Histological types of malignant mesothelioma and asbestos exposure.

The Los Angeles County Cancer Surveillance Program abstracts hospital pathology records on almost all cases of cancer occurring in the county. Those cases of pleural and peritoneal mesothelioma that occurred between 1972 and 1978 were identified. Occupational histories were obtained from interviews, and the histopathology of the tumours was reviewed by a member of a mesothelioma reference panel who was unaware of the exposure histories. The relation of asbestos exposure to the three histological types of mesothelioma (epithelial, mesenchymal, and mixed) was studied among the 29 cases for whom occupational histories were available and who were also considered to have histopathology consistent with mesothelioma. The proportion of cases exposed to asbestos was high for both the epithelial (11/17, 65%) and mixed histological types (6/11, 55%). The single case of mesothelioma classified as a mesenchymal type was also exposed to asbestos. Cases who had worked in shipyards were represented in each of the three groups. In cases who had worked in asbestos production and manufacture an exclusively epithelial type of tumour was observed. In cases who had worked as insulators or in heating trades the histological type was predominantly (3/4) mixed. These data do not support the hypothesis that any specific histological type of mesothelioma is especially related to asbestos exposure.     

Histological types of malignant mesothelioma and asbestos exposure

The Los Angeles County Cancer Surveillance Program abstracts hospital pathology records on almost all cases of cancer occurring in the county. Those cases of pleural and peritoneal mesothelioma that occurred between 1972 and 1978 were identified. Occupational histories were obtained from interviews, and the histopathology of the tumours was reviewed by a member of a mesothelioma reference panel who was unaware of the exposure histories. The relation of asbestos exposure to the three histological types of mesothelioma (epithelial, mesenchymal, and mixed) was studied among the 29 cases for whom occupational histories were available and who were also considered to have histopathology consistent with mesothelioma. The proportion of cases exposed to asbestos was high for both the epithelial (11/17, 65%) and mixed histological types (6/11, 55%). The single case of mesothelioma classified as a mesenchymal type was also exposed to asbestos. Cases who had worked in shipyards were represented in each of the three groups. In cases who had worked in asbestos production and manufacture an exclusively epithelial type of tumour was observed. In cases who had worked as insulators or in heating trades the histological type was predominantly (3/4) mixed. These data do not support the hypothesis that any specific histological type of mesothelioma is especially related to asbestos exposure.     

Malignant mesothelioma of the pleura among women

BACKGROUND: The epidemiological features of mesothelioma among women differ from those observed among men. OBJECTIVES: To trace the outline of pleural mesothelioma among women in the Monfalcone area, Italy. METHODS: Thirty-three malignant mesotheliomas of the pleura observed in female patients at the Hospital of Monfalcone, Italy, in the period 1979-2002 were reviewed. The diagnosis was based on/or confirmed by necropsy findings in 30 cases. Occupational and social histories were obtained from the patients themselves or from their relatives by personal or telephone interviews. In 29 necropsy cases thoracic cavities were examined for the presence of pleural plaques. Routine lung section were examined for asbestos bodies in 30 cases. In 21 cases asbestos bodies were isolated and counted after chemical digestion of lung tissue. RESULTS: The age of the patients ranged between 48 and 89 years (mean 72.85, median 73.00). All the patients had histories of exposure to asbestos, single in 25 cases and mixed in 8. Exposure at home due to cleaning of work clothes was the most frequent type of exposure. Various patients had been exposed in non-asbestos text industries (cotton mills). Unusual types of exposure occurred in some cases (distillery, small sodium carbonate factory, starch factory). The latency periods (time intervals elapsed between first exposure to asbestos and diagnosis of the tumour), calculated in 23 cases, ranged from 34 to 62 years. Pleural plaques were found in 21 cases. Twelve patients showed asbestos bodies on routine lung sections. The asbestos body burden ranged between only a few bodies and 92,000/g dried tissue. CONCLUSIONS: In contrast with other series of mesothelioma among women, all the present cases were attributable to asbestos. The detection of objective signs of exposure (pleural plaques, lung asbestos bodies) played a key role in attribution.     

