ABSTRACT
Early experiments in asbestosis were limited to chrysotile and produced conflicting evidence on the toxicity of this dust. The initial experiments were inhalation studies using the Venturi method of exposure based on the investigations on silicosis undertaken previously in Johannesburg. Inhalation experiments required exposure chambers large enough to accommodate an adequate number of animals to provide statistically viable results. In the inoculation experiments, fiber bypassed the lung defenses and was delivered to the test site. The pulmonary histological findings in these studies were first interpreted on an arbitrary basis, usually a consensus of opinion in a single research establishment. The methods of diagnosing pulmonary thoracic tumors and the severity of pulmonary fibrosis have been defined and standardized by a working party of expert pathologists. The initial intrapleural inoculation established that it was possible to produce mesotheliomas. The methods and techniques developed for the study of asbestos have been adapted for the investigation of the biological effects of other mineral fibers.
