US EPA

3101623 

Technical Report 

Asbestos And Related Fibers 

Rom, WN 

1983 

NIOSH/00150643 

pages 157 

157-182 

The characteristics of diseases associated with exposure to asbestos (1332214) and related fibers are reviewed. Pulmonary asbestosis is a parenchymal fibrosis with or without pleural fibrosis. The initial lesion is a peribronchiolar fibrosis caused by asbestos fibers that become lodged in the alveoli and terminal respiratory bronchioles. The pathological classification of asbestosis is based on extent and severity of parenchymal lung involvement. The predominant symptom of asbestosis is dyspnea, which may have a variable but progressive course. Asbestos bodies may be observed in lung tissue and sputum in large quantities in persons with asbestosis. Pulmonary function is characterized by a restrictive impairment with reductions in forced vital capacity, total lung capacity, and diffusing capacity. Thickening and calcifications of the pleura are characteristic of asbestosis and may occur in the absence of parenchymal abnormalities. The prevalence of asbestosis increases as the length of employment increases among cohorts of asbestos workers. Immunological and cellular abnormalities are present in 25 to 30 percent of asbestosis patients. Asbestos is associated with lung cancer and cancers of other organs, including buccal cavity, larynx, gastrointestinal tract, and kidney. The risk for lung cancer increases if exposed workers also smoke. Asbestos causes diffuse malignant mesothelioma which most commonly involves the pleura or peritoneum, and is characterized by pain and effusion. Animal studies show that fine, long, durable fibers correlate most positively with carcinogenicity. The standard time weighted average for asbestos is a maximum of 2 fibers per cubic centimeter. Other fibers with pleural effects include man made vitreous fibers and fibrous zeolites.