Information about occupational exposure to asbestos given to cases in an etiological study: ethical aspects

The aim of the study is to consider some ethical aspects of the provision of information, to the cases or their families, about the assessment of occupational asbestos exposure obtained in a case–control study of malignant mesothelioma of the pleura. An informative letter with the result of the evaluation of their occupational exposure to asbestos was sent to the participating cases (and/or their family). Those whose exposure was classified as certain/probable were also informed of the legislation regarding occupational diseases. Of the 132 cases, 32.6% of subjects and/or their families made telephone calls expressing interest in the content of the informative letter. Among the 63 cases classified as certain/probable exposure, this proportion was 47.6%. Out of 43 cases in which the age at diagnosis was 65 years and the exposure to asbestos was certain/probable, only two (4.6%) were signed off work owing to occupational disease. Only one of the mesothelioma cases was recognized by the Spanish National Institute for Social Security (INSS) as having an occupational disease. The process of communication of the results of an epidemiological research should include the provision of information on the exposure data to each one of the subjects, and/or their families. There is a great disparity between the number of cases of certain/probable exposure to asbestos identified in our study, and the number registered as an occupational disease by the INSS.     

Medico-legal aspects of malignant mesothelioma

The object of this investigation was to discuss medico-legal aspects of malignant mesothelioma in relation to social insurance legislation for occupational injuries and diseases in Norway. During the period 1960-79 the Cancer Registry of Norway recorded a total of 155 men and 35 women with malignant mesothelioma. However, only 21 men and no women were notified to the National Insurance Institution as occupational disease cases before 31 December 1979, in spite of the well established causal association between occupational asbestos exposure and the disease. The investigation is based on these 21 patients. The long latency period from first asbestos exposure until appearance of the disease and the short survival were evident in this study. Furthermore, the legislation and provisions for occupational injuries and diseases in Norway are obviously intended for occupational accidents, and consequently the legal assessment of patients with malignant mesothelioma was complicated. For those notified, the delay in notification was considerable, and only 50% were notified before death. Delay in the claim procedure was also substantial, and few patients survived the claim procedure period. The decisions were not consistent, particularly decisions regarding "the year of injury" and appeared to have been more restrictive during recent years. One of the 21 cases was not accepted as occupational disease, because domestic exposure was considered more probable than occupational exposure.     

La ricostruzione dell’esposizione ad amianto in un’azienda tessile di produzione filati cucirini attraverso l’utilizzo di un’insolita fonte informativa

«Reconstruction of the asbestos exposure in a textile company producing sewing threads through the use of an unusual information source».Background:The Tuscan Regional Operating Center (ROC) of Malignant Mesotheliomas has identified a cluster of 11 cases of malignant mesothelioma occurred in a textile plant manufacturing sewing thread. Using the common research method, the ROC had not previously been able to identify the specific sources of asbestos exposure causing such a large cluster.Objectives:The ROC’s objective was to review all cases of the cluster and to better identify their occupational asbestos exposures.Methods:The cases’ occupational histories of asbestos exposure have been reviewed, using information deriving from the annual reports sent to the Tuscany Region since 1988 by all the asbestos removal companies according to the Law no. 257/1992, article 9, and from interviews to former employees of the plant.Results:The work cycle has been reconstructed and enriched with the new information about the asbestos presence and its uses in the plant. The eleven cases were all reclassified as “certainly occupational exposed” given that the new collected information depicted a widespread asbestos pollution of the workplace during the period of employment of all cases.Conclusions:Using different sources of information, in addition to those traditionally collected through questionnaires, to reconstruct past asbestos exposuresallowed us to clarify the existence of the cluster of mesothelioma cases and the highest level of occupational asbestos exposure was attributed to all cases with consequent activation of the medico-legal procedure.Key words: Asbestos, malignant mesothelioma, occupational exposure, textile, sewing threads     

Predictors of filing claims and receiving compensation in malignant mesothelioma patients

Although the predominant occupation origin of mesothelioma is well known, determinant factors involved in filing compensation are scarcely investigated. A linkage between incident mesothelioma cases collected by Italian mesothelioma register (ReNaM) and compensation claims and assignment by Italian national insurance Institute (INAIL) has been conducted for cases diagnosed in the period 2010–2015 and occupational exposure to asbestos. Logistic regression models and decision tree models have been used to identify demographic, diagnostic and anamnestic factors significant for filing and receiving compensation. We have included in the analyses 5019 mesothelioma cases, and among them, 3321 (66.2 %) were found in INAIL archives as mesothelioma cases who fil claims for compensation. The modalities of asbestos exposure, sector of working activities and job type are crucial factors. Furthermore, gender, age at diagnosis, area of residence have been found to be significant predictors of probability to fil claims. Relative risks to fil claims were obtained for the above determinants and conditions to maximize the probability to obtain compensation identified. Our findings demonstrate that there is a need to enforce policies for improving awareness of the occupational origin for mesothelioma cases. Stakeholders, occupational health and safety institutions can play an important role for improving the sensitization regarding the rights of compensation benefits, ensuring the equity and the effectiveness of insurance, welfare and public health systems.     

