An outbreak of pleural mesothelioma and chronic fibrosing pleurisy in the village of Karain/Urgüp in Anatolia

Peritoneal mesothelioma and malignant lymphoma in mice caused by fibrous zeolite

Dust from the village of Karain containing the fibrous zeolite erionite, talc, and physiological saline were tested by intraperitoneal injection in 486 Swiss albino mice. Malignant tumours were found in 84 (41 mesotheliomas, 31 lymphomas, 1 peripheral epidermoid carcinoma, and 11 lymphomas and mesotheliomas together) of the 321 animals which died spontaneously within nine to 32 months after injection of Karain dust (26.1%). Three mesotheliomas and no lymphomas were found among 24 animals injected in the same way with talc during the same time (12.5%). In 46 control animals injected with physiological saline three mesotheliomas and one lymphoma were seen (8.7%). Thus Karain dust appears to be a potent carcinogen, causing both mesotheliomas and malignant lymphomas.

Zeolite exposure and associated pneumoconiosis

Naturally occurring zeolite minerals are aluminum silicates widespread in the earth's crust. Several of these minerals have fibrous forms and have been implicated as a possible cause of benign and malignant diseases of the lung and pleura in Turkey. This report describes a patient, living in an area of Nevada rich in zeolites, who presented with idiopathic pleural thickening and pulmonary fibrosis associated with extensive pulmonary deposition of zeolites.

Erionite exposure and mesotheliomas in rats

Epidemiological and environmental surveys in the Cappadocian region of Turkey have linked the high incidence of pleural and peritoneal mesothelioma in the occupants of some villages with the zeolite fibres released from the locally occurring volcanic tuff. In view of the low ambient fibre concentrations and the extraordinary incidence of mesothelioma a study to test the hypothesis of high biological activity for the zeolite fibres was required. Experimental studies using both intrapleural inoculation and inhalation techniques have been undertaken with the erionite from this region and from Oregon in the United States. Additionally a non-fibrous zeolite from Japan and a synthetic non-fibrous zeolite of similar chemical composition to erionite have been included in the experiments. In these studies the samples from Oregon and Turkey produced a very high incidence of tumours. All the rats inoculated intrapleurally with Oregon erionite and almost all those inoculated with the Turkish fibre died with a mesothelioma. Inhalation of the Oregon erionite induced a similar effect. No other dusts we have investigated have produced this high incidence of tumours particularly following inhalation. These studies demonstrate that we now have a valuable new fibre for experimental study and a possible hazard to man in regions other then Turkey.

Lung response to particulates with emphasis on asbestos and other fibrous dusts

Many theories have been proposed to explain asbestosis and asbestos-related pulmonary disease. However, none of the theories give a completely plausible explanation for the pathogenesis. Recently, attention has been drawn to a theory that the fibrogenicity or carcinogenicity of fibrous dust particles is related to fiber diameter and length rather than to chemical properties. This theory may help partially elucidate the disease process but is still far from solving the enigma of pulmonary fibrosis or carcinogenesis. The theory cannot explain the absence of these pathological effects among fiberglass workers or experimental animals exposed by inhalation (even though mesotheliomas are induced by intrapleural implantation and fiber dimension-related fibrogenicity is demonstrated by intratracheal injection). Little information regarding the pulmonary response to manmade fibrous particles is available in animals following inhalation exposure. Attempts should be made to confirm the absence of adverse effects using animal inhalation experiments even though to this point there is no conclusive evidence that either lung cancer or pulmonary diseases can be produced among employees in manmade fiber industries. A new research trend seems concentrated on testing the durability of asbestos or manmade fibers. This is based on the concept that biological effects of fibrous particles are the result of relative durability and that particles which can be fragmented or shortened may be less pathogenic. In the last two decades, considerable understanding about pulmonary fibrosis and carcinogenesis of asbestos has been achieved by clinical and animal experiments. In vitro tests including cytotoxicity, hemolysis, immunology, and enzyme biochemistry have provided important information on the interrelationships among these various biological effects of asbestos.

