Hard metal interstitial pulmonary disease associated with a form of welding in a metal parts coating plant

Tungsten toxicity and carcinogenesis

Tungsten is an emerging contaminant in the environment. Research has demonstrated that humans are exposed to high levels of tungsten in certain settings, primarily due to increased use of tungsten in industrial applications. However, our understanding of the potential human health risks of tungsten exposure is still limited. An important point we have learned about the toxicity profile of tungsten is that it is complex because tungsten can often augment the effects of other co-exposures or co-stressors, which could result in greater toxicity or more severe disease. This has shaped the tungsten toxicology field and the types of research questions being investigated. This has particularly been true when evaluating the toxicity profile of tungsten metal alloys in combination with cobalt. In this chapter, the current state of the tungsten toxicology field will be discussed focusing on data investigating tungsten carcinogenicity and other major toxicities including pulmonary, cardiometabolic, bone, and immune endpoints, either alone or in combination with other metals. Environmental and human monitoring data will also be discussed to highlight human populations most at risk of exposure to high concentrations of tungsten, the forms of tungsten present in each setting, and exposure levels in each population.

Family-based case-control study of exposure to household humidifier disinfectants and risk of idiopathic interstitial pneumonia

Background

In Korea, several household humidifier disinfectants (HDs) were clinically confirmed to cause HD-associated lung injury (HDLI). Polyhexamethylene guanidine (PHMG) phosphate is the main ingredient of the HDs found to be associated with lung disease. However, the association of HDs with other interstitial lung disease including idiopathic interstitial pneumonia (IIP) is not clear. We examined the relationship between HD exposure and IIP in a family-based study.

Methods

This case-control study included 244 IIP cases and 244 family controls who lived with the IIP patients. The IIP cases were divided into two groups, HDLI and other IIP, and were matched to family controls based on age and gender. Information on exposure to HDs was obtained from a structured questionnaire and field investigations. Conditional logistic regression was used to estimate odds ratio (ORs) and their corresponding 95% confidence interval (CI), investigating the association of HD-related exposure characteristics with IIP risk.

Results

The risks of IIP increased two-fold or more in the highest compared with the lowest quartile of several HD use characteristics, including average total use hours per day, cumulative sleep hours, use of HD during sleep, and cumulative exposure level. In analyses separated by HDLI and other IIP, the risks of HDLI were associated with airborne HD concentrations (adjusted OR = 3.01, 95% CI = 1.34–6.76; Q₄ versus Q₁) and cumulative exposure level (adjusted OR = 3.57, 95% CI = 1.59–8.01; Q₄ versus Q₁), but this relationship was not significant in the patients with other IIP. In comparison between HDLI and other IIP, the odds ratios of average total use hours, cumulative use hours, and cumulative sleeps hours was higher for other IIP.

Conclusion

The use of household HDs is associated not only with HDLI but also with other IIP.

Tungsten: an Emerging Toxicant, Alone or in Combination

PURPOSE OF REVIEW

Tungsten is an emerging environmental toxicant, yet our understanding of the potential risks of exposure on human health is still limited.

RECENT FINDINGS

In this review, we will discuss populations most at risk of exposure to high concentrations of tungsten. In addition, we will highlight what is known about the toxicity profile of tungsten compounds, based on epidemiological, in vitro, and in vivo studies, focusing on bone, immune, pulmonary, and cancer outcomes. Of note, emerging evidence indicates that tungsten can augment the effects of other stimulants, stressors, and toxicants. Of particular importance may be tungsten-cobalt mixtures that seem to be more toxic than either metal alone. This is important because it means that we cannot just evaluate the toxicity of tungsten in isolation. Finally, we still have limited information of how many of the in vitro and in vivo findings translate to human populations, so it will be important to conduct epidemiology studies in highly exposed populations to adequately address the potential risks of tungsten exposure on human health. Together, we discuss recent findings that support further investigation into the toxicities of tungsten alone and in combination with other metals.