Asbestos-related diseases in the federal Republic of Germany

Until recently, in the Federal Republic of Germany there has been a lack of epidemiological data on asbestos-related tumors. Only the numbers of occupational diseases accepted for compensation by the German industrial injuries insurance institutes (Berufsgenossenschaften) can be stated. These show, for 1979, 94 cases of asbestosis, 21 cases of asbestosis associated with lung cancer, and 34 cases of mesothelioma. Since 1972 employees exposed to asbestos dust have been included in a central register by the industrial injuries insurance institutes and are medically examined periodically. By December 31, 1979, 28,476 persons were registered. Of those, 6,582 were still being followed medically, although they were no longer working with asbestos dust exposure. In January 1, 1977, a prospective epidemiological study was started with these people who were formerly exposed to asbestos dust. Up to December 31, 1980, altogether 2,944 people were enrolled in the study. Besides several other enrollment criteria, the individual's permission was required to evaluate his personal data. Of the people enrolled, 85 had died by December 31, 1980. Even if five questionable cases of lung cancer are excluded (n = 80), the observed rates of about 43% tumours of all sites, with 15% lung cancer and 6% mesothelioma, seem to be comparable to the international epidemiological mortality pattern.     

Incidence trends and gender differences in malignant mesothelioma in New South Wales, Australia

OBJECTIVES: Features of malignant mesothelioma reportedly differ between men and women, including occupational asbestos exposure, histological subtype, and median survival. In this study, incidence trends and clinical features for malignant mesothelioma were compared between genders in New South Wales (NSW), where notification of malignant mesothelioma to the Central Cancer Registry is a statutory requirement. METHODS: Notifications to the Central Cancer Registry were compared with those to the registry of the NSW Workers' Compensation (Dust Diseases) Board. The latter includes occupational and clinical data. RESULTS: Of the 3090 cases of malignant mesothelioma reported to the Central Cancer Registry between 1972 and 2004, 456 (15%) were female. Altogether 1995 malignant mesotheliomas were compensated between 1969 and 2004, of which 105 (5%) occurred among women. The incidence increased for both genders by approximately 15-fold. Median survival was similar for the men and women for all of the cases (7 versus 6 months), but was better among the women who received compensation (8.5 versus 10.4 months, P<0.0001). The mean disease latency (42.8 years) increased over the study period (P<0.001). CONCLUSIONS: In New South Wales over the last 30 years, the total number of malignant mesotheliomas and the number of compensated cases of malignant mesothelioma have risen for both genders. The mean latency is increasing, and increasing numbers of "nonoccupational" cases are being reported. Survival remains poor.     

Occupational asbestos exposure, lung-fiber concentration and latency time in malignant mesothelioma

Mineral fiber concentration in lung tissue was analyzed by scanning electron microscopy in 73 males with malignant mesothelioma and in 36 referents who died of cardio- or cerebrovascular diseases. The investigation showed apparent differences in the median lung-fiber concentration between occupational groups with different levels of asbestos exposure, as judged from their occupational history. Thus the mineral fiber content in human lung tissue provides a useful indicator of cumulative asbestos exposure. There was also a statistically significant difference between the median lung-fiber concentration among mesothelioma cases with unlikely or unknown occupational asbestos exposure and the reference group. The latency times in 42 of the cases with definite or probable occupational asbestos exposure showed a log-normal distribution with a median of 37 years and a range of 19-68 years. No statistically significant correlation was found between the logarithm of the latency time and the logarithm of the lung-fiber concentration.     

Asbestos-related lung cancer and mesothelioma in Japan

In Japan, crocidolite had been used for asbestos cement pipe and spraying, and amosite had been used for building board and spraying. These two types of asbestos had stopped to use in Japan in the late 1970s. An extreme increase in imported asbestos (all 3 commercial types) was observed between 1960 and 1974. In 1960, 77,000 tons of asbestos were imported, and reached the peak as 352,316 tons in 1974. This extreme rise of asbestos imports corresponds with the recent rapid increase in mortality of malignant pleural mesothelioma. Between 1995 and 1999, an estimated mean annual death from pleural mesothelioma was about 500. The annual number of compensated occupational respiratory cancers due to asbestos exposure has also been increasing. Up to the end of March 2000, 162 cases with malignant mesothelioma and 197 cases with lung cancer were compensated. As for lung cancer, epidemiological studies are scanty in Japan. Limited environmental data of the working places in asbestos textile factories suggests that heavy asbestos exposure in the past made deaths from respiratory diseases. Less asbestos exposure will enable exposed workers to survive enough to reach cancer age. Even now smoking rate among males in Japan are over 50%. So lung cancer deaths caused by the interaction between smoking and asbestos exposure will be continuing.     

