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High-resolution CT in the evaluation of occupational and environmental disease.

The most common of the pneumoconioses are silicosis, CWP, and asbestosis. The former two are characterized by the presence of small nodular opacities predominantly distributed in the upper zones of the lung. The small nodular opacities are classified into two patterns on HRCT: (1) ill-defined fine branching lines and (2) well-defined discrete nodules. Asbestosis demonstrates thickened interlobular and intralobular lines, subpleural dot-like or curvilinear opacities, and honeycombing on HRCT, predominantly distributed in the bases of the lungs. Although HRCT findings of other pneumoconioses are variable and nonspecific, there are predominant and characteristic findings for each type of pneumoconiosis. HRCT is useful in achieving more accurate categorization of the parenchymal changes in each type of pneumoconiosis.

Adult↗

Fiber counting and analysis in the diagnosis of asbestos-related disease.

Analysis of numbers and types of asbestos fibers present in lung tissue may provide insights into the pathogenesis of asbestos-induced disease, as well as diagnostic information concerning the relationship of a given lesion to asbestos exposure. This type of analysis requires extraction of fibers and asbestos bodies from lung tissue, preferably by means of a digestion-and-concentration technique, and examination with a combination of electron optical techniques, including electron diffraction and energy-dispersive x-ray spectroscopy. The combination permits definitive identification of asbestos fibers. Asbestos bodies have been shown to contain asbestos no matter what population they are found in, but they appear to be of value in ascertaining unusual exposure only when present in very large numbers. Numbers of asbestos bodies markedly underestimate total numbers of fibers present in lung. In patients from the general population, the mean number of asbestos fibers is about 1 X 10(6)/g dry lung; of this number, more than 80 per cent are fibers of chrysotile less than 5 microns long. Patients in the general population who have pleural plaques have about the same total number of fibers, but their lungs contain about a 50-fold increase in long thin amphibole fibers of commercial origin. Patients who have asbestosis and most patients who have mesothelioma have 100 to 200 X 10(6) fibers/g dry lung; the grade of asbestosis appears to be related to total fiber content. Occasional patients may develop mesotheliomas with much smaller fiber burdens. Both benign and malignant pleural diseases appear to be closely related to the presence of long thin amphibole fibers. Analysis of pulmonary fiber burden suggest that asbestos-related disease is not merely a matter of total numbers of fibers present, but that factors such as fiber type and size are equally important.

Asbestos↗

Numbers of asbestos bodies on iron-stained tissue sections in relation to asbestos body counts in lung tissue digests.

Utilization of tissue digestion techniques has demonstrated the presence of large numbers of asbestos bodies within lungs of persons after occupational exposure to asbestos, and smaller numbers in the vast majority of persons with no identifiable exposure. Because of the wide variability in results of such studies among different observers, the presence of more than one asbestos body on light microscopy has been recommended recently as one of the morphologic requirements (together with peribronchiolar fibrosis) for the tissue diagnosis of asbestosis. However, data that correlate the occurrence of asbestos bodies in paraffin-embedded tissue sections with the quantification of asbestos bodies by tissue digestion techniques have not been available. The authors counted the asbestos bodies in multiple paraffin-embedded sections of lung tissues stained for iron, and compared those numbers with the asbestos body counts determined by hypochlorite digestion of wet formalin-fixed lung tissue in six cases of asbestosis or asbestos-associated neoplasia. When adjustments were made for asbestos body orientation in tissue sections, shrinkage of sections during processing, and conversion of lung volume to wet weight, the agreement between the two techniques was excellent (r = 0.98, P less than 0.001). An average of two asbestos bodies on 2 X 2 cm (4 cm2) iron-stained tissue sections 5 microns thick is equivalent to approximately 200 asbestos bodies per gram of wet fixed lung tissue.

Adult↗

The value of ear lobe oximetry in the assessment of disability in asbestos-related disease.

Thirty-four asbestos workers, with either asbestosis, diffuse pleural thickening, calcified pleural plaques, or with comparable asbestos exposure but no evidence of asbestos-related disease and seven normal controls underwent a progressive exercise test. The subjects were categorized on the basis of lung function tests and PA chest X-rays. During the exercise test oxygen saturation was measured continuously by an ear lobe oximeter. The asbestosis and diffuse pleural thickening groups showed significant oxygen desaturation on exertion, confirming that both these conditions give rise to appreciable respiratory disability.

