Pneumoconiosis prevalence among working coal miners examined in federal chest radiograph surveillance programs--United States, 1996-2002

Coal workers' pneumoconiosis (CWP) is a chronic lung disease caused by inhalation of coal mine dust. To characterize the prevalence of CWP, the National Institute for Occupational Safety and Health (NIOSH) analyzed recent radiographic information from the U.S. National Coal Workers' X-ray Surveillance Program (CWXSP). Established under the Federal Coal Mine Health and Safety Act of 1969, CWXSP is administered by NIOSH under federal regulations. NIOSH is responsible for approving coal miner examination plans, submitted approximately every 5 years by companies that operate underground coal mines. This report summarizes the results of the analysis, which indicate that the overall prevalence of CWP among participating miners continues to decline; however, new cases are occurring among miners who have worked exclusively under current dust exposure limits. An evaluation of the mining conditions that have resulted in these cases is underway.

Occupational respiratory diseases in the Czech Republic

This paper presents the profile of occupational respiratory diseases in the Czech Republic. In a retrospective study the author analyzes structure, causes, occurrence, and trends of occupational diseases. Between 1996 and 2000, a total of 2,127 new cases were recorded, of which 62.0% were pneumoconioses caused by dust containing free silica, 21.0% were occupational asthma or allergic rhinitis and the rest were divided between lung cancer (10.0%), asbestos-related disorders (4.4%) and variety of other respiratory diseases (2.7%). During the period of the investigations, the decreasing trend of occupational respiratory diseases, which began in 1992, has continued.

Effect of TNF and LTA polymorphisms on biological markers of response to oxidative stimuli in coal miners: a model of gene-environment interaction. Tumour necrosis factor and lymphotoxin alpha

INTRODUCTION

Interaction between genetic background and oxidative environmental stimuli in the pathogenesis of human lung disease has been largely unexplored.

METHODS

A prospective epidemiological study was undertaken in 253 coal miners. Intermediate quantitative phenotypes of response to oxidant exposure, including erythrocyte glutathione peroxidase (GSH-Px) and catalase activities, were studied. Oxidant exposures studied were smoking habits and cumulative dust exposure assessed by job history and ambient measures. Disease phenotypes included subclinical computed tomography score at the first survey and x ray profusion grades twice, five years apart, to assess established coal workers' pneumoconiosis (CWP). Miners were genotyped for common functional polymorphisms in the gene for tumour necrosis factor alpha (TNF) and lymphotoxin alpha (LTA), two proinflammatory cytokines that have been implicated in the pathogenesis of chronic lung diseases.

RESULTS

Regarding gene-environment interaction on intermediate phenotypes, results showed interaction of a promoter polymorphism at the -308 position in TNF with occupational exposure on erythrocyte GSH-Px activity with a significant association in those with high exposure (p=0.003), whereas no association was observed among those with low exposure (interaction p=0.06). Regarding gene intermediate phenotype interaction on clinical outcome, results showed an association of CWP prevalence with an NcoI polymorphism in LTA in those with low catalase activity (p=0.05), whereas no association was observed in those with high activity (interaction p=0.03). No other significant association was observed.

CONCLUSION

The results suggest that interactions of genetic background with environmental exposure and intermediate response phenotypes are important components in the pathogenesis of CWP.

Occupational disease in Connecticut, 2000

BACKGROUND

Occupational illnesses in Connecticut are tracked to better understand patterns and trends by industry, cause, and time, which allows for interventions such as cluster investigations and education.

METHODS

Data were collected for occupational illnesses from three data sources: the Connecticut Bureau of Labor Statistics (BLS) annual survey, workers' compensation reports, and physician reports.

FINDINGS

There were 6,396 reports of occupational illness in Connecticut in 2000. Reports increased sharply based on two of the three databases. Reports were dominated by musculo-skeletal disorders (MSD), followed by lung conditions. Manufacturing, the State of Connecticut, and municipalities tended to have the highest number of cases and rates. Acute respiratory conditions were the most common lung condition, followed by occupational asthma and asbestos-related conditions.

CONCLUSION

Occupational illnesses are very prevalent in Connecticut and appear to be increasing. Improved diagnosis and reporting are needed to improve patient care and to direct preventive efforts.

Update on respiratory disease from coal mine and silica dust

Coal mine and silica dust cause significant respiratory disease in spite of modern dust control regulations. Susceptible individuals in exposed populations may develop fibrosing lung disease, obstructive airways disease, including chronic bronchitis and emphysema, or lung cancer. A careful occupational history that elicits exposure to respiratory hazards is the cornerstone of an accurate diagnosis. Treatment involves removal from exposure, supportive care, pulmonary rehabilitation, and when disabling disease is present, assistance obtaining compensation.

