The prevalence of pleural plaques and/or pulmonary changes among construction workers in Okayama, Japan

BACKGROUND: Since asbestos has been widely used in Japanese building materials since 1960s, a large number of Japanese construction workers may be exposed to asbestos occupationally. METHODS: Among 2951 construction workers in Okayama, Japan, the prevalence of asbestos-induced pleural or pulmonary changes was examined by screening chest x-rays; these findings were confirmed by computed tomography (CT) scanning of the chest. RESULTS: Among 2951 construction workers, 168 (5.7%) were found to have significant findings for pleural plaque or pulmonary changes on chest x-ray. Seventy-four had both pleural plaque and asbestosis, 85 pleural plaques alone, and 9 asbestosis alone. In 11 subjects, pleural plaques were suggested by chest x-ray, but neither pleural plaque nor asbestosis was demonstrated by chest CT. Honeycombing as one of the characteristic findings of asbestosis was found in 29 subjects. Others showed subpleural spots or curvilinear shadow, which suggested the early stage of asbestosis. The occupations of these workers were carpenters (64), plasterers (27), and concrete board cutters (14). About 30% of the workers with these findings were aware that they were handling asbestos in activities such as installation of asbestos boards, and/or asbestos spraying. CONCLUSIONS: As the incidence of malignant mesothelioma and primary lung cancer associated with asbestos exposure are high, screening by chest CT is necessary for detecting asbestos-induced pulmonary and/or pleural lesions. Education for protection such as telling about the presence of asbestos in building materials is also necessary.     

Ventilatory decrements in former asbestos cement workers: a four year follow up

A four year follow up of the ventilatory function in former asbestos cement workers has been performed to determine whether any further decrease occurred after cessation of exposure. Seventy five of 125 subjects were eligible for re-examination and were compared with local referents. None showed signs of asbestosis but 32% had pleural plaques at the renewed examination. Cumulative asbestos exposure calculated as fibre x years had been estimated individually in the original examination. After adjustment for age, height, tracheal area, and smoking category the FVC and FEV1 for all exposed subjects were on average 7% v 6% less than predicted from the referents and twice as much for the subjects with the highest exposure. The four year declines in FVC and FEV1 were larger than in the referents, significantly so for FEV1. There were no significant correlations between pleural plaque and ventilatory function after adjustment for exposure. Thus the age adjusted reduction in ventilatory function had progressed during the follow up period despite the cessation of exposure and the lack of radiological signs of asbestosis.     

Ventilatory decrements in former asbestos cement workers: a four year follow up.

A four year follow up of the ventilatory function in former asbestos cement workers has been performed to determine whether any further decrease occurred after cessation of exposure. Seventy five of 125 subjects were eligible for re-examination and were compared with local referents. None showed signs of asbestosis but 32% had pleural plaques at the renewed examination. Cumulative asbestos exposure calculated as fibre x years had been estimated individually in the original examination. After adjustment for age, height, tracheal area, and smoking category the FVC and FEV1 for all exposed subjects were on average 7% v 6% less than predicted from the referents and twice as much for the subjects with the highest exposure. The four year declines in FVC and FEV1 were larger than in the referents, significantly so for FEV1. There were no significant correlations between pleural plaque and ventilatory function after adjustment for exposure. Thus the age adjusted reduction in ventilatory function had progressed during the follow up period despite the cessation of exposure and the lack of radiological signs of asbestosis.     

Malignant mesothelioma from neighborhood exposure to anthophyllite asbestos

BACKGROUND: Anthophyllite asbestos has been reported to cause asbestosis, lung cancer, mesothelioma, and pleural plaques in occupationally exposed workers. Anthophyllite has also been associated with pleural plaques in Finland and Japan among those who live near mines and mills and have neighborhood or environmental exposure. METHODS: We evaluated a 38-year-old patient with pleural mesothelioma who lived, attended school, and delivered newspapers near a manufacturing facility that used exclusively anthophyllite asbestos fiber from ages 8-17 years. He had no work exposure to asbestos. RESULTS: The pleural mesothelioma was an epithelial type with tubulopapillary structures and was treated with an extrapleural pneumonectomy followed by radiation therapy. The malignant cells were positive by immunohistochemistry for cytokeratin but negative for carcinoembryonic antigen, S100, B72.3, and leu M1 antigen. Anthophyllite fibers were > 5 microm in length in lung tissue compared to 3 microm from a general population study. CONCLUSIONS: Anthophyllite asbestos has been associated with neighborhood environmental exposure and pleural plaques; we now report a neighborhood exposure and pleural mesothelioma.     