Environmental exposure to asbestos in the area around Goor has been established as the cause of pleural mesothelioma in women

OBJECTIVE: To determine whether a disease cluster of 22 additional cases of pleural mesothelioma among women could be attributed to environmental asbestos exposure due to asbestos fibers from waste material on roads and property yards. The women studied were observed in an area with substantial environmental exposure to asbestos during the period 1989-2002. DESIGN: Ecological study. METHOD: In the study period of 1989-2002, all cases of mesothelioma among women, based on a strict histopathologic definition, occurring in the region of Twente, The Netherlands (n = 59) were provided by the regional cancer register. Additional information was collected on the occupational histories of the cases and their partners and addresses of residence through medical records, general practitioners, and next-of-kin. Environmental asbestos exposure was assigned to all cases that had had a long-term stay in a house in the area around Goor with demonstrated local environmental asbestos pollution and where any contact with asbestos through occupation or in the household had been excluded. RESULTS: In the risk area around Goor, out ofa total of 28 cases ofwomen with pleural mesothelioma, asbestos in the environment was found to be the only source of asbestos exposure for to women. In a further 4 women, environmental asbestos exposure was found to be the most likely cause of pleural mesothelioma. The average cumulative exposure was around 0.11 fiber/ml x exposure years. The observed extra incidence of 22 cases was attributed to the environmental exposure to asbestos in 64% (14/22) of cases. CONCLUSION: The environmental pollution to asbestos waste materials in the area around Goor was the main cause of the strongly increased incidence of pleural mesothelioma among women in this area. Taking into account an equal risk among men, the consequences of asbestos exposure in the area around Goor in the next 25 years are likely to result in 2 cases of pleural mesothelioma each year.     

The incidence of malignant mesothelioma (1977-1996) and asbestos exposure in the population of an area neighboring Lake Iseo, northern Italy

The study was stimulated by the occurrence of malignant mesotheliomas among the workers of two adjacent factories located in Sarnico, near Lake Iseo (province of Brescia, northern Italy), one of which manufactured crocidolite and chrysotile ropes and gaskets until 1993. The aim of the study was: identification of malignant mesotheliomas occurring between 1977 and 1996 among the residents of 11 villages, which constituted the recruitment area of the work-force; estimation of the incidence of malignant pleural mesothelioma; collection of working histories of all cases to evaluate previous exposure to asbestos and radiation therapy. 21 cases of mesothelioma were detected (20 pleural, 1 peritoneal; 9 among males), and 20 were supported by histopathologic diagnosis. The incidence (x 100,000 person-years, standard: European population) was 2.5 (0.7-4.2) and 2.8 (1.2-4.3) among males and females, respectively, corresponding to a three-fold increase among males and a more than ten fold increase among women in comparison with the incidence reported by the Lombardy Cancer Registry. No cases had been exposed to radiation therapy, whereas all cases had been occupationally exposed to asbestos. Occupational exposure to asbestos had occurred in work on the production of crocidolite and chrysotile ropes and gaskets (6 males); in work in a textile factory producing cotton garments that was adjacent to and polluted by the former, where, in addition, chrysotile blankets were used for fireproofing in the weaving area and pipes were insulated using amosite-containing materials (10 cases, 6 among females); 5 cases occurred among women working in silk factories, where asbestos exposure was possible because of the presence of pipes insulated with asbestos and because women were handling temperature-controlled trays insulted with asbestos. In conclusion, the study demonstrated that the occurrence of mesothelioma was higher among females than males in the study area and that all cases of mesotheliomas had been occupationally exposed to asbestos.     

Mesothelioma and asbestos in the Province of Quebec, 1969-1972

All records of patients who died of mesothelioma in the Province of Quebec during the period 1969-1972 were collected and reviewed. Asbestos exposure in this group was compared with that in two control groups, one of persons dying of accidental causes and the other of those dying of cardiovascular disease. The mortality rate for mesothelioma was estimated at between 2.3 and 2.8 per million per year. Men were affected twice as frequently as women, this difference being related exclusively to pleural mesothelioma. The incidence in urban regions was much higher than in rural areas, and areas involved in mining showed an incidence in the expected range. Thirty-four percent of the patients with mesothelioma and only 2% of controls had histories of direct exposure to asbestos. This exposure was related to asbestos processing and not its production. No woman gave a history of occupational exposure to asbestos. It appeared that chrysotile may be less related to the production of mesothelioma than other types of asbestos fibers.     

