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PubMed2005

Risk of silicosis in cohorts of Chinese tin and tungsten miners and pottery workers (II): Workplace-specific silica particle surface composition.

BACKGROUND: It is hypothesized that surface occlusion by alumino-silicate affects the toxic activity of silica particles in respirable dust. In conjunction with an epidemiological investigation of silicosis disease risk in Chinese tin and tungsten mine and pottery workplaces, we analyzed respirable silica dusts using a multiple-voltage scanning electron microscopy-energy dispersive X-ray spectroscopy (MVSEM-EDS). METHODS: Forty-seven samples of respirable sized dust were collected on filters from 13 worksites and were analyzed by MVSEM-EDS using high (20 keV) and low (5 keV) electron beam accelerating voltages. Changes in the silicon-to-aluminum X-ray line intensity ratio between the two voltages are compared particle-by-particle with the 90th percentile value of the same measurements for a ground glass homogeneous control sample. This provides an index that distinguishes a silica particle that is homogeneously aluminum-contaminated from a clay-coated silica particle. RESULTS: The average sample percentages of respirable-sized silica particles alumino-silicate occlusion were: 45% for potteries, 18% for tin mines, and 13% for tungsten mines. The difference between the pottery and the metal mine worksites accounted for one third of an overall chi-square statistic for differences in change in measured silicon fraction between the samples. CONCLUSION: The companion epidemiological study found lower silicosis risk per unit cumulative respirable silica dust exposure for pottery workers compared to metal miners. Using these surface analysis results resolves differences in risk when exposure is normalized to cumulative respirable surface-available silica dust.

Ceramics↗
PubMed1986

Silica, silicosis and lung cancer among ceramic workers: a case-referent study.

A case-referent study has been carried out regarding a possible connection between silica exposure and lung cancer (ICD 162) in Central Italy, where the pottery industry has a long tradition. Silicosis among 72 cases of lung cancer and among 314 referents, all deceased, was ascertained through checking the individual files of compensated cases of silicosis. Questionnaires on past employments and smoking habits were blindly administered to the next-of-kin of the deceased subjects. Controlling for age, period of death, and smoking, workers in the ceramic industry were found to have a higher lung cancer risk than workers in other occupations free from silica exposure (Mantel-Haenszel rate ratio = 2.0; 95% confidence interval (CI) = 1.1-3.5). This increased risk was mainly due to a rate ratio of 3.9 (95% CI = 1.8-8.3) for silicotic individuals, while for nonsilicotic ceramic workers it was only 1.4 (95% CI = 0.7-2.8). The result of this study seems to suggest that lung cancer might be merely indirectly associated with exposure to silica through the silicotic process, although the dose may differ for silicotic and nonsilicotic individuals.

Ceramics↗
PubMed1989

Silica exposure and silicosis among Ontario hardrock miners: I. Methodology.

An epidemiological investigation was undertaken to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (crystalline silica--alpha quartz) dust. This first report describes the cohort, the method of classifying the radiographs, and the identification of a case of silicosis.

Cohort Studies↗
PubMed1991

Silicosis and lung cancer in North Carolina dusty trades workers.

Since 1940, 760 cases of silicosis have been diagnosed as part of the State of North Carolina's (NC) pneumoconiosis surveillance program for dusty trades workers. Vital status was ascertained through 1983 for 714 cases that had been diagnosed since 1940 and death certificates were obtained for 546 of the 550 deceased. Mortality from tuberculosis, cancer of the intestine and lung, pneumonia, bronchitis, emphysema, asthma, pneumoconiosis, and kidney disease was significantly increased in whites. Mortality from tuberculosis, ischemic heart disease, and pneumoconiosis was significantly increased in non-whites. The standardized mortality ratio (95% CI) for lung cancer based on U.S. rates was 2.6 (1.8-3.6) in whites, 2.3 (1.5-3.4) in those who had no exposure to other known occupational carcinogens, and 2.4 (1.5-3.6) in those who had no other exposure and who had been diagnosed for silicosis while employed in the NC dusty trades. Age-adjusted lung cancer rates in silicotics who had no exposure to other known occupational carcinogens were 1.5 (.8-2.9) times higher than that in a referent group of coal miners with coalworkers' pneumoconiosis (CWP) and 2.4 (1.5-3.9) times higher than that in a referent group of non-silicotic metal miners. Age- and smoking-adjusted rates in silicotics were 3.9 (2.4-6.4) times higher than that in metal miners. This analysis effectively controls for confounding by age, cigarette smoking, and exposure to other known occupational carcinogens, and it is unlikely that other correlates of silica exposure could explain the excess lung cancer mortality in the silicotics.

