibasilar rales is the typical physical finding in patients with asbestosis. Dyspnea on exertion is the primary symptom. Asbestos insulators, shipyard workers, and other workers heavily exposed to asbestos in the past have an increased risk for asbestosis, lung cancer, and malignant mesothelioma. High-resolution computerized tomography (HRCT) is more sensitive than conventional radiography in detecting asbestosis. Findings by HRCT include interstitial lines, subpleural curvilinear lines, parenchymal bands, and honeycombing. Normal and abnormal values exist for sputum and lung lavage samples (asbestos bodies) and lung tissue (asbestos bodies and fiber counts). [Harber, p. 93-96, 297-310] Medical surveillance is required if exposed above the PEL >30 days per year or if must wear negative pressure respirator when working with asbestos. [Rosenstock, p. 1266] Of 706 retired workers with an average age of 65 years and a history of occupational asbestos exposure, the mean duration of asbestos exposure was 25 years with a mean cumulative-exposure index (CEI) of 140 fibers/ml x years. The study found a fibrosis threshold of 25 fibers/ml x years in that only 2 cases of HRCT asbestosis were found in 112 workers under this threshold. No cases of HRCT asbestosis were found in the 52 workers below the threshold and with no signs or symptoms of asbestosis. [PMID 15250649] "It has been suggested that concentrations of more than 1 to 2 million fibers/gram of dry tissue indicate occupational exposure to asbestos." [PMID 22937893] "The correlation observed between deaths with asbestosis and asbestos consumption, coupled with the downward trend in consumption, suggests that the disease will eventually decline in importance and could even disappear. A preliminary tentative analysis undertaken by juxtaposition of the consumption and mortality curves suggests that this might occur around 2050 for the oldest age-at-death group, and before then for the younger age groups." [http://iopscience.iop.org/article/10.1088/1742-6596/151/1/012051/pdf] "Workers with heavy exposure to asbestos have a similar risk of lung cancer as persons with low or no exposure 20 years after the exposure has ended." [PMID 25479300] See "Asbestos." See "Asbestos-related pleural disease."
Usually at least 20 years; [LaDou, p. 380]
Chest x-ray; Pulmonary function test; HRCT
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Symptoms/Findings associated with this disease:
High risk job tasks associated with this disease:
Hazardous agents that cause the occupational disease: