The present review summarizes the results of several follow-up studies assessing an asbestos product manufacturing plant in Chongqing, China, and discusses three controversial issues related to the carcinogenicity of asbestos. The first issue is the amphibole hypothesis, which asserts that the carcinogenicity of asbestos is limited to amphiboles, such as crocidolite, but not serpentines, such as chrysotile. However, considering the possible multiple component of asbestos carcinogenicity in the presence of tobacco smoke or other carcinogens, chrysotile cannot be regarded as non-carcinogenic. Additionally, in a practical sense, it is not possible to assume "pure" chrysotile due to its ubiquitous contamination with tremolite, which is a type of amphibole. Thus, as the International Agency for Research on Cancer (IARC) assessed, all forms of asbestos including chrysotile should be regarded carcinogenic to humans (Group 1). The second issue is the chrysotile/tremolite paradox, which is a phenomenon involving predominant levels of tremolite in the lung tissues of individuals who worked in locations with negligible levels of tremolite due to the exclusive use of chrysotile. Four possible mechanisms to explain this paradox have been proposed but this phenomenon does not support the claim that amphibole is inert. The final issue discussed is the textile mystery, i.e., the higher incidence of cancer in asbestos textile plants compared to asbestos mines where the same asbestos was produced and the exposure levels were comparable. This phenomenon was first reported in North America followed by UK and then in the present observations from China. Previously, levels of fiber exposure were calculated using a universal converting coefficient to estimate the mass concentration versus fiber concentration. However, parallel measurements of fiber and mass concentrations in the workplace and exposed air indicated that there are wide variations in the fiber/mass ratio, which unjustifies the universal conversion. It is possible that contamination by airborne non-fibrous particles in mines with mass fiber conversion led to the overestimation of fiber concentrations and resulted in the textile mystery. Although the use and manufacturing of asbestos has been banned in Japan, more than 10 million tons of asbestos had been imported and the majority remains in existing buildings. Thus, efforts to control asbestos exposure should be continued.
Asbestos ; classification ; toxicity ; Asbestos, Amphibole ; toxicity ; Asbestos, Serpentine ; toxicity ; Carcinogens ; China ; Follow-Up Studies ; Humans ; Lung Neoplasms ; chemically induced ; epidemiology ; Manufacturing and Industrial Facilities ; statistics & numerical data ; Mining ; statistics & numerical data ; Occupational Diseases ; epidemiology ; Occupational Exposure ; adverse effects ; Textiles ; Tobacco Smoking ; epidemiology

OBJECTIVE: This study evaluated the CT characteristics of pleural plaques in asbestos-exposed individuals and compared occupational versus environmental exposure groups. MATERIALS AND METHODS: This study enrolled 181 subjects with occupational exposure and 98 with environmental exposure from chrysotile asbestos mines, who had pleural plaques confirmed by a chest CT. The CT scans were analyzed for morphological characteristics, the number and distribution of pleural plaques and combined pulmonary fibrosis. Furthermore, the CT findings were compared between the occupational and environmental exposure groups. RESULTS: Concerning the 279 subjects, the pleural plaques were single in 2.2% and unilateral in 3.6%, and showed variable widths (range, 1-20 mm; mean, 5.4 +/- 2.7 mm) and lengths (5-310 mm; 72.6 +/- 54.8 mm). The chest wall was the most commonly involved (98.6%), with an upper predominance on the ventral side (upper, 77.8% vs. lower, 55.9%, p < 0.001) and a lower predominance on the dorsal side (upper, 74.9% vs. lower, 91.8%, p = 0.02). Diaphragmatic involvement (78.1%) showed a right-side predominance (right, 73.8% vs. left, 55.6%, p < 0.001), whereas mediastinal plaques (42.7%) were more frequent on the left (right, 17.6% vs. left, 39.4%, p < 0.001). The extent and maximum length of plaques, and presence and severity of combined asbestosis, were significantly higher in the occupational exposure group (p < 0.05). CONCLUSION: Pleural plaques in asbestos-exposed individuals are variable in number and size; and show a predominant distribution in the upper ventral and lower dorsal chest walls, right diaphragm, and left mediastinum. Asbestos mine workers have a higher extent of plaques and pulmonary fibrosis versus environmentally exposed individuals.
Adult ; Aged ; Aged, 80 and over ; Asbestos, Serpentine/*toxicity ; Asbestosis/*etiology/radiography ; Asian Continental Ancestry Group ; Environmental Pollutants/toxicity ; Female ; Humans ; Male ; Middle Aged ; Mining ; Occupational Exposure ; Pleural Diseases/*etiology/radiography ; Republic of Korea ; Tomography, X-Ray Computed