Adult↗
PubMed1992

Silicosis surveillance in New Jersey: targeting workplaces using occupational disease and exposure surveillance data.

To identify workplaces in New Jersey with potential for silica exposure, the New Jersey Department of Health compared four-digit Standard Industrial Classifications (SICs) identified by three different data sources: the National Occupational Exposure Survey (NOES), a new Jersey silicosis case registry, and regulatory agency compliance inspections in New Jersey. In total, the three data sources identified 204 SICs in New Jersey with potential for silica exposure. Forty-five percent of these SICs were identified by NOES only, 16% by registry cases only, 6% by compliance inspections only, and 33% by two or more sources. Since different surveillance sources implicate different SICs, this type of analysis is a useful first step in planning programs for prevention of silicosis.

Humans↗
PubMed1994

Lung cancer among tin miners in southeast China: silica exposure, silicosis, and cigarette smoking.

The Dachang Tin Mine is an industrial facility with high rates of lung cancer compared to the resident population in Guangxi province in southern China. Historically, exposure to silica dust was very high in the 1950s, falling in recent years to levels in keeping with international standards. Radon levels in the mine are low. We report the findings of a case-control study nested into a cohort study on miners working in Dachang. Cases of lung cancer among miners incident from 1973-1989 were obtained from local comprehensive medical records covering workers employed at the mine. These were matched approximately 3 to 1 with miners randomly chosen from the district surrounding the mine within the same birth decade. Matched odds ratios of 2.42 (95% confidence limit [CL] 1.3, 4.4) for underground employment, 3.52 (95% CL 1.7, 7.5) for smoking, and 2.04 (95%) CL 1.2, 3.7) for silicosis as determined on chest film were noted. Multifactor analysis of unconditional logistic regression showed that among the risk factors for excess mortality from lung cancer only the years spent drilling underground and the cumulative smoking index (product of daily cigarette consumption and number of years smoking) were independent contributors to risk and there was no interaction observed. The presence of silicosis did not contribute to predicting risk independently of the years spent underground.

Case-Control Studies↗
PubMed1995

Silicosis in Brazilian pit diggers: relationship between dust exposure and radiologic findings.

The incidental diagnosis of two cases of silicosis at Messejana Hospital, Fortaleza, capital of Ceará state, triggered a field research conducted with the objective of investigating the incidence of silicosis in pit diggers in four towns in the Ibiapaba Mountain Range, at the state's northwestern area, northeastern Brazil. Out of a universe of 1,050 pit diggers in the area, 366 participated in the study; they were all males ranging in age between 16 and 76 years old (average 39 years). The excavation and the sickening process were described and a dust exposure index in pit diggers (DEIPD) was defined. The study sample indicated a rate of 121 (33.06%) silicotics and possibly silicotics. The radiologic findings were related to the DEIPD and indicated significant prevalence of disease. Furthermore, during the research period, from 1986 to 1989, 30 (34.9%) silicotics died of respiratory failure and wasting of body tissues. The data suggested that these men were afflicted with a severe occupational health problem, possibly scattered throughout a large area in northeastern Brazil, where manual pit excavations occur during the whole year and increase during drought periods.

Adolescent↗
PubMed1992

Lung function in silicosis.

