Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study

The prevalence of respiratory symptoms and lung function impairment was studied in a sample of men from a population screening of asbestos-related disorders. When the rates were adjusted for age and smoking habits, 83 subjects with lung fibrosis had an increased prevalence of respiratory symptoms, in particular, phlegm when coughing and breathlessness grades 1-3. Among 200 subjects under 70 years of age who had pleural plaques only, a statistically significant increase was observed in the prevalence of breathlessness grade 1 compared to an external reference population. Among 98 asbestos-exposed subjects who had normal chest X-rays, there was an increase in the prevalence of breathlessness grade 2, cough during the day, and phlegm when coughing. There was a higher proportion of subjects with lung fibrosis who were below 80% of the predicted values for forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) than in the other groups. There was also a higher proportion of subjects with pleural plaques only who were below 90% of the predicted value for FVC than in a group of 90 subjects without asbestos exposure. In accordance with previous studies, these results indicate that pleural plaques in asbestos workers may be of greater importance as a clinical feature than has been recognized in the past.     

胸膜增厚对石棉工人肺功能的影响

[目的]探讨胸膜增厚对石棉工人肺功能的影响。[方法]接触组为某温石棉厂134名男性工人，对照组为同一地区不接触粉尘、劳动强度与接触组大体相似的某仪表厂135名男性工人。对两组对象的肺功能测定和后前位X射线胸片检查结果进行对比分析。[结果]与对照组相比，在控制了肺内小阴影改变和累积吸烟量等混杂因素的影响后，石棉接触工人中胸膜正常细和双侧胸膜增厚组用力肺活量（FVC）和一秒钟用力呼气容积（FEV1）均显著下降（P〈0．05），单侧胸膜增厚组仅FVC显著下降（P〈0．05）；而与胸膜正常组相比，在控制了肺内小阴影改变、累积吸烟量和接尘年限等混杂因素的影响后，双侧胸膜增厚组FVC和FEV1显著下降（均为P〈0．05）；在控制了肺内小阴影改变、累积吸烟量和接尘年限等混杂因素的影响后，胸膜增厚范围与FVC呈负相关，与弥散系数（Kco）呈正相关（均为P〈0．05）。[结论]胸膜增厚范围越大，肺功能损害也越严重，呈限制性肺功能障碍的特征。     

Calcified plaques on mediastinal pleural reflections associated with asbestos dust exposure: four case reports

Four cases with marked calcified plaque formation on the mediastinal pleural reflections are described and discussed.     

Asbestos plaques in a typical veteran's hospital population

Previous authors have described several pleural abnormalities on chest radiography as being pathognomonic for asbestos exposure. We sought to determine the percentage of admissions and outpatients at a typical Veteran's Affairs hospital with these findings, and researched medical records to verify the frequency at which patients having positive radiographs were suspected either by clinical/occupational history or radiologically to have had prior significant exposure to asbestos. Radiographs of 1,212 consecutive patients were evaluated by a certified B reader, and the medical records as well as previous radiology reports of all positive patients were reviewed. Twenty-eight (2.3%) of the radiographs had pleural abnormalities consistent with asbestos exposure, with the patients, all male, ranging in age from 50 to 98 years (mean 75.6). Radiology reports described pleural plaques in only 12 of the 21 (57%) cases with prior exams available; in only seven (33%) was an asbestos etiology considered by the interpreting radiologist. The plaques were misdiagnosed in four instances as being indicative of other, unrelated pathology. A history of known dust exposure was expressed by only five patients (18%). Eleven described working in occupations now known to have a high incidence of exposure, but neither patient nor examining physician expressed consideration of dust inhalation. In conclusion, we have found that a significant percentage of patients in certain subpopulations show radiographic evidence of asbestos exposure that may be a harbinger of related pathology. Unfortunately, because of a low index of suspicion, thorough environmental histories are often deferred, many radiographic changes are either not recognized or are misdiagnosed, and these patients are not followed with the stringent protocols they deserve. © 1996 Wiley-Liss, Inc.     