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 induced by asbestos and zeolite in the mouse peritoneal cavity

The carcinogenicity of asbestos (amosite and chrysotile) and zeolite (fibrous erionite, mordenite, and synthetic zeolite 4A) were studied in the peritoneum of 586 BALB/C male mice after a single intraperitoneal or intraabdominal wall injection. As controls, 182 mice treated with and without saline solution were used. Both asbestos types and fibrous erionite frequently produced malignant peritoneal tumors after long latency; tumors developed in 93 of 394 animals (23.6%) treated with asbestos or fibrous erionite 7 months or more after administration. All of the induced peritoneal tumors were intimately associated with marked peritoneal fibrosis, in which asbestos or erionite fibers were regularly detected. Histopathologically, 83 (73 fibrous, 9 biphasic, and 1 epithelial) of 93 were consistent with malignant mesotheliomas. Other tumors consisted of 6 plasmacytomas, 1 histiocytoma, 1 liposarcoma, 1 osteosarcoma, and 1 adenocarcinoma of the pancreas. Two of the cases of mesotheliomas were associated with plasmacytoma. In many instances, the primary site of the mesotheliomas seemed to be multiple, the favorite sites being the omentum, mesentery, serosae of the gastrointestinal and genital organs, the diaphragm, the capsule of the liver and spleen, and the abdominal wall peritoneum. In these cases, asbestos or erionite-tissue burden followed by fibrosis was frequently observed. In addition to the 93 peritoneal tumors, 3 extraperitoneal tumors (1 fibrosarcoma and 2 rhabdomyosarcomas) were induced by amosite which was probably accidentally injected into the extraperitoneal connective tissue and the striated muscle tissue of the abdominal wall, respectively. These three tumors were also intimately associated with focal fibrosis in which amosite fibers were detected. Among the three different types of zeolite, only fibrous erionite showed striking carcinogenicity and marked fibrogenicity. The erionite-induced mesotheliomas were similar to those induced by asbestos in exhibiting long latency, in gross appearance, in histology, and in close association with fibrosis. Long-term persistence of asbestos or fibrous erionite around progenitor cells of the induced tumors and the consequent fibrosis seemed to be an important precondition of the malignant transformation of the progenitor cells.

Non-asbestos-related malignant mesothelioma. A review

Malignant mesothelioma is an uncommon, but increasingly important, neoplasm. The existing English-language medical literature concerning non-asbestos-related malignant mesotheliomas was reviewed for evidence of other agents associated with the induction of malignant mesothelioma. Both animal and human data were reviewed. In most reviews of malignant mesothelioma, there are a significant proportion of cases without documented asbestos exposure (range, 0% to 87%). Furthermore, there are several fairly well-documented agents other than asbestos that induce malignant mesothelioma in animals, and strong evidence exists that such is the case in man. In reviews of malignant mesothelioma, the percentage of cases with asbestos exposure varies, but a significant number are apparently not asbestos related. It is believed that sufficient evidence exists to suggest that non-asbestos agents can induce malignant mesotheliomas in man, and additional epidemiologic studies in this area are needed.

Ferruginous bodies in sputum as an indication of exposure to airborne mineral fibers in the mesothelioma villages of Cappadocia

The counts of ferruginous bodies (pulmonary-coated mineral fibers) in sputum samples from inhabitants in each of the two agricultural villages of Karain and Tusköy (Cappadocia, central Turkey) increased with subjects' age, whereas 94% of samples collected in the neighboring villages were free of ferruginous body. These findings are consistent with the previous hypothesis that the very high frequency of mesothelioma in Karain and Tusköy was related to exposure to airborne mineral fibers of natural origin.

Effects of nonfibrous minerals in the V79-4 cytotoxicity test

The use of the V79-4 system as a primary screen for fiber carcinogenicity is dependent on the observed correlation between cytotoxicity of the test material in the system and mesothelioma following intrapleural injection in animals. This correlation has been established for relatively pure samples of fibrous minerals. The wider application of the system as a screen for industrial dusts may depend on the ability of the system to show an unequivocal response to small yet significant percentages of fibrous dust in the presence of a large excess of nonfibrous material. Some materials tested, including platy minerals, show a response in the test which, while clearly less than that from UICC asbestos samples, could be construed as a positive result. Some, though not all, of these minerals show a nonlinear dose response in the test. This anomalous dose response may aid in the identification of some false positive results but the variety of responses to nonfibrous minerals places a limit on the predictive value of the test mixtures. Results obtained from mixtures of "standard" dust samples suggest this limit is reached at or above 10% fibrous content. Such levels would be significant in terms of human exposure. Extension of the concentration range tested does not improve the predictive value of the test.

Natural fibrous zeolites and their carcinogenicity-a review

More than 50 cases of pleural mesothelioma have been reported during the period 1974-1978 in a relatively small area of Turkey, centered in and around the villages of Karain and Tuzköy, in the province of Cappadocia. The area of Karain and Tuzköy is covered with volcanic tuffs, in which asbestos, glass and zeolite fibers were detected. The inhaled dusts of these fibrous materials might be the cause of the high mesothelioma rate. The most important publications on this problem are reviewed and the results of our own examinations are discussed.

