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PubMed1997

Silicosis in the 1990s.

OBJECTIVE: To describe state-based surveillance for silicosis that estimates prevalence of this condition, describes characteristics of affected individuals, and targets public health interventions. DESIGN: The data presented are a case series of patients with silicosis reported to a state health department. Patients were interviewed using a standardized questionnaire, chest radiographs interpreted by a "B-reader," pulmonary function tests obtained from medical records, and follow-back investigations conducted at the worksites where the cases had been exposed to silica. SETTING: All individuals with silicosis in the state of Michigan reported to the Michigan Department of Public Health (MDPH). SUBJECTS: Individuals included in this article were reported from 1987 through 1995. Cases were reported by hospitals, physicians, the state workers' compensation bureau, or from death certificates. Only data on individuals who met the criteria for silicosis developed by the National Institute for Occupational Safety and Health (NIOSH) are included. RESULTS: Between 1987 and 1995, 577 people were reported to MDPH who met the NIOSH criteria for silicosis. About 60% of the reports came from hospitals. The disease is occurring mainly among men born before 1940 who began working in a Michigan ferrous foundry in the 1930s or 1940s and worked there > 20 years. Over 40% of the patients are black. The overall annual average incidence rate of silicosis among black men (14.3 cases per 100,000) is seven times higher than among white men (2.1 cases per 100,000). The individuals identified with silicosis generally have severe disease. Almost 30% have progressive massive fibrosis and another 31.7% have advanced simple silicosis. Only about a third of all patients have normal results of breathing tests. Thirteen percent had been told they had tuberculosis (includes both clinical disease and a positive skin test). They have an increase of over 300% in the likelihood of dying of nonmalignant respiratory disease, both restrictive and obstructive, and an 80% increase in the likelihood of dying of lung cancer. Despite the severity of disease, over 45% of the individuals had not applied for workers' compensation. Although silicosis typically occurs after a long duration of exposure to silica, some individuals developed silicosis after a relatively short time. Three people developed silicosis who began working with silica in the 1980s, 18 in the 1970s, and 66 in the 1960s. Initial industrial hygiene follow-up inspections where the individuals had worked showed ongoing exposure above recommended and/or legal levels. Repeated inspections to these same facilities have subsequently shown reductions in silica exposure. CONCLUSION: This state-based surveillance system has proved useful in characterizing individuals with silicosis, estimating its prevalence, increasing the medical community's awareness of the condition, and targeting effective public health interventions.

Aged↗
PubMed2003

Estimating the total number of newly-recognized silicosis cases in the United States.

BACKGROUND: The US employer-based surveillance system for documenting occupational injuries and illnesses undercounts chronic diseases. We suggest a method to estimate the number of individuals who are newly-recognized with silicosis each year in the United States. METHODS: Data from US death certificates, the Michigan state-based surveillance system, and capture-recapture analysis were used to calculate national estimates of silicosis. RESULTS: From 1987 to 1996, 2,787 deaths occurred in the United States where silicosis was mentioned on the death certificates. During the same period, in Michigan 77% of death certificates with a mention of silicosis were confirmed as silicosis-related deaths and the ratio of the number of living to deceased confirmed silicosis cases was 6.44. The proportion of confirmed silicosis deaths, the ratio of the living to deceased silicosis cases and capture-recapture analysis from the Michigan surveillance system, were used to estimate that there were 3,600-7,300 cases per year of silicosis in the United States from 1987 to 1996. CONCLUSIONS: Our estimate of the annual number of newly-recognized silicosis cases is significantly larger than the estimate from the employer-based reporting system used for counting occupational disease in the United States. This employer-based surveillance system is inadequate for determining the frequency of occupational disease. Our analysis which combines a readily-available and relatively inexpensive national administrative database (i.e., death certificates) with a more costly state-based active surveillance system is a cost-effective model that could be used to provide better estimates of a number of different occupational diseases. Accurate estimates of occupational illnesses are essential to both determine temporal trends and evaluate efforts to prevent silicosis.

Death Certificates↗
PubMed2006

Natural course of silicosis in dust-exposed workers.

To provide a scientific basis for determining the health surveillance period of dust-exposed workers, data of a retrospective cohort study was re-analyzed with emphasis on natural course of silicosis. 33640 workers exposed to silica dust who were employed for at least 1 year from 1972 to 1974 in twenty Chinese mines or pottery factories were included as subjects, and were followed up till December 31, 1994. The cohort included subjects from 8 tungsten mines, 4 tin mines and 8 pottery factories. Our results showed that the mean latency of silicosis, for all the cases of the cohorts, was 22.9 +/- 9.8 y. 52.2 % of silicosis was diagnosed approximately 9.1 +/- 5.7 y after the dust exposure had ceased. The progression rates of silicosis from stage I to II and from stage II to III were 48.2 % and 18.5 %, and the duration was 4.1 +/- 0.2 and 6.8 +/- 0.2 y, respectively. The survival times of silicosis stage I , II and III, from the year of diagnosis to death, were 21.5, 15.8 and 6.8 years, respectively. There was 25 % of the silicosis patients whose survival time was beyond 33 y. The mean death age of all silicosis cases was 56.0 y. The death age increased to 65.6 y in the middle of 1990s. Among dust-exposed workers, subjects who became suspected case (0+ ) accounted for 15.0 %. 48.7 % of the suspected silicosis cases developed to silicosis, and the average year from the time of being suspected of the disease to the first stage of silicosis was 5.1 y. The natural characteristics, as mentioned above, varied with different mines and factories. We are led to conclude that silicosis is chronic in nature, but progress quickly. As a serious occupational disease it significantly reduces the life span of exposed workers. The study of its natural history is of importance for the development of health surveillance criteria for dust-exposed workers.

Cohort Studies↗
PubMed1994

The epidemiology of tuberculosis in gold miners with silicosis.

The elevated risk of tuberculosis in subjects with silicosis is widely accepted but has not been quantified in a population with a high prevalence of tuberculosis. In this study, a cohort of 1,153 older gold miners with and without silicosis who had not had tuberculosis have been followed for 7 yr by a routine mine surveillance program for detection of tuberculosis. One hundred seventy-eight of the men developed tuberculosis. The annual incidence of tuberculosis was 981/100,000 in the 335 men without silicosis and 2,707/100,000 in the 818 men with silicosis. The relative risk for tuberculosis was 2.8 (95% CI, 1.9 to 4.1) for men with silicosis compared with that in the men without silicosis. The incidence of tuberculosis increased from 1% per annum (pa) for the men without silicosis to 2.2% pa for the men with silicosis with Category 1 nodule profusion, 2.9% pa for those with Category 2, and 6.3% pa for those with Category 3 silicosis. This study has confirmed and quantified the high risk of pulmonary and of extrapulmonary tuberculosis in men with silicosis. The incidence of tuberculosis during this 7-yr study suggests that one quarter of these men with silicosis will have developed tuberculosis by 60 yr of age.

Cohort Studies↗
PubMed1989

The prevention of silicosis and prediction of its future prevalence in China.

We studied the effects of preventive and therapeutic interventions on the 18-year cumulative incidence of silicosis of 26,603 dust-exposed workers in seven Chinese mines and industrial plants. Cumulative silicosis incidence decreased from 36.1 percent in workers employed before 1950 to 1.5 percent in workers employed after 1960. From the 1950s to 1970s, eight-year cumulative incidence of tuberculosis decreased from 54.7 percent to 16.7 percent and case fatality of silicosis patients dropped from 53.9 percent to 18.3 percent. From 1950s to 1980s, the average age at the detection of silicosis increased from 41.3 to 52.7 and the average survival time of silicosis patients prolonged from 2.0 to 12.2 years. Workers over age 40 who began exposure to dust before 1960 will be the main source of new silicosis patients in future. Most expected new cases of silicosis will occur within the next 15 years. The silicosis population will remain unchanged for the next 20 years and will decrease dramatically after 25 years. There will be few silicosis patients in 30 years and new cases of silicosis will be difficult to find in 45 years. These results show that the preventive and therapeutic actions against silicosis in China have been effective.

Adult↗
PubMed2005

Risk of silicosis in cohorts of Chinese tin and tungsten miners, and pottery workers (I): an epidemiological study.

BACKGROUND: Epidemiological evaluations of the risk of silicosis in relation to exposure to crystalline silica have raised the question of whether different types of silica dust exposures vary with respect to their ability to cause silicosis. The aim of this study is to compare the risk of silicosis among cohorts of silica dust-exposed Chinese tin miners, tungsten miners, and pottery workers and to assess whether gravimetric measurements of respirable silica dust sufficiently determine the risk of silicosis or whether other factors of exposure may play a significant role. METHODS: Cohorts were selected from 20 Chinese mines and potteries. Inclusion criteria were starting employment after January 1, 1950 and being employed for at least 1 year during 1960-1974 in one of the selected workplaces. Radiological follow-up for silicosis onset was from January 1, 1950 through December 31, 1994. Silicosis was assessed according to the Chinese radiological criteria for diagnosis of pneumoconiosis (as suspect, Stage I, II, or III). Exposure-response relationships were estimated for silicosis of Stage I or higher. Silica dust exposure was estimated in terms of cumulative total dust exposure, calculated from a workplace, job title, and calendar year exposure matrix, and individual occupational histories. Cumulative total dust exposure was converted in two steps into cumulative respirable dust exposure and cumulative respirable silica dust exposure using conversion factors estimated from side-by-side measurements conducted in 1988-89. RESULTS: The male cohorts included 4,028 tin miners, 14,427 tungsten miners, and 4,547 pottery workers who had similar onset of employment and duration of follow-up. For a given exposure level, the risk of silicosis was higher for the tin and tungsten than the pottery workers. CONCLUSION: The observed differences in the risk of silicosis among the three cohorts suggest that silica dust characteristics, in addition to cumulative respirable silica dust exposure, may affect the risk of silicosis.

Adult↗
PubMed2002

Polymorphisms in the tumor necrosis factor-alpha gene promoter may predispose to severe silicosis in black South African miners.

Susceptibility to silicosis is in part genetically determined. Polymorphisms in the promoter region of tumor necrosis factor (TNF)-alpha, a cytokine with a central role in the pathophysiology of silicosis, have been associated with predisposition to several infectious and inflammatory diseases. Polymorphisms at positions -308, -238, and -376 in the TNF-alpha promoter region were compared in nine patients with severe silicosis with International Labour Office (ILO) grade 3 nodularity, 112 patients with less severe silicosis (ILO grades 1/1 to 2/2), and 120 black South African gold miners without silicosis (ILO grades 0/0) in an age-frequency-matched case- control study. There were no significant differences between miners with less severe silicosis and controls at any loci in the TNF-alpha promoter region, but miners with severe silicosis were significantly more likely than controls to have -238A (33% versus 6%, Fisher's exact p value = 0.022) and -376A (33% versus 5%, Fisher's exact p value = 0.016). These alleles were in linkage disequilibrium (p < 0.001), and so were not independent. The association remained significant (Fisher's exact p values = 0.011 and 0.011, respectively) when analysis was limited to the majority tribe (Basotho), which included all subjects with severe silicosis. Subjects with severe silicosis were also significantly more likely to have the -308A allele (Fisher's exact p value = 0.034), but this result was confounded by ethnicity and was not significant within Basotho tribe members (Fisher's exact p value = 0.15). TNF-alpha promoter polymorphisms are associated with severe, but not less severe, silicosis in this population. A predominant effect on disease severity, rather than on disease frequency, appears to be a general feature of promoter polymorphism in diseases in which TNF-alpha has a critical role.

Adult↗
PubMed1990

Emphysema in silicosis. A comparison of smokers with nonsmokers using pulmonary function testing and computed tomography.

The presence of emphysema in silicosis is believed to be secondary to the development of progressive massive fibrosis (PMF). However, it is difficult to separate out other causative factors, particularly cigarette smoking. In order to attempt to distinguish these factors, we examined 30 patients with silicosis by means of pulmonary function testing and computed tomography (CT) scans of the chest. Eighteen of these patients were either exsmokers or current smokers, and 12 of them were nonsmokers. The CT scans were read independently by two observers on two separate occasions. Silicosis was graded on a 5-point scale from 0 to 4; emphysema was graded as a percentage of lung involved. Percent emphysema was associated with level of pulmonary function (FEV1, FVC, and DLCO) independent of its association with either cigarette smoking or silicosis grade (p less than 0.01). Silicosis grade was associated with DLCO (p less than 0.05) independent of its association with either cigarette smoking or percent emphysema, but was not associated with level of FEV1 or FVC. In the group without PMF (silicosis Grade 0, 1, or 2), smokers had worse emphysema than nonsmokers (p less than 0.01); there was no such difference among the patients with PMF (silicosis Grade 3 or 4). Only one of the nonsmoking subjects with silicosis but without PMF had any emphysema detected on CT. Our data suggest that silicosis, in the absence of PMF, does not cause significant emphysema, and that it is primarily the degree of emphysema rather than the degree of silicosis that determines the level of pulmonary function.

Adult↗
PubMed1999

Pulmonary dysfunction in silica-exposed workers: a relationship to radiographic signs of silicosis and emphysema.

BACKGROUND: It has been established that occupational exposure to silica dust may cause significant impairment of pulmonary function. To compare the contribution of silicosis and emphysema to pulmonary dysfunction, radiographic signs of silicosis and emphysema in silica exposed workers were analyzed. METHODS: Two hundred and twenty workers exposed to silica working in a Chinese refractory plant were selected as study subjects. Their findings of silicosis and emphysematous changes on radiograph were classified and evaluated. A questionnaire on respiratory symptoms, smoking, and occupational history was administered. All the workers performed measurements of spirometry and CO single-breath diffusing capacity. RESULTS: Radiographic hyperinflation was detected in 9% of the workers without silicosis and in 33% of the workers with silicosis. Silicosis was significantly associated with hyperinflation after adjusting for exposure duration, age, and smoking. Respiratory symptoms were more frequent in the more severe cases of silicosis. Regression analysis showed that silicosis was significantly associated with decreases in the parameters of pulmonary function, but the significance disappeared when the hyperinflation term was added to the models. Radiographic hyperinflation was strongly associated with decreases in FEV1 and FEV1/FVC while relevant factors were controlled. Comparison between workers with and without hyperinflation showed that the former had significantly lower pulmonary function values. CONCLUSIONS: The results suggest that emphysema associated with silicosis is likely to be responsible for pulmonary obstruction and decreased diffusing capacity occurring in silica-exposed workers.

Adult↗
PubMed2004

Differences in cellular and inflammatory cytokine profiles in the bronchoalveolar lavage fluid in bagassosis and silicosis.

BACKGROUND: Little is known about the crucial mediators involved in the inflammation and fibrogenesis in bagassosis. The aim of this study was to characterize the cellular and cytokine patterns in the airways of bagassosis and to compare these with silicosis subjects and controls. METHODS: Bronchoalveolar lavage (BAL) was performed in 11 patients with bagassosis, 16 cases with silicosis, and 8 controls. Differential cell counts, total protein concentration, TNF-alpha, IL-1beta, IL-5, IL-6, and IL-8 were analyzed in the bronchoalveolar lavage fluid (BALF). RESULTS: Bagassosis was characterized with hypercellularity with neutrophilia in BALF; while the predominant cell in the BALF in silicosis was macrophage. Compared with control subjects, increased TNF-alpha, IL-1beta, IL-8, and IL-6 levels were found in the BALFs in both bagassosis and silicosis. Furthermore, IL-6 levels in the BALF of silicosis subjects were significantly higher than that seen in bagassosis. In contrast, bagassosis had higher level of IL-8 in BALF than that in silicosis. Relationship among these parameters were found between IL-8 levels and neutrophils, lymphocytes and IL-1 beta in bagassosis, macrophages and IL-1beta in silicosis. No significant differences of total protein concentrations and IL-5 in BALF were found between controls or bagassosis, and silicosis. CONCLUSIONS: The findings of this study suggest that neutrophils, TNF-alpha, IL-1beta, IL-8, and IL-6 are involved in the pathogenesis in bagassosis. The mechanisms underline the different cellular and cytokine profiles in bagassosis and silicosis warrant further investigation.