The current state of workers' pneumoconiosis in relationship to dusty working environments in Okayama Prefecture, Japan

This study involved the examination of 1,006 chest x-ray films of workers from the industries devoted to shipyard welding, stone grinding, and refractory crushing in southern Okayama prefecture. Of the reviewed films, analysis was focused on subjects with a profusion rate of 0/1 as well as pneumoconiotic subjects (exhibiting profusion rates of 1/0 or greater) in order to discover cases in the beginning stages. One-hundred-and-seventy-four films illustrated a profusion rate of 0/1 or greater, and the proportion of this profusion rate was revealed to be highest in shipyard welders. Even some workers under 40 years of age were found to have already developed pneumoconiosis. Of these 1,006 subjects, 30 volunteers permitted us to measure their personal dust exposure concentrations. The measured concentration of the shipyard welders' dust exposure (respirable dust; 3.3 86.3 mg/m3, total dust; 7.5-117.0 mg/m3) was higher than those of the other 2 industries. Statistical differences among the industries were observed in the respirable dust concentrations. A statistically significant positive correlation was demonstrated between the working duration in dusty environments and the rate of profusion. The present findings suggest the need for taking adequate measures in Okayama in order to prevent workers from developing, or to help retard the progression of, pneumoconiosis.

Reproducibility of survey results from a study of occupation-related respiratory health in the aluminum industry

Confidence in dose-response relationships arising from occupational studies is dependent upon the reliability and validity of relevant exposure and morbidity estimates. Often self-reported occupational histories are a surrogate for direct exposure measures, and self-report of symptoms serves a similar purpose in place of more objective measures of morbidity. Unfortunately, there are few methods for validating either of these sources of information. This study attempts to evaluate the reproducibility of a survey instrument, and resulting cumulative exposure estimates, utilized in a study of work-related respiratory morbidity in the aluminum industry. The survey instrument comprised measures of pulmonary function, atopic status, smoking, occupational history, and respiratory symptoms. A Task Exposure Matrix was used to estimate exposure categories and cumulative exposure scores. Two groups of employees were administered the survey instrument on two separate occasions. Group A (n = 74) completed their two surveys more than ten weeks apart and Group B (n = 43) completed their surveys less than two weeks apart. Reproducibility was assessed using Cohen's Kappa for categorically measured outcome measures and intraclass correlation coefficients for continuously measured outcomes. Agreement across most variables, for both groups, was generally high. Repeatability of self-reported respiratory symptoms ranged from 70 to 98 percent (Group A) and 88 to 100 percent (Group B). Cumulative exposure scores were highly reproducible, despite some discrepancies in the self-reported occupational histories across interviews, with most of the calculated intraclass r scores exceeding 0.8. These results give strength to studies reporting dose-response relationships derived from similarly collected data. Reproducibility of the survey data was enhanced by use of standardized questionnaire material, consistent interview structure, and calibrated equipment for objective observation. In particular the authors recommend use of a company job dictionary to optimize reproducibility of self-reported occupational information.

[Occupational diseases--epidemiologic evaluation of the situation in Poland]

The incidence of occupational diseases is one of the basic indices of the effectiveness of prevention in the area of occupational health. It allows for the identification of jobs, plants and branches of the national economy with potentially increased risks for pathologies induced by working conditions. However, we should be aware of the fact that many of the recently diagnosed diseases result from long-term exposures experienced at work sites which are no longer under operation. The analysis was based on data included in occupational disease certificates. All sanitary and epidemiological stations throughout the country are committed to notify cases of occupational diseases to the National Register of Occupational Diseases at the Nofer Institute of Occupational Medicine in Łódź. After a significant increase in the number of occupational diseases (8305-12,017 cases per year) observed in 1980-1998, its decrease has been noted in Poland over the recent two years (9982 cases in 1999 and 7339 in 2000). In 1998-2000, a substantial decrease in the decreasing rate was also found (from 117.3 to 73.9 per 100,000 employed), which means that the decreasing trend does not result only from the increasing size of the working population in Poland. In 2000 like in previous years, among occupational diseases the following ones were most often diagnosed: diseases of vocal organ due to excessive voice effort most common in teachers, occupational hearing loss, pneumoconiosis, contagious and invasive diseases, dermatoses, chronic diseases of bronchi, vibration syndrome as well as acute and chronic poisonings. There were registered 6626 cases of the above listed diseases, that is 90.3% of all occupational diseases. In 1998-2000, a significant decrease in the incidence of this category of diseases was noted. The largest decrease applied to the vocal organ diseases, occupational hearing loss and contagious and invasive diseases (by 30%, 51% and 40%, respectively). Neither in the member states of the European Union, nor in the USA, vocal organ pathologies are listed among occupational diseases. The main reason for this is an inappropriate medical prevention in the group of teachers and somewhat limited opportunity to teach them how to use techniques of voice emission. A decreased incidence of occupational diseases observed in Poland in 1998-2000 results partly from improvements in working conditions and partly from more effective prevention.

Coal dust exposures in the longwall mines of New South Wales, Australia: a respiratory risk assessment

This paper presents an analysis of personal respirable coal dust measurements recorded by the Joint Coal Board in the underground longwall mines of New South Wales from 1985 to 1999. A description of the longwall mining process is given. In the study, 11 829 measurements from 33 mines were analysed and the results given for each occupation, for seven occupational groups, for individual de-identified mines and for each year of study. The mean respirable coal dust concentration for all jobs was 1.51 mg/m(3) (SD 1.08 mg/m(3)). Only 6.9% of the measurements exceeded the Australian exposure standard of 3 mg/m(3). Published exposure-response relationships were used to predict the prevalence of progressive massive fibrosis and the mean loss of FEV(1), after a working lifetime (40 years) of exposure to the mean observed concentration of 1.5 mg/m(3). Prevalences of 1.3 and 2.9% were predicted, based on data from the UK and the USA, respectively. The mean loss of FEV(1) was estimated to be 73.7 ml.