Asbestosis↗

The effects of the inhalation of asbestos in rats.

Two experiments in which SPF Wistar rats were exposed by inhalation to dust clouds of the UICC standard reference samples for periods of between one day and 2 years are described. All the samples of asbestos produced asbestosis which continued to progress after removal from exposure but only a little fibrosis was observed in control rats. Lung tumours, ranging in severity from adenomata to squamous carcinomata, were produced by all samples but in the controls there were only a few adenomata and none of the more serious tumours. Of the 20 tumours which metastasized, 16 occurred after exposure to one or other of the 2 chrysotile samples. In addition, a total of 11 mesotheliomata occurred, 4 of which were with crocidolite and 4 with Canadian chrysotile. Two of the mesotheliomata occurred with only one day's exposure to asbestos. There was a positive association between asbestosis and lung tumours.

Adenocarcinoma↗

[Computed tomography and conventional x-ray diagnosis of interstitial lung diseases].

One hundred and sixty-four patients with pulmonary fibrosis were examined by CT and by conventional radiological methods. Sixty patients had asbestosis, thirty-nine silicosis, forty sarcoidosis and twenty-five had idiopathic pulmonary fibrosis. CT is superior to conventional radiography in evaluating interstitial pulmonary changes, particularly of the pleura and the lung parenchyma. Areas of fibrosis and of emphysema can be demonstrated without any overlap. In sixty-nine patients there were some findings which could only be demonstrated by CT. In asbestosis, silicosis and sarcoidosis the CT classification of the lung parenchyma which we have suggested produces significantly better correlation with vital capacity than can be achieved from conventional chest films, according to the guide-lines of the I.L.O.

Adult↗

Asbestos-associated diseases in a cohort of cigarette-filter workers.

To estimate the effects on health of occupational exposure to crocidolite, a highly toxic form of asbestos, we studied a cohort of 33 men who worked in 1953 in a Massachusetts factory that manufactured cigarette filters containing crocidolite fibers from 1951 to 1957. Twenty-eight of the men have died, as compared with 8.3 deaths expected. This increased mortality was attributable to asbestos-associated diseases. Fifteen deaths were caused by cancer, as compared with 1.8 expected (relative risk, 8.2; 95 percent confidence interval, 4.6 to 13.4), including eight from lung cancer, five from malignant mesothelioma, and two from other types of cancer. There were seven deaths from nonmalignant respiratory disease, as compared with 0.5 expected (relative risk, 14.7; 95 percent confidence interval, 5.9 to 30.3), of which five were due primarily to asbestosis. In contrast, the mortality rates from cardiovascular diseases and all other causes were not increased. Four of the five living workers have pulmonary asbestosis; three of them have recently diagnosed cancers, including two additional lung cancers. We conclude that the extremely high morbidity and mortality in these workers were caused by intense exposure to crocidolite asbestos fibers.

Asbestos↗

Cement, asbestos, and cement-asbestos pneumoconioses.

The incidence and characteristics of cement-asbestos pneumoconiosis were compared with those of asbestosis and cement pneumoconiosis in three homogeneous samples of cases. The clinical, functional, and radiological features of cement-asbestos pneumoconiosis are similar to those of classical asbestosis, but the observed changes are less common and occur after a longer exposure.

Asbestosis↗

Visceral pleural thickening in asbestos exposure: the occurrence and implications of thickened interlobar fissures.

We evaluated fissural (ie, visceral pleural) thickening on radiographs in two asbestos-exposed study populations and a control group. Asbestos workers had an incidence of fissural thickening of 54.5% compared with 16.0% in the unexposed control group, with a strong positive statistical effect due to asbestos exposure beyond that attributable to age. Fissural thickening occurred in 85% of workers with parietal plaques and in 36% without pleural plaques. Fissural thickening occurred in 45% without radiographic evidence of pulmonary fibrosis, but it was very common (85%) in those with pulmonary fibrosis. Data analysis showed that fissural thickening responds more strongly to asbestos exposure than does plaque formation, with 21 years of asbestos exposure needed for a 50% chance of developing fissural thickening, while 31 years of exposure were needed for a 50% chance of forming pleural plaques. From a second group of 57 asbestos workers evaluated clinically, 8 were diagnosed as having asbestosis with radiographically clear lungs and fissural thickening. We conclude that visceral pleural thickening is common in asbestos exposure, that it is related to the years since first asbestos exposure, and that its presence may indicate the presence of pulmonary asbestosis, even with radiographically normal lungs.

