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PubMed1984

Serum beta-N-acetylglucosaminidase and beta-glucuronidase activities in silicosis patients and in workers exposed to silica dust.

The serum activities of two lysosomal enzymes, beta-N-acetylglucosaminidase (EC 3.2.1.30; NAG) and beta-glucuronidase (EC 3.2.1.31; GLU) were analysed in 116 male patients with silicosis. Twenty-eight of the patients were matched with controls of similar sex, age and exposure to silica dust but with no radiographical evidence of silicosis. A control group which had not been exposed to silica dust consisted of male blood donors. The mean activity of NAG in serum was higher in the silicosis patients than in the blood donors (P less than 0.01). Similarly, the NAG level in the silicosis patients with matched controls was higher than that in the silica-exposed controls (P less than 0.05). The silicosis patients who showed a progression of small opacities by one or more subcategories had a slightly higher mean NAG activity in their sera than the patients with no progression but this difference did not reach statistical significance; the activity was higher than in silica-exposed controls (P less than 0.05). We suggest that these findings may be related to the effects of silica on macrophages which have been observed experimentally in vitro and in vivo and might indicate an increased turnover of macrophages caused by silica dust and active, progressive silicotic fibrosis.

Acetylglucosaminidase↗
PubMed1984

Serum lysozyme concentration in silicosis patients and workers exposed to silica dust.

Lysozyme in serum (LZM, EC 3.2.1.17) was assayed in 135 male patients with silicosis. Twenty-eight of the patients had controls matched for exposure to silica dust, age and sex but with no radiographical signs of silicosis. A reference group without exposure to silica dust was composed of 34 lumberjacks. The mean concentration of serum LZM was higher in silicosis patients (7.8 +/- 2.8 mg/l, n = 28) than in the controls exposed to silica (6.0 +/- 1.7 mg/l, p less than 0.05), or in the lumberjacks (5.7 +/- 2.1 mg/l, p less than 0.01). There was an association between serum LZM concentration and radiographic severity of silicosis, and on a group basis an association of serum LZM concentration with the progression of silicosis. In the multivariate regression analysis the highest regression coefficients were found for progression of small opacities as well as patient age. The results suggest that the elevation of LZM concentration is associated with the progression of the disease.

Adult↗
PubMed1980

[Importance of ergooxytensiometry in the evaluation of dust exposure and of patients with lung silicosis].

After retrospective evaluation of numerous expertises of patients exposed to dust with and without silicosis the high value of the arterial partial oxygen pressure and of the ergooxytensiometry in the estimation of the cardiorespiratory functional breadth is explained. On an average in patients with silicosis III and silicotuberculosis, respectively, more frequently a respiratory insufficiency is found than in patients exposed to dust with lower stages of silicosis or without clue to the presence of a silicosis. In the individual case there is no firm relation between the x-ray-morphological findings and the result of the ergooxytensiometry. The roentgenological stage of silicosis does not allow a conclusion to the loss of function, on the contrary, the frequently existing bronchitis in patients exposed to dust plays an important part in the development of the disturbances of the pulmonary function.

Adult↗
PubMed1995

Dustiness, silicosis & tuberculosis in small scale pottery workers.

Studies were carried out in eight small scale potteries to find out the airborne dust concentrations and the prevalence of dust related diseases like silicosis and tuberculosis in 292 workers. Chest radiography revealed that 44 (15.1%) pottery workers were suffering from silicosis and an equal number showed radiological evidence of tuberculosis. The environmental study showed that the concentrations of airborne dust, containing free silica, in the work environment of all departments (except packing department) of potteries were higher than threshold limit values (TLVs). The prevalence of silicosis and tuberculosis correlated with the levels of airborne dust. The prevalence of tuberculosis increased with radiological severity of silicosis. Dust control measures combined with pre-employment and periodical medical examinations are recommended for the control of silicosis and tuberculosis in the pottery industry.

Air Pollutants, Occupational↗
PubMed1995

Assessment of silicosis risk for occupational exposure to crystalline silica.

Epidemiologic studies of workers exposed to silica were reviewed to identify data on airborne concentrations of quartz that are not associated with an increased risk of silicosis, the lowest concentrations associated with silicosis, and studies that used statistical models to quantitate the risk of silicosis as a function of silica exposure. The no observed adverse effect levels varied from 7 to 100 mu g center dot m-3, and the lowest observed adverse effect levels ranged from 8 to 252 mu g center dot m-3 in five different cohorts. Studies using quantitative exposure-response models revealed a wide difference in the cumulative risk estimates for silicosis. The differences in the risk estimates and the no observed and lowest observed effect levels may have been the result of errors in exposure estimates, physicochemical characteristics of silica and quartz content of the dust, cohort differences, and reader variability. Further research is needed to define the dose-response relationship between silica exposure and silicosis.