OBJECTIVETo analyze asbestos exposure level between 1984 and 2010 in a district of malignant mesothelioma with clustering incidence in Zhejiang Province, in order to improve the recognizing and early diagnosis of malignant mesothelioma, protect the health of workers.

METHODSMonitoring data of total asbestos dust concentration in the air of workplace from 1984 to 2010 in asbestos textile enterprises, family hand spinning operation, brake production, and asbestos board production in Zhejiang Province were collected in the local CDC. A total of 766 TWA copies of mass concentration were collected, and 1233 copies of MAC data. Asbestos mass concentration and fibre counting concentration of 29 points of family hand spinning operation were parallel determinated in the same time and the same sampling point. Raw asesbtos materials and dust composition of local asbestos processing corporations were collected and analyzed using X-ray diffraction method.

RESULTSRaw materials of asbestos used between 1984 and 2010 in this area were chrysotile from Sichuan, Qinghai, Xinjiang, Russia, Zimbabwe, and some were mixed with SiO2, CaCO3 and other impurities. Raw materials used in asbestos board production were blue asbestos. Dust concentration between 1960s and 1980s in asbestos processing plants far exceeded the national standard. After then the dust concentration decreased significantly, but still higher than the national standard. 95.2% of air dust concentrations in the workplaces of asbestos factories exceeded the standard, and dust concentrations of workplaces of raw material, spinning, weaving, carding and labor insurance were above 90% in which carding work had the highest median concentration. 37.9% of dust mass concentrations in hand spinning work exceeded the standard where textile machinery side had the highest value. Beating job in asbestos board manufacturing and grinding job in brake production had higher concentrations.

CONCLUSIONSMost of production technologies in asbestos processing industry exceed the standard level, indicating that the workers were at risk for malignant mesothelioma and other asbestos related diseases, which should draw high attention.

Asbestos ; analysis ; Asbestos, Crocidolite ; analysis ; Asbestos, Serpentine ; analysis ; China ; epidemiology ; Dust ; analysis ; Humans ; Lung Neoplasms ; epidemiology ; Mesothelioma ; epidemiology ; Occupational Diseases ; epidemiology ; Silicon Dioxide ; analysis ; Workplace

OBJECTIVES: Asbestos is a carcinogenic mineral substance formerly used widely in the construction industry, all forms of which, except for chrysotile asbestos, have been banned in the Philippines. This article aims to propose policy alternatives to reduce the health and economic effects of continued asbestos use in the country.
METHODS: Records of asbestos-related diseases, and asbestos industry-related data in the country were consolidated. The impact of continued asbestos use on the national economy were estimated incorporating natural mortality, regulations of the Department of Labor and Employment (DOLE), and concepts of multiplier effect and net present value. Round table discussions validated data and generated policy recommendations.
RESULTS: Filipinos directly and indirectly exposed to asbestos-containing materials (ACMs) are 5,289 and 30,000, respectively. The contributions of these groups to the national economy were estimated at PhP 1.08 Billion annually for workers directly exposed to ACMs and PhP 6.83 Billion annually for workers indirectly exposed. Two policy options--adjustment of threshold limit values, and a total ban--are presented.
CONCLUSION: A total ban on all forms of asbestos is shown to be the more cost-effective policy option for the country. It is recommended that government agencies, stakeholders in the asbestos industry, and the general public be involved in strategies for improving surveillance on asbestos exposure, increasing public awareness, and promoting the use of asbestos alternatives.