The epidermiologic relationship between pleural mesothelioma and asbestos exposure.

This paper describes an investigation of 85 notifications of either probable or possible mesothelioma to the Finnish Cancer Registry from 1953 through 1969. The investigation covers characteristic epidemiologic features and the possibility of the mesothelioma being connected with occupational or other exposure to asbestos. The incidence rate of pleural mesothelioma was estimated at 1.1 per million per year. The male/female ratio was 1.3:1, which greatly differed fsrom that for malignant neoplasms of the bronchus or lung in Finland in 1960. The mean age at dealth from mesothelioma was over 7 years lower than that for bronchial carcinoma. The ratio of the crude incidence rates for the urban and rural populations was 4.2; the corresponding ratio for cases of carcinoma oopulations was 4.2; the corresponding ratio for cases of carcinoma of the bronchus or lung was 1.2 in Finland in 1960. THE LAST OCCUPATIONS OF THE 82 DECEASED PERSONS, OBTAINED FROM THE DEATH CERTIFICATES, WERE DIVIDIED INTO THREE CATEGORIES ACCORDING TO POSSIBLE ASBESTOS EXPOSURE. Exposure was present or probable in 9 (11.0) cases, 28 (34.2 %) had a possible exposure, and in 33 (40.2 %) cases exposure was absent or unlikely. The occupation of 12 (14.6) persons was unknown. Additional information of possible exposure history was obtained by interviewing the relatives of 10 mesothelioma patients. For half of the persons a definite, although in some cases trivial, exposure to asbestos could be ascertained. For the other five persons no exposure, either occupational, neighborhood or domestic, to asbestos could be traced. The residental distribution of the 85 persons with mesothelioma revealed no clustering of cases.     

Malignant pericardial mesotheliomas and asbestos exposure: A case report

Three cases of malignant pericardial mesotheliomas are presented with evidence of occupational asbestos exposure. Examination results are compared with findings from experimental and epidemiological research on biological effects of asbestos dust. There are sufficient indications that time-limited effects of asbestos dust established either by measurements or assessment of the amount of concentration after a latency of more than 20 years are apt to result in the development of mesotheliomas of the pleura and peritoneum and, moreover, the pericardium. It is suggested that malignant pericardial mesothelioma also be recognized as another form of occupational disease caused by asbestos dust.     

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.     

National epidemiologic surveillance systems of asbestos-related disease and the exposed workers register

INTRODUCTION: Italy was the main European producer of asbestos for most of the 20th century and raw asbestos imports wee also significant until the 1990's; there was a mean delay of about ten years in the pattern of asbestos consumption in Italy compared with the USA, Australia, UK and Scandinavian countries. METHODS: A national surveillance system (ReNaM) was implemented to identify cases of mesothelioma and investigate the modalities of asbestos exposure. A register of exposed workers and a database of companies presumably involved in the asbestos exposure problem was also developed. ReNaM has a regional structure and an operative centres (COR) have been established in 16 Italian regions. RESULTS: The ReNaM database currently contains more than 5,000 mesothelioma cases and for 3,500 of these exposure modalities have been defined. Cases of pleural mesothelioma represent 93% of the total but there were also 334 cases of peritoneal mesothelioma, 15 of the pericardium and 14 of the tunica vaginalis of the testicle. Cases with ascertained exposure are thus distributed: 67.4% occupational exposure (ascertained, probable, possible), 4.3% domestic, 4.2% environmental and 1.3% hobby-related exposure, totalling 77.2%; 22.8% had unlikely or unknown exposure. The latency period is very long: on average 43.6 years. The register of asbestos-exposed workers contains figures on exposed workers notified to ISPESL up to 2004 and refers to the exposure period 1993-2003. The data registered cover 160 firms and about 700 workers. CONCLUSIONS: A national, coordinated and uniform epidemiological surveillance system of cases of mesothelioma and the definition of asbestos exposure through active research is extremely important in identifying unexpected contaminating sources. The register of asbestos-exposed workers allows risk to be monitored and protection measures to be implemented.     

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.     

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.     