Crystallization↗
PubMed1996

[Role of genetic factors in the etiology of silicosis].

Examination of 15 systems of hereditary polymorphism including HLA system was conducted in 284 patients suffering from silicosis and 431 healthy subjects. The results provided genetic factors showing propensity to and resistance against silicosis. The data served as a base for silicosis risk groups formation among the staffers at occupational risk of silicosis, for occupational selection during placement to enterprises with silicosis danger.

Disease Susceptibility↗
PubMed1976

[Silicosis, chronic bronchitis and smoking habits].

In 333 patients suffereing from silicosis the incidence of chronic bronchitis and/or obstruction of the respiratory tract has been correlated with cigarette smoking. The incidence of chronic bronchitis and/or airway obstruction in patients who had acquired either slight or severe silicosis in Switzerland was over 50%. A positive correlation between cigarette smoking and chronic bronchitis and/or airway obstruction could be found only in younger patients with slight silicosis. Chronic bronchitis and/or airway obstruction was not more frequent in foundry-workers suffering from silicosis where they had been exposed to fumes which irritated the respiratory tract. Deformation of the respiratory tract due to silicosis has a greater bearing on the development of chronic bronchitis and airway obstruction than immoderate cigarette smoking.

Adult↗
PubMed1998

Silicosis deaths among young adults--United States, 1968-1994.

Silicosis is a potentially fatal and typically chronic fibrotic lung disease caused by occupational exposure to respirable crystalline silica dust. In the United States, most silicosis-associated deaths occur among persons aged > or = 65 years, often following many years of silica dust exposure. However, the continuing occurrence of silicosis deaths in young adults reflects relatively recent overexposures, some of sufficient magnitude to cause severe disease and death after relatively short periods of exposure. This report describes deaths among two young adults with silicosis and underscores the risk for deaths from silicosis at relatively young ages.

Adolescent↗
PubMed2006

Interleukin-12 is not essential for silicosis in mice.

BACKGROUND: Silicosis features foci of inflammation where macrophages and lymphocytes precede and accompany fibroblast proliferation, alveolar epithelial hyperplasia, and increased deposition of connective tissue matrix material. In the mouse following silica inhalation there is recruitment of natural killer-, B-, and CD4+ and CD8+ lymphocytes to the alveolar spaces, enlargement of bronchial-associated lymphoid tissues (BALT), and aggregation of lymphocytes surrounding small airways and blood vessels. A substantial fraction of the recruited lung lymphocytes produce interferon-gamma (IFN-gamma), and IFN-gamma gene-deleted mice develop less silicosis than wild-type mice. Interleukin-12 (IL-12) is an important pathway for driving the adaptive immune response towards a TH1-like phenotype. We hypothesized that IL-12 might stimulate lymphocyte activation and the up-regulation of IFN-gamma, and consequently be an essential mediator for silicosis. RESULTS: C57Bl/6 wild-type (WT) and IL-12 deficient (IL-12 KO) mice were exposed to sham-air or crystobalite silica (61 mg/m3) by inhalation for 5 hours/day for 12 days and then studied from 1 to 112 days after exposure. Mice exposed to sham-air had normal lung histology at all time points. WT mice exposed to titanium dioxide (72 mg/m3) showed pulmonary macrophage recruitment but no increase in lung collagen. Both WT and IL-12 KO mice exposed to silica showed similar progressive lung pathology, increased wet lung weight and increased total lung collagen (hydroxyproline). IL-12 p35 mRNA was not increased in either strain after silica exposure; IL-12 p40 mRNA was up-regulated after silica in WT mice and constitutively absent in the IL-12 KO mice. IL-18 mRNA was not increased after silica exposure. The expression of IL-15 (an important driver for innate immunity, Natural Killer cell activation, and IFN-gamma production) was abundant in air-exposed mice and was increased slightly in the lungs of mice with silicosis. CONCLUSION: The axis of IL-12 driving IFN-gamma production is not essential for the full manifestations of silicosis in mice exposed to a crystobalite silica aerosol.

Journal Article↗
PubMed1989

[Dynamics of interstitial silicosis in relation to the state of the intrathoracic lymphatic system].

The time course of interstitial silicosis in 150 patients was investigated retrospectively by the roentgenograms for a follow-up varying from 2 to 20 years. It was shown that silicosis progress followed the affection of the intrathoracic lymph nodes. The latter was mainly predetermined by tuberculous infection in person working under silicosis-hazardous and unfavourable sanitary and hygienic conditions. The picture of pulmonary lesions developing after adenopathy in patients with silicosis was roentgenologically completely identical to that of polymorphous tuberculosis. In this connection it was recommended that thorough clinical and bronchological examinations for silicotuberculosis of adenogenic genesis be performed in all the cases with progressing silicosis.

Humans↗
PubMed1998

Radiographic silicosis and lung cancer risk among workers in Ontario.