Mesothelioma of the pleura in the Province of Trieste

BACKGROUND: The Province of Trieste, north-eastern Italy (population about 240,000), has been identified as an area with a high incidence of pleural mesothelioma. OBJECTIVES: (i) To obtain preliminary data on the trend of the mesothelioma epidemic in the Province of Trieste during the last six years; (ii) to define the cases in terms of asbestos exposure. METHODS: Pleural mesotheliomas diagnosed at the Department of Surgery, Thoracic Surgery Unit, Trieste University, in the period January 2001-May 2006 were reviewed. The histological diagnosis was generally based on material obtained at thoracoscopy, pleurectomy, or pleuropneumonectomy. In three cases the pathological diagnosis was made by biopsy of the thoracic wall, and in a further three cases by cytological examination ofpleuralfluid. Detailed occupational histories were obtained from the patients themselves at the time of first admission. RESULTS: The group included 99 people resident in the Province of Trieste (89 men and 10 women, aged between 43 and 89 years). On the basis of the occupational history, 95 cases were defined as asbestos-related. A majority ofpatients had been employed in marine work, including shipbuilding (46 cases), port activity (13 cases), and maritime trades (8 cases). Thirteen patients had worked in other industries (iron industry, petrochemical, etc.). Fourteen people had been employed in a variety of occupations (fire-fighter, lift mechanic, cinema projectionist, pastry worker, telephone technician, etc.). Five women had histories of exposure to asbestos at home. About 70% of the patients had their first exposure to asbestos before 1960. Two-thirds of the cases were exposed to asbestos for 20 years or more. Latency periods (time intervals elapsed between first exposure to asbestos and diagnosis of mesothelioma) rangedfrom 25 to 71 years (mean 49.3, median 49.0). One patient had a history ofprior thoracic irradiationfor Hodgkin's disease. CONCLUSIONS: In the Province of Trieste the mesothelioma epidemic does not show any signs of abatement. Besides marine work, a variety of other occupations appear to be associated with the tumour in this area.     

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.     

Asbestos-related mesothelioma in monfalcone,Italy

The Monfalcone area, in northeastern Italy, is a small industrial territory (population about 60,000), with a large shipyard. Between October 1979 and April 1992, ninety-two malignant mesotheliomas were diagnosed at the Monfalcone Hospital. The series included 84 men and 8 women, aged 42 to 89 years (median age 68 years). There were 89 pleural and 3 peritoneal tumors. Seventy patients (69 men and 1 woman) had worked in the shipyards; six were seamen, and four insulators. Five men had been exposed to asbestos in various industries; six women had histories of domestic exposure, and one woman had a history of possible environmental exposure. The latency periods (intervals between first exposure to asbestos and diagnosis of the tumor) ranged from 20 to 65 years (median 52 years). Latency periods among insulators were significantly lower than among shipyard workers, as well as lower than among the other categories (p<0.01). Lung asbestos bodies were isolated after chemical digestion in 73 cases at necropsy, and in two cases at surgery. In necropsy cases, asbestos body burdens ranged between 100 and 10,000,000 bodies per gram of dried tissue (median 11,000). Pleural plaques were observed at necropsy in 62 out of 73 cases, and in two cases at surgery. In the time period we considered, the annual incidence rates for pleural mesothelioma were very high among male Monfalcone residents, being 189 per 100,000 among people aged 75 years or more. On the basis of occupational data and of objective signs (lung asbestos bodies, pleural plaques), all the cases of the present series but one (that with possible environmental exposure) were considered as asbestos-related. The role of co-factors in the development of asbestos-related mesothelioma is suggested. © 1993 Wiley-Liss, Inc.     

Environmental malignant mesothelioma in southern Anatolia: a study of fifty cases

Malignant mesothelioma is a highly aggressive tumor of the serous membranes, which in humans results from exposure to asbestos and asbestiform fibers. Although occupational malignant mesothelioma is still the most common form of this lesion, naturally contaminated soil can play an important role in the development of environmental malignant mesothelioma in some parts of the world. Fifty cases of malignant mesothelioma (MM) from southern Turkey with no occupational history of asbestos exposure were reviewed regarding pathologic and clinical features. A case of hyaline fibrous plaque of the pleura was also included in this series. Histologically the cases were classified as epithelial (36 cases); sarcomatous (7 cases); and biphasic (7 cases). One of the sarcomatous cases was desmoplastic. Ultrastructural examination of the tumor tissue in three cases revealed long-surface microvilli in epithelial cells. Interstitial cells of the lung in one case showed electron-dense asbestos fibers in the cytoplasm. Mineralogical analyses of the lung tissue in three cases of MM and the case of pleural plaque showed high amounts of asbestos fibers most consistent with tremolite and actinolite. The clinical and pathologic features of our cases support that the environmental inhalation of asbestos is still a major health problem in some parts of Turkey.     