Mineralogical analysis of bronchoalveolar lavage fluid as an aid to diagnosis of "imported" pleural asbestosis

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Radiological study of pleural changes in relation to mesothelioma in Turkey

In some villages in central Turkey pleural changes occur as a result of environmental exposure to mineral fibres. In most cases the fibre is asbestos but in some cases the non-asbestos fibre erionite, a zeolite, is responsible. The incidence of malignant mesothelioma is much higher in "erionite villages" than in "asbestos villages" despite similar frequencies of pleural changes. In this study chest radiographs from 466 people from asbestos villages, 549 from erionite villages, and 382 controls were compared. The frequency of pleural calcification was about the same in the two groups of villages studied, but the minor fissures were visible to a greater degree in erionite cases. In people from erionite villages "atypical" pleural calcification, due to calcification of the visceral rather than the parietal pleura, was more common. These differences may indicate that the fibres have different lengths and diameters.

Wollastonite exposure and lung fibrosis

Wollastonite is a naturally occurring acicular or fibrous metasilicate used in ceramics and as a substitute for asbestos in some applications. Wollastonite fibers are rather similar in form, length, and diameter to amphibole asbestos fibers but mineralogically they are different. Dust measurements in both the Finnish limestone--wollastonite quarry and in the flotation plant yielded high concentrations of both total dust and respirable fibers in some operational stages. The clinical study comprised a total of 46 men who had been exposed to wollastonite at the quarry for at least 10 years. Three of the fifteen nonsmokers showed chronic bronchitis. Radiographs revealed slight lung fibrosis among fourteen men, and slight bilateral pleural thickening among thirteen men. Their sputum specimens were normal. Spirometry and nitrogen single breath tests indicated the possibility of small airways disease.

Characterization of zeolite fiber sizes using scanning electron microscopy

A synthetic zeolite and four natural zeolites from the western United States were examined for fibers using a scanning electron microscope. The distributions of fiber sizes were compared to distributions of fiber sizes of erionite and fibrous glass to determine if the fiber sizes were similar to those associated with mesothelioma in humans and animals. Fibers were abundant in two samples of natural erionite, rare in two samples of natural mordenite, and not present in the sample of synthetic mordenite. Although the majority of the erionite fibers were short (less than 8 mu long) and thicker than the tumorigenic erionite (greater than 0.25 mu wide), 6% and 11% of the fibers corresponded to fiber size categories of fibrous glass that have correlated with pleural mesothelioma production in rats. Even a single species of zeolite (erionite) is not uniform in its distribution of fiber sizes. On the basis of fiber size, these natural zeolites should be evaluated because of their potential carcinogenic risk.

Environmental fiber-induced pleuro-pulmonary diseases in an Anatolian village: an epidemiologic study

This study was designed to determine the prevalence of pleural mesothelioma and other malignancies in the Anatolian village of Tuzköy, where neither asbestos nor any environmental carcinogen has been detected. Another village (Kizilköy) located 12 km from Tuzköy was selected as a control. Three hundred twelve subjects from Tuzköy who were at least 25 yr of age and 95 subjects from Kizilköy were studied. Analysis of X-rays of the Tuzköy group revealed that subjects had calcified pleural plaques (17%), pleural thickening (10.5%), obscured costophrenic angles (15%), and diffuse interstitial pulmonary fibrosis (12.1%). Sixty-seven deaths were records in Tuzköy during the previous 3 yr, 41 of which resulted from malignant diseases. There were no X-ray abnormalities or deaths resulting from malignancies in the control group. Because of the high incidence of mesothelioma and lung cancer which usually results from asbestos exposure, the presence of asbestos in Tuzköy was investigated, but none was detected in spite to Tuzköy's volcanic location. Nevertheless, zeolite, an asbestiform mineral, was detected in the stones of buildings and in the village soil, as well as in the lung and pleura of the patients during biopsy. Thus, this mineral was considered to be responsible for the fiber-induced pleuro-pulmonary diseases in Tuzköy. No zeolite was found in the soil and stones of the control village.

Endemic pleural disease associated with exposure to mixed fibrous dust in Turkey

Pleural mesothelioma, lung cancer, pleural calcification and fibrosis, and interstitial parenchymal fibrosis have been observed among inhabitants of several villages in south-central Turkey. Earlier reports have stated that environmental and lung tissue samples from this area contained the fibrous zeolite mineral erionite, and this mineral has generally been assumed to be the agent responsible for these endemic pathological conditions in the absence of asbestos outcroppings and usage. Several different kinds of asbestos minerals in addition to erionite have now been found in environmental samples taken from the villages where these diseases occur. The lung tissues of mesothelioma patients from these villages contain both fibrous zeolites and asbestos minerals.

