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Query: UMLS:C0037116 (silicosis)
 1,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This review deals with some of the emerging events that are assuming increasing relevance as work-related respiratory diseases (indoor air pollution and sick building syndrome, respiratory toxicity of formaldehyde, pollutant-induced asthma, dental technician lung diseases, lung cancer from diesel exhaust, environmental silicosis). The industrial hygienist's role in recognition, evaluation, and control of health hazards is stressed as an essential contribution to both prevention and diagnosis of occupational lung disease.
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PMID:New trends in occupational and environmental diseases: the role of the occupational hygienist in recognizing lung diseases. 808 23

Validations of retrospective methods of assessment used in occupational epidemiological studies have rarely been published. This study is an indirect validation of a quantitative retrospective assessment of exposure to silica used in a nested case-control study of lung cancer among workers at 29 metal mines and pottery factories in China. Indices of cumulative total dust and cumulative respirable dust were calculated by merging work histories with the historical exposure profile for each subject. To validate indirectly the methods of exposure assessment used in the study of lung cancer, trends for exposure response relation between the two indices of exposure to silica and risk of silicosis were evaluated with 376 patients with silicosis from the study population as the cases, and 1262 controls without silicosis for comparison. Age adjusted odds ratios (ORs) as a measure of risk of silicosis showed striking trends with both indices of exposure to silica. For cumulative respirable dust, the OR (95% confidence interval) rose from 7.6 (5.1-11.4) for low exposure to 20.0 (13.2-30.6) for medium exposure, and to 51.7 (31.0-86.8) for high exposure. The strength of the association between exposure to silica and risk of silicosis suggests that the retrospective assessment of exposure used in the case-control study of lung cancer would accurately reflect an exposure response relation between silica and lung cancer, if it existed.
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PMID:Indirect validation of a retrospective method of exposure assessment used in a nested case-control study of lung cancer and silica exposure. 811 62

The presence of radiographic silicosis as a risk factor for lung cancer was assessed in a case-control study conducted within a study cohort of New Mexico underground uranium miners. Chest radiographs were interpreted for the presence of silicosis for 65 lung cancer cases and 216 controls. The presence of silicosis on the chest radiograph taken closest to the start of employment or on the latest radiograph available was not associated with lung cancer risk after adjustment for cumulative exposure to radon progeny. The odds ratio associated with the presence of any type of opacity indicative of pneumoconiosis on the chest x ray closest to the start of employment was 1.33 (95% confidence interval, 0.31-5.72). For the most recent available chest x ray, the corresponding odds ratio was 1.16 (95% confidence interval, 0.35-3.84). Although the findings are limited by the relatively small number of subjects, the lack of association of silicosis with lung cancer suggests that silica exposure should not be regarded as a major uncertainty in extrapolating radon risk estimates from miners to the general population.
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PMID:Silicosis and lung cancer risk in underground uranium miners. 813 13

Twelve preparations of crystalline silica, with a wide range of particle sizes, were assayed by a new method, which measures surface adsorption of the cationic dye Janus green B to crystalline silica samples in a buffered aqueous suspension. The same samples were also assayed for total surface area by the Brunauer-Emmett-Teller (BET) method of surface adsorption of nitrogen gas. A strong linear correlation was found between the two methods of measurement (r = 0.977). Reproducible specific surface area measurements by the Janus green B adsorption method were made on 2-mg samples using ordinary visible wave-length spectrophotometric equipment, whereas the BET method necessitated sample sizes in excess of 100 mg and more specialized instrumentation. Five size-fractionated preparations from the same Min-U-Sil alpha-quartz sample showed an increase in BET surface area and Janus green B binding per unit weight with decreasing particle size. Among four standard alpha-quartz samples tested, Min-U-Sil 5 and F600 had the lowest specific surface areas, whereas DQ-12 and Chinese standard alpha-quartz had much higher surface areas. The synthetic silica preparations cristobalite and tridymite had intermediate surface areas. Binding by the cationic dye Janus green B is consistent with a surface charge mechanism and provides a useful new technique for the assessment of surface characteristics of crystalline silica samples. Its linear relationship to surface area suggests that the ratio of aqueous surface charge to surface area is constant for different crystalline silica preparations. Comparison of surface areas for different preparations of crystalline silica is important in understanding the relative activities of these preparations in studies on mechanisms of silicosis and silica-induced lung cancer.
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PMID:Binding of the cationic dye, Janus green B, as a measure of the specific surface area of crystalline silica in aqueous suspension. 823 62

A case of pulmonary silicosis associated with triple lung cancers is presented. Two of the three tumors were unexpected clinically. The discussion deals with the diagnostic difficulty in radiological differentiation between the pneumoconiotic mass lesion and superimposed tumor shadows, as well as the possible causal relationship between the two conditions. From the practical point of view, elderly patients with pneumoconiosis should be carefully monitored for the development of lung cancer.
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PMID:Triple lung cancers in a patient with silicosis. 839 Jul 66

