Incidence of malignant mesothelioma in Aboriginal people in Western Australia

Objectives : To describe the incidence of malignant mesothelioma (MM) in Aboriginal people in Western Australia (WA) and determine the main routes of exposure to asbestos in this population. Methods : All MM cases in Western Australia, as well as the primary source of asbestos exposure, are recorded in the WA Mesothelioma Register. Aboriginal cases up to the end of 2013 were extracted from the register and compared with non‐Aboriginal cases with respect to the primary means/source of exposure. Age‐standardised incidence rates for each decade from 1980 were calculated for both Aboriginals and non‐Aboriginals. Age‐standardised mortality rates were calculated for the period 1994–2008 and compared with international rates. Results : There were 39 cases (77% male) of MM among WA Aboriginal people. Twenty‐six (67%) were a direct result of the mining of crocidolite at Wittenoom and the subsequent contamination of the surrounding lands. Of the non‐Aboriginal MM cases (n = 2070, 86.3% male), fewer than 25% can be attributed to Wittenoom. Aboriginals had consistently higher 10‐year incidence rates than non‐Aboriginals and, when compared to world populations, the highest mortality rate internationally. Conclusion : When incidence rates in Aboriginal people are compared with non‐Aboriginal people, the Wittenoom mining operation has had a disproportionate effect on MM incidence in the local Aboriginal population.     

Asbestos burden predicts survival in pleural mesothelioma

BACKGROUND: Malignant pleural mesothelioma (MPM) is a rapidly fatal asbestos-associated malignancy with a median survival time of <1 year following diagnosis. Treatment strategy is determined in part using known prognostic factors. OBJECTIVE: The aim of this study was to examine the relationship between asbestos exposure and survival outcome in MPM in an effort to advance the understanding of the contribution of asbestos exposure to MPM prognosis. METHODS: We studied incident cases of MPM patients enrolled through the International Mesothelioma Program at Brigham and Women's Hospital in Boston, Massachusetts, using survival follow-up, self-reported asbestos exposure (n=128), and a subset of cases (n=80) with quantitative asbestos fiber burden measures. RESULTS: Consistent with the established literature, we found independent, significant associations between male sex and reduced survival (p<0.04), as well as between nonepithelioid tumor histology and reduced survival (p<0.02). Although self-reported exposure to asbestos was not predictive of survival among our cases, stratifying quantitative asbestos fiber burden [number of asbestos bodies per gram of lung (wet weight)] into groups of low (0-99 asbestos bodies), moderate (100-1,099), and high fiber burden (>1,099), suggested a survival duration association among these groups (p=0.06). After adjusting for covariates in a Cox model, we found that patients with a low asbestos burden had a 3-fold elevated risk of death compared to patients with a moderate fiber burden [95% confidence interval (CI), 0.95-9.5; p=0.06], and patients with a high asbestos burden had a 4.8-fold elevated risk of death (95% CI, 1.5-15.0; p<0.01) versus those with moderate exposure. CONCLUSION: Our data suggest that patient survival is associated with asbestos fiber burden in MPM and is perhaps modified by susceptibility.     

Quantitative analysis of asbestos burden in women with mesothelioma

BACKGROUND: Lung tissue from 15 women who died from mesothelioma was evaluated for tissue burden of ferruginous bodies and uncoated asbestos fibers. The group contained individuals who had occupational exposure to asbestos and others had family members whose work history included vocations where contact with asbestos containing materials occurred. METHODS: Tissue samples from tumor free lung were digested and filtered and then investigated for ferruginous bodies by light microscopy and asbestos and non-asbestos fibers by analytical transmission electron microscopy (ATEM). Size and type of fibers were also analyzed. RESULTS: Asbestos bodies were found in 13 of the 15 samples and asbestos fibers were found in all cases. The most commonly found uncoated asbestos fiber in these individuals was amosite whereas tremolite was the second most commonly found form. The asbestos fiber burden in these females was often of mixed types. CONCLUSIONS: The asbestos body and fiber burden in these cases show variation in tissue burden. Some cases in this study had appreciable burden, which was attributed to secondhand exposure from occupationally exposed family members. Mesothelioma can occur also in individuals with comparatively low tissue burdens of asbestos.     