Adult↗
PubMed2004

Silicosis and smoking strongly increase lung cancer risk in silica-exposed workers.

It remains controversial whether silica is a human lung carcinogen. In this study, we estimated the relative risks of lung cancer due to silica and silicosis by meta-analysis. We collected papers published from 1966-2001 which epidemiologically reported on the relationship between silica/silicosis and lung cancer. We removed papers which did not exclude the effects of asbestos and radioactive materials including radon. We selected the most recent one if some papers were based on the same cohort. Based on the selected papers, we summarized the lung cancer risks from silica, silicosis and non-silicosis with exposure to silica, by meta-analysis using a random effects model. The pooled relative risks were 1.32 (95% confidence interval (CI), 1.23-1.41) for silica, 2.37 (95% CI, 1.98-2.84) for silicosis and 0.96 (95% CI, 0.81-1.15) for non-silicosis with exposure to silica. Since some papers on silica did not exclude silicosis, the risk due to silica itself may be smaller than 1.32. It was less possible that silica exposure directly increases lung cancer risk. On the other hand, the relative risk, 2.37 for silicosis suggested that silicosis increases lung cancer risk. Meta-analysis also revealed that cigarette smoking strongly increased the lung cancer risk in silicotic patients (relative risk, 4.47; 95% CI, 3.17-6.30). Thus, the present study suggested the great importance of preventing silicosis and smoking cessation in reducing lung cancer incidence in silica-exposed workers.

Carcinogens↗
PubMed1983

[Silicosis in Switzerland. A half century of observation. The physician's viewpoint].

In Switzerland, the first cases of silicosis were recorded by Zangger in 1900. Since 1930, patients with silicosis have been provided with certain services by the "Caisse Nationale Suisse d'Assurances" (i.e. Swiss National Insurance Fund), an organization enforcing the Occupational Accidents and Diseases Bill. However, it took another two years before an effectively organized struggle against silicosis was started. Eventually, by 1938, this specific pneumoconiosis was acknowledged as an occupational disease under Swiss Law. Thus, the CNSA has been concerned with this disease for half a century, and it seems relevant now to take stock of the situation. From 1930 to late 1980, 9690 cases of silicosis were accepted by the CNSA. Nearly one half (46%) of these silicotic patients were still alive on December 31, 1980; another third had died of silicosis and the rest of other affections not related The origin of cases has remained remarkably constant over the course of time. Underground working and the stone-working industry account for the majority of cases (70%), followed by smelting works (16%) and the ceramic industry (5%). The remaining 9% are due to various causes. Silicosis hazards have declined but still remain real. In late 1980, 1287 companies in Switzerland were being monitored from this standpoint. More than two-thirds (67%) belong to the stone-working industry (even though only 30% of hazard-exposed workers are employed in this sector), 10% are involved in underground work (10% of hazard-exposed workers), 10% are smelting industries (36% exposed) and 6% belong to the ceramic industry (17% exposed). Since 1950, the number of hazard-exposed people has fluctuated between relatively narrow limits (i.e. 15,000 and 20,000). Corresponding figures for previous periods are not known. Some facts indicate that silicosis is becoming less problematic: a) The annual incidence rate of silicosis in Switzerland has evolved in three distinct phases. From 1930 to 1940 the number of new cases recorded each year rose regularly. From 1940 to the late 1960s, the incidence levelled off (200-300 cases yearly); then, from 1974, it dropped rather sharply and less than 100 new cases have been recorded yearly since 1978 (97 in 1978, 69 in 1979 and 68 in 1980). b) The average age at diagnosis of silicosis has regularly increased. Until 1940, the average age of recorded silicotic patients was about 40. The threshold of 50 years was reached between 1953 and 1957. More recently (between 1978 and 1980) the corresponding figure was 68.2.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1997

Surveillance for silicosis, 1993--Illinois, Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin.