Mesothelioma in South Africa, 1976-84: incidence and case characteristics

Malignant mesothelioma is a rare tumour known to be associated with prior exposure to asbestos. Previous studies have described the occupational and clinical features of cases of mesothelioma in the Republic of South Africa (RSA) but none has set out to determine incidence of this disease. To estimate incidence, a case register was compiled for 1976-84 by contacting all medical practitioners and institutions likely to have seen cases of mesothelioma in this period; demographic, diagnostic and exposure details were sought. Cases were accepted if they provided evidence of histological diagnosis of mesothelioma. Fifty-two per cent of 1347 cases identified were in whites, 31% in blacks, 16% in coloureds and 1% in Asians. Seventy-three per cent of cases occurred in males. The majority of whites were aged 51-70 years, while the majority in other race groups were aged 41-60 years. The ratio of only pleural to only peritoneal mesothelioma was 11:1, although there were marked differences by race. Eighty-five per cent of males with exposure information available had prior exposure to asbestos, mostly occupational. A similar proportion of women had contact with asbestos but mostly through other types of exposure. Standardized incidence rates per million population aged 15 years and over were calculated for sex-race subgroups and were highest in white males (32.9 per million per year, 95% Cl 22.7-46.4), coloured males (24.8 per million per year, 95% Cl 16.2-36.9) and coloured females (13.9 per million per year, 95% Cl 7.7-23.5). These incidence rates are amongst the highest ever reported for a national population. Age-specific standardized incidence rates were highest in white males (over 100 per million per year in men over 55 years). Reasons for the differing rates by population group are likely to include differential access to health services. More rigorous control of asbestos exposure in the RSA is recommended.     

Tuscany mesothelioma registry (1988-2000): evaluation of asbestos exposure

BACKGROUND: The Tuscany Mesothelioma Register (ARTMM) records pleural malignant mesothelioma cases of Tuscany residents, diagnosed by histological, cytological, or clinical (radiography or computerized tomography) examinations. The ARTMM began in 1988 and estimates mesothelioma incidence in Tuscany and collects information on past asbestos exposure of mesothelioma cases. OBJECTIVES: The aim of this paper was to describe the incidence of pleural mesothelioma cases in Tuscany and to analyse their possible past asbestos exposures. METHODS: We considered pleural mesothelioma cases recorded in ARTMM in the period 1988-2000 and interviews collected for these cases. In order to identify past asbestos exposure in the occupational and non-occupational history of patients, interviews were carried out using a standardised questionnaire. RESULTS: In the period 1988-2000, 494 pleural malignant mesothelioma cases were recorded in the ARTMM; 82% were males. In the periods 1988-1993, 1994-1997, 1998-2000 the incidence rates, standardised on the Italian population (per 100,000), were respectively 1.15, 1.57, 2.58 among males; 0.29; 0.27; 0.29 among females. Information on occupational history was collected for 418 mesothelioma patients (85% of recorded cases): 173 mesothelioma cases were directly interviewed; for 245 cases relatives or work colleagues were interviewed. Occupational asbestos exposure was ranked as certain, probable or possible in 72% of the interviewed cases (80% of males; 20% of females). Environmental and non-occupational asbestos exposure was identified in 1% of males, and 3% of females. In 24% of the interviewed cases (15% of males; 74% of females) no known asbestos exposure was identified. Occupational asbestos exposure occurred in maritime activities (shipyards, dock work, merchant and regular Navy), the building industry, railway carriage construction and maintenance, rail transport, textile industries (mainly rag sorting), electricity production, asbestos cement manufacture, chemical, iron and steel industries and in glass manufacturing. In Tuscany two areas are distinguished for their well-documented and massive use of asbestos: the coastal areas (Livorno and Massa Carrara) for maritime activities, and the areas of Pistoia and Arezzo for railway carriage construction and repair. Mesothelioma incidence rates in these areas are the highest in the whole region. CONCLUSIONS: Further investigation is needed in order to identify unknown asbestos uses and consequent exposure, in particular for females. Uncertainty as regards occurrence of asbestos exposure persists in the textile industries where the mesothelioma epidemics have not yet declined. Research hypotheses are addressed on the re-use of jute bags previously containing asbestos, therefore collection of further information on periods and methods of this recycling activity is essential.     