Asbestosis↗

Computed tomography in the diagnosis of asbestos-related thoracic disease.

High-resolution computed tomography (HRCT) has improved the radiologist's ability to detect and potentially quantify the abnormalities of asbestos exposure. It has proved to be more sensitive than chest radiography for detecting pleural plaques and for discriminating between pleural fibrosis and extrapleural fat. HRCT is also more sensitive than chest radiography or conventional CT for detecting parenchymal abnormalities in asbestos-exposed persons. The HRCT findings that correlate with other parameters of asbestosis include (1) septal and centrilobular thickening, (2) parenchymal fibrous bands, (3) honeycomb patterns, (4) subpleural density persisting in the prone position, and (5) subpleural curvilinear lines that persist in the prone position. CT has an important role in evaluating benign and malignant lung and pleural masses in asbestosis.

Asbestosis↗

Pulmonary fibrosis and lung cancer in the United States: analysis of the multiple cause of death mortality data, 1979 through 1991.

We determined the relationship between pulmonary fibrosis and lung cancer in the United States from 1979 through 1991 by analyzing death certificate reports compiled by the National Center for Health Statistics. Of the 26,866,600 people who died during the study period, 107,312 died with pulmonary fibrosis, 1,739,725 died with lung cancer, 2,040,634 died with chronic obstructive pulmonary disease, and 7,807 died with asbestosis. Lung cancer occurred less frequently among decedents with pulmonary fibrosis (4.81%) and more frequently among decedents with chronic obstructive pulmonary disease (10.06%) and decedents with asbestosis (26.60%) than among decedents in the general population (6.48%). We conclude that the prevalence of lung cancer among people who died with a diagnosis of pulmonary fibrosis is lower than the 10% to 40% prevalence that has been reported in case series of pulmonary fibrosis.

Adolescent↗

Respiratory symptoms and functional status in workers exposed to silica, asbestos, and coal mine dusts.

This study aims to provide further understanding of physiologic and symptomatic changes and radiographic abnormalities due to exposure to silica, asbestos, and coal dusts. Questionnaires and pulmonary function tests were given to 220 silica, 277 asbestos, and 511 coal workers from three different industries in China. Posteroanterior chest radiographs were classified as stages 0, I, II, and III according to degree of parenchymal fibrosis. Significantly poorer pulmonary function and a higher prevalence of dyspnea and chronic cough were observed in workers with pneumoconiosis than those without, irrespective of dust type. Workers with stages II and III silicosis had worse pulmonary function and more common symptoms relative to workers with equivalent coal workers' pneumoconiosis or asbestosis. After adjusting for relevant confounders, reductions in the spirometric parameters and single breath diffusing capacity for carbon monoxide (DLCO) and the occurrence of respiratory symptoms were associated with increasing stage of silicosis, whereas lower DLCO and the occurrence of symptoms were associated with increasing stage of asbestosis and coal workers' pneumoconiosis. The study suggests that despite the differences in degree and pattern due to exposure to different fibrogenic dusts, respiratory impairments of all of the workers are associated with the presence and progression of parenchymal fibrosis and smoking.

Adult↗

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.

Adult↗

Skin tests with tuberculin (PPD) Candida albicans and Trichophyton spp. in cryptogenic fibrosing alveolitis and asbestos related lung disease.

Delayed skin hypersensitivity responses were elicited in patients with cryptogenic fibrosing alveolitis (CFA) (twenty-eight), asbestosis (eight), mesothelioma (eight) and a "control" group, having miscellaneous lung diseases not normally believed to be associated with T cell deficiency (twenty). Three antigens, Candida albicans, trichophyton and purified protein derivative (PPD) in a range of doses were used. There was no evidence of impaired cellular immunity in CFA or in mesothelioma, indeed there was a significantly increased frequency of reactions to PPD in both of these conditions (P less than 0.05 and P less than 0.01 respectively). There was, however, a trend of decreased responsiveness in the group with asbestosis. The dosage regimen used rarely gave completely negative results (only one of thirty-two completed tests), and may provide a basis for a simple and standard regimen for screening patients suspected of having defective T cell responses.

