Respiratory hazards in hard metal workers: a cross sectional study

Hard metal lung disease: a case series

Objective:

To describe diagnostic and treatment aspects of hard metal lung disease (HMLD) and to review the current literature on the topic.

Methods:

This was a retrospective study based on the medical records of patients treated at the Occupational Respiratory Diseases Clinic of the Instituto do Coração, in the city of São Paulo, Brazil, between 2010 and 2013.

Results:

Of 320 patients treated during the study period, 5 (1.56%) were diagnosed with HMLD. All of those 5 patients were male (mean age, 42.0 ± 13.6 years; mean duration of exposure to hard metals, 11.4 ± 8.0 years). Occupational histories were taken, after which the patients underwent clinical evaluation, chest HRCT, pulmonary function tests, bronchoscopy, BAL, and lung biopsy. Restrictive lung disease was found in all subjects. The most common chest HRCT finding was ground glass opacities (in 80%). In 4 patients, BALF revealed multinucleated giant cells. In 3 patients, lung biopsy revealed giant cell interstitial pneumonia. One patient was diagnosed with desquamative interstitial pneumonia associated with cellular bronchiolitis, and another was diagnosed with a hypersensitivity pneumonitis pattern. All patients were withdrawn from exposure and treated with corticosteroid. Clinical improvement occurred in 2 patients, whereas the disease progressed in 3.

Conclusions:

Although HMLD is a rare entity, it should always be included in the differential diagnosis of respiratory dysfunction in workers with a high occupational risk of exposure to hard metal particles. A relevant history (clinical and occupational) accompanied by chest HRCT and BAL findings suggestive of the disease might be sufficient for the diagnosis.

Objetivo:

Descrever aspectos relacionados ao diagnóstico e tratamento de pacientes com doença pulmonar por metal duro (DPMD) e realizar uma revisão da literatura.

Métodos:

Estudo retrospectivo dos prontuários médicos de pacientes atendidos no Serviço de Doenças Respiratórias Ocupacionais do Instituto do Coração, localizado na cidade de São Paulo, entre 2010 e 2013.

Resultados:

Entre 320 pacientes atendidos no período do estudo, 5 (1,56%) foram diagnosticados com DPMD. Todos os pacientes eram do sexo masculino, com média de idade de 42,0 ± 13,6 anos e média de tempo de exposição a metal duro de 11,4 ± 8,0 anos. Os pacientes foram submetidos a avaliação clinica, história ocupacional, TCAR de tórax, prova de função pulmonar, broncoscopia com LBA e biópsia pulmonar. Todos apresentaram distúrbio ventilatório restritivo. O achado de imagem à TCAR de tórax mais frequente foi de opacidades em vidro fosco (em 80%). Em 4 pacientes, o LBA revelou presença de células gigantes multinucleadas. Em 3, foi diagnosticada pneumonia intersticial por células gigantes na biópsia pulmonar. Houve o diagnóstico de pneumonia intersticial descamativa associada à bronquiolite celular em 1 paciente e de pneumonite de hipersensibilidade em 1. Todos foram afastados da exposição e tratados com corticoide. Houve melhora em 2 pacientes e progressão da doença em 3.

Conclusões:

Apesar de ser uma entidade rara, a DPMD deve ser sempre considerada em trabalhadores com risco ocupacional elevado de exposição a metais duros. A história clínica e ocupacional associada a achados em TCAR de tórax e LBA sugestivos da doença podem ser suficientes para o diagnóstico.

Nanotoxicity: emerging concerns regarding nanomaterial safety and occupational hard metal (WC-Co) nanoparticle exposure