PROBLEM/CONDITION: Silicosis is an occupational respiratory disease caused by the inhalation of respirable dust containing crystalline silica. Public health surveillance programs to identify workers at risk for silicosis and target workplace-specific and other prevention efforts are currently being field-tested in seven U.S. states. REPORTING PERIOD COVERED: Confirmed cases ascertained by state health departments during the period January 1, 1993, through December 31, 1993; the cases and associated workplaces were followed through December 1994. DESCRIPTION OF SYSTEMS: As part of the Sentinel Event Notification System for Occupational Risks (SENSOR) program initiated by CDC's National Institute for Occupational Safety and Health (NIOSH), development of state-based surveillance and intervention programs for silicosis was initiated in 1987 in Michigan, New Jersey, Ohio, and Wisconsin and in 1992 in Illinois, North Carolina, and Texas. RESULTS: From January 1, 1993, through December 2, 1994, the SENSOR silicosis programs in Illinois, Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin confirmed 256 cases of silicosis that were initially ascertained in 1993. Overall, 185 (72%) were initially identified through review of hospital discharge data or through hospital reports of silicosis diagnoses; 188 (73%) were associated with silica exposure in manufacturing industries (e.g., foundries; stone, clay, glass, and concrete manufacturers; and industrial and commercial machinery manufacture). Overall, 42 (16%) cases were associated with silica exposure from sandblasting operations. Among the 193 confirmed cases for which information was available about duration of employment in jobs with potential exposure to silica, 37 (19%) were employed < or = 10 years in such jobs and 156 (81%) were employed > or = 11 years. A total of 192 primary workplaces associated with potentially hazardous silica exposures were identified for the 256 confirmed silicosis cases. Of these, nine (5%) workplaces were inspected by state health department (SHD) industrial hygienists, 19 (10%) were referred to the Occupational Safety and Health Administration (OSHA) for follow-up, and seven (4%) were routinely monitored by the Mine Safety and Health Administration. Of the 157 (82%) remaining workplaces, follow-up activities determined that 82 were no longer in operation, eight were no longer using silica, 18 were assigned a lower priority for follow-up, six were associated with building trades and could not be inspected because of the transient nature of work in the construction industry, and 43 workplaces were not inspected for other reasons. Fourteen (7%) of the 192 workplaces were inspected. At 10 of the 14 workplaces, airborne levels of crystalline silica were measured; in nine, silica levels exceeded the NIOSH-recommended exposure level of 0.05 mg/m, and in six, airborne silica levels also exceeded federal permissible exposure limits. ACTIONS TAKEN: Employee-specific and other preventive interventions have been initiated in response to reported cases. In addition, special silicosis prevention projects have been initiated in Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin. To facilitate the implementation of silicosis surveillance by other states, efforts are ongoing to identify and standardize core data needed by surveillance programs to describe cases and the workplaces where exposure occurred. These core variables will be incorporated into a user-friendly software system that states can use for data collection and reporting.

Female↗
PubMed1999

Connective tissue disease and silicosis.