Adolescent↗

Long-term mortality experience of chrysotile miners and millers in Thetford Mines, Quebec.

Among a cohort of 544 men with at least 20 years of employment in chrysotile mining and milling at Thetford Mines, Canada, 16% of the deaths were from lung cancer and 15% from asbestosis. The excess over expected deaths from these causes account for 43 of 178 deaths in the group. The risk of death of asbestosis, at equal times fron onset of exposure, is very similar in miners and millers, factory workmen and insulators. The ratio of observed to expected deaths from lung cancer is similar in the miners and millers and factory workers, but higher in insulators. The risk of death of mesothelioma in miners and millers is decidedly less than the other two groups. The exact causes of the reduced risk in this category are not yet completely clarified.

Adult↗

Radiographic search for asbestos-related disease in a naval shipyard.

The Long Beach Shipyard underwent a chest x-ray survey of 6640 employees, or 88.6% of the total shipyard population, to determine the level of asbestotic changes. For computer classification purposes, the findings were divided into five groups: abnormal findings consistent with inhalation of asbestos fiber; normal; pulmonary fibrosis, nonspecific, questionable; and other findings not related to asbestosis. Asbestos-related abnormal findings, were encountered in 1061 workers, or 16.0%. No change was noted in 4806, or 72.4%. Pulmonary fibrosis was encountered in 140, or 2.1%. Other abnormalities not related to the inhalation of free asbestos fiber were encountered in 624, or 9.4%. The interpretation was questionable in nine individuals, or 0.1%. Of the male employees, 17.2% were positive for asbestos-related chest x-ray changes, and four women, or 0.8%, showed comparable findings. Of the men, 71.5% had normal chest x-rays, and 83.3% of the 402 women demonstrated normal films. Positive x-ray changes for asbestosis were encountered in a linear relationship when viewed by age of the worker. Employees aged 25--29 years exhibited 1.3% positive findings, and this level increased to a maximum of 38.2% positives among workers aged 65 years and over. Normal chest films descended, conversely, in a linear relationship. Similarly, the percentage of positive findings for asbestos-related disease increased in a linear configuration with length of service. Persons with 2--6 years of asbestos contact displayed 12.4% positive findings, while individuals with 22-26 years of work at the shipyard manifested 37.0% positive chest film findings. Although the shipyard was operational between 1943 and 1949, the system of allocation of badge numbers precludes the inclusion of these 7 years of work among persons who had had at least 26 years of service. When studied by work site, dividing the subjects into production and nonproduction personnel, it was found that production workers accounted for 74.5% of the asbestos-positive films. Overall, the 780 production workers manifested 11.8% of the positive findings of all persons studied, while nonproduction employees accounted for 4.1% of the positives out of the population studied. A figure that approximates the total finding of asbestos-related disease is 16.0%.

Adult↗

Correlation between lung asbestos count at necropsy and radiological appearances.

In the first 100 of a series of 600 consecutive necropsies for which a chest x-ray film had been taken within a year of death the features of asbestosis were observed in eight of the nine cases where the asbestos count at subsequent necropsy exceeded 40. In only one of these cases had the diagnosis of asbestosis been suggested during life. The higher the asbestos count the greater the likelihood of radiographic abnormalities, particularly calcified and non-calcified pleural plaques on the chest wall and diaphragm.

Aged↗

The HL-A system in asbestos workers.

In a study of the HL-A system in 56 selected asbestos workers referred to the Pneumoconiosis Medical Panel with definite or suspected asbestosis, the W 27 antigen was found more often than among a control population. Six of the 10 asbestos workers with the W 27 antigen had definite radiographic evidence of asbestosis compared to 13 out of 46 without the W 27 antigen. These observations, if confirmed, suggest that the W 27 antigen may provide a useful marker of an enhanced susceptibility to the tissue-damaging effects of asbestos dust.

Adult↗