Abnormal pulmonary function associated with diaphragmatic pleural plaques due to exposure to asbestos.

Pulmonary function was measured in 79 men with diaphragmatic pleural plaques (DPP) as the only abnormality characteristic of asbestos disease on chest radiographs. They were selected from 4572 construction and shipyard workers exposed to asbestos. Abnormalities of pulmonary function in 21 non-smokers and 43 current smokers were compared with referent values adjusted for height, age, and duration of cigarette smoking. In the non-smokers, flows (FEV1) FEF75-85 and FEV1/FVC) were reduced and TGV and RV/TGV were raised. Current smokers had similar significant reductions. Thus by contrast with some current opinion that plaques are "an index only of past asbestos exposure," workers with plaques, even limited to the diaphragm, have functional impairment typical of pulmonary asbestosis. This suggests that they have pulmonary asbestosis, which is below the threshold of radiographic recognition.     

Abnormal pulmonary function associated with diaphragmatic pleural plaques due to exposure to asbestos

Pulmonary function was measured in 79 men with diaphragmatic pleural plaques (DPP) as the only abnormality characteristic of asbestos disease on chest radiographs. They were selected from 4572 construction and shipyard workers exposed to asbestos. Abnormalities of pulmonary function in 21 non-smokers and 43 current smokers were compared with referent values adjusted for height, age, and duration of cigarette smoking. In the non-smokers, flows (FEV1) FEF75-85 and FEV1/FVC) were reduced and TGV and RV/TGV were raised. Current smokers had similar significant reductions. Thus by contrast with some current opinion that plaques are "an index only of past asbestos exposure," workers with plaques, even limited to the diaphragm, have functional impairment typical of pulmonary asbestosis. This suggests that they have pulmonary asbestosis, which is below the threshold of radiographic recognition.     

Lung cancer in a female non-smoker with occupational exposure to asbestos: a case report

BACKGROUND: Until recently, asbestos was widely used in a variety of industrial processes. Workers exposed to asbestos may develop lung and pleural diseases such as asbestosis, lung cancer, benign pleural effusion, pleural plaques and mesothelioma. OBJECTIVE: To describe a clinical case of lung cancer in a female non-smoker with occupational exposure to asbestos. METHODS: The clinical and occupational history was based on the information kindly provided by the Occupational Unit of the National Health Service and on the case history of a hospital admittance in 2001, when the patient underwent surgery for lung cancer. RESULTS: The patient worked for 6 years in an asbestos manufacturing industry where she was exposed to high concentrations of asbestos, and then worked for 14 years in a sugar refinery only during the summer. She had benign pleural effusion, pleural plaques, asbestosis and lung cancer. CONCLUSIONS: We concluded that a six-year exposure to high doses of asbestos may induce lung cancer and asbestosis in a female non-smoker.     

Asbestos content of lung tissue and carcinoma of the lung: a clinicopathologic correlation and mineral fiber analysis of 234 cases