As the number of commercial and consumer products containing engineered nanomaterials (ENMs) continually rises, the increased use and production of these ENMs presents an important toxicological concern. Although ENMs offer a number of advantages over traditional materials, their extremely small size and associated characteristics may also greatly enhance their toxic potentials. ENM exposure can occur in various consumer and industrial settings through inhalation, ingestion, or dermal routes. Although the importance of accurate ENM characterization, effective dosage metrics, and selection of appropriate cell or animal-based models are universally agreed upon as important factors in ENM research, at present, there is no “standardized” approach used to assess ENM toxicity in the research community. Of particular interest is occupational exposure to tungsten carbide cobalt (WC-Co) “dusts,” composed of nano- and micro-sized particles, in hard metal manufacturing facilities and mining and drilling industries. Inhalation of WC-Co dust is known to cause “hard metal lung disease” and an increased risk of lung cancer; however, the mechanisms underlying WC-Co toxicity, the inflammatory disease state and progression to cancer are poorly understood. Herein, a discussion of ENM toxicity is followed by a review of the known literature regarding the effects of WC-Co particle exposure. The risk of WC-Co exposure in occupational settings and the updates of in vitro and in vivo studies of both micro- and nano-WC-Co particles are discussed.

In vitro inflammatory effects of hard metal (WC-Co) nanoparticle exposure

Identifying the toxicity of nanoparticles (NPs) is an important area of research as the number of nanomaterial-based consumer and industrial products continually rises. In addition, the potential inflammatory effects resulting from pulmonary NP exposure are emerging as an important aspect of nanotoxicity. In this study, the toxicity and inflammatory state resulting from tungsten carbide–cobalt (WC–Co) NP exposure in macrophages and a coculture (CC) of lung epithelial cells (BEAS-2B) and macrophages (THP-1) at a 3:1 ratio were examined. It was found that the toxicity of nano-WC–Co was cell dependent; significantly less toxicity was observed in THP-1 cells compared to BEAS-2B cells. It was demonstrated that nano-WC–Co caused reduced toxicity in the CC model compared to lung epithelial cell monoculture, which suggested that macrophages may play a protective role against nano-WC–Co-mediated toxicity in CCs. Nano-WC–Co exposure in macrophages resulted in increased levels of interleukin (IL)-1β and IL-12 secretion and decreased levels of tumor necrosis factor alpha (TNFα). In addition, the polarizing effects of nano-WC–Co exposure toward the M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophage phenotypes were investigated. The results of this study indicated that nano-WC–Co exposure stimulated the M1 phenotype, marked by high expression of CD40 M1 macrophage surface markers.

Comparison between exhaled breath condensate analysis as a marker for cobalt and tungsten exposure and biomonitoring in workers of a hard metal alloy processing plant

OBJECTIVE

Cobalt (Co), Tungsten (W) and Tungsten Carbides (WC) are major constituents of hard metal alloys. Whereas little is known about potential health hazards due to tungsten carbide exposure, occupational exposure to cobalt has been shown to induce a variety of respiratory diseases. Since the concentration of a potentially hazardous substance in the target organ is the most meaningful risk indicator in occupational medicine, the detection of hard metals in exhaled breath condensate (EBC) has been proposed to be a valuable instrument. The present study examines the correlation of Co and W concentrations in EBC and urine with one another and various spirometrical and clinical parameters to scrutinize this potential.

METHODS

A total of 62 subjects (90.3% males, age 40.6 +/- 9.2 years) were recruited from a hard metal processing plant in Germany. Examinations included the airborne workplace exposure, a complete spirometry, measurements of Co and W concentrations in EBC and urine with high resolution inductive coupled plasma mass spectrometry (HR ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS).

RESULTS

Air concentrations ranged between 0.0019 mg/m(3) and 0.074 mg/m(3) for Co and 0.012 mg/m(3) and 0.021 mg/m(3) for W. Median urine concentrations and interquartile ranges of the exposed subjects ranged from 0.81 (0.0-1.46) microg/l for Co and 30.5 (14.5-57.7) microg/l for W. Median breath condensate metal concentrations and interquartile ranges ranged from 8.4 (5.0-13.9) microg/l for Co and 8.8 (4.4-18.5) microg/l for W. Urine concentrations of Co and W were closely related to the airborne workplace exposure that had been assessed by air monitoring. EBC concentrations of Co and W showed no correlations to urinary W and Co concentrations and the ambient monitoring results of the individual workplace, respectively. Cobalt EBC concentration was elevated in subjects who reported to have suffered from respiratory disease; both Co and W concentrations in EBC, however, decreased with increasing spirometrical signs of obstruction.