Malignant mesothelioma in Australia, 1945-2002

Using register data, time trends in mesothelioma incidence in Australia from 1945 to 2002 were calculated. Incidences are reported by age, sex, anatomic site, and state of notification. Associations with occupational and environmental asbestos exposure histories and lifetime risks in different exposure categories were investigated. Lung-fiber content was measured in a subset of cases. Australia had 7,027 cases from 1945 to 2001, with 488 more in January 2002 through June 2003. Incidence rates for Australia per million population > or = 20 years old (1999) were: male 53.3; female 10.2; total 31.8. Rates have continually increased and are the highest reported national rates in the world. Western Australia had the highest rate (1999 total 47.7), but most cases arose from the two most populous eastern states, New South Wales and Victoria. In 88% of cases (male 90%, female 61%), histories of asbestos exposures were obtained. In 80% of cases with no history of exposure, TEM lung asbestos fiber counts > 200,000 fibers > 2 microm length/g dry lung were obtained, suggesting unrecognized exposure. Australia's high incidence of mesothelioma is related to high past asbestos use, of all fiber types, in a wide variety of settings. The number of cases is expected to be about 18,000 by 2020, with about 11,000 yet to appear.     

A case of malignant mesothelioma in a rice-starch factory

Introduction Recent reports of cases of malignant mesothelioma (MM) in “non-traditional” areas of employment are an indication of the numerous occasions in which exposure to asbestos has occurred in the workplace. We describe an unusual case of occupational exposure to asbestos to stress the importance of careful history taking when assessing a patient’s work history, especially in generic occupations in which there is apparently no exposure to asbestos. Case report Malignant mesothelioma was diagnosed in a woman worker employed in a factory making rice starch. She had worked in the storehouse of the factory for approximately 40 years. From circumstantial interviews with relatives and workmates, it emerged that her job involved retrieving, for re-use, the jute sacks in which the rice was transported. More than one source remembered distinctly that some of the sacks had “Asbestos” written on the outside. Discussion This case provides further confirmation of the importance of careful history taking among workers with mesothelioma to avoid failing to diagnose occupational disease. It also highlights the risk of asbestos exposure represented by recycling asbestos-contaminated sacks in both occupational and non-occupational settings.     

Malignant mesothelioma in Basse-Normandie, a French population study. Descriptive analysis, prognostic factors and survival

BACKGROUND: Malignant mesothelioma is a pleural and/or peritoneal tumor closely related to asbestos exposure, and its incidence should continue to increase during the first two decades of the 21(rst)century. The main prognostic factors described for this tumor are older age, sex, tumor stage and histological type. The aim of this study was to assess the incidence of pleural and peritoneal malignant mesothelioma in the County of Basse-Normandie (France), as well as their epidemiological characteristics, and the prognostic factors related to survival duration. METHODS: Cases were identified through repeated inquiries among all chest physicians and pathologists of the County of Basse-Normandie. A special care was taken in the validation of the diagnosis of each case. Incidence of mesothelioma was determined according to sex and age (5 years categories). Qualitative and quantitative variables were compared with the use of chi-square or Student's t tests respectively. Survival rate was calculated by Kaplan-Meier method, and prognostic factors were studied by means of Cox model. RESULTS: Study population consisted in all 80 malignant mesothelioma cases diagnosed in Basse-Normandie between the 1(rst) of September 1995 and the 31(rst) of August 1999. Annual incidence rates of pleural mesothelioma were 1.1/100 000 in men and 0.23/100 000 in women; annual incidence rates for peritoneal mesothelioma were 0.21/100 000 in men and 0.13/100 000 in women. Asbestos exposure was present in 63 cases (78.8%). The study of geographic distribution of mesothelioma cases revealed the influence of the main asbestos industrial settings, as well as the numerous scattered cases related to other occupational exposure. Mean survival duration was 9 months for pleural mesothelioma and 5 months for peritoneal mesothelioma. After adjustment on age, death risk was higher in asbestos-exposed than in non asbestos-exposed cases. CONCLUSION: This study confirms that malignant mesothelioma is closely related to asbestos exposure, but not only in main asbestos industrial settings. It suggests that asbestos exposure may take place among prognostic factors of this tumor.     