The aim of this study was to investigate the asbestos content of lung tissue in a series of patients with lung cancer and some history of asbestos exposure. This information was then correlated with demographic information, occupational and smoking history, presence or absence of pathologic asbestosis or pleural plaques, and pathologic features of the cancer. The pulmonary concentration of asbestos fibers in 234 cases of primary carcinoma of the lung was determined by means of a tissue digestion technique. Asbestos body counts were performed in 229 cases and fiber analysis by scanning electron microscopy in 221 cases. Asbestos content was recorded as total asbestos fibers, commercial amphibole fibers, noncommercial amphibole fibers, and chrysotile fibers 5 microm or greater in length per gram of wet lung tissue. The study group included 70 patients with asbestosis (Group I), 44 patients with parietal pleural plaques but without asbestosis (Group II), and 120 patients with neither (Group III). The median asbestos body content of Group I was more than 35 times greater than Group II and more than 300 times greater than Group III. The total asbestos fiber count for Group I was nearly 20 times greater than Group II and more than 50 times greater than Group III. The difference was due almost entirely to commercial amphiboles.In a series of primary lung cancer cases with some history of asbestos exposure, a markedly elevated asbestos content was identified among those with pathologic asbestosis as compared with patients with pleural plaques alone or with neither plaques nor asbestosis.     

Asbestos-related disease in upholsterers

Before its use was banned in developed countries, asbestos was widely applied in upholstery. However, the risk of asbestos diseases among upholsterers has only rarely been reported. In this case series, we present a first series of 6 workers employed in small workshops who developed several asbestos-related diseases, including pleural plaques, pleural fibrosis, and asbestosis. Exposures were intermittent and difficult to quantify, but lung asbestos content assessed by bronchoalveolar lavage was high in the 3 patients evaluated. In conclusion, upholstery work should be considered an at-risk occupation for developing asbestos-related diseases during the 20th century.     

Pulmonary function in long-term asbestos workers in China

The relationship of pulmonary function to exposure to asbestos and radiographic abnormalities has been controversial, especially when smoking is present as a confounder. The aim of the study was to provide further understanding on the radiographic-physiologic associations in nonsmoking and smoking asbestos workers. Radiographic asbestosis, pleural lesion, and pulmonary function were studied in 269 Chinese asbestos workers, with average exposure years of 23 for male workers and 18 for female workers. Their functional data were compared with those of 274 controls without exposure to dust. Although most of the male workers were smokers, none of the female workers smoked. In comparison with controls, asbestos workers had significantly lower lung volume and diffusing capacity, irrespective of gender. Female workers and smoking male workers had lower measurements of forced expiratory volume in 1 second and instantaneous forced expiratory flow at 50% and 25% of forced vital capacity. After adjustment for relevant covariates, asbestos exposure, asbestosis, and pleural abnormalities were associated with decreased parameters of pulmonary function, including lung volume, diffusing capacity, and airway flow. These data indicate that asbestos-related functional defects manifested by lung restriction and mild airway obstruction correlate with exposure to asbestos and with parenchymal and pleural abnormalities, independent of smoking.     

The additional risk of malignant mesothelioma in former workers and residents of Wittenoom with benign pleural disease or asbestosis

Aims: To examine the hypothesis that people with benign pleural disease or asbestosis have an increased risk of malignant mesothelioma beyond that attributable to their degree of asbestos exposure. Methods: Former workers and residents of the crocidolite mining and milling town of Wittenoom are participating in a cancer prevention programme (n = 1988). The first plain chest radiograph taken at the time of recruitment into the cancer prevention programme was read for evidence of benign pleural disease and asbestosis, using the UICC classification. Crocidolite exposure of former workers was derived from employment records and records of dust measurements performed during the operation of the asbestos mine and mill between 1943 and 1966. Based on fibre counts, exposure for former residents was determined using duration of residence and period of residence (before and after a new mill was commissioned in 1957) and interpolation from periodic hygienic measures undertaken from personal monitors between 1966 and 1992. Cox proportional hazards modelling was used to relate benign pleural disease, asbestosis, asbestos exposure, and mesothelioma. Results: Between 1990 and 2002, there were 76 cases of mesothelioma (56 of the pleura and 20 of the peritoneum). Cases had more radiographic evidence of (all) benign pleural disease, pleural thickening, blunt/obliterated costophrenic angle, and asbestosis than non-cases. Adjusting for time since first exposure (log years), cumulative exposure (log f/ml-years), and age at the start of the programme, pleural thickening (OR = 3.1, 95% CI 1.2 to 7.6) and asbestosis (OR = 3.3, 95% CI 1.3 to 8.6) were associated with an increased risk of peritoneal mesothelioma. There was no increased risk for pleural mesothelioma. Conclusion: The presence of benign pleural disease, in particular pleural thickening, and asbestosis appears to increase the risk of mesothelioma of the peritoneum, but not of the pleura beyond that attributable to indices of asbestos exposure in this cohort of subjects exposed to crocidolite.     