[Study on the prevention, control and elimination of pneumoconiosis in fluorite mine]

OBJECTIVE

To prevent pneumoconiosis by strengthening comprehensive dust-proof and controlling its pathogenesis, and to discuss feasibility of pneumoconiosis elimination in our country.

METHODS

Comprehensive dust-proof was used for reducing the concentration of dust. Epidemiological investigation of pneumoconiosis was employed for evaluating the efficiency of pneumoconiosis prevention. Prospective tracking investigation was used for identifying the feasibility of the pneumoconiosis elimination.

RESULTS

The outcomes of dynamic observation of 35 years from 1962 to 1996 and results of prospective thirty years tracking investigation showed that after comprehensive dustp-roof, the average dust concentration and time weighted mean dust concentration in workers' operating conditions decreased from 366.0 mg/m3 and 163.4 mg/m3 to 1.2 mg/m3 and 1.3 mg/m3 respectively, and the declined rates reached 99.7% and 92.1%, respectively. After controlling pneumoconiosis pathogensis, the incidence rate of pneumoconiosis, its prevalence rate and mortality rate decreased from 24.8%, 85.5% and 5.9% to zero respectively.

CONCLUSION

The thirty years prospective tracking investigation validated that the incidence of pneumoconiosis was zero. So the goal to eliminate pneumoconiosis was achieved.

Review: occupational and environmental lung disease

Occupational and environmental lung disease is a vast topic. Therefore, this review focuses on areas that represent new clinical insights that have not been addressed recently in Current Opinion in Pulmonary Medicine. The topics are considered important for the future and emphasize diseases that strike large numbers of people or exposures that affect large segments of the population. This review highlights literature published between the years 2000 to 2001 related to air pollution, occupational asthma, lung diseases in agricultural workers, nylon flock workers lung disease, pneumoconiosis, and environmental exposure to biomass smoke, including environmental tobacco smoke. These publications highlight the changing world of occupational and environmental lung diseases. Traditionally, this field dealt with chronic diseases caused by very high levels of exposure to materials that affected virtually all workers to a similar degree. Disease could be recognized readily by characteristic symptoms, signs, and radiographic abnormalities. Dose-effect relationships were usually clear, and the solution to disease was generally to limit exposure for all workers. This approach served well for conditions such as coal workers pneumoconiosis or toxic responses to chlorine gas. The new world of occupational and environmental lung diseases often involves low levels of exposure to complex mixtures of materials that produce nonspecific or intermittent symptoms in a subgroup of exposed individuals. Interactions between genetic susceptibility, concomitant tobacco smoke exposure, and co-morbid diseases hugely complicate both diagnosis and prevention. New tools, and possibly new thought paradigms, are needed to detect, treat, and prevent occupational and environmental lung diseases in a changing world.

From quartz hazard to quartz risk: the coal mines revisited

Following the classification of quartz as a human carcinogen by the IARC, many standard-setting committees are currently trying to convert this hazard into their national or EU standards. Since human data to set a safe exposure limit for quartz are limited, we hypothesized that lung burden data on quartz in coal miners' lungs after lifetime exposure could be used to set a non-carcinogenic lung burden of quartz, and that this might be valid for other groups occupationally exposed to quartz. A review of data shows that lungs of coal miners with simple coal workers' pneumoconiosis (sCWP) typically contain up to 30 g of dust, and in one specific study lung burdens between 0.7 and 1.7 g of quartz were associated with macules only, and no sCWP. Assuming independent actions of coal and quartz and no clearance of quartz, and sCWP as a prerequisite for lung cancer due to quartz exposure in coal mine dust, a simple kinetic approach was applied. A no observed adverse effect level (NOAEL) for quartz of between 0.03 and 0.13 mg/m3 (40 yr exposure) is derived, but it is concluded that more refined physiologically based pharmacokinetic modelling is needed for a better estimate, also including interindividual differences in lung clearance. Considering the independent effects of, and the well-known interaction between coal and quartz, these data could be important to other workplaces with usual mixed-dust exposure.

Characteristics of workers attending the pneumoconiosis clinic for silicosis assessment in Hong Kong: retrospective study

OBJECTIVE

To describe and analyse the baseline characteristics of workers attending the pneumoconiosis clinic for assessment of silicosis.

DESIGN

Retrospective cross-sectional study.

SETTING

Outpatient clinic.

PATIENTS

One thousand and fifty-six patients with silica dust exposure attending the pneumoconiosis clinic for compensation assessment.

MAIN OUTCOME MEASURES

Baseline demographic characteristics, lung function parameters, and radiographic findings.