Malignant pleural mesothelioma in parts of Japan in relationship to asbestos exposure

Malignant pleural mesothelioma is induced by asbestos exposure. Many reports have described this situation in America and European countries, but a few have been published in Japan. In this study malignant pleural mesothelioma cases in hospitals located in an area facing the Seto Inland Sea were evaluated. A total of 106 patients were examined with 100 patients having had occupational exposure to asbestos and 6 patients without such histories of asbestos exposure. Ninety seven were male and 9 were female. Ages ranged from 41 to 87 yr with mean of 64.8+/-5.3 yr. Thirty seven cases showed epithelial type of tumor, 25 biphasic type and 15 showed sarcomatous. The remaining 23 cases had insufficient evidence for typing the tumor. The mean survival rate for all cases was 9.2+/-11.6 months. Fifty-one patients had occupational histories of shipyard work, 16 patients worked in asbestos cement piping, and the remainder were employed in miscellaneous jobs related asbestos exposure. The duration of asbestos exposure ranged up to 20 yr or longer with the mean of 17.2+/-8.9 yr and the average latent period for the occurrence of malignant pleural mesothelioma was more than 31 yr with the mean of 37.0+/-13.3 yr. Quantification of asbestos bodies in the lungs indicated a high concentration in most patients and the major types of asbestos fibers were crocidolite and amosite. Six cases appeared after exposure to chrysotile. These results indicated that ninety four percent of malignant pleural mesothelioma appeared due to the exposure to asbestos including crocidolite and amosite. The remainder may be blamed on exposure to chrysotile.     

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.     

The French National Mesothelioma Surveillance Program

Objectives

The French National Mesothelioma Surveillance Program (NMSP) was established in 1998 by the National Institute for Health Surveillance (InVS). Its objectives are to estimate the trends in mesothelioma incidence and the proportion attributable to occupational asbestos exposure, to help improve its pathology diagnosis, to assess its compensation as an occupational disease, and to contribute to research.

Methods

The NMSP records incident pleural tumours in 21 French districts that cover a population of approximately 16 million people (a quarter of the French population). A standardised procedure of pathological and clinical diagnosis ascertainment is used. Lifetime exposure to asbestos and to other factors (man made mineral fibres, ionising radiation, SV40 virus) is reconstructed, and a case‐control study was also conducted. The proportion of mesothelioma compensated as an occupational disease was assessed.

Results

Depending on the hypothesis, the estimated number of incident cases in 1998 ranged from 660 to 761 (women: 127 to 146; men: 533 to 615). Among men, the industries with the highest risks of mesothelioma are construction and ship repair, asbestos industry, and manufacture of metal construction materials; the occupations at highest risk are plumbers, pipe‐fitters, and sheet‐metal workers. The attributable risk fraction for occupational asbestos exposure in men was 83.2% (95% CI 76.8 to 89.6). The initial pathologist''s diagnosis was confirmed in 67% of cases, ruled out in 13%, and left uncertain in the others; for half of the latter, the clinical findings supported a mesothelioma diagnosis. In all, 62% applied for designation of an occupational disease, and 91% of these were receiving workers'' compensation.

Conclusions

The NMSP is a large scale epidemiological surveillance system with several original aspects, providing important information to improve the knowledge of malignant pleural mesothelioma, such as monitoring the evolution of its incidence, of high risk occupations and economic sectors, and improving pathology techniques.     

Asbestos-related mesothelioma: epidemiological evidence for asbestos as a promoter

A series of 144 cases of mesothelioma among asbestos workers indicated important divergences from the epidemiological pattern shown to exist for asbestos-related lung cancer. Consideration of exposure duration and intensity and the latent period between first exposure and death suggests that asbestos does not act as a complete carcinogen, but as a promoter. A threshold seems probable for both duration and intensity of exposure in the induction of mesothelioma. This threshold may, in part, be related to the passage of fibers from the lungs to the pleura or peritoneum, and would, in any case, be masked in lung cancer by the retention of asbestos in the lungs. Reported cases of mesothelioma in immediate family members indicate the existence of an additional factor in mesothelioma induction, acting earlier in life than the first asbestos exposure.     

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.     

Occupation and risk of malignant pleural mesothelioma: A case-control study in Spain

BACKGROUND: The association of mesothelioma and asbestos exposure is well known, but some data suggest that probably many people are still being exposed to asbestos without knowing it. METHODS: Between 1993 and 1996, 132 cases (77% males) of histologically confirmed malignant pleural mesothelioma and 257 controls, residents in two provinces of Spain (Barcelona and C?adiz), were interviewed. They were classified according to their probability and intensity of occupational asbestos exposure by a panel of industrial hygienists, based on a detailed occupational history. RESULTS: Age and sex-adjusted odds ratio (OR) for the highest probability of exposure to asbestos was 13.2 (95% confidence interval 6.4-27.3), and 27.1 (9. 28-79.3) for high intensity. A dose-response trend was observed for both, probability and intensity. Overall, 61% of cases and 42% of controls had ever worked in an occupation with risk of asbestos exposure, with an OR of 2.59 (1.60-4.22). In our population 62% of cases could be attributed to occupational asbestos exposure. CONCLUSIONS: A high risk of pleural mesothelioma due to occupational asbestos exposure is confirmed, but there is still a sizeable proportion for which no evidence of occupational exposure was found. Most of these cases could be due to other sources of asbestos exposure, mainly domestic or environmental.