Asbestos-related pleural diseases: dimensional criteria are not appropriate to differentiate diffuse pleural thickening from pleural plaques

BACKGROUND: In the literature, the criteria used to define pleural plaques (PP) and diffuse pleural thickening (DPT) are very heterogeneous and often imprecise. A multicenter restropective study was conducted to assess the relevance of two radiographic definitions of DPT. METHODS: The study population consisted of 287 subjects with asbestos-related pleural thickening. Two definitions were used to characterize DPT on postero-anterior chest radiographs: definition 1: pleural thickening associated with obliteration of the costophrenic angle; definition 2: pleural thickening at least 5 mm wide, extending for more than one quarter of the chest wall. Prevalence of respiratory symptoms and pulmonary function tests were compared in the DPT and PP groups resulting from the two definitions of DPT. RESULTS: According to definition 1, 34 patients (11.8%) were classified in the DPT group. Prevalence of chronic sputum, dyspnea, and chest pain was significantly higher in this group than in the PP group. FEV(1), FVC, and TLC were significantly lower. The differences persisted after adjustment for confounding factors. According to definition 2,102 patients (36.6%) were classified in the DPT group. DPT and PP groups did not differ in terms of prevalence of respiratory symptoms, or pulmonary function tests. Agreement between readers was significantly better when using definition 1. CONCLUSIONS: Obliteration of costophrenic angle is a much more reliable sign than dimensional criteria to characterize DPT.     

Pleural plaques as risk indicators for malignant pleural mesothelioma: A necropsy-based study

Pleural plaque is recognized as a reliable marker of previous exposure to asbestos. However, it is controversial whether pleural plaque is a risk indicator for asbestos-related malignancies. In the present study, the thoracic cavities were examined for pleural plaques in 3,005 necropsies performed at the Monfalcone Hospital in people aged 15 years or older. Plaques were classified into three classes: 1, small (plaques measuring 1–4 cm in major diameter); 3, large (plaques involving a major part of a hemithorax); and 2, moderate (intermediate conditions). The prevalences of pleural plaques were 70.9% among men, and 24.0% among women. The prevalences of plaques (total plaques, various classes) among subjects with pleural mesothelioma were compared with those observed in the remaining cases. The series included 92 subjects with malignant pleural mesothelioma (82 men and 10 women). Mesothelioma cases showed higher prevalences of total plaques as well as higher prevalences of classes 1, 2, and 3, when compared with controls. These differences reached the statistical significance for total plaques, and classes 2,3. The present data are consistent with the idea that pleural plaque is a risk indicator for pleural mesothelioma. Am. J. Ind. Med. 32:445–449, 1997. © 1997 Wiley-Liss, Inc.     

Loss of lung function among sheet metal workers: Ten-year study

One hundred and twenty-two sheet metal workers in New England were examined over a 10-year interval for loss of pulmonary function and the development of asbestosis or asbestos-related pleural fibrosis. Regression models using the generalized estimating equation (GEE) approach were created to investigate the relationship between exposure and pulmonary function after adjusting for smoking status, age, height, and asbestos-related x-ray changes. A history of shipyard work was a significant contributor to the loss of forced vital capacity (FVC). Among smokers, loss in forced expiratory volume at 1 sec (FEV₁) also had a significant relationship to prior shipyard work. There was a borderline significant relationship between percentage predicted FEV₁ and cumulative years of asbestos exposure in smokers, as well as years-since-initial-exposure in never-smokers. This study supports previous findings of obstructive airway changes in asbestos-exposed workers and identifies shipboard work as an important predictor of loss in pulmonary function even years after shipyard exposure to asbestos has ceased. Am. J. Ind. Med. 32:460–466, 1997. © 1997 Wiley-Liss, Inc.     

Decreased lung function in long-term asbestos cement workers: a cross-sectional study

The effect on lung function of exposure in an asbestos cement plant was investigated in male workers, employed more than 10 years. The exposed group was selected to exclude subjects with pneumoconioses and ex-smokers and consisted of 77 smokers and 48 never-smokers. Referents were chosen from plants where asbestos had not been in use and restricted to those without X-ray signs of chest disease. The primary type of asbestos used was chrysotile and the general dust level in the two decades 1950-1970 seems to have been around 10 mg/m3 while the asbestos fiber concentration averaged 2 fibers/ml. The mean differences between exposed and referents were statistically significant for forced vital capacity and forced expiratory volume, -0.25 and -0.30 liters, respectively, after adjustment for age, height, tracheal area, and smoking category. No significant differences were detected between those with and without pleural plaques. Smokers and never-smokers were similarly affected. In conclusion, the group exposed to dust with comparatively low asbestos fiber concentration had a minor impairment of lung function, mainly due to obstructive changes.     