RESULTS

Six hundred and forty-eight patients were diagnosed with silicosis, of which 10 were female. Excluding the data on female patients, the mean duration of dust exposure was 24.2 years. The majority of patients were involved in caisson work and stone splitting. Most newly diagnosed patients had simple silicosis. Less than a quarter (24.8%) had progressive massive fibrosis. Lung function parameters at diagnosis were within the normal range. Pulmonary tuberculosis remained an important co-existing disease.

CONCLUSION

The major cause of silicosis in Hong Kong is chronic silica dust exposure in the construction industry. Simple silicosis predominated at diagnosis, with normal lung function parameters seen in the majority of patients.

[Analysis of morbidity and testing of trends for qualitatively variable incidence of occupational diseases induced by industrial dust in selected workplaces]

The paper addresses the problem of occupational diseases induced by industrial dust (items 2-4 on the Polish list of occupational diseases) during the years 1970-89. The data were obtained from the Section of Work Hygiene of the former Sanitary and Epidemiological Station in Zielona Góra. In the population of workers under study, the incidence of chronic respiratory diseases (CRD) (items 3 and 4 on the Polish list of occupational diseases) was higher as compared with pneumoconiosis in terms of both the number of cases and the number of plants where they were observed. In case of pneumoconiosis, welding smoke and foundry dust were found to be etiologic factors responsible for its incidence, and organic dusts of plant and plastic origin together with industrial dust induced CRD. First cases of CRD were observed in the exposure interval of 6-10 years, and pneumoconiosis already in the interval of 0-5 years. The intensified incidence of both pneumoconiosis and CRD was observed after 11-25 years of occupational exposure. An upward trend in the incidence of pneumoconioses determined by the concentration of industrial dusts and the duration of exposure was found in one plant, and of CRD determined by the same factors in two plants under study.

Occupational lung diseases among former goldminers in two labour sending areas

OBJECTIVES

To compare and contrast the prevalence of pneumoconiosis in two groups of former migrant mineworkers in southern Africa, and to examine the effectiveness of the South African compensation system for occupational lung diseases.

DESIGN

Comparison of two cross-sectional studies and follow-up data on compensation results.

SETTING

The village of Thamaga, Botswana and the rural area of Libode, Eastern Cape, South Africa.

SUBJECTS

Two hundred and thirty-four former underground mineworkers in Thamaga, and 238 in Libode.

MAIN OUTCOME MEASURES

Prevalence and severity of pneumoconiosis, prevalence of radiological signs of tuberculosis (TB), Medical Bureau for Occupational Diseases (MBOD) certification committee decisions, and compensation results.

RESULTS

Prevalence of pneumoconiosis > or = 2/1 was 15.4% in Libode and 13.6% in Thamaga. Significantly more Libode than Thamaga subjects (51.1% versus 29.0%) reported past TB treatment. Radiological signs of pulmonary TB were also more prevalent in Libode (33.3% v. 23.9%). Twenty-six per cent of Libode men and 16.1% of Thamaga men were certified with compensable disease. Libode payments were finalized within 30 months, whereas Thamaga cases only began receiving payments 52 months after medical examination, with 11 cases still pending 66 months after medical examination.

CONCLUSION

There was a high prevalence of pneumoconiosis in both study groups. Many men were eligible for compensation but were previously uncompensated. The higher rate of compensable disease in the Libode group may relate to the higher prevalence of TB, as well as more active follow-up by the study group, including a large number of appeals. Socio-political changes in South Africa between 1994 and 1996 may also have influenced compensation results.

SWORD '99: surveillance of work-related and occupational respiratory disease in the UK

Systematic reports from chest and occupational physicians under the SWORD and OPRA (Occupational Physicians Reporting Activity) surveillance schemes continue to provide a picture of the incidence of occupational respiratory disease in the UK. An estimated total of 4393 incident cases (comprising 4530 diagnoses) were reported during the 1999 calendar year, an increase of 1427 cases over the previous year. Benign pleural disease was the single most frequently reported condition (28% of all diagnoses reported). Occupational asthma cases (1168; 26%) remained high, as did mesothelioma (1032; 23%). Analysis of trends over the past 8 years shows an increase in mesothelioma cases, but little change in asthma. The annual incidence per 100,000 employed people, 1996-1999, for mesothelioma, lung cancer and pneumoconiosis was high amongst construction workers (28.7), miners and quarrymen (26.5), woodworkers (18.9) and gas, coal and chemical workers (15.2). Trends in mesothelioma incidence by birth cohort continue to show an increase in construction workers and a continuing decline in shipyard and insulation workers. The relative proportion of pneumoconiosis cases attributed to coal mining has fallen steadily in workers born since approximately 1920 and most cases are now in men who have been employed in quarrying and rock drilling.

[The effects of dust inhalation in slate industry workers]

BACKGROUND

Slate industries involve the risk of causing silicosis; these industries are now on the increase, which implies an increasing number of workers too. The effects of this type of mining on respiratory health are not yet known.

SUBJECTS AND METHOD

A cross section study of active workers. Radiological and functional alterations, and their relation to risk factors, were assessed.