In order to assess the effect of silicosis on lung function, 61 gold miners with radiological silicosis were compared with 61 controls. Each pair was matched for age, dust exposure, and smoking habits. A full range of lung function tests was performed, and with two exceptions the results showed no significant differences between the two groups. The exceptions are the slope of the alveolar plateau (phase 3) and the closing volume, for which the silicotic cases had significantly higher values. The reason for the higher readings in the silicotic patients remains unexplained.

Blood Gas Analysis↗
PubMed1999

Switzerland: the status of silicosis from the past to the end of the 20th century. Control and prevention.

The silicosis issue in Switzerland is reviewed on the basis of data provided by Suva, the Swiss National Insurance Fund, in charge of law enforcement and of prevention. Pictures of the past period and nowadays consecutively to the occupational medicine surveillance and industrial hygiene practice showed that major improvements have been realized. In the 30's, a constant rise of new cases of silicosis has been observed every year. From 1940 to end of the 60's, a plateau was reached with about 200 to 300 cases per year. Since 1974, a significant decrease is observed, the annual number of new cases being about 100. Since 1989, the new cases level off at 30-50 per year due to drastic control measures and present announced cases are residuals of previous exposures. The number of annual deaths ranges at the unit level with a patient's life expectancy nearly equal to that of the general population. Prevention efforts however should be continued since the activities of concern have changed. Small enterprises with a limited number of personnel dispersed throughout the country, working in the sectors of stone cutting and grinding, civil engineering and cleaning of building surfaces make prevention difficult and may lower its efficiency. In addition, information should also reach categories of individual workers like professional pottery crafstmen or leisure-exposed persons.

Adult↗
PubMed1990

Enzyme activities of lung lavage in silicosis.

The cytotoxic effect of quartz on lung cells has been well documented by in vitro and animal studies, but the pertinence of these findings to humans has not yet been documented. We measured lactate dehydrogenase (LDH) activities in the lung lavage of 24 long-term workers in the Québec granite industry and 25 control subjects. We found significant increases in LDH activities in the workers' lung lavage, even in the absence of established silicosis (9 subjects). We looked at a similar observation in the sheep model of early silicosis, measured quartz content of lung lavage, and found significant correlation with LDH levels (R = 0.64, p less than 0.001). All of the quartz particles in human and sheep lung lavage were in the alveolar macrophages. To test further the relationship of macrophage damage (cytotoxicity of quartz) we measured the release of LDH by sheep alveolar macrophage in 24 h cell culture under control conditions, exposure to inert dust, titanium, minusil-5 quartz, or aluminum-treated quartz. The LDH release was at control levels during titanium exposure and showed a significantly dose-related increase during quartz exposure. The latter cytotoxic effect was largely attenuated by aluminum treatment of quartz. These in vitro data agreed with previous reports. This study presents evidence of a cytotoxic effect of quartz inhalation in humans. The effect is related to the intensity of quartz retention in the lung macrophages; it is not a nonspecific dust exposure effect and can be attenuated by surface modification of the quartz.

Adult↗
PubMed2003

Two cases of hypertrophic pachymeningitis associated with myeloperoxidase antineutrophil cytoplasmic autoantibody (MPO-ANCA)-positive pulmonary silicosis in tunnel workers.

Two cases of hypertrophic pachymeningitis (HP) associated with pulmonary silicosis in tunnel workers are described. In both cases the myeloperoxidase antineutrophil cytoplasmic autoantibody (MPO-ANCA) was positive. Two patients with pulmonary silicosis developed headache and neurological disturbance, and a diagnosis of HP was made. In both cases the serum CRP level and the MPO-ANCA titer were elevated. Corticosteroid therapy produced a rapid improvement in all the clinical and laboratory parameters. Although an association has been noted between exposure to silica dust and ANCA-associated vasculitis, particularly glomerulonephritis, central nervous system involvement is rare. However, there have been some recent reports of HP cases that were positive for ANCA, and the association between HP and vasculitis has been discussed in the medical literature. HP may be one feature of multiorgan involvement in ANCA-associated disease, and the association between silica dust exposure and HP should be considered, as with other forms of ANCA-associated vasculitis.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1981

Immune complexes and autoantibodies in silicosis.