Because some evidence indicates that there is an increased incidence of lung cancer in silicosis, we studied the effects of exposing rats to silica on the pulmonary microsomal cytochrome P-450 system. Rats were exposed to silica by intratracheal administration, lung microsomes were obtained from untreated and silica-treated animals, and the amount of microsomal tissue, the level of total cytochromes P-450 (all isozymes), the activity of NADPH cytochrome P-450 reductase, the metabolism of two xenobiotics, and the relative amounts of cytochrome P-4502B1 and P-4501A1 were measured. Lungs from silica-treated rats were almost 2-fold heavier and contained more than 10 times more alveolar phospholipids than lungs from untreated animals, indicating that acute silicosis had been produced. In lungs from silica-treated animals, the concentration of microsomal tissue, expressed as milligrams of microsomal protein per gram of lung, was increased by more than 2-fold, and total microsomal protein content was increased by almost 5-fold relative to untreated animals. When expressed as activity or amount per milligram of protein, the microsomal concentrations of NADPH cytochrome P-450 reductase, total cytochromes P-450, 7-ethoxycoumarin (EC)-0-deethylase, and cytochrome P-4502B1 are reduced by approximately 50% in silica-treated rats. However, when expressed as total activity or amount in the lungs, all are increased by approximately 1.5- to 2.5-fold in silica-treated lungs. On the other hand, total lung 7-ethoxyresorufin (ER)-0-deethylase activity and cytochrome P-4501A1 are increased by 4- to 5-fold in silica-treated lungs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Alterations in the pulmonary microsomal cytochrome P-450 system after exposure of rats to silica. 839 26

Mortality study was carried out on the cohort of 11,224 men with coal workers' pneumoconiosis or silicosis diagnosed during the period 1970-1985. The cohort was selected from the register of occupational diseases and was traced up to the end of 1991. The general male population of Poland was a reference group. The study showed small but significant excess of total mortality (SMR = 115; p < 0.01). The analysis of death causes revealed an elevated mortality from infectious diseases, among which tuberculosis was most prevalent (SMR = 212; p < 0.01) and from pneumoconioses predominant in diseases of the respiratory system, (SMR = 426; p < 0.01) and lung cancer (SMR = 116; p < 0.01). The comparison of the prevalence of smoking in the population under study with that in the reference general male population of Poland indicated that this habit is mostly responsible for the excess of lung cancer deaths. This finding contradicts the hypothesis that there is a causal relationship between exposure to dusts containing crystalline silica, pneumoconiosis and lung cancer.
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PMID:Mortality pattern in men with pneumoconiosis in Poland. 858 29

The relation between exposure to crystalline silica and lung cancer has been a controversial topic, and findings have appeared inconsistent. In this paper, we focus on lung cancer risks in epidemiologic studies of silicotics. We abstracted data from 29 studies for quantitative evaluation. We identified several studies that suffered from biases due to competing risks of different causes of death--in particular, death due to silicosis itself. After adjustment for competing risks, all 29 studies demonstrated lung cancer relative risk (RR) estimates greater than one. The pooled RR estimate for the 23 studies that could be combined was 2.2, with a 95% confidence-interval (CI) of 2.1-2.4. The pooled estimates by study design were 2.0 (95% CI = 1.8-2.3) for cohort studies and 2.5 (95% CI = 1.8-3.3) for case-control studies. The proportional mortality studies combined gave a summary RR of 2.0 (95% CI = 1.7-2.4), whereas the studies of cancer incidence gave a summary RR of 2.7 (95% CI = 2.3-3.2). Although statistical tests demonstrated heterogeneity between studies, and the confidence intervals given above may therefore be a little too narrow, the overall findings could not be attributed to chance, confounding by smoking, or other sources of bias. We conclude that the association between silicosis and lung cancer is causal, either due to silicosis itself, or due to a direct effect of the underlying exposure to silica.
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PMID:Meta-analysis of studies of lung cancer among silicotics. 858 94

Examination of 315 lung cancer patients with silicosis or silicotuberculosis gave grounds for recognition of 3 variants of bronchial stenosis. The efficacy of bronchoscopic techniques was related both to anatomic variant of the tumor and primary tumor position against the involved bronchus lumen. Central peribronchial cancer in silicosis and silicotuberculosis has specific features: combination of true tumor stenosis with false rigidity of the trachea and large bronchi, advanced scar anthracotic deformity of the bronchi and diffuse atrophy of bronchial mucosa, distinctive pattern of metastatic spreading.
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PMID:[Bronchoscopic diagnosis of central peribronchial lung cancer in silicosis and silicotuberculosis]. 865 89

Because some evidence suggests that there may be an increased incidence of lung cancer in silicosis and because previous studies have shown that exposure of rats to silica alters the pulmonary cytochrome P-450 system, we studied the effects of exposing rats to silica on the lung microsomal metabolism of benzo[a]pyrene (BaP). Rats were exposed to silica by intratracheal administration, lung microsomes were obtained 2 wk later from untreated and silica-treated animals, and the amounts of microsomal tissue and metabolites formed during the in vitro microsomal metabolism of BaP were measured. When the formation of BaP metabolites in equal amounts of lung microsomal tissue from the 2 treatment groups is compared, 3-OH BaP, BaP 4,5-diol, and BaP 9,10-diol are reduced by 45-70%, but the formation of BaP 7,8-diol or the BaP-quinones is not significantly altered following exposure to silica. In fact, the ratio of the BaP diols and BaP quinones, potentially toxic metabolites, to the relatively nontoxic 3-OH BaP produced by equal amounts of lung microsomal tissue is increased more than threefold following exposure of rats to silica. Since exposure of rats to silica leads to increased levels of lung microsomal protein, the amounts of BaP metabolites that could be produced by all microsomal tissue in the lungs were calculated. In silica-treated animals, the calculated total lung production of 3-OH BaP, BaP 4,5-diol, and BaP 9,10-diol tends to be increased by 1.2- to 2.0-fold, but BaP 7,8-diol and the BaP quinones are increased by 3.5-fold. These results demonstrate that exposure of rats to silica may alter the capacity of the lungs to metabolize benzo[a]pyrene, and the greatest effect seems to be enhanced accumulation of BaP 7,8-diol and the BaP quinones.
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PMID:Pulmonary microsomal metabolism of benzo[a]pyrene following exposure of rats to silica. 875 37


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