RESULTS

A prevalence of 2.1% simple pneumoconiosis was found. The value of the FEV1 probed to be significantly related to smoking and to existence of nodulation of a 1/0 or higher profusion; these risk factors, when multiple regression is applied, work independently.

CONCLUSION

Slate industry involves a risk of pneumoconiosis and other respiratory alterations.

Disturbance of respiratory system in workers in smelter plants

Workers from smelter plants are at high risk from lung injuries due to exposure to quartz sand, clay, resin, loams, airborne metals etc. The aim of this study was to investigate the relevance of the problem and the risk of occupational pathology in metallurgy at "ELMA" plant--Troyan. The study revealed decreased number of occupational lung diseases but the percentage rate (about 10%) of registered new cases with occupational lung diseases was maintained. No new cases with mixed silicosis were recorded. The results were compared to respective national data. Slowly evolving forms of diffusely outlined lung chart with late functional breathing disturbances were prevailing. Chronic bronchitis are presented as a polyetiologic paraoccupational disease.

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

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

Mineral dust exposure and systemic diseases

Based on clinical and immunological studies, we have proposed the hypothesis that occupational dust exposure might cause not only pneumoconiosis but also autoimmune diseases and malignancies of various organs such as neoplasms of lymphatic and hematopoietic tissues and gastric cancer. Evidence from cohort studies of pneumoconiotic patients in Japan, copper miners, and stone masons support our hypothesis. The carcinogenicity and cytotoxic effect of inhaled dust on immune cells are considered to contribute to the development of these diseases.

Characterization of dust exposure for the study of chronic occupational lung disease: a comparison of different exposure assessment strategies

Various exposure assessment strategies were compared in the study of the relation between dust exposure and 11-year lung function change in 1,172 miners with 36,824 concurrently measured personal dust samples available from the 1969-1981 US National Study of Coal Workers' Pneumoconiosis. A miner's average exposure was assessed by calculating average exposures based on dust samples taken from each individual and by using different job exposure matrices (JEMs) with different underlying exposure categorizations, based on occupational categories, job title, mine, and time, to obtain average exposure estimates. For each grouping procedure, intragroup and intergroup variances and the pooled standard error of the mean were calculated to assess relative efficiency. The results show that considerable variation in slopes of exposure-response relations was found using different exposure assessment strategies. Standard errors of the slopes of the exposure-response relations with exposure on an individual basis compared with JEMs. Exposure assessment on an individual basis was extremely sensitive to the number of exposure measurements per individual. The study demonstrates the advantages and disadvantages of different exposure assessment strategies and shows the need for explicit publication of exposure assessment strategies for epidemiologic studies. Careful assessment of the influence of misclassification error in the exposure assessment on exposure-response modeling is warranted.

Refractory ceramic fiber: toxicology, epidemiology, and risk analyses--a review

Refractory ceramic fiber (RCF) is an energy-efficient, high-temperature insulation, used principally in industrial furnaces, heaters, and reactors. Prior to the 1980s, there were few publications dealing with the potential health effects of this material. However, with the advent of higher energy costs and the need for thermally efficient high-temperature insulating materials, production of RCF grew rapidly, as did interest in its potential health effects. This article provides a comprehensive and integrated review of the toxicology (in vitro and in vivo), epidemiology, and risk analysis literature of RCF. Based on the available literature, we conclude that an occupational exposure of 0.5 fibers per cubic centimeter (cm(3)) [8-h time-weighted average (8-h TWA)] results in an occupational health risk no greater than 9.1 x 10(-5).

Occurrence and prevention of coal miners' pneumoconiosis in Poland

BACKGROUND

Coal production is one of the largest industries in Poland and incidence of coal miners' pneumoconiosis is high.

METHODS

Data concerning the epidemiology of coal miners' pneumoconiosis stem from the national register and previous investigations performed in Poland. Improvements in medical and technical methodologies for the prevention of pneumoconiosis is discussed.

RESULTS

Analysis of the dust concentration measurements shows that TLV values are exceeded in 90% of underground workplaces. The number of new pneumoconiosis cases diagnosed annually ranges from 400-800 and has been showing a diminishing tendency in the last five years. Recently, a new system of medical and technical prevention has been introduced in seven collieries.

CONCLUSIONS

The current epidemiological situation of coal miners pneumoconiosis in Poland is unfavorable and needs vast improvement.

[Radiological observations in relation to occupational exposure to silicon carbide (SiC)]

There have been investigated radiologically 191 workers from a SiC factory, exposed to dust concentrations exceeding largely that TLV and with a content of non-reactive SiO2 less than 1%. Radiological examinations were performed systematically at a three years interval, beginning with 1988. Radiology interpreting was performed according to ILO 1980 classification for persistent radiological opacities due to mineral dusts. Our results sustain the idea of the pneumoconiogen potential of SiC: there is a high prevalence of radiological findings (16.2%) and the opacities have an extend from 2 to 6 areas and the profusion from 0/1 to 2/2.