Serum specimens from 53 patients with silicosis were examined for the presence of antinuclear antibodies (ANA), rheumatoid factor (RF), immunoglobulins, and immune complexes. These humoral immunologic parameters were compared with radiographic changes and pulmonary function studies. A significant percentage of patients had an increased prevalence of ANA, RF, and immunoglobulin elevation (IgG, IgA). Immune complexes determined by the Raji-cell assay were detected in 31% of the patients. However, there was no significant correlation between any humoral immunologic abnormality and radiographic changes or declines in pulmonary function tests. These findings suggest that humoral immunologic abnormalities are not directly responsible for the lung changes in silicosis and cannot be used as "guides" to predict severity or progression of disease.

Adult↗
PubMed1982

Current concepts about the pathogenesis of silicosis and asbestosis.

Silicosis and asbestosis are two forms of fibrotic lung disease resulting from the inhalation of inert materials indigestible by pulmonary alveolar macrophages. Results of studies of the host response to these particulates have not always been consistent. It is clear, however, that after phagocytosis, both cause alveolar macrophage damage, with resultant release of macrophage products, including fibrogenic factors and chemotactic factors for neutrophils. The latter cells also release lysosomal enzymes and free radicals when exposed to silica and asbestos. The net effect of these observations suggests that the combination of tissue damage and fibroblast stimulation results in the pulmonary fibrosis characterizing these diseases. Patients with silicosis and asbestosis have normal or decreased cell-mediated and increased humoral immunity with a high incidence of circulating immune complexes and autoantibodies. Whether these abnormalities are related to the pathogenesis of pulmonary fibrosis or are epiphenomena remains to be determined.

Animals↗
PubMed1988

Treatment of experimental silicosis with antifibrotic agents.

We tested the efficacy of 2 antifibrotic agents, the proline analogue cis-4-hydroxy-L-proline (cHyp) and the lathyrogen beta-aminopropionitrile (BAPN), on experimental silicosis in hamsters. Silica (75 mg) was instilled intratracheally, and 3 months later lung hydroxyproline content, the volume density of silicotic nodules in lung parenchyma, fluid-filled lung pressure-volume curves, body weight and survival were measured. Animals were injected with cHyp, 200 mg/kg body weight, or BAPN, 150 mg/kg body weight, twice daily for 3 months. Hydroxyproline contents (mg/lung) at 3 months were: control, 0.8 +/- 0.1; silica, 1.4 +/- 0.1 (P less than 0.05 compared to control); silica-cHyp, 1.2 +/- 0.2; silica-BAPN, 1.4 +/- 0.1 (both NS compared to silica). The volume density of granuloma (% of surface area) was: silica, 0.7 +/- 0.1; silica-cHyp, 5.9 +/- 1.0; silica-BAPN, 9.7 +/- 1.5 (both P less than 0.5 compared to silica). There was no difference among the groups as assessed by lung pressure-volume curves. No toxic effects were produced on the skeletal system as assessed by bone hydroxyproline content and skeletal roentgenograms. Final body weights (g) were: silica, 114 +/- 5; silica-BAPN, 108 +/- 6; silica-cHyp, 88 +/- 7 (the latter P less than 0.05 compared to silica). Survival (%) was: silica, 62%; silica-BAPN, 34%, silica-cHyp, 28% (both P less than 0.05 compared to silica). These data show that cHyp and BAPN treatment did not prevent silica-induced pulmonary fibrosis, led to more extensive silicotic nodules, and were toxic. Both cHyp and BAPN have some efficacy in other models of fibrosis, and the observations in the present study could be specific to silicosis in the hamster.