Cobalt related interstitial lung disease

Cobalt exposure in the hard metal and bonded diamond tool industry is a well-established cause of ILD. The primary theories regarding the underlying mechanism of cobalt related ILD include an immunologic mechanism and an oxidant injury mechanism. Cobalt related ILD may present in subacute and chronic forms and often has associated upper respiratory symptoms. The evaluation begins with a thorough occupational history and includes PFTs, HRCT, and bronchoalveolar lavage. HRCT findings are nonspecific and may resemble NSIP, UIP, sarcoidosis, or HP. The finding of cannibalistic multinucleated giant cells is diagnostic provided there is a history of exposure and appropriate changes on imaging; however, when these cells are not found on lavage, lung biopsy is required for diagnosis. Giant cell interstitial pneumonia is the classic pathologic pattern, but cobalt related ILD may also present with pathologic findings of UIP, DIP, or HP. When cobalt related ILD is suspected, removal from exposure is the most important step in treatment. Case reports suggest that treatment with steroids results in symptomatic, physiologic, and radiographic improvement.

Characterization of exposures among cemented tungsten carbide workers. Part I: Size-fractionated exposures to airborne cobalt and tungsten particles

As many as 30,000 workers in the United States of America are exposed to cemented tungsten carbides (CTC), alloys composed primarily of tungsten carbide and cobalt, which are used in cutting tools. Inhalation of cobalt-containing particles may be sufficient for the development of occupational asthma, whereas tungsten carbide particles in association with cobalt particles are associated with the development of hard metal disease (HMD) and lung cancer. Historical epidemiology and exposure studies of CTC workers often rely only on measures of total airborne cobalt mass concentration. In this study, we characterized cobalt- and tungsten-containing aerosols generated during the production of CTC with emphasis on (1) aerosol "total" mass (n=252 closed-face 37 mm cassette samples) and particle size-selective mass concentrations (n=108 eight-stage cascade impactor samples); (2) particle size distributions; and (3) comparison of exposures obtained using personal cassette and impactor samplers. Total cobalt and tungsten exposures were highest in work areas that handled powders (e.g., powder mixing) and lowest in areas that handled finished product (e.g., grinding). Inhalable, thoracic, and respirable cobalt and tungsten exposures were observed in all work areas, indicating potential for co-exposures to particles capable of getting deposited in the upper airways and alveolar region of the lung. Understanding the risk of CTC-induced adverse health effects may require two exposure regimes: one for asthma and the other for HMD and lung cancer. All sizes of cobalt-containing particles that deposit in the lung and airways have potential to cause asthma, thus a thoracic exposure metric is likely biologically appropriate. Cobalt-tungsten mixtures that deposit in the alveolar region of the lung may potentially cause HMD and lung cancer, thus a respirable exposure metric for both metals is likely biologically appropriate. By characterizing size-selective and co-exposures as well as multiple exposure pathways, this series of papers offer an approach for developing biologically meaningful exposure metrics for use in epidemiology.

Inhalation of inorganic particles as a risk factor for idiopathic pulmonary fibrosis--elemental microanalysis of pulmonary lymph nodes obtained at autopsy cases

Exposure to inorganic particles may induce fibrosis in the lung. However, the association between exposure to inorganic particles and the pathogenesis of idiopathic pulmonary fibrosis (IPF)/usual interstitial pneumonia (UIP) is obscure. We examined inorganic particles in the pulmonary hilar lymph nodes affected by IPF/UIP to investigate whether inhaled elements are involved in the etiology, and whether there is an increasing risk of developing IPF/UIP. Twenty-three IPF/UIP cases and 23 controls without IPF/UIP were investigated. Pulmonary hilar lymph nodes constituted the study material. The elemental analysis was performed using scanning electron microscopy with an energy dispersive X-ray spectroscope, and we analyzed particles quantitatively and qualitatively. The results showed that the cases contained silicon and aluminum as compared with the control in lymph nodes, and these deposits were statistically significantly associated with an increased risk of IPF/UIP (adjusted odds were 2.99, 95% CI: 1.29-6.85 and 57.84, 95% CI: 1.45-2306.19, respectively). In addition, higher nickel levels in lymph nodes were associated with lung cancer. This study shows that inorganic particles, such as Si and Al, have higher concentrations in the hilar lymph nodes in IPF/UIP, and may play a role in one of the risk factors in the pathogenesis of IPF/UIP.