The importance of lung function, non-malignant diseases associated with asbestos, and symptoms as predictors of ischaemic heart disease in shipyard workers exposed to asbestos.

The mortality from ischaemic heart disease was studied in a prospective cohort of 1725 shipyard workers exposed to asbestos. The analyses were stratified for age and smoking habits and restricted to men. In agreement with other findings, men with impaired lung function had a significantly higher risk (relative risk (RR) = 3.5) of dying from ischaemic heart disease than men with normal lung function. Men with asbestosis or suspected asbestosis had a significantly higher risk (RR = 3.1) of dying from ischaemic heart disease than men without asbestosis. Thus asbestosis or suspected asbestosis also seemed to be a risk factor for ischaemic heart disease. This finding was independent of respiratory function. There was no increased risk for ischaemic heart disease in men with compared with men without pleural plaques. Men with production of phlegm or sputum and wheezing or whistling had no increased risk for ischaemic heart disease compared with men without these symptoms. In the group with normal lung function men with dyspnoea had a significantly higher risk of dying from ischaemic heart disease than men without dyspnoea. The findings for men with asbestosis or suspected asbestosis indicated a further risk factor besides impaired lung function, in persons exposed to asbestos. Perhaps this risk factor is due to lesions of the pericardium with consequences for heart function.     

Lung cancer risk in past asbestos workers a few decades after exposure cessation and prospects for screening

To ascertain whether the current risk of lung cancer in former asbestos workers was higher than in the general population, 1,557 past asbestos workers were recruited during statutory health examinations (from 2000 onward) and followed up for mortality. Standardized mortality ratios (SMRs) were calculated. Poisson regression was used to adjust the rate ratios (RRs) for confounders. SMR was about 1.00 in workers with or without pleural plaques and 4.62 (95% confidence interval: 0.61–18.1) in those with asbestosis. Adjusted RRs for lung cancer were 4.70 (0.99–22.5) for asbestosis, 4.35 (0.97–19.5) for former smokers, 6.82 (1.38–34.4) for current smokers. Currently, lung cancer mortality in past asbestos workers is similar to the general population, probably because workers more exposed /more susceptible could have died from lung cancer before the beginning of follow-up.     

Diffuse pleural fibrosis--an unreliable indicator of heavy asbestos exposure?

OBJECTIVES: This study aimed at testing the hypothesis that diffuse pleural fibrosis is associated with a heavier exposure to asbestos than that of benign pleural plaques, and hence diffuse pleural fibrosis can be used as a marker of heavy exposure. METHODS: Asbestos burden was estimated for 192 naval dockyard workers (96 with diffuse pleural fibrosis, 96 with plaques) by calculating the exposure ratings from the trade and the years spent in that trade. In 53 cases the diffuse pleural fibrosis was bilateral. RESULTS: No difference was found in the mean estimated asbestos burden between all diffuse pleural fibrosis and plaques, nor between plaques and unilateral and bilateral diffuse pleural fibrosis, analyzed separately by a one-factor analysis of variance. The mean asbestos burden was significantly greater for bilateral than for unilateral diffuse pleural fibrosis. A wide spread of asbestos exposure was noted among the men with diffuse pleural fibrosis. CONCLUSIONS: Diffuse pleural fibrosis may arise after widely varying exposure to asbestos. The mean exposure ratings for diffuse pleural fibrosis do not differ from those for pleural plaques, although the ratings are significantly higher for men with bilateral diffuse pleural fibrosis than for those with unilateral diffuse pleural fibrosis. Diffuse pleural fibrosis cannot be used as a reliable marker of heavy asbestos exposure.     

Radiographic assessment of pleuropulmonary disease in asbestos workers: posteroanterior, four view films, and computed tomograms of the thorax.