Asbestos, Serpentine ; Threshold Limit Values ; Construction Industry ; Philippines ; Asbestos ; Carcinogens ; Policy ; Government Agencies ; Employment

OBJECTIVETo clarify the dose-response relationship between asbestos dust exposure and lung cancer incidence in chrysotile asbestos miners by fixed cohort study and to investigate the incidence rates of lung cancer in exposure to different concentrations of asbestos dust.

METHODSA retrospective cohort study was conducted in 1932 asbestos miners who registered from January 1, 1981 to December 31, 1988, had worked for at least 1 year, and had no obvious cardiopulmonary diseases; the cohort study began in July 2009 and covered a time span of 29 years (1981 - 2009). The personal information, occupational history, disease history, and health data of these miners were recorded, and the monitoring data on dust concentrations in the mine over the years were collected. The dose-response relationship between asbestos dust concentration and lung cancer incidence was established by the method of life table; a regression equation was fitted to predict the excess incidence rates of lung cancer under the conditions of different working years and dust concentrations.

RESULTSA significant dose-response relationship was observed between cumulative exposure (Ce) and cumulative probability (Px) of lung cancer incidence, and the smokers hada higher Px than nonsmokers. When Ce was less than 2000 mg/m(3)·each year, Px reached 6.58/10000; when Ce was not less than 2000 mg/m(3)·and less than 3000 mg/m(3)·each year, Px reached 91.72/10000; when Ce was more than 5000 mg/m(3)·each year, Px was as high as 141.02/10000. The three models were fitted to obtain the optimal regression equation: Px = -0.0004Ce(2) + 0.0052Ce - 0.0011 (r(2) = 0.9387). In the workshop of asbestos mine in this study, the average dust concentration was 85 times higher than the limit in 2009, so the excess incidence rate of lung cancer was 112.598/10000 if the miners worked under this condition for 40 years, according to the equation.

CONCLUSIONThere is a significant dose-response relationship between cumulative asbestos exposure and lung cancer incidence in chrysotile asbestos miners. The risk for lung cancer rises as asbestos exposure increases.

Asbestos, Serpentine ; toxicity ; Dust ; Female ; Humans ; Lung Neoplasms ; etiology ; Male ; Mining ; Occupational Exposure ; Retrospective Studies

OBJECTIVETo study the cytotoxicity induced by chrysotile asbestos (CA), rock wool (RW) and wollastonite (WS).

METHODSV79 cells were divided into 4 groups. i.e. CA group, WS group, RW group and control group (200 microl PBS). The exposure concentration of dusts was 100 mg/L, The cell viability was detected by MTT and lactate dehydrogenase (LDH) activity assays. The technique of scanning electron microscopy was used to examine the change of V79 cells.

RESULTSSiO2 was main constituent for 3 kinds of dusts. In MTT assay, the cell viability of RW and WS groups was 64.8% and 65.7%, respectively, which were significantly higher than that (54.5%) of CA group (P < 0.01). In LDH assay, the LDH activity of RW and WS groups [(15.7 +/- 50.9), (12.3 +/- 3.7) U/L, respectively] was significantly lower than that [(20.2 +/- 0.9) U/L] of CA group (P < 0.05). In scanning electron microscopy examination, it was found that the two ends of V79 cells in CA group contained a great deal of fibers remaining bodies, but the V79 cell appearance in RW and WS groups was normal.

CONCLUSIONThe cytotoxicity induced by RW and WS is significantly lower than that induced by CA for V79 cell.