A case-control study, nested in a cohort of workers under surveillance for silicosis in 1979 or later, was undertaken to assess lung cancer risk in relation to the ILO coding scheme for the pneumoconioses. The subjects of this study are from the 41 matched quarters, consisting of one workers with silicosis and three age-matched controls, in which a lung cancer case was diagnosed. The odds ratio for lung cancer among subjects with ILO classification 1/0 or more, in comparison to subjects with category < or = 0/1, was 3.27 (95% CI =1.32-8.2). Adjustment of the radiographic risk for the effect of cumulative radon exposure had the effect of increasing the odds ratio for the association between ILO category > or = 1/0 and lung cancer. Although small smoking differences could account for the increased lung cancer odds ratio among workers with silicosis, the empirical evidence suggests that these smoking differences do not exist. It is concluded on the basis of two North American studies of silica exposed workers that radiographic silicosis is a marker for an increased risk of lung cancer.

Case-Control Studies↗
PubMed1998

Cost-effectiveness of hospital discharge records for reaching selected endpoints in the surveillance of silicosis.

BACKGROUND: The Sentinel Event Notification System for Occupational Risks (SENSOR) is a state/federal system for the surveillance and intervention of occupational conditions. The Ohio SENSOR program identifies silicosis cases from a number of data sources, although hospital discharge records have largely been considered the most successful means of carrying out SENSOR objectives. However, the cost-effectiveness of hospital discharge records has not been evaluated. Thus, a cost analysis was conducted to compare the effectiveness of hospital discharge records with other data sources for achieving prevention-related endpoints of silicosis surveillance. METHODS: Total costs of reaching three endpoints (obtaining case names, identifying work sites, and identifying silica problems in work sites) were estimated retrospectively and measured in 1996 dollars for four data sources: hospital discharge records, physician reports, workers' compensation claims, and death certificates. Total costs were then divided by output for each source/endpoint combination to produce estimates of average costs. RESULTS: The average cost per case was $30 for hospital records, $212 for physician reports, $19 for workers' compensation claims, and $7 for death certificates. However, for identifying problem work sites, hospital records were most expensive at $2,883 per work site, compared with $2,558 for physician reports, $1,318 for workers' compensation claims, and $1,310 for death certificates. CONCLUSIONS: Hospital discharge records were least cost-effective for accomplishing prevention-related goals of surveillance. A change in the mix of resources applied to silicosis surveillance and intervention under SENSOR, i.e., a shift away from follow-up of hospital records toward more cost-effective methods for identifying work sites with silica problems may result in more efficient use of public health resources devoted to the prevention of silicosis.

Cost-Benefit Analysis↗
PubMed2001

Lung cancer risk, silica exposure, and silicosis in Chinese mines and pottery factories: the modifying role of other workplace lung carcinogens.

BACKGROUND: Aims of our study were to explore whether and to what extent exposure to other lung carcinogens, or staging and clinical features of silicosis modify or confound the association between silica and lung cancer. METHODS: We used data from a nested case-control study, conducted in the late 1980s in 29 Chinese mines and potteries (10 tungsten mines, 6 copper and iron mines, 4 tin mines, 8 pottery factories, and 1 clay mine), that included 316 lung cancer cases and 1,356 controls, matched by decade of birth and facility type. The previous analysis of these data presented results by type of mine or factory. RESULTS: In our study, pooling all 29 Chinese work sites, lung cancer risk showed a modest association with silica exposure. Risk did not vary after excluding subjects with silicosis or adjusting the risk estimates by radiological staging of silicosis. Strong correlation among exposures prevented a detailed evaluation of the role of individual exposures. However, lung cancer risk was for the most part absent when concomitant exposure to other workplace lung carcinogens, such as polycyclic aromatic hydrocarbons (PAHs), nickel or radon-daughters, was considered. The cross classification of lung cancer risk by categories of exposure to respirable silica and total respirable dust did not show an independent effect of total respirable dust. Silicosis showed a modest association with lung cancer, which did not vary by severity of radiological staging, or by radiological evidence of disease progression, or by level of silica exposure. However, among silicotic subjects, lung cancer risk was significantly elevated only when exposure to cadmium and PAH had occurred. CONCLUSIONS: Our results suggest that, among silica-exposed Chinese workers, numerous occupational and non-occupational risk factors interact in a complex fashion to modify lung cancer risk. Future epidemiological studies on silica and lung cancer should incorporate detailed information on exposure to other workplace lung carcinogens, total respirable dust, and on surface size and age of silica particles to understand whether and to what extent they affect the carcinogenic potential of silica.

Adult↗
PubMed1985

Silicosis in slate pencil workers: I. An environmental and medical study.