Aminopropionitrile↗
PubMed2006

Conglomerated masses of silicosis in sandblasters: high-resolution CT findings.

The purpose of this study was to describe the high-resolution CT aspects of the silicosis and progressive massive fibrosis in sandblasters. The study was performed with 25 consecutive patients with silicosis and large opacities on chest radiography according to the International Labor Office (ILO) classification of pneumoconiosis. All patients presented with conglomerate masses involving the upper lobes, and in 92% of the cases the lesions were located in the posterior region of the lungs. The masses frequently showed nodular contour (76%), air bronchograms (76%), foci of calcification (72%), paracicatricial emphysema (72%), and adjacent pleural thickening (92%). Calcification of hilar or mediastinal lymph nodes (96%), mainly of the egg-shell type (56%), was also a common finding. In conclusion, in this specific group of patients, the sandblasters, the high-resolution CT demonstrated conglomerated masses with nodular contour, air bronchograms and foci of calcification, which were distributed mainly in the posterior region of the upper lobes. Calcification of hilar or mediastinal lymph nodes was also commonly seen.

Adult↗
PubMed2004

Silicosis in dental supply factory workers.

Dental products contain a variety of potentially hazardous materials, including metals, organic chemical compounds, plastics, and inorganic mineral dusts. The risk of silicosis has been documented for workers of dental laboratories, but not dental supply factories, where the exposures could be expected to be higher. We report in this article five cases of silicosis, four of them with progressive massive fibrosis, in workers from two dental supply factories. This report underlines the need for effective occupational health programs in this type of industrial facilities.

Adult↗
PubMed2005

Antifibrotic effect of interferon gamma in silicosis model of rat.

This study presents the antifibrotic effect of interferon gamma (IFN-gamma) in silicosis of rats. Wistar rats were received saline or 20 mg of quartz by intratracheal instillation. The next day after instillation, silicosis model of rats were daily treated IFN-gamma (1.0 x 10(5) units/rat) or saline by intramuscular route. At 1 month or 2 months after instillation, rats were sacrificed to determine hydroxyproline content and observe the change of fibrosis and expression of interleukin-4 (IL-4) and transforming growth factor-beta1 (TGF-beta1) in the lung of rats. The hydroxyproline content of IFN-gamma treated groups was significantly lower than that of quartz groups (P<0.05). At 1 month after instillation, there were Stage II and II+ of silicotic nodules in quartz group; however, in IFN-gamma treated group only cellular nodules (Stage I) were observed. At 2 months after instillation, there was Stage II+ and III of silicotic nodules in quartz group. In IFN-gamma treated group Stage II was found. The expressions of IL-4 (2.19+/-0.90, 0.61+/-0.22, respectively) and TGF-beta1 (1.37+/-0.31, 1.76+/-0.72, respectively) in IFN-gamma treated groups were significantly lower than those in quartz groups (IL-4: 3.33+/-1.27, 1.99+/-0.80; TGF-beta1: 3.67+/-0.63, 4.90+/-1.11, respectively; P<0.05 or P<0.01). It may be concluded that the decreased expression of IL-4 and TGF-beta1 may be associated with decreased hydroxyproline synthesis, which then results in decreased lung fibrosis.

Animals↗
PubMed1995

Extrapulmonary silicosis in two water buffaloes.

Two cases of extrathoracic silicosis in buffaloes raised near a quartz quarry and suffering from clinically severe silicosis are described. The extrapulmonary changes were characterized by silicoconiotic nodules in the tonsils, mesenteric lymph nodes and spleen. A combination of energy dispersive X-ray microanalysis and scanning electron microscopy revealed that the mineral component of these lesions consisted mainly of silicon, aluminium, iron, calcium, magnesium, zinc, sulphur and potassium. It is concluded that domestic animals raised in polluted environmental conditions represent an important biological source from which helpful data may be obtained for assessing risks to human health and gaining new insight into pathogenetic mechanisms.

Animals↗