Pericardial mesothelioma and asbestos exposure

Pericardial mesothelioma (PM) accounts for 0.7% of all malignant mesotheliomas. Although asbestos exposure is a recognized etiological factor for pleural and peritoneal mesotheliomas, its role in the development of PM is controversial. The aim of this study is to describe the characteristics of PM cases occurred in Lombardy, a highly industrialized Region of Northern Italy. From the Lombardy Mesothelioma Registry we selected the incident cases of PM registered in the Lombardy Region between 2000 and 2009 and we abstracted clinical characteristics and history of asbestos exposure. We identified 8 cases (6 men and 2 women), with a median age at diagnosis of 55.5 years, representing 0.3% of all mesothelioma cases (n = 3059). The age-standardized incidence rate was 0.09 per million/year. Occupational exposure to asbestos was documented in 5 of the 7 cases for which we obtained an interview. Our findings support the role of asbestos in the pathogenesis of PM.     

Distribution of mesothelioma cases in different occupational groups and industries in Australia, 1979-1995

Australia was a producer and user of asbestos and has one of the highest national incidences of mesothelioma in the world. The incidence is still rising and expected to do so for another 10-20 years. A study was conducted in 1996 to examine the past and current incidence rates of mesothelioma in a number of industries and occupations as the basis for predicting future outcomes. Occupational histories of a total of 3758 mesothelioma cases collected by two sequential national schemes--the Australian Mesothelioma Surveillance Program (1979-1985) and Australian Mesothelioma Register (1986-1995)--were reviewed and coded by the authors. The building industry contributed the largest number of cases nationwide followed by shipbuilding and repair, asbestos cement production, crocidolite mining and milling, railway locomotive construction and repair, coal-fired power stations, and other engineering operations. The mean latency between initial occupational asbestos exposure and diagnosis of the disease was 37.4 years (range = 4-66 years) for cases notified between 1979 and 1985, and 41.4 years (range = 6-84 years) for those between 1986 and 1995. Trends for each industry group have been changing considerably in the past 16 years, with the traditional primary asbestos industry cases from crocidolite mining and milling now on the decline and cases from asbestos cement production having plateaued. In contrast, more recently, more cases were observed from the asbestos user industries such as the building industry, and from occupations such as plumbers, carpenters, machinists, and car mechanics. These increases might be a reflection of the longer latency effects of the intermittent and less severe exposures in these larger occupational groups.     

Malignant mesothelioma: attributable risk of asbestos exposure.

OBJECTIVES--To evaluate a case-control study of malignant mesothelioma through patterns of exposure to asbestos based upon information from telephone interviews with next of kin. METHODS--Potential cases, identified from medical files and death certificates, included all people diagnosed with malignant mesothelioma and registered during 1975-1980 by the Los Angeles County Cancer Surveillance Program, the New York State Cancer Registry (excluding New York City), and 39 large Veterans Administration hospitals. Cases whose diagnosis was confirmed in a special pathology review as definite or probable mesothelioma (n = 208) were included in the analysis. Controls (n = 533) had died of other causes, excluding cancer, respiratory disease, suicide, or violence. Direct exposure to asbestos was determined from responses to three types of questions: specific queries as to any exposure to asbestos; occupational or non-vocational participation in any of nine specific activities thought to entail exposure to asbestos; and analysis of life-time work histories. Indirect exposures were assessed through residential histories and reported contact with family members exposed to asbestos. RESULTS--Among men with pleural mesothelioma the attributable risk (AR) for exposure to asbestos was 88% (95% confidence interval (95% CI) 76-95%). For men, the AR of peritoneal cancer was 58% (95% CI 20-89%). For women (both sites combined), the AR was 23% (95% CI 3-72%). The large differences in AR by sex are compatible with the explanations: a lower background incidence rate in women, lower exposure to asbestos, and greater misclassification among women. CONCLUSIONS--Most of the pleural and peritoneal mesotheliomas in the men studied were attributable to exposure to asbestos. The situation in women was less definitive.     

Asbestos and mesothelioma in Scotland

Summary A retrospective study of the incidence of mesothelioma in Scotland and its association with asbestos is described. For the years 1950–1967, 80 cases were traced from pathological reports and biopsy material of malignant tumours invading the peritoneum and pleura. Detailed histories of residence, occupation and degree of exposure to asbestos were obtained from relatives or friends for these 80 cases and also for two sets of controls matched for age and sex. The incidence of mesothelioma in Scotland was confirmed to be associated with exposure to asbestos and its incidence was shown to be similar to that in other areas of Britain.