An environmental and medical survey was undertaken in the slate-pencil industry in the central part of India. The industrial hygiene survey revealed that concentrations of free silica dust were very high. The medical survey, involving 593 workers, revealed that the prevalence of silicosis in this industry was 54.6%. Of these, 17.7% of workers had conglomerate silicosis (progressive massive fibrosis, PMF). The radiologic appearance of simple and conglomerate silicosis resembled closely the simple pneumoconiosis and progressive massive fibrosis (PMF) among other occupational groups exposed to free silica and also found in coal workers. The pulmonary lesions were detectable after a relatively short duration of exposure. The short latent period of development and the high prevalence of silicosis observed among these workers are related to exposure to high concentrations of siliceous dust in the work environment.

Adult↗
PubMed1989

Prevalence of silicosis at death in underground coal miners.

This study was initiated by the National Institute for Occupational Safety and Health (NIOSH) and the Bureau of Mines (BOM) to determine the prevalence and pathological features of silicosis in coal miners. The population base was 3,365 autopsied underground miners whose records were submitted to the U.S. National Coal Workers' Autopsy Study between 1971 and 1980. This program is voluntary and covers an estimated 10% of all coal workers who die. The mean age at death of the population was 62 years, of whom 75% were current or ex-smokers at the time of death. The average work tenure was 26 years. Lung sections from all cases were reviewed and the type and severity of pneumoconiosis documented. These findings were correlated with years of mining, job history, and geographic location of mine. Classical silicotic nodules were found in 12.5% of the population. There was a significant relationship between length of underground mining and prevalence and severity of silicosis consistent with a dose-response effect. The study also showed that job category and geographic location of the mine were important determinants of silicosis prevalence and that silicosis was strongly associated with higher categories of coal workers' pneumoconiosis.

Aged↗
PubMed1991

Silicosis among gemstone workers in South Africa: tiger's-eye pneumoconiosis.

Six cases of silicosis in workers involved in the processing of semiprecious gem stones have been seen in our clinic since 1976. They had been employed as stone sculptors in lapidaries where they processed tiger's-eye, rose quartz, amethyst, quartz crystal, and a variety of other locally occurring semiprecious stones. In five of the cases, exposure was in small and poorly regulated lapidaries without specific dust control measures. The sixth was detected during the course of a health and hygiene survey (including dust sampling) that was conducted in one of two lapidaries still operating in our area. Progressive massive fibrosis (PMF) or accelerated silicosis was noted in four of the six cases, three of whom had progression of their disease after cessation of exposure. With the development of PMF, the initial restrictive pulmonary function abnormalities were followed by steadily worsening airflow obstruction. Lung biopsies confirmed silicosis in three cases. Tuberculosis was confirmed in two cases and suspected and treated in a third. Workmen's Compensation was awarded in five cases. The survey confirmed that in semiprecious gem stone processing, the risk of silicosis appears to be confined to stone sculptors. Tried and proven techniques of general and local exhaust ventilation combined with water or oil to control dust at source were capable of effectively reducing dust emission to acceptable levels.

Adult↗
PubMed1993

Correlation between radiological and pathological diagnosis of silicosis: an autopsy population based study.

The radiological findings for the profusion of rounded opacities were compared to pathological findings for parenchymal silicosis in 557 gold miners who had, on average, 2.7 years between the radiological and pathological examination. Three readers read the radiographs, and ILO category 1/1 or more was defined as a positive diagnosis of silicosis. The sensitivity values were 0.393, 0.371, and 0.236, and the specificity values were 0.987, 0.965, and 0.978, for the three readers, respectively. The sensitivity of the readers improved with increasing degree of autopsy silicosis, but a large proportion of those with a moderate and marked degree of silicosis were not diagnosed radiologically. The diagnostic sensitivity of the radiological test could be improved by using category 0/1 as a cutoff point for workers exposed to a high average concentration of respirable silica dust. The diagnostic specificity of radiology could be improved by using category 1/0 or 1/1 as a cutoff point for a positive diagnosis for workers exposed to a low average concentration of respirable silica dust.

Autopsy↗
PubMed1994

Silicosis surveillance in Ontario: detection rates, modifying factors, and screening intervals.

The Province of Ontario has had a surveillance program for workers in dusty industries for almost 70 years. This paper reports the detection rates of silicosis among 68,701 silica-exposed individuals who were first exposed to dust in 1950 or later, and who were still employed in 1979 or later. The detection rate varied strongly with latency, being less than two new cases per 10,000 examinations during the first two decades from first exposure, reaching two new cases per 1,000 examinations at 27 years from first exposure, and averaging between two and four new cases per 1,000 examinations thereafter. The silicosis incidence rate among miners was only about half that among foundry workers. Cigarette smoking was also found to be a risk factor for the diagnosis of silicosis. These data were used to model the detection rate of new cases of silicosis as a function of the time interval between examinations, and results are presented for examination cycles between 2 and 10 years.

Humans↗