In September 2010, Dr. J. Corbett McDonald published a Commentary on the epidemiology of malignant mesothelioma in the Annals of Occupational Hygiene, prepared on behalf of the British Occupational Hygiene Society. Dr. McDonald's work as an epidemiologist in the field of asbestos research is unparalleled. At 93 years of age he is still publishing and to our great honor, traveled from his home in Montreal to Las Vegas "in May 2010" to participate in the Mesothelioma Conference that Gordon & Rees chaired. Other notable speakers in attendance included Drs. Peto, Roggli, Churg, Berman, Pooley, Gibbs, Henderson, Bernstein, Hammar, Hillerdal and others Please click here to read Dr. McDonald's Commentary.
In this Commentary, Dr. McDonald takes the reader through a 50 year journey of asbestos research on mesothelioma fiber types, from Wagner's initial study in 1960 in South Africa involving crocidolite exposure, to the recent tragedy in Libby, Montana where the vermiculite that was mined was contaminated with tremolite asbestos.
In discussing what he terms "The Tremolite Factor" Dr. McDonald recounts how in the 1960s, when the first asbestos epidemiological studies were undertaken in Quebec, Canada, the scientists believed they were dealing with exposures to chrysotile asbestos only. Soon thereafter it was evident that pleural thickening and calcification were much more frequent in workers at the Thetford mines than at the mines in the city of Asbestos. In the 1970s, Drs. Pooley and others showed that tremolite fibers were present in similar concentrations to chrysotile in the lungs of the Thetford employees. It was in the early 1980s that McDonald demonstrated the carcinogenicity of tremolite in the miners in Libby, Montana where the vermiculite ore contained 4-6% tremolite. These findings were not heeded and a national tragedy in Libby, Montana occurred years later. Dr. McDonald concludes that amphibole asbestos fibers - crocidolite, amosite and tremolite - can explain almost all cases of mesothelioma in North America.