In 1994, the patient noted an increase of exertional dyspnea during his half-mile walks. In 1995, he experienced some difficulty while mowing his lawn. By 1996, his exercise tolerance changed from being able to actively walk and climb stairs to experiencing shortness of breath after walking a few blocks or climbing less than one flight of stairs. Mowing his lawn became extremely difficult. His chest x-rays showed mild progression of interstitial fibrosis from 1988 to 1992 and more rapid progression from 1992 to 1996.
Asbestos is a mineral made of hydrated fibrous silicates.
Its physical properties, including high tensile strength and acid heat resistance, make it an important manufacturing material. From 1940 to 1979, over 27 million workers were exposed to asbestos in the United States. As a result of the increased recognition of the hazardous nature of asbestos, there is at present less exposure to asbestos in the workplace and in the environment. Although the annual production of asbestos in the United States has decreased since the 1970s as a result of stricter regulatory standards and product liability litigation related to its health effects, the use of asbestos is on the rise in developing countries. On the other hand, asbestosis is less common and results in greater decline in pulmonary function.