CONCLUSION

According to our study, urinary concentrations of Co and W seem to be more reliable indicators of current workplace exposure than EBC concentrations. As far as new methods and exposure matrices for valid concentration measurements in respiratory organs and possible hazardous effects--especially of cobalt--in the lung are concerned, the present results are less clear-cut, and further research is required.

Characteristics of dusts encountered during the production of cemented tungsten carbides

Inhalation of cobalt (Co) and tungsten carbide (WC) particles, but not Co or WC alone, may cause hard metal disease, risk of which does not appear to be uniform across cemented tungsten carbide (CTC) production processes. Inhalation of Co alone or in the presence of WC may cause asthma. Hypothesizing that aerosol size, chemical content, heterogeneity, and constituent compaction may be important exposure factors, we characterized aerosols from representative CTC manufacturing processes. Six work areas were sampled to characterize aerosol size distributions (dust, Co) and 12 work areas were sampled to characterize physicochemical properties (using scanning electron microscopy with energy dispersive x-ray spectrometry [SEM-EDX]). Bulk feedstock and process-generated powders were characterized with SEM-EDX and x-ray diffraction. The dust mass median diameter was respirable and the cobalt respirable mass fraction was highest (37%) in grinding. Morphology of particles changed with processing: individual, agglomerate, or aggregates (pre-sintered materials), then mostly compacted particles (subsequent to sintering). Elemental composition of particles became increasingly heterogeneous: mostly discrete Co or W particles (prior to spray drying), then heterogeneous W/Co particles (subsequent work areas). Variability in aerosol respirability and chemical heterogeneity could translate into differences in toxicity and support detailed characterization of physicochemical properties during exposure assessments.

Inorganic dust pneumonias: the metal-related parenchymal disorders

In recent years the greatest progress in our understanding of pneumoconioses, other than those produced by asbestos, silica, and coal, has been in the arena of metal-induced parenchymal lung disorders. Inhalation of metal dusts and fumes can induce a wide range of lung pathology, including airways disorders, cancer, and parenchymal diseases. The emphasis of this update is on parenchymal diseases caused by metal inhalation, including granulomatous disease, giant cell interstitial pneumonitis, chemical pneumonitis, and interstitial fibrosis, among others. The clinical characteristics, epidemiology, and pathogenesis of disorders arising from exposure to aluminum, beryllium, cadmium, cobalt, copper, iron, mercury, and nickel are presented in detail. Metal fume fever, an inhalation fever syndrome attributed to exposure to a number of metals, is also discussed. Advances in our knowledge of antigen-specific immunologic reactions in the lung are particularly evident in disorders secondary to beryllium and nickel exposure, where immunologic mechanisms have been well characterized. For example, current evidence suggests that beryllium acts as an antigen, or hapten, and is presented by antigen-presenting cells to CD4+ T cells, which possess specific surface antigen receptors. Other metals such as cadmium and mercury induce nonspecific damage, probably by initiating production of reactive oxygen species. Additionally, genetic susceptibility markers associated with increased risk have been identified in some metal-related diseases such as chronic beryllium disease and hard metal disease. Future research needs include development of biologic markers of metal-induced immunologic disease, detailed characterization of human exposure, examination of gene alleles that might confer risk, and association of exposure data with that of genetic susceptibility.

Epidemiological study of hard metal asthma

OBJECTIVES

To elucidate factors contributing to hard metal asthma, the entire workforce of a corporation producing hard metal tools (n = 703) was examined.

METHODS

The variables evaluated were the atopy reflected by immunoglobulin E (IgE) antibody against mite allergen, history of exposure to hard metal, smoking, concentration of airborne cobalt, specific IgE antibody reaction against cobalt, and the respiratory symptom of attacks of reversible dyspnoea with wheeze (asthmatic symptoms).