To study the clinical usefulness of computed tomography (CT) scanning of the thorax in asbestos related pleuropulmonary disease, 127 long term asbestos workers of the mines and mills in the Eastern Townships of Québec were examined. The CT scan was compared with the standard posteroanterior (PA) chest film and the four view films using the ILO grading system for profusion of disease. Six lung areas and six pleural sites were studied. On the basis of the usual diagnostic criteria, 41% of the workers had asbestosis. For profusion of parenchymal disease, there was an excellent correlation (r = 0.96, p less than 0.001) between PA and four view films and the latter did not significantly increase the total profusion score; the CT scan correlated less well with the PA film (r = 0.79, p less than 0.01) and the scatter of the data was larger. In 10 of the 53 (19%) workers with asbestosis the pulmonary lesions were not recognised by CT scan. For profusion of pleural plaques, there was an excellent correlation (p = 0.91, p less than 0.001) between PA and four view films; scores were identical in 73%, higher for PA in 7%, and higher for four view films in 19%. CT scan scores, however, were identical with PA films in 31%, higher for CT scan in 13% (owing to higher scores on lateral pleural sites), and lower for CT scan in 56% (owing to lower scores at diaphragm and costophrenic angle sites). Pleural calcifications were identified in 24 workers for a total of 40 sites; 13 as possible, 31% identified by two modes, and 27 as definite. Of the latter, 14 were seen only on CT scan. In the workers with rigid pressure volume curve of the lung and increased Gallium-67 lung uptake only, CT scan total scores were not significantly higher than in those without these markers of early interstitial lung disease (5 +/- 1 v 4 +/- 1, p less than 0.05). Thus the four view films and CT scan appear to be useful mainly in the assessment of pleural disease. The four view film identifies more sites of pleural plaques and the CT scan more pleural calcified plaques.     

Epidemiology of occupational asbestos-related diseases in China

In 1950s and 60s, asbestosis had been a major health hazard for asbestos exposed workers. In the late 1970s, lung cancers with or without asbestosis were found among asbestos workers. All cohort studies on asbestos workers and on chrysotile miners in China showed excess deaths from lung cancer. In a large scale of cohort study on asbestos workers, a synergistic effect was found between cigarette smoking and asbestos exposure in the production of lung cancer. There have been not so many cases of malignant mesotheliomas reported, so far. In the cohort of chrysotile miners, 4 cases of pleural mesothelioma were observed. In the large scale of cohort study on asbestos workers in 9 factories using only chrysotile only one case of pleural mesothelioma was detected for 10 years' observation. In another 2 cohort studies, 2 cases of peritoneal mesotheliomas were found, one in Shanghai asbestos factory where a small amount of crocidolite had been used in 1960s, and one in Anqing asbestos factory that was located near tremolite mine. Further study is needed especially for the relationship between exposure to Chinese chrysotile and malignant mesotheliomas.     

石棉工人肺功能与X射线胸片变化关系的研究

目的 探讨石棉工人肺功能与X射线胸片变化之间的关系。为早期发现石棉肺和对石棉肺患者肺代偿功能评价提供客观依据。方法 接触组为某温石棉制品厂134名男工，对照组为同一地区不接触粉尘，劳动强度与研究组工人大体相似的某仪表厂135名男工，对肺功能测定和X射线胸片检查结果进行对比分析。结果 胸膜和肺组织均有纤维化者，肺功能均明显下降。呈混合性肺功能障碍的特点；弥漫性胸膜增厚则与FVC，FEV1.0,FEV1.0/FVC%,DLco和Kco均呈显著负相关（r值分别为-0.20,-0.26,-0.21,-0.27,-0.19)。单纯胸膜斑与Kco呈正相关（r=0.23)；胸膜病变范围越大，肺功能损害也越严重。呈限制性肺功能障碍的特征。结论 石棉工人肺代偿功能指标的异常。可以早期反映肺内纤维化和胸膜病变的程度和范围。     