BACKGROUND: To determine the prevalence of connective tissue disease in a cohort of individuals with silicosis, we reviewed the medical records and questionnaires from individuals reported from 1987 to 1995 to a state surveillance system for silicosis. Reporting of individuals with silicosis is required by state law. Cases were reported by hospitals, physicians, the state workers' compensation bureau, or from death certificates. Only individuals who met the criteria for silicosis developed by the National Institute for Occupational Safety and Health (NIOSH) were included in the analysis. RESULTS: A questionnaire was completed for all 583 cases. Medical records were available for 463. There were 24 people with rheumatoid arthritis, one with scleroderma, and one with systemic lupus erythematosus. All were men. The prevalence of rheumatoid arthritis was 5.2% (relative risk (RR) 2.73, 95% confidence limit (CL) 1.75-4.06). The prevalence of scleroderma was 0.2% (RR 15.65, 95% CL 0.21-87.03) and the prevalence of systemic lupus erythematosus was 0.2% (RR 11.37, 95% CL 0.15-63.23). This is an approximately 2.5-15-fold increased risk for these connective tissue diseases compared to estimated prevalences in the general population. Individuals with silicosis and connective tissue disease did not differ from individuals with silicosis but without connective tissue disease by race, age, type of industry where exposed to silica, history of tuberculosis, whether or not they had applied for workers' compensation, and whether or not they had progressive massive fibrosis on chest x-ray. CONCLUSION: Although the association between scleroderma and silicosis has been more widely reported in the literature, the prevalence of rheumatoid arthritis was greater than the prevalence of scleroderma or systemic lupus erythematosus among a cohort of individuals with silicosis.

Arthritis, Rheumatoid↗
PubMed2006

Continued exposure to silica after diagnosis of silicosis in Brazilian gold miners.

BACKGROUND: There is a paucity of studies analyzing the effect of continued silica exposure after the onset of silicosis with regard to disease progression. The present study investigates differences in clinical and radiological presentation of silicosis among former workers with a diagnosis of silicosis, and compares workers who continued to be exposed to silica with those who stopped silica exposure after having received their diagnosis. METHODS: A sample of 83 former gold miners with a median of 21 years from the first diagnoses of silicosis, had their clinical and occupational histories taken and underwent both chest radiography (International Labor Organization standards) and spirometry. Their silica exposure was assessed and an exposure index was created. The main outcome was the radiological severity of silicosis and tuberculosis (TB). The statistical analysis was done by multiple logistic regression. RESULTS: Among the 83 miners, 44 had continued exposed to silica after being diagnosed with silicosis. Continuation of silica exposure was associated with advanced radiological images of silicosis (X-ray classification in category 3, OR = 6.42, 95% CI = 1.20-34.27), presence of coalescence and/or large opacities (OR = 3.85, CI = 1.07-13.93), and TB (OR = 4.61, 95% CI = 1.14-18.71). CONCLUSIONS: Differential survival is unlikely to explain observed differences in silicosis progression. Results reinforce the recommendation that silica exposure should be halted at an early stage whenever X-ray is suggestive of the disease.

Adult↗
PubMed1993

Studies on production of anticollagen antibodies in silicosis.

Silicosis is characterized by pulmonary fibrotic changes which consist primarily of an increase in collagen. In this study, anticollagen antibodies in the serum of 134 silicosis patients versus 40 normal subjects were examined and their relationship with immunoglobulin, autoantibodies, and procollagen III peptide (PIIIP) was investigated by enzyme-linked immunosorbent assay (ELISA). The mean levels of anti-human type I collagen (HI) and anti-human type III collagen (HIII) antibodies were significantly higher in the silicosis patients versus the normal subjects (P < 0.001). However, no differences were observed in the mean levels of anti-human type IV collagen (HIV) antibodies in the silicosis patients versus the normal subjects. Anticollagen antibodies in the sera of silicosis patients appear to be formed at an early stage of the disease. We observed a correlation between anticollagen antibodies and immunoglobulin. There was a tendency toward high values of anticollagen antibodies in the sera of patients positive for antinuclear antibodies (ANA) and rheumatoid factor (RF), both of which are autoantibodies. However, no correlation was observed between serum PIIIP and anticollagen antibodies. These observations suggest that, in silicosis, there is a relationship between anticollagen antibodies and immunoglobulins, as well as between anticollagen antibodies and autoantibodies. Measurement of anticollagen antibodies in the sera of silicosis patients offers a useful index for evaluating the prognosis of pulmonary fibrosis and autoimmune abnormality in silicosis.

Aged↗
PubMed2000

8-Hydroxydeoxyguanosine in leukocyte DNA and urine of quartz-exposed workers and patients with silicosis.