RESULTS

Univariate analysis showed that the prevalence of the asthmatic symptoms was significantly higher in formerly and currently exposed male workers than in non-exposed male workers. Positive IgE reaction against cobalt was found in seven men (2.0%), all of whom had asthmatic symptoms. Furthermore, it was found that atopy, positive IgE antibody against cobalt, and age of 40 or older were significantly correlated with asthmatic symptoms. Multilogistic analysis on the same factors and smoking in all of the workers showed that the age, experience of hard metal exposure, and atopy were significant risk factors associated with the asthmatic symptoms. Multilogistic analysis of data for currently exposed and non-exposed workers also showed that age and atopy were risk factors, and that the exposure to cobalt at the low concentration (at or below 50 micrograms/m3) but not at the higher concentration was a significant risk factor. Exposure to mist of coolants containing ionic cobalt, used during grinding, was not found to be any more hazardous in terms of onset of asthmatic symptoms than exposure to hard metal dust containing metallic cobalt.

CONCLUSIONS

Accordingly, it is concluded that both environmental factors and individual susceptibility should be taken into consideration in efforts to reduce the prevalence of hard metal asthma.

Decreased ventilatory function in hard metal workers

OBJECTIVES

To study individual effects on pulmonary function of exposure to hard metal including cobalt.

METHODS

All of the workers in a hard metal company (583 men and 120 women) were examined for smoking, respiratory symptoms, ventilatory function, occupational history of exposure to hard metal, and present exposure to airborne cobalt. The ventilatory function indices (forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory volume in one second per cent (FEV1%), peak expiratory flow (PEF), mid-maximal flow (MMF), forced expiratory flow at 50% vital capacity (V50), forced expiratory flow at 25% vital capacity (V25)) were standardised for height and age and expressed as a percentage of predicted values.

RESULTS

Two way analysis of variance of indices of ventilatory function showed that an interaction of hard metal exposure and smoking decreased %V50 for both men and women. Among the currently exposed men, those with asthmatic symptoms (defined as reversible dispnoea with wheeze) had significantly lower %FVC, %FEV1%, %PEF, %MMF, %V50, and %V25 than did workers without asthma. The ventilatory disfunction did not differ between exposed and non-exposed workers with asthmatic symptoms. Even among the men without asthmatic symptoms, %V50 was significantly lowered by the interaction of hard metal exposure and smoking. The multilinear regression analysis of indices of ventilatory function for all of the subjects on sex, smoking (Brinkman index), exposure to hard metal, and asthmatic symptoms showed that asthmatic symptoms and smoking had significant effects on all variables and that the decrease in %V25 was associated with hard metal exposure. In the currently exposed and non-exposed workers, multilinear regression analysis applying indices for cobalt exposure (mean cobalt concentration, duration of exposure, and cumulative dose) showed that not only asthmatic symptoms or smoking but also duration of exposure had significant decreasing effects on %FVC, %MMF, and %V25.

CONCLUSIONS

Occupational exposure to hard metal probably causes impairment of ventilatory function in a dose dependent manner.

Maintenance of stellite and tungsten carbide saw tips: respiratory health and exposure-response evaluations

OBJECTIVE

To study exposure to cobalt and chromium in saw maintenance rooms and test respiratory health among saw filers at lumber mills. Hard-metal lung disease is associated with cobalt in the manufacture of tungsten carbide tools; recently it has also been reported among tool maintenance workers. Lumber mills often use saws tipped with tungsten carbide or with a newer alloy, stellite (containing more cobalt, as well as chromium).

METHODS

A cross sectional study of 118 saw filers at eight lumber mills was carried out that included a standardised questionnaire, spirometry, personal air sampling, and examination of tasks every 10 minutes (by observation). Comparison data were from a study of bus mechanics tested with similar methods.

RESULTS AND CONCLUSION

Cobalt exposure was associated with tungsten carbide grinding but not with stellite grinding. Chromium exposure was associated mainly with stellite welding. Saw filers had a twofold increase in phlegm and wheeze (P < 0.01) and a threefold increase in cough, phlegm, and wheeze related to work (P < 0.001), but no increase in breathlessness. Stellite welding was associated with a significant increase in nasal symptoms and cough related to work and a small decrease in airflow (forced expiratory volume in one second/forced vital capacity (FEV1/FVC%), P < 0.05). Saw filers wet grinding with tungsten carbide had significant reductions in forced expiratory lung volumes (FEV1 and FVC, P < 0.05) and were significantly more likely to have FEV1 and FVC values in the abnormal range. Cobalt exposure (in wet grinding) and duration of work that involved tungsten carbide grinding were both associated with significant reductions in FEV1 and FVC. Average cobalt exposures in this study were about 5 micrograms/m3, well below the currently accepted permissible concentration, which suggests that the current workplace limit for cobalt may be too high.