Pneumoconiosis among Cretan dental technicians

Pneumoconiosis among dental technicians has recently emerged as an area of research in interstitial lung disease. This study was carried out to estimate the prevalence of pneumoconiosis in Greek dental technicians on the island of Crete. Fifty-one of the 58 dental technicians of the Heraklion Dental Technicians' Association completed an exposure history questionnaire and underwent a clinical examination, including chest radiographs, and spirometric assessment of lung volume and diffusing capacity. Values were compared with 51 control subjects. Five dental technicians showed radiological evidence of pneumoconiosis. Mean lung function values of the dental technicians, even in those with pneumoconiosis, were not significantly different from controls. No significant changes in lung function parameters were associated with smoking, exposure to metals and other contaminants. Dental technicians, however, reported more respiratory symptoms than controls (p = 0.008). Symptoms were associated to the absence of a ventilation system. We concluded that occupational exposure in dental technicians in Crete did not affect lung function. The prevalence of pneumoconiosis in this study was 9. 8%.

Mycobacterium kansasii and M. scrofulaceum isolates from HIV-negative South African gold miners: incidence, clinical significance and radiology

SETTING

A South African gold mining hospital.

OBJECTIVE

To investigate the clinical significance of non-tuberculous mycobacteria (NTM) isolates, and estimate NTM disease incidence in human immunodeficiency virus (HIV) negative miners.

DESIGN

Retrospective case series describing clinical and radiological features associated with NTM sputum isolates from HIV-negative miners between January 1993 and July 1996, and a comparison group with Mycobacterium tuberculosis infection.

RESULTS

Of miners with NTM isolates, 90% had been HIV-tested and 81% were HIV-negative. M. kansasii and M. scrofulaceum accounted for 202 (68%) and 41 (14%) isolates respectively. More than 80% of miners with M. kansasii or M. scrofulaceum were smear positive, and new cavitation was present in 78% and 74% respectively. Treatment failure occurred in 3% of M. kansasii and 12% of M. scrofulaceum patients. A normal pre-morbid radiograph was significantly less common in NTM than M. tuberculosis patients (odds ratio 0.26 and 0.10 for M. kansasii and M. scrofulaceum, respectively). NTM disease incidence, defined as NTM isolate plus new cavitation, was estimated at 66 and 12 per 100000 person-years for M. kansasii and M. scrofulaceum, respectively.

CONCLUSIONS

M. kansasii and M. scrofulaceum disease are common in HIV-negative South African gold miners. Most isolates are associated with new cavitation against a background of silicosis or old TB scarring.

Airways inflammation among workers in a paper industry

Exposure to organic dusts may cause airways inflammation in a large proportion of exposed persons. Most studies have relied on questionnaires and spirometry for diagnosis. To assess the possibility of determining the presence of inflammation using clinical diagnostic procedures, a study was undertaken among workers in a paper industry. Participants were 83 workers and 44 controls. Airborne endotoxin and (1-->3)-beta-D-glucan levels at the worksites were determined. The effects of this exposure were evaluated using a questionnaire, spirometry and measurements of airway responsiveness (methacholine) and levels of eosinophil cationic protein (ECP), myeloperoxidase (MPO), and C-reactive protein (CRP) in serum. The workers had a decreased baseline forced expiratory volume in one second (FEV1) and an increased airway responsiveness compared with controls. The concentrations of ECP and MPO were elevated compared with controls. There was a relation between exposure to endotoxin and (1-->3)-beta-D-glucan and airway responsiveness as well as ECP levels, when controlling for age, sex, smoking habits, atopy and asthma. The results suggest an increased prevalence of subjective respiratory symptoms, and an increased airway responsiveness among exposed workers. There was also a relationship between the serum concentration of eosinophil cationic protein and airway responsiveness. Taken together, the results suggest the presence of airways inflammation in the workers.

Temporal trends in coal workers' pneumoconiosis prevalence. Validating the National Coal Study results

Evidence from four successive rounds of the National Study of Coal Workers' Pneumoconiosis indicates diminishing prevalence of coal workers' pneumoconiosis (CWP) from 1969 to 1988. However, methodological inconsistencies across surveys have raised concerns. This study confirms the reported downward trend in CWP prevalence, utilizing a standardized methodological approach. A single team of three x-ray readers using the 1980 International Labour Office classification independently re-evaluated 3143 Appalachian-region cases to derive overall, tenure- and age-specific prevalences. Prevalence of small rounded opacities declined, with 12.7% in Round 1, 11.2% in Round 2, 3.0% in Round 3, and 3.9% in Round 4. These findings support the National Institute for Occupational Safety and Health's recommendation of a reduced exposure limit of 1 mg/m3 because the present coal dust standard does not sufficiently protect miners against adverse health effects over a working lifetime of exposures.

Pneumoconiosis problem among the Vietnamese coal mine workers

In this report, the authors present the pneumoconiosis problem among Vietnamese coal mine workers. As coal is one of the most important products for export, its production has been intensified recently. With the strong incentive for rapid economic development, health problems of miners tend to take second place. As shown in the present report, miners' working conditions are very bad, and health protection measures are not sufficiently implemented. It is apparent that official statistics underestimate the actual situation because of the inadequacy of the reporting system. Because the financial barrier to establishing a sufficient reporting system for pneumoconiosis is enormous, an epidemiologic study is the most effective way to assess the actual situation. It is also useful to conduct epidemiologic studies as part of an international collaborative project, in order to transfer necessary knowledge and epidemiologic skills from the developed countries to Vietnam.

