Comments on cases
Some published reports of mesothelioma cases have discussed potential exposures to chrysotile. In a multicentered casecontrol study of 123 mesothelioma patients in South Africa, no case with a history of chrysotile mining was identified, and there was no case involving exclusively environmental exposure to chrysotile (Rees et al., 1999). A case series from Zimbabwe describes 3 mesothelioma cases among 51 workers who worked for some time in an asbestos mining or manufacturing facility and certified subsequently for compensation for lung disorders. Twenty-seven claimants had suspected asbestos-related illnesses. Three cases were noted to have mesothelioma based on "best evidence." One died in 1987 having a pleural mass but no tissue to examine; for another, vital status was unknown but the person had a biopsy; and the third was a manager who had a postmortem examination in 1954 but worked in an asbestos plant from 1951 to 1952. Due to the extent of asbestosrelated disease, the authors expressed a concern of the hazard of locally mined chrysotile asbestos (Cullen and Baloyi, 1991). Excluded from consideration was that standard chrysotile from Zimbabwe contains 2% fibrous anthophyllite, a regulated amphibole, as an impurity (Kohyama et al., 1996). Six cases of asbestos-related disease, including two mesothelioma cases, were reported in railway men in Rhodesia (now Zimbabwe), a chrysotile mining region that coincidentally supplied the South Carolina textile plant. However, a careful review indicates that they were exposed also to nonlocally mined amphibole (Mostert and Meintjes, 1979). A case series report comes from the former East Germany in which the authors state that 67 cases of 812 mesothelioma patients (8.25%) were due to exposure only to Russian chrysotile (Sturm et al., 1994). Countering the notion that asbestos from Russia was only chrysotile as suggested by airborne dust analyses (Kashansky et al., 2001), a lung tissue study of workers in the Russian chrysotile industry located in the area of the world's largest asbestos mine, at Asbest in the Ural Mountains, was published 6 years later. This pathology study showed that about 5% of all mineral fibers were amphiboles, ranging from 2% in chrysotile millers and users, to 9% in miners. No mesothelioma cases had been observed in Russia (Dobrovolsky, 1998). The pattern of lung chrysotile fibers in workers of the mine in Asbest, Russia, was about the same as reported earlier from the Canadian mining and milling industry (Tossavainen et al., 2000). Their results are similar to those for Brazilian chrysotile workers (case et al., 2002b).