Animals ; Asbestos, Serpentine ; toxicity ; Calcium Compounds ; toxicity ; Cell Line ; drug effects ; Cricetinae ; Cytotoxins ; toxicity ; Lactate Dehydrogenases ; metabolism ; Mineral Fibers ; toxicity ; Silicates ; toxicity

OBJECTIVETo investigate the apoptosis rate and the reactive oxygen species (ROS) level induced by chrysotile fibers in BEAS-2B cells and the blockage effect of free radical scavengers on the induction of chrysotile fibers.

METHODSThe cell survival rate, the morphological variation of BEAS-2B cells, the apoptosis rate, the expression levels of gene caspase-3 and the ROS generation level were measured by using trypan blue phagocytosis, hematoxylin and eosin staining, oligonucleosomal DNA fragmentation assay, FCM, RT-PCR and fluorescent probe DCFH-DA in the suspension (0, 5, 10, 20, 100 and 200 microg/cm(2)) and the filtrate (0, 100, 200, 400, 800 and 1600 microg/ml) of chrysotile fibers. Addition of free radical scavengers such as catalase, dimethyl sulfoxide and mannitol prevented the radical generation and gene expression.

RESULTSSurvival rates of BEAS2B cells treated by the suspension (0, 5 and 10 microg/cm(2)) and the filtrate (0, 100 and 200 microg/ml) of chrysotile fibers for 24 hours were above 90%. The apoptotic rates of BEAS-2B were increased with the concentration of suspension and filtrate from chrysotile fibers (P < 0.05). Otherwise, caspase-3 mRNA and ROS were stimulated by chrysotile fibers. Free radical scavengers such as CAT, DMSO and mannitol could reduce these stimulations. The ROS blocking rate of suspension of chrysotile fibers was 23.7%, 21.6% and 11.2% respectively, and that of filtrate was 37.9%, 40.3% and 10.6% respectively.

CONCLUSIONApoptosis is induced in BEAS-2B cells exposed to chrysotile fibers suspension and filtrate. Generation of ROS plays an important role in chrysotile fibers-induced BEAS-2B cell apoptosis.

Apoptosis ; drug effects ; Asbestos, Serpentine ; toxicity ; Cell Line ; Drug Antagonism ; Epithelial Cells ; drug effects ; metabolism ; pathology ; Free Radical Scavengers ; pharmacology ; Humans ; Oxidative Stress ; Reactive Oxygen Species ; metabolism

BACKGROUND: Foundry workers are known to be exposed to silica and have an increased risk of silicosis. There are also reports that state these foundry workers were associated with asbestos-related change in the X-ray results of the lungs. This report discusses a case of localized asbestosis developed in a foundry worker who worked in 12 Korean foundries. CASE REPORT: A 49-year-old man who worked at molding and melting for 30 years, presented with sore throat, cough and yellow sputum for 1 month. From physical and clinical examination, pulmonary tuberculosis was highly suspicious; therefore, he was medicated for 6 months. After tuberculosis medication, the radiological finding was reactivation of tuberculosis, and an asbestos body was detected at a transbronchial lung biopsy. During an operation, operators found multiple palpable masses and bullae localized in the right upper lobe (RUL) and performed right upper lobectomy and right middle lobe wedge resection. Using hematoxylin-eosin stain and iron stain, we could detect asbestos bodies by light microscopy. We analyzed the asbestos fiber burden in dry lung tissue by transmission electron microscopy with energy dispersive X-ray spectrometer (TEM-EDX). The fiber type was chrysotile and the fiber burden was 23.26x106 fiber/g dry lung. DISCUSSION: This case study of a foundry worker with localized asbestosis is uncommon in Korea. We found an occupational relationship between the foundry worker and localized asbestosis through various investigative techniques such as measurements taken at his working environment, clinical, radiological and pathological examination of the foundry worker and mineralogical examination of the asbestos fiber.
Asbestos ; Asbestos, Serpentine ; Asbestosis ; Biopsy ; Blister ; Cough ; Freezing ; Fungi ; Humans ; Investigative Techniques ; Iron ; Korea ; Light ; Lung ; Microscopy ; Microscopy, Electron, Transmission ; Middle Aged ; Pharyngitis ; Silicon Dioxide ; Silicosis ; Sputum ; Tuberculosis ; Tuberculosis, Pulmonary