OBJECTIVE: To examine radical-induced DNA damage and its elimination in workers exposed to quartz and in patients with silicosis, and to assess the relationship of these effects to lung function. METHODS: Blood and spontaneous urine samples were obtained from active, quartz-exposed workers without silicosis (n = 63), and from retired workers with silicosis (n = 42). Levels of 8-hydroxydeoxyguanosine (8-OHdG) were determined in peripheral blood leukocyte DNA and urine, by the use of high-performance liquid chromatography coupled with ultra violet- (UV) and electrochemical detection. RESULTS: No significant differences in the mean levels of 8-OHdG in leukocyte DNA and of urinary excretion of 8-OHdG were found between silicosis patients and quartz-exposed healthy workers. However, in the group of silicosis patients with increased oxidative DNA damage the urinary excretion of 8-OHdG was lower than in the corresponding group of active workers without silicosis. In the case of silicosis, urinary 8-OHdG correlated positively, and 8-OHdG in DNA correlated negatively, with forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Healthy workers with a personally estimated high dust exposure in the workplace showed higher levels of 8-OHdG in DNA than did workers with moderate dust exposure. No association of 8-OHdG formation and/or elimination with duration of employment, field of activity, smoking or age was found. CONCLUSION: Our findings suggest that a less effective repair of 8-OHdG is associated with a higher degree of pulmonary airway obstruction in patients with silicosis.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2007

Genetic polymorphisms in alveolar macrophage response-related genes, and risk of silicosis and pulmonary tuberculosis in Chinese iron miners.

Alveolar macrophages (AMs) play a prominent role in influencing the development of lung inflammation and injury. The aim of this study is to investigate the roles of AMs response-related genes TNF-alpha, iNOS, and NRAMP1 (SLC11A1) in susceptibility to silicosis and pulmonary tuberculosis (PTB), and to analyze the interaction of dust exposure and genetic susceptibility to silicosis, interactions of TNF-alpha-308 and Natural Resistance-associated Macrophage Protein 1 (NRAMP1) INT4, D543N polymorphisms to PTB. Several epidemiological designs were used: retrospective investigations on dust exposure, case-control studies of 184 silicosis cases and 111 miners occupationally exposed to silica dust, and 1:2 matched case-control studies of 61 PTB cases and 122 PTB-free miners. The miners and controls were recruited from an iron mining operation in Anhui province, China. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was applied to detect single nucleotide polymorphisms. Despite the recruitment of high dust exposure among the controls, silicosis patients still had significantly higher dust exposure than controls (242.6 +/- 98.8 vs. 217.6 +/- 100.7 mg a/m(3)). The mutation of iNOS Ser608Leu is associated with protection against silicosis and against severity of silicosis in the miners. There is a 0.47-fold (95% CI: 0.28-0.79) decrease in risk of silicosis for individuals with C/T, T/T genotype compared with the wild-type homozygous (C/C) individuals after adjustment for occupational exposure, smoking, and drinking. The protection effect of the iNOS polymorphism was particularly detected in the > or = 150 mg a/m(3) exposure group (OR: 0.44, 95% CI: 0.22-0.91). However, no interaction of dust exposure with the iNOS polymorphism was observed. Furthermore, the variant NRAMP1 INT4 genotype is significantly associated with PTB in miners. No association of other polymorphisms (NRAMP1 D543N, TNF-alpha-308) and susceptibility to silicosis or PTB in Chinese miners was found. Our data showed a 3.26-fold (95% CI: 1.47-7.23) increased risk of PTB for miners carrying both the NRAMP1 D543N G/G and NRAMP1 INT4 G/C+C/C genotypes. Additionally, in miners with TNF-alpha-308 G/G genotype, the risk of PTB increased 2.38-fold if they carry the NRAMP1 INT4 G/C+C/C genotype (95% CI: 1.14-4.98). In conclusion, the C>T mutation of iNOS Ser608Leu may be an important protective factor to miners. On the other hand, the variant NRAMP1 INT4 may play a role in the development of PTB in Chinese miners. Therefore, the novel information can be used as guideline for further mechanistic investigations and for strengthening specific protection protocols for workers.

Aged↗