Health hazard of poorly regulated exposure during manufacture of cemented tungsten carbides and cobalt

Forty two of 125 former workers in a factory in Syracuse, New York, which manufactured hard metal parts from tungsten carbide and cobalt, were studied by chest radiographs, spirometry, and plethysmographically determined lung volumes. The plant was closed in 1982 and the studies were performed in 1983-5. Recorded measurements of carbide dust concentrations were only mildly excessive by modern standards, but deceitful efforts to reduce the apparent concentration of dust were known to have occurred during an inspection by the Occupational Safety and Health Administration. Lung biopsies in four cases in the study and necropsy in one of the 83 cases not studied during life showed giant cell interstitial pneumonia and appreciable concentrations of tungsten carbide. This information indicates that exposure was substantial. Four workers had evidence of pulmonary fibrosis by chest radiographs; two of these workers had normal pulmonary function. Fourteen had abnormal pulmonary function, five of whom had a restrictive pattern, eight a pattern of air trapping, and one a combined pattern. Thus radiographic, or functional abnormalities, or both occurred in 16 of the 42 cases studied. No correlation with duration of exposure was established. Progressive clinically important disease (one fatal) has been found in four ex-workers, two in each of the restrictive and air trapping groups. These findings suggest that poorly regulated dust concentrations in a hard metals factory possibly cause pulmonary abnormalities and sometimes severe illness.

Lung function in retired coke oven plant workers

Lung function was studied in 354 coke oven plant workers in the Lorraine collieries (Houillères du Bassin de Lorraine, France) who retired between 1963 and 1982 and were still alive on 1 January 1988. A spirometric examination was performed on 68.4% of them in the occupational health service. Occupational exposure to respiratory hazards throughout their career was retraced for each subject. No adverse effect of occupational exposure on ventilatory function was found. Ventilatory function was, however negatively linked with smoking and with the presence of a respiratory symptom or discrete abnormalities visible on pulmonary x ray films. The functional values were mostly slightly lower than predicted values and the most reduced index was the mean expiratory flow, FEF25-75%. The decrease in forced expiratory volume in one second (FEV1) was often parallel to that in forced vital capacity (FVC), but it was more pronounced for subjects who had worked underground, for smokers of more than 30 pack-years, and for subjects having a respiratory symptom. Pulmonary function indices were probably overestimated because of the exclusion of deceased subjects and the bias of the participants.

Clinical findings among hard metal workers

In 1940, the first report appeared describing a pulmonary disorder associated with occupational exposures in the cemented tungsten carbide industry. The disease, known as "hard metal disease," has subsequently been characterised in detail and comprises a wide range of clinical signs and symptoms. In this report, clinical findings in a group of 41 hard metal workers employed until recently are described. A high prevalence of respiratory symptoms was found. Thirteen workers (31%) had abnormal chest radiographs indicative of interstitial lung disease. Fifty per cent of these had been employed in hard metal manufacturing for less than 10 years. Abnormalities of pulmonary function were also frequent and included a restrictive pattern of impairment and decrease in diffusing capacity (27%). Associations were found between diffusing capacity, chest radiographic abnormalities and right ventricular ejection fraction at exercise indicating cardiopulmonary effects. The findings show the continuous need to control excessive occupational exposures to prevent hard metal disease, the history of which now enters its sixth decade.

Ventilatory function of workers exposed to cobalt and diamond containing dust

The ventilatory function of 48 workers occupied on the average for six years in a plant producing diamond-cobalt circular saws was compared with that of 23 control subjects. The geometric mean airborne cobalt concentrations in the two main work areas amounted to 15.2 and 135.5 micrograms/m3 respectively. The spirometric changes found in the exposed workers were compatible with a moderate restrictive syndrome and were correlated with duration of exposure.