Localized pleural plaques and lung cancer.

In a mass chest radiography survey conducted in 1971 for 7,986 residents of three Finnish communities, 604 subjects (7.6%) with pleural plaques but not other asbestos-related radiographic signs were identified. The same number of referents, each individually matched to each plaque carrier on sex, birth year, and community, was selected from among persons in the same source population with no pleural plaques. The two groups were followed for investigation of incidence of lung cancer during 1972-1989. Twenty-eight of those with plaques and 25 referents contracted lung cancer (crude conditional RR = 1.1; CL95 = 0.7, 1.9). The application of the proportional hazards model, with adjustment for sex, age, and residence, resulted in a hazard ratio of 1.1 (CL = 0.6, 1.8). The risk ratio estimate may be biased; hence, the result is inconclusive in regard to the predictive assessment of lung cancer risk among carriers of pleural plaques.     

Signs of asbestosis and impaired pulmonary function in women who worked in shipyards

Fifteen of 71 women (21.1%) who had worked in shipyards before May, 1961 had radiographic signs of asbestos disease. There were irregular opacities in the lung parenchyma in seven and pleural disease in eight, two of whom had pleural calcifications. The 71 women who volunteered to be studied had a mean age of 61.5 years. Chronic bronchitis was diagnosed in 21%, 71% had dyspnea on climbing two flights of stairs, and 42% had wheezing. These prevalences were 50% higher than in wives of shipyard workers. In 50 white women, mean values for expiratory flow rates, log (FEF25-75) and log (FEF75-85), were decreased for non-, ex- and current smokers as compared to normal nonsmokers. Ex-smokers and current smokers showed the greater effects. Diffusing capacity (DLCOsb) and alveolar volume (ALV) were also reduced in all three smoking categories. Comparison to a reference population without asbestos exposure showed that for current, ex- and nonsmoking subgroups, there were significant reductions in log (FEF25-75), DLCOsb, and ALV for nonsmokers, reductions in FEV1, log (FEV25-75), and log (FEF75-85) in ex-smokers, and reduced ALV in current smokers. These decreases may reflect a locality effect. Further studies are recommended.     

Follow-up study of respiratory function in Hemp workers

A 3-year follow-up study was performed on 38 women and 28 men from the originally studied textile workers employed in a soft hemp processing mill. Acute and chronic respiratory symptoms and ventilatory capacity were recorded during the cross-sectional and the follow-up studies. Maximum expiratory flow-volume (MEFV) curves were obtained on these workers, and forced vital capacity (FVC), 1-second forced expiratory volume (FEV₁) and flow rates at 50% and at 25% of the VC (FEF₅₀, FEF₂₅) were measured. High prevalences of acute and chronic respiratory symptoms persisted at the follow-up study. In particular, high prevalences of byssinosis were documented at both studies (women: 47.4% and 47.4%; men: 64.3% and 67.9%, respectively). Statistically significant mean across-shift reductions were recorded for all ventilatory capacity tests at the initial study. A large mean annual decline was calculated for FEV₁ in women and for all ventilatory capacity parameters in men; these declines were greater for workers with symptoms of byssinosis than for those without. The accelerated decline in FEV₁ noted in the women workers, who were predominantly nonsmokers, suggests an independent hemp effect. Exposures in the work environment were measured with Hexhlet filters and revealed very high dust concentrations (mean total: 21.4 mg/m³, 22.4 mg/m³; respirable: 8.4 mg/m³, 9.9 mg/m³) at both initial and follow-up studies. These levels are much higher than those found in mills processing organic materials in North America. Our data demonstrate that work in the hemp industry, particularly in small poorly regulated mills, continues to have deleterious effects on respiratory function.     

Asbestos-related lesions of the pleura: parietal plaques compared to diffuse thickening studied with chest roentgenography, computed tomography, lung function, and gas exchange

Lung function tests, tests of working capacity with gas exchange, and computed tomography (CT) with density measurements with the patient supine and prone were performed in 23 males with asbestos-related bilateral pleural lesions. Two had pulmonary asbestosis grade 1/0 or more; all the others had normal lung parenchyma. On x-ray, the pleural lesions were divided into plaques involving only the parietal pleura There was a and diffuse pleural fibrosis of various degrees involving the visceral pleura. There was a good correlation between the findings at plain chest roentgenography and CT, but more lesions were seen on the CT scan. However, a few pleural plaques seen on conventional films were not observed at CT. Individuals with plaques had slightly lowered lung function compared to reference subjects. Bilateral diffuse pleural fibrosis was associated with a marked decrease in pulmonary function. The two patients with radiologically evident pulmonary asbestosis were found in this group. Decreased lung function was also observed in subjects with pleural fibrosis of only grade 1 (involving less than one fourth of the hemithorax) and a normal exercise capacity. The study shows the importance of differentiation between various asbestos-related pleural lesions.     

