Doctors in Iowa City, Iowa have concluded that patients with pleural scarring only that is caused by asbestos suffer from decreased gas exchange in the lungs during maximum exercise. Asbestos companies will argue at trial that plaintiffs with pleural disease only, as opposed to internal scarring of the lung, do not have any impairment or compensable Injury.  The study also concluded that the pulmonary function abnormalities may indicate that patients with pleural asbestos disease probably also have internal scarring (asbestosis), but the fine scarring simply was not detected on routine chest films. Shih, Schwartz, et al., Chest (May 1994).

In Los Angeles, doctors at the U.S.C. Medical School studied over 8,720 asbestos-exposed construction and shipyard workers to determine whether asbestos fibers injure the large airways in the lungs, as opposed to the small airways only. Asbestos companies argue at trial that asbestos affects only the small airways. Obstruction of the large airways, typically referred to as COPD, is conventionally attributed to smoking, not asbestos.

The U.S.C. Medical School found, however, that asbestos exposure caused obstruction in the large airways of asbestos-exposed workers who never even smoked. They also determined that smoking tended to increase these abnormalities. Kilburn, et al., Chest (Oct. 1994). Asbestosis is generally diagnosed based upon the full clinical picture (symptoms, latency period, exposure history, pulmonary function tests, chest films, etc.). Because of the risks, pain and expense involved, doctors are not advised to biopsy the lungs simply to diagnose asbestos scarring.

A recent study at the University of California, San Francisco ranked the following diagnostic methods in terms of their accuracy: biopsy, high resolution CT scan, and regular chest films. They determined that the CT scan detected asbestos scarring that was not present on regular chest films. They also concluded that asbestosis can be present (as diagnosed by biopsy) even with a normal high resolution CT scan. Gamsu, et al., Am. J. Roentgenol (Jan. 1995). Even with a CT scan, the borderline between normal and abnormal is ill defined. The diagnosis must be based on the full clinical picture.