Non-malignant asbestos pleural disease

During a 10-year period (1970-79) all patients in Uppsala County found to have pleural changes related to asbestos exposure were followed. The lesions could be divided into four types: parietal pleural plaques, exudative pleurisy, thickening of the visceral pleura, and progressive pleural fibrosis. There were 891 cases. The most common type was parietal plaques, which was seen in 827 patients, some of whom later developed other changes. In 22 types exudation was proven radiologically, and in 84 more cases obliteration of the costo-phrenic angle was seen. The exudations almost all had a benign course, despite sometimes fairly large and bloody effusions. They were practically all symptom-free, being a surprise finding on chest radiography. Thickening of the visceral pleura can only be seen radiologically in the fissures and occurred in a few cases in addition to other changes. In a small group of more heavily exposed individuals, a progressive pleural fibrosis developed, sometimes after an initial effusion.

Malignant mesothelioma and radiological chest abnormalities in two villages in Central Turkey. An epidemiological and environmental investigation

A comparative epidemiological and environmental study in two neighbouring villages, Karain and Karlin, in Central Turkey showed an excess adult mortality, shortening of life expectancy, and an excess of pleural radiological abnormalities in Karain. This supports an earlier report of an endemic of pleural mesothelioma in the village. Concentrations of airborne respirable fibres were uniformly very low in Karlik and higher in some of the air samples from Karain, the fibres being similar in composition to those of erionite-a mineral of the zeolite family and the major contributor to the Karain clouds. This is compatible with the hypothesis of a causal association between endemic mesothelioma and inhalation of erionite fibres, but the fibre concentrations in all samples are so low as to leave in question the aetiological role of erionite. In addition to their local importance these results may have relevance for the wider scientific and public-health issue of long-term inhalation of mineral fibres at low concentrations.

Asbestos and metals as carcinogens

Increased incidences of lung carcinoma and pleural mesothelioma in humans exposed to asbestos have been irrefutably established. Different forms of asbestos may have different tumorigenic activities, depending on surface properties, durability, and size of the fibers. A number of metals, such as nickel, chromium, and arsenic, are known to be carcinogenic to humans; for beryllium and cadmium the epidemiologic evidence is less extensive. All these metals also induce genetic toxicity in vitro. For chromium the molecular mechanism of metal tumorigenesis has been extensively investigated; the hexavalent form is generally a much more potent mutagen than is chromium (III). Solubility seems to be necessary for the genotoxicity of nickel. At present it cannot be concluded that all metals act by the same carcinogenic mechanism, even though direct modification of DNA seems to be the common experimental finding.

Pleural calcification, pleural mesotheliomas, and bronchial cancers caused by tremolite dust

Around the town of Cermik in south-east Turkey there are many deposits of asbestiform minerals, some of which are used to make whitewash or stucco. A sample of 7000 of the population revealed 461 (6.5%) with pleural thickening and calcification, of whom 103 (1.47% of the total) had evidence of interstitial pulmonary fibrosis. Forty-one patients with respiratory cancer were admitted to the Diyarbakir Chest Hospital from around Cermik and from a comparable area of equal population (but without asbestos deposits) in 1977-8. Of these 23 were mesotheliomas, 22 coming from around Cermik. In addition, 11 of the 18 primary bronchial cancers came from around Cermik. A similar excess of mesothelioma and bronchial cancer had been admitted from the Cermik area in previous years. The whitewash or stucco material has been shown to contain fibrous tremolite and non-fibrous antigorite/lizardite, chlorite, and talc. A lung biopsy of a patient from Cermik contained large numbers of tremolite fibres, both free and forming asbestos bodies. There were only occasional chrysotile fibres.

The in vitro activities of pathogenic mineral dusts

The pathogenic properties of mineral dusts are described and the range of relatively new materials requiring study is indicated. Since the animal facilities available for testing these potential hazards are limiting the authors describe an in vitro screen being used to select interesting dusts for in vivo experimentation, the type of results obtained are illustrated with some data for dusts derived from the industrially important Zeolites.

French mesothelioma register

A total of 197 definite cases of mesothelioma (mainly of the pleura) have been reported by pathologists to the French Mesothelioma Register for the period 1965--78. A moderate linear increase in the annual incidence of mesothelioma cases since 1965 was noted. In men and women over the ages of 47 and 41 years, respectively, the annual death rate was higher in those with mesothelioma than in those of the general population. The proportions of mesothelioma patients who had experienced occupational, para-occupational, and unknown asbestos exposures were 77%, 3%, and 20% respectively. The number of cases reported to the register is obviously an underestimate of the true number of mesothelima cases in France, because such cases are not reported to the register systematically. Mesothelioma registers cannot provide information about dose-response relationships; however, with good management of the register, such relationships could be obtained, since a good assessment of dose can be accomplished by biologic monitoring.