Reliability of reported occupational history information for US coal miners, 1969-1977

For estimating reliable exposure-response relations it is necessary that random variation in both the response and the exposure variables be sufficiently small. Variability in cumulative exposures can arise from uncertainties in self-reported work histories from interviews. In most epidemiologic surveys, the information gathered from questionnaires is used without knowing the validity or reproducibility of these data. This paper investigates the reliability of occupational histories reported by the same individuals on two occasions separated by 9 years in the US National Study of Coal Workers' Pneumoconiosis and its implications on the exposure-response relation for simple coal workers' pneumoconiosis. For 480 coal miners, from whom occupational histories were obtained twice (in 1969-1971 and 1977-1981), the reliability (intraclass correlation coefficient) of the cumulative exposures generated from each work history was 87%. Logistic model fitting of simple coal workers' pneumoconiosis prevalence to the cumulative coal dust exposure produced almost identical results. After accounting for intersurvey variability in the occupational histories, the authors found that the exposure-response coefficients estimated from information reported at the surveys were attenuated by 12%. In epidemiologic studies, knowledge of the reproducibility of self-reported occupational history information is important to ascertain whether the true exposure effect is underestimated.

Prevalence of and factors related to pneumoconiosis among foundry workers in central Taiwan

The objective of this study was to investigate the prevalence of and factors related to pneumoconiosis in foundry workers. Seven hundred and eighteen workers from 50 foundries in central Taiwan were interviewed using a constructed questionnaire. A full-sized PA chest radiograph was used to diagnose pneumoconiosis, according to ILO criteria. Overall, pneumoconiosis was found in 7.5% of the workers. The highest prevalence was found among furnace workers (15.9%) and molding workers (8.40%). All foundry workers except those in administrative positions had a significantly increased risk of developing pneumoconiosis. Using a multiple logistic regression, compared to administrative workers, furnace workers had the highest risk (10.63 times), followed by post-treatment workers (6.63 times), and molding workers (5.41 times). In conclusion, the prevalence of pneumoconiosis was significantly related to high concentrations of dust, especially with a high proportion of free silica, however, smoking and length of exposure were also contributing factors.

Health and safety in the Lesotho Highlands Dam and Tunnel Construction Program

To review health and safety practices and to determine the occupational health status of dam workers in the Lesotho Highlands, a health and safety audit and a health study of 258 workers was undertaken. The workers were administered respiratory health questionnaires and underwent chest x-rays and lung function and audiometric testing. The audit revealed a low level of awareness of health and safety issues at all levels of management and a lack of occupational medicine and industrial hygiene systems. Noise-induced hearing loss occurred among 92% of the study subjects. Among the 158 dam construction workers, 5.4% had pneumoconiosis. With poorly developed laws and regulatory bodies, unsophisticated trade unions, and little client supervision, health and safety had a low priority in this construction project. Recommendations are made that are pertinent to health and safety management where international companies are operating in developing countries.

Prevalence of occupational lung disease in a random sample of former mineworkers, Libode District, Eastern Cape Province, South Africa

BACKGROUND

Gold mineworkers in South Africa are exposed to high levels of silica dust as a result of which they are at risk of developing silicosis, which is a compensable disease. The incidence of tuberculosis is also high.

METHODS

To determine the prevalence of occupational lung disease and the previous compensation history in former migrant mineworkers, a study was undertaken in a random sample of men living in Libode, a rural district of Eastern Cape Province, South Africa. Two hundred thirty-eight ex-mineworkers were examined according to a protocol that included chest radiography and spirometry. Chest radiographs were read into the International Labour Organisation (ILO) classification for pneumoconioses by two readers.

RESULTS

The mean age was 52.8 years, and the mean length of service was 12.15 years. The prevalence of pneumoconiosis (> or = ILO 1/0) was 22% and 36% (variation by reader). For both readers, a significant association between length of service and pneumoconiosis and between pneumoconiosis and reduction in FVC and FEV was found. Twenty-four percent of study subjects were eligible for compensation.

CONCLUSION

There is a high prevalence of previously undiagnosed, uncompensated pneumoconiosis in the study group. As a result of the failure to diagnose and compensate occupational lung disease, the social and economic burden of such disease is being borne by individuals, households, and the migrant labor-sending communities as a whole.

[Spirometry in workers in a wheat-processing industry]

In order to determine both clinical and spirometric changes due to high environmental concentrations of wheat dust at a wheat processing plant mill, 48 exposed men and 48 age and antroprometrically-matched, non-exposed apparently healthy men were studied. In both groups a medical and occupational history were taken, and spirometric measurements were carried out, that included Forced Vital Capacity (FVC), Forced Expiratory Volume at the first second (FEV1), Peak Flow Rate (PFR), Forced Percentual Expiratory Volume (FEV%), Forced Percentual Vital Capacity (FVC%), Forced Expiratory Flow at 25% (FEV25%), at 50% (FEV50%) and at 75% (FEV75%) of their Forced Vital Capacity, which were analyzed through Corzo's predictive equations and the lung deterioration's criteria by USA's Thoracic Association. The environmental wheat dust was determined by gravimetry and its concentration was higher than the legally admitted (3/5, 60%). There was a decrease in the PFR, FEV%, FEV25% and FEV75%. (p < 0.05). In addition, 4 restrictive and 1 obstructive syndrome were detected in the exposed workers and none in the control group. The spirometric values diminished in a positive correlation with the time of exposure and smoking habits. There was no correlation between the clinical findings and the dust concentration but it did exist with the spirometric values. It is concluded that in this plant, the wheat dust exposed workers have a diminished spirometric values.