BACKGROUND: Foundry workers are known to be exposed to silica and have an increased risk of silicosis. There are also reports that state these foundry workers were associated with asbestos-related change in the X-ray results of the lungs. This report discusses a case of localized asbestosis developed in a foundry worker who worked in 12 Korean foundries. CASE REPORT: A 49-year-old man who worked at molding and melting for 30 years, presented with sore throat, cough and yellow sputum for 1 month. From physical and clinical examination, pulmonary tuberculosis was highly suspicious; therefore, he was medicated for 6 months. After tuberculosis medication, the radiological finding was reactivation of tuberculosis, and an asbestos body was detected at a transbronchial lung biopsy. During an operation, operators found multiple palpable masses and bullae localized in the right upper lobe (RUL) and performed right upper lobectomy and right middle lobe wedge resection. Using hematoxylin-eosin stain and iron stain, we could detect asbestos bodies by light microscopy. We analyzed the asbestos fiber burden in dry lung tissue by transmission electron microscopy with energy dispersive X-ray spectrometer (TEM-EDX). The fiber type was chrysotile and the fiber burden was 23.26x106 fiber/g dry lung. DISCUSSION: This case study of a foundry worker with localized asbestosis is uncommon in Korea. We found an occupational relationship between the foundry worker and localized asbestosis through various investigative techniques such as measurements taken at his working environment, clinical, radiological and pathological examination of the foundry worker and mineralogical examination of the asbestos fiber.
Asbestos ; Asbestos, Serpentine ; Asbestosis ; Biopsy ; Blister ; Cough ; Freezing ; Fungi ; Humans ; Investigative Techniques ; Iron ; Korea ; Light ; Lung ; Microscopy ; Microscopy, Electron, Transmission ; Middle Aged ; Pharyngitis ; Silicon Dioxide ; Silicosis ; Sputum ; Tuberculosis ; Tuberculosis, Pulmonary

Asbestos is a fibrous silicate that was widely used because of its heat resistance properties. Asbestos exposure affects workers involved in mining or processing asbestos or those involved in the use of asbestos in the shipbuilding, construction, and textile- and insulation-manufacturing industries. There are three commonly available types of asbestos; chrysotile (white asbestos), amosite (brown asbestos), and crocidolite (blue asbestos). All three have been associated with cancerous and non-cancerous lung disease. Asbestos-related diseases includes benign pleural effusion, pleural plaques, diffuse pleural thickening (a non-malignant disease affecting the lung lining), rounded atelectasis, asbestosis (a scarring of the lung tissue caused by asbestos), mesothelioma and lung cancer. Mesothelioma is a malignant pleural or peritoneal tumor that rarely occurs in patients who have not been exposed to asbestos. The latency period of most asbestos-related disease is 10 years or longer, asbestos-related disease remains an important public health issue. The clinical diagnosis of asbestos related diseases should be based on a detailed interview of the patient and occupational data on asbestos exposure, signs and symptoms, radiological and lung physiological findings and selected cytological, histological and other laboratory studies. Radiological imaging plays a pivotal role in the diagnosis and management of asbestos-related disease.
Asbestos ; Asbestos, Amosite ; Asbestos, Crocidolite ; Asbestos, Serpentine ; Asbestosis ; Cicatrix ; Compensation and Redress ; Hot Temperature ; Humans ; Latency Period (Psychology) ; Lung ; Lung Diseases ; Lung Neoplasms ; Mesothelioma ; Mining ; Pleural Effusion ; Public Health ; Pulmonary Atelectasis ; Silicates ; Workers' Compensation