Mineral fiber concentration in lung tissue of mesothelioma patients in Finland

The mineral fibers in lung tissue samples of 19 mesothelioma patients and 15 randomly selected autopsy cases were analyzed using low-temperature ashing, scanning electron microscopy (SEM) and x-ray microanalysis. The fiber concentration ranged from 0.5 to 370 million fibers per gram of dry tissue in the mesothelioma group and from less than 0.01 to 3.2 million fibers per gram of dry tissue in the autopsy group. In 80% of the mesothelioma patients and in 20% of the autopsy cases, the fiber concentration exceeded 1 million fibers per gram of dry tissue. Amphibole asbestos fibers predominated in both groups, and only a few chrysotile fibers were found. In the lungs of six mesothelioma patients, anthophyllite was the main fiber type. The overall analytical precision of sample preparation and fiber counting with SEM was 22%.     

Accumulation of long asbestos fibers in the peripheral upper lobe in cases of malignant mesothelioma

Animal studies suggest that mesothelioma is most effectively induced by fibers longer than 8 mu. However, studies of asbestos fibers recovered from human lungs in cases of mesothelioma indicate that, at least in large-scale samples, relatively few fibers meet this size criterion, perhaps implying that the animal data do not apply to man. Since asbestos concentration in lung is known to be extremely inhomogeneous, it is also possible that long fibers may selectively accumulate in specific sites, such as under the pleura. To examine this possibility, we selected ten cases of mesothelioma that contained relatively large amounts of amosite asbestos and extracted fibers from an 0.5-cm-thick strip of subpleural tissue and an area 3-cm deep to the subpleural sample for upper and lower lobes. Amosite fibers were identified and sized by electron microscopic techniques. Fibers in the peripheral upper lobe were significantly longer, broader, and of higher aspect ratio than those in the central upper lobe. The lower lobe showed a reverse pattern, with longer fibers and broader fibers in the central sample. These data indicate that the two lobes behave differently in regard to fiber size, with selective accumulation of long fibers in the peripheral upper lobe, but not in the peripheral lower lobe. Whether these differences reflect differences in initial deposition of fibers within the lung, or, more likely, specific redistribution of fibers, is unclear, but in either case, accumulation of long fibers immediately under the upper lobe pleura may be important in the genesis of mesothelioma.     

Determination of Environmental Exposure to Asbestos (Tremolite) and Mesothelioma Risks in the Southeastern Region of Turkey

In this study, the authors examined the concentrations and mineralogical analyses of asbestos, and investigated mesothelioma risk in southeastern Anatolia, Turkey. They used a gravimetric dust sampler to collect samples from 2 villages and 2 asbestos mines (1 active). Samples were then evaluated by an X-ray diffractometer and an electron microscope. The authors found high concentrations of asbestos in an active mine (4.9 fibers[f]/cm³) and at a house that was plastered with asbestos (1.24 f/cm³) and had a very active population. They found a low concentration (0.0042 f/cm³) in indoor measurements taken in Armutova village, and an even lower concentration (0.000081 f/cm³) in the inactive mine environment. Outdoor measurements included a low concentration of 0.007 f/cm³ in the village environment, and a high concentration of 1.17 f/cm³ on the mine road during the passing of a sheep herd. The people in the region are continuously exposed to asbestos during normal activities. This cumulative exposure to asbestos carries sufficient risks for mesothelioma development.     

The incidence of malignant mesothelioma in Australia 1982-1988.

From 1980 to 1985, the Australian Mesothelioma Surveillance Program, and since 1986, the Australian Mesothelioma Register, have been collecting data on all cases of malignant mesothelioma that could be ascertained in Australia. Incidence rates were calculated on 854 Program and 696 Register cases (total 1271) diagnosed in Australia between January 1, 1982 and December 31, 1988. Australia has one of the highest national rates of mesothelioma in the world (15.8 cases per million of population aged 20 years and older), and the rate is rising. The rate is far higher in males (28.3) than females (3.3). The Western Australian rate (28.9) is the highest among the states, as may be expected because of the crocidolite mine at Wittenoom; however, the largest numbers of cases occur in the more populous and industrial New South Wales. The high incidence rate, its expected continuing increase, and absence of a history of exposure to asbestos in approximately 28% of cases, demand consideration of potential environmental factors other than asbestos in the causation of this tumor, as well as continued surveillance.     

Fibrous minerals in the lungs of mesothelioma patients: comparison between data on SEM, TEM, and personal interview information.