Pulmonary function testing: detection of invalid performance

We surveyed physician members of the American Thoracic Society and their technicians regarding indicators of the validity of PFTs. Surveys were returned by 50 physicians and 52 technicians. Both groups felt that consistency of effort and the shape/slope of the curve were important indicators, with behavioral observations rated slightly lower. Approximately 38% of physicians and 19% of technicians felt that they detected 75% or fewer of individuals giving inadequate effort during PFTs. Twenty percent of physicians and 29% of technicians were using quantitative criteria other than those recommended by the 1979 "Snowbird" technical paper to determine acceptability of PFTs. Twenty-eight percent of physicians and 31% of technicians spontaneously indicated that patients pursuing compensation or disability claims for pulmonary disorders were most likely to give suboptimal effort. Empirical research into the impact and detection of suboptimal effort on PFTs is encouraged.

Radiographic and spirometric findings in diatomaceous earth workers

Diatomaceous earth is a noncrystalline form of silica; in processing, calcining leads to formation of cristobalite, a form of crystalline silica. Four hundred ninety-two currently employed diatomaceous earth workers in a large mine and processing facility had chest radiographs performed and interpreted by the International Labour Office (ILO) system. Two hundred sixty-seven subjects underwent spirometry testing. Exposure indices for total dust (largely diatomaceous earth) and cristobalite were reconstructed for each individual based upon personnel records. Analysis demonstrated the following prevalences of radiographic findings: 5% had ILO scores > or = 1/0, and 25% had scores of 0/1 or higher. Regression analyses showed that there was a relationship between both total cristobalite exposure and total dust (largely diatomaceous earth) exposure and the ILO score. Radiographic patterns are not typical of those of classic silicosis. Linear regression analyses for forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio did not demonstrate a relationship between cumulative exposure and lung function. Such analyses were performed using all subjects and stratified by smoking status. There were differences in spirometric data according to radiographic ILO category, but the results were inconsistent and did not permit determining if physiologic changes are associated with radiographic change or if this is due to confounding. Overall, the study suggests that diatomaceous earth pneumoconiosis (radiographically defined) is an entity distinct from silicosis. Recent exposure levels may produce radiographic abnormalities but do not lead to demonstrable physiologic effect. The prevalence of the disorder has diminished markedly in response to modern dust control measures. Ongoing medical surveillance is recommended in workers with potential exposure to significant quantity of material.

Studies on the hazardous effects and the maximum allowable concentration of pyrophyllite dust

Pyrophyllite (H2Al2Si4O22) dust (P-dust) is a mixture of silica (10-40%), different proportions of a luminium oxide (Al2O3), and various metal compounds. People with occupations known to be associated with exposure to P-dust include miners, other industrial workers and persons engaged in artistic carving. Currently, little is known about pyrophyllite pneumoconiosis from P-dust. This study was designed to investigate the hazardous effects of P-dust and to suggest a maximum allowable concentration (MAC) of the dust. This study included four parts: (i) Occupational epidemiology survey in 781 workers from 1 pyrophyllite mine (PM) and four pyrophyllite carving mills (PCM), with a registration rate of 98%. (ii)

IN VITRO STUDIES

Six groups of rats were exposed to different levels of P-dust; the cytotoxicity of P-dust on rat alveolar macrophages (AM) was investigated by determining the potassium content of AM and the activity levels of lactate dehydrogenase (LDH) in AM culture fluid, (iii) Mineralogical analysis of P-dust: The contents of silica (SiO2), aluminum (Al), ferrum (Fe), nickel (Ni), zinc (Zn) and copper (Cu) in both PM-dust and PCM-dust were determined. (iv) Determination of P-dust MAC: Using the life-talbe method, an investigation of the hygiene standard of P-dust was carried out in 625 workers exposed to either PM-dust or PCM-dust, upon whom routine radiographs were performed. The results suggest that the risk of developing pneumoconiosis from pyrophyllite dust is significantly higher for PM workers than for PCM workers. The prevalence rate of PCM-dust pneumoconiosis is significantly higher in men than in women. The content of SiO2 and Al2O3 in the mixture of P-dust is the most important factor in the etiology of pyrophyllitosis. Depending on the different P-dust MAC values, we suggest that 2 mg/m3 and 4 mg/m3 should be considered as the MAC for PM-dust and PCM-dust, respectively, and 3 mg/m3 for P-dust. We believe that establishing different hygiene standards is more accurate even though workers are exposed to the "same" dust.