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All ascertainable cases of malignant mesothelioma in Australia were notified to a national surveillance program in the period January 1, 1980 to December 31, 1985. There were 854 cases obtained and 823 confirmed on clinical (77) or histologic (746) ground. Tumor site was known in 759 cases (685 pleural and 74 peritoneal). Lung fiber content analyses by light microscopy and analytic transmission electron microscopy with energy-dispersive x-ray analysis were done on 226 cases in which postmortem material was available, using the method of Rogers. Cell type was determined by a five-member expert panel of pathologists appointed by the Royal College of Pathologists of Australasia. There was a statistically significant trend between lung fiber content (fibers/g dry lung) and cell type from epithelial (low fiber content) through mixed to sarcomatous (high fiber content). This trend was most apparent for total uncoated fibers (chi-square = 6.8, df = 1, P less than 0.01) and crocidolite (chi-square = 6.7, df = 1, P less than 0.01). Lung fiber content also was associated with tumor site; higher lung fiber content being associated with peritoneal tumors. This relationship was significant for all fiber content measures except chrysotile and was independent of the fiber content-cell type relationship (log-linear analysis). Survival from time of provisional diagnosis was significantly longer for epithelial (mean, 13 months; standard deviation [SD], 12.8) and mixed (mean, 10.2 months; SD, 8.7) types than sarcomatous cell types (mean, 5.8 months; SD, 6.5; P less than 0.0001, by analysis of variance on log10 survival time). Survival time was significantly greater for pleural tumors (mean, 11.4 months; SD, 13.4) than peritoneal tumors (mean, 8.6 months; SD, 12.5) (P less than 0.005, by Student's t test on log10 survival time).

Lung tissue from 221 definite and probable cases of malignant mesothelioma reported to the Australian Mesothelioma Surveillance Program from January 1980 through December 1985 and from an age-sex frequency matched control series of 359 postmortem cases were examined by light microscopic (LM) and analytical transmission electron microscopic (TEM) analysis and energy dispersive x-ray analysis (EDAX). Concentrations of total fibers (coated and uncoated) (LM), crocidolite, amosite, chrysotile, and unidentified amphibole (TEM) (fibers/g dry lung tissue) were measured. Fiber concentrations less than 10 microns in length and greater than or equal to 10 microns in length were separately quantified. By comparing cases (221) and controls (359 LM, 103 TEM), odds ratios for increasing fiber concentrations compared with less than 15,000 fibers/g (LM) and less than 200,000 fibers/g (TEM) (the respective detection limits) were calculated. Univariate analyses showed statistically significant dose-response relationships between odds ratio and fiber concentration for all fiber concentration measures. The relationship between log(odds ratio) and log(fiber concentration) was linear. Multiple logistic regression analysis showed that a model containing crocidolite greater than or equal to 10 microns, amosite less than 10 microns, and chrysotile less than 10 microns as explanatory variables best described the data. The odds ratios for a X10 increase in fiber concentration (fibers/micrograms) were as follows: crocidolite greater than or equal to 10 microns, 29.4 (95% confidence interval [CI], 3.6 to 241); chrysotile less than 10 microns, 15.7 (95% CI, 6.1 to 40); amosite less than 10 microns, 2.3 (95% CI, 1.0 to 5.3). An additive risk model gave similar results. In a subgroup of cases and controls with only chrysotile in the lungs, a significant trend in odds ratio with increasing fiber content was found.