Diagnosis of asbestos-related pleuropolmonary diseases

A revision of criteria for diagnosis of asbestos-related pathological conditions was performed studying specially asbestosis, pleural plaques and malignant mesothelioma, also taking into account the problems connected with histopathology. As regards the histological diagnosis of asbestosis, it requires the presence of diffuse interstitialfibrosis in a well inflated tissue remote from the site of a tumour or other large lesion, plus the presence of two or more asbestos bodies in a 1 cm2 section. As regards the imaging diagnosis, the HRTC 4-point scale proposed by Paris et al. (2004) has been adopted:--0 images not suggestive of interstitial pneumonia;--1 modest unilateral or bilateral interstitial abnormalities, involving restricted areas if bilateral;--2 interstitial abnormalities of limited extent, but consistent with a diagnosis of asbestosis, i.e. honeycombing, even without other parenchymal changes and even though unilateral, or else any two abnormal findings among thickened interlobular septa, intralobular lines or subpleural curved lines;--3 numerous bilateral changes on several slices involving more than 2/3 of the posterior third of each hemi thorax. Only points 2 and 3 were considered consistent with the diagnosis of lung fibrosis. Such HRCT findings are not specific for asbestosis, changes in the pleural wall such as diffuse plaques and thickenings contribute to the diagnosis of asbestosis. As regards the pleural plaques and asbestos bodies we remark that they are merely exposition markers. We also discussed the problems the pathologist may encounter in diagnosing mesothelioma; in this field the prospects are encouraging as microarray analysis are beginning to identify new molecular markers for mesothelioma.     

Electron microscopy analysis of mineral fibers in human lung tissue.

In the present study, lung samples from 126 autopsied cases were examined to determine the content of mineral fibers using analytical transmission electron microscopy (ATEM). The cases were divided into four groups (22 lungs of persons exposed to ambient environmental pollution, 32 cases of mesothelioma, 38 cases of primary lung cancer, and 34 asbestosis cases, 13 of these with additional pleural plaques). Fibers were counted, measured, and mineralogically identified using a combination of X-ray microanalysis and electron diffraction of the non-oriented fiber. Concentration of fibrous particles (defined as particles above 1 micron in length with roughly parallel long sides and an aspect ratio of 5:1 and greater) was calculated as fibers 10(6)/g dry lung weight. The concentration of chrysotile was found to be similar throughout the groups except for two cases in the asbestosis group with comparably high numbers of chrysotile. However, a remarkable difference for amphiboles could be observed between the groups. Asbestos bodies were mostly found in the asbestosis group. There was a rather good correlation between numbers of amphibole fibers and asbestos bodies, with an average ratio of 10:1. For comparison purposes between occupationally exposed/non-exposed individuals, a transition was found in the concentration range of 3-10(7) asbestos fibers/g dried lung weight.     

Relationship between pleural plaques prevalence and extension and biomarkers of cumulative asbestos dose. A necropsy study

Background:The relationship between pleural plaques and cumulative asbestos exposure is controversial.Objectives:To evaluate the relationship between lung asbestos bodies (AB) and fibres (AF) and plaques presence and extension.Methods:In a necropsy series of shipyard workers with asbestos-related diseases, we measured counts (per g of dry lung tissue) of AB (thousands) and AF>1 μm (millions). Pleural plaques were classified into three extension grades. We fitted univariate and multivariable linear (dependent variables: AB and AF, log₁₀ transformed) and multinomial (dependent variable: plaques grade) regression models.Results:We analysed 124 subjects, 13 without plaques 20 with grade 1, 69 with grade 2, and 22 with grade 3 plaques. Geometric means (GM) of AB were 10.6, 23.3, 126, and 140 in the four groups respectively (P=0.0001). GMs for AF (mostly amphiboles) were 1.2, 1.4, 7.3, and 12.9 (P=0.0001). AB and AF were strongly correlated (r=0.81). The likelihood of no plaques and grade 1 plaques decreased with increasing AB and AF doses, with a corresponding increase of grade 2 and 3 plaques. Plaque presence and extension was also associated with histologically verified asbestosis (P<0.001).Conclusions:Our study showed a strong positive relationship between pleural plaque presence and extension and both lung asbestos burden and asbestosis.Key words: Pleural plaques, lung asbestos fibre burden