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[[File:Open_pit_mine.jpg|thumbnail|300px|left|The Big Hole next to Kimberely, South Africa]]

A pathologist who worked with Wagner in Kimberly, informed Wagner and Kleggs that he had seen similar mesothelioma tumors in Johannesburg, South Africa. Kleggs and Wagner contacted Dr. Paul Marchand, the physician who had treated many of the Johannesburg patients. The three physicians immediately suspected that blue asbestos might of the tumors. After taking another look at the samples of lung from deceased patients, they found fragments of asbestos mineral. Initially, the physicians struggled to link asbestos and mesothelioma for two reasons: First, many of the patients (both black and white) denied working in asbestos mines. Second, mesothelioma tumors were typically fatal within a year or two within diagnosis, but these patients were developing tumors 10-20 years after their first exposure to asbestos. The physicians needed to establish that the tumors were not a result of some other source. Eventually, the doctors realized that their patients had lied to them because their was social stigma attached to working with asbestos. The patients had worked in and around asbestos, but were loath to admit. Eventually, patients began to reveal that they had worked in asbestos mines or mills. In some cases, these patients described living in "a blue haze" in their communities that were located next to mines and mills. The mills and mines west of Kimberly worked with blue asbestos.<ref>Wagner, J.C., "The discovery of the association between blue asbestos and mesotheliomas and the aftermath," <i>British Journal of Industrial Medicine</i>, 1991; 48:399-403 and Tannapefel, <i>Malignant Mesothelioma</i>, p. 15.</ref>

In order to determine if asbestos was the cause, the physicians had an unlikely resource. The South African Pneumoconiosis Bureau had keep records and samples of the thoracic organs of most of the miners who had died. The South African government had already determined that working with asbestos was dangerous, but they did not know exactly why. On the other hand, mining companies were not interested in delving too deeply into why their miners died. The physicians were allowed to review these samples and learned that miners exposed to amosite (blue) and occasionally chrysolite asbestos developed fatal pleura tumors. After further study, it became clear that all types of asbestos could cause cancer, but some types of asbestos were much more dangerous. It was also confirmed that cigarette smokers who were exposed to asbestos faced even higher risks of developing mesothelioma.<ref>Wagner, J.C.,"The discovery of the association between blue asbestos and mesotheliomas and the aftermath," <i>British Journal of Industrial Medicine</i>, 1991; 48:399-403: 433.</ref>