To determine and compare the fiber types and size distributions in the lung tissue of mesothelioma patients in Finland, samples from 29 patients with known work history were analyzed with transmission electron microscopy (TEM) and X-ray microanalysis. Compared with the earlier results using scanning electron microscopy (SEM), the fiber concentrations were about three times as high and ranged from 0.1 million to 5,200 million fibers per gram of dry tissue. In 15 patients (52%), crocidolite/amosite were the dominating fiber types, representing more than 70% of all fibers. Anthophyllite asbestos was the most prevalent fiber type in eight patients (28%), and it was found in the samples of 13 patients (45%). One-half of the anthophyllite fibers were longer than 5 microns, whereas other fiber types were somewhat smaller.     

Asbestos disease in sheet metal workers: the results of a proportional mortality analysis

The results of a proportional mortality analysis of a cohort of sheet metal workers who have only intermittent exposure to asbestos demonstrates a significant excess of cancer at the three sites most frequently associated with asbestos: lung, colon and rectum, and the mesothelium. No excess nonmalignant respiratory disease was detected. These data strongly suggest that significant asbestos-related disease is present in populations with secondary exposure to asbestos and emphasize the importance of considering possible asbestos-related disease when treating patients with a history of employment in the construction industry.     

Occupational exposure and regional variation of malignant mesothelioma in Norway, 1970-79

This investigation is based on a study of 117 men and 24 women with malignant mesothelioma registered by the Cancer Registry of Norway, 1970-79. The age-adjusted incidence rate in men for each county varied from 1.7 to 13.3 per million per year. Eighty-two percent of the men revealed possible occupational asbestos exposure. They were evenly distributed between counties with high and low mesothelioma incidence. Only 17% of the women had possible occupational asbestos exposure. Total lung fiber concentration was analyzed with scanning electron microscopy in 65 men and 13 women. The median lung fiber concentration in men was 2.4 million per gram of dried tissue (range less than 0.4-490), in women 1.0 million per gram (range less than 0.4-41), and in male controls less than 0.4 million per gram (range less than 0.4-4.8). The median year of first exposure was 1937 (range 1909-60) for men from counties with a high incidence rate and 1945 (range 1938-59) for men from counties with a low incidence rate. The counties with a high compared to a low incidence rate of malignant mesothelioma, 1970-79, showed an apparent difference in the percentage of population employed in industry in 1946. The regional variation in the incidence of malignant mesothelioma in men is mainly attributable to the proportion of population exposed to asbestos in industry per county prior the 1950s and the time since exposure started.(ABSTRACT TRUNCATED AT 250 WORDS)     

Malignant mesothelioma in Australia, 1945-2000

BACKGROUND: Australia has maintained a total national malignant mesothelioma case register since 1980. There has been a marked increase in the incidence of mesothelioma in the last 20 years. Currently 450-600 cases are notified annually in a population of 20 million. While the history of the Wittenoom (Western Australia) crocidolite mine and its aftermath is well known, these cases comprise only 5% of the total. This study describes the incidence of mesothelioma in Australia from 1945 to 2000. METHODS: Using register data, time trends in mesothelioma incidence were calculated. Analyses of incidence are reported by age, sex, anatomical site, and state of notification. Associations with occupational and environmental asbestos exposure histories are described. Lung fiber content measurements were made on a subset of cases. RESULTS: Australia has had 6,329 cases of mesothelioma from 1 January 1945 to 31 December 2000. (A further 620 cases were notified in the period from 1 January 2001 to 31 October 2001.) Annual incidence rates for Australia per million population > or = 20 years (1997) were: male, 59.8; female, 10.9; total, 35.4. Incidence rates have been continually increasing and are the highest reported national rates in the world. While Western Australia has the highest rate (1997 total rate, 52.8), most cases arise from the two most populous eastern states, New South Wales and Victoria. In 88% (male 90%, female 61%) of cases, a history of asbestos exposure was obtained. Exposures occurred in a wide variety of occupational and environmental circumstances. In 80% of cases with no history of exposure, TEM lung asbestos fiber counts > 200,000 fibers > 2 microm length per gm dry lung were obtained, suggesting unrecognized exposure. CONCLUSIONS: Australia's high incidence of mesothelioma is related to high past asbestos use, of all fiber types, in a wide variety of occupational and environmental settings. The number of cases in total is expected to be about 18,000 by 2020, with about 11,000 yet to appear.