Fiber size and number in workers exposed to processed chrysotile asbestos, chrysotile miners, and the general population

We analyzed chrysotile and chrysotile-associated amphibole (largely tremolite) asbestos fibers in 21 workers exposed to various types of processed (milled) chrysotile ore, 20 long-term chrysotile miners, and 20 members of the general population (controls). Significantly greater amounts of both chrysotile and tremolite were found in processed-ore workers and miners than in controls. On average, the mean fiber lengths and aspect ratios for the mining and processed-ore-exposed workers were similar and were significantly greater than the values seen in the controls; within the processed-ore group, there was a marked variation in these parameters, and some workers appeared to be exposed to fairly long, thin fibers. It was found empirically that the fiber size data, and to a lesser extent the concentration data, could be used to classify workers accurately into those with processed-ore exposure and controls. We conclude that fiber sizes in the lungs of processed-ore-exposed workers are similar to those of chrysotile miners and are considerably longer than those found in the general population; some processed-ore workers have longer fibers which might be responsible for higher disease incidences in certain working groups; tremolite accompanies chrysotile in a variable proportion of workers exposed to processed chrysotile products and might be important in the genesis of mesothelioma in such workers; and mineralogic analysis will usually detect exposure even when chrysotile has largely disappeared from lung tissue.     

Pleural lesions and the ILO classification: the need for a revision

The ILO system for radiographic classification of pneumoconioses is a very important epidemiological tool. Unfortunately, the classification is not precise for pleural lesions, which are especially important for evaluation of asbestos-related diseases. The classification cannot separate extrapleural fat from diffuse thickening of the pleura, nor large plaques from diffuse thickening. In this paper, a short review of the different lesions are given and a revised scheme is suggested. This scheme includes as separate lesions: pleural fat; lesions of the parietal pleura, i.e., pleural plaques; and lesions of the visceral pleura, i.e., diffuse thickening and rounded atelectasis. The extent and width, as in the present ILO scheme, could be abolished.     

Immunological and respiratory changes in tobacco workers

BACKGROUND: Tobacco workers develop respiratory changes following occupational exposure to tobacco dust. METHODS: This study investigated 102 tobacco workers as well as a group of 30 matched control workers. Immunological testing, symptom questionnaire, and lung function measurements were performed in all workers. RESULTS: Increased total IgE was found in 12.7% of tobacco workers but in none of the controls (P < 0.05). Increased specific IgE (tobacco allergen) was recorded in 26.7% of tobacco workers with positive skin tests to tobacco extract but in none of the controls (P < 0.05). Regression analysis of ventilatory tests in female tobacco workers indicated a significant association of FEF75 to employment and smoking among workers with positive skin tests to tobacco. There were, however, no other associations between positive immunologic findings and lung function abnormalities and symptoms. CONCLUSIONS: Our study found increased immunological reactions in the tobacco workers. However, with the possible exception of lung function at low lung volume in female workers, these reactions do not appear to contribute significantly to the symptoms and lung function abnormalities seen in these workers. Am. J. Ind. Med. 45:76-83, 2004.     

Assessment of respiratory symptoms and lung function values among the brick field workers of West Bengal,India

Brick manufacturing process releases large amounts of silica dust into the work environment due to the use of silica-containing materials. The main aim of the study was to investigate the impairment of lung function and prevalence of respiratory symptoms among the different groups of brick field workers in comparison with control subjects. A total of 250 brick field workers and 130 unexposed control subjects were randomly selected in which demographic characteristics, respiratory symptoms, and lung function values were recorded. The result showed significantly lower p value (<.001) in lung function and respiratory symptoms among brick field workers when compared with control group. The prevalence of respiratory symptoms was dyspnea (46.8%), phlegm (39.2%), and chest tightness (27.6%). Dust exposure in working environment affected the lung function values and increased the respiratory symptoms among the brick field workers.