Inorganic dust exposure causes pulmonary fibrosis in smokers: analysis using light microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy

Smoking is alleged to cause pulmonary fibrosis, but the role of inorganic dust particulates has not been adequately examined. The authors hypothesize that inorganic dust exposure is an independent risk factor for the development of fibrosis in smokers. They studied a prospective series of 34 subjects with open lung biopsies, 18 of whom had adequate lung parenchyma for evaluation. They also examined the relationships between smoking (pack-years), respiratory bronchiolitis (RB), inorganic dusts, and interstitial fibrosis. They graded RB, fibrosis, and particulate dust by means of light microscopy. They performed a semiquantitative analysis of dust burden by using scanning electron microscopy with energy-dispersive X-ray spectroscopy. A logistic regression analysis demonstrated a significant association between smoking and RB (p = .03), but not between smoking and fibrosis or between RB and fibrosis. Fibrosis was significantly associated with silica (p = .004) and titanium (p = .0006) concentrations. The results support the authors' hypothesis.

Clinical approach to chronic beryllium disease and other nonpneumoconiotic interstitial lung diseases

Exposures in the workplace result in a diverse set of diseases ranging from the pneumoconiosis to other interstitial lung diseases to acute lung injury. Physician awareness of the potential disease manifestations associated with specific exposures is important in defining these diseases and in preventing additional disease. Most occupational diseases mimic other forms of lung disease, including pulmonary fibrosis, sarcoidosis, adult respiratory distress syndrome (ARDS), and bronchiolitis. A "sarcoidosis"-like syndrome, usually limited to the lungs, may result from exposure to bioaerosols and a number of metals. Exposure to beryllium in the workplace produces a granulomatous lung disease clinically indistinguishable from sarcoidosis, chronic beryllium disease (CBD). Beryllium's ability to produce a beryllium-specific immune response is used in the beryllium lymphocyte proliferation tests to confirm a diagnosis of CBD and exclude sarcoidosis. Exposure to other metals must also be considered in the differential diagnosis of sarcoidosis. When an individual presents acutely with ARDS or acute lung injury, an acute inhalational exposure must be considered. Exposure to a number of irritant substances at high levels may cause a "chemical pneumonitis" or acute lung injury, depending on the solubility and physicochemical properties of the substance. Some of the most notable agents include nitrogen and sulfur oxides, phosgene, and smoke breakdown products. Ingestion of paraquat may also result in an ARDS syndrome, with pulmonary fibrosis eventually resulting. Bronchiolitis is a rare manifestation of inhalational exposures but must also be considered in the clinical evaluation of inhalational exposure.

Occupational and environmental risk factors for idiopathic pulmonary fibrosis: a multicenter case-control study. Collaborating Centers

Occupational exposures were investigated in a multicenter case-control study of clinically and histologically diagnosed idiopathic pulmonary fibrosis (IPF), a chronic diffuse interstitial lung disease of unknown etiology. Results are based on 248 cases, aged 20-75 years, diagnosed at 16 referral centers between January 1989 and July 1993. There were 491 controls ascertained by random digit dialing and matched to cases on sex, age, and geographic region. Data were collected using a standard telephone questionnaire. Occupational factors were based on a detailed history of jobs lasting 6 months or more and job activity, hobby, and specific substance checklists. Several occupational factors, adjusted for age and smoking in conditional multivariate logistic regression analyses, were significantly associated with IPF: farming (odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.0, 2.5); livestock (OR = 2.7, 95% CI: 1.3, 5.5); hairdressing (OR = 4.4, 95% CI: 1.2, 16.3); metal dust (OR = 2.0, 95% CI: 1.0, 4.0); raising birds (OR = 4.7, 95% CI: 1.6, 14.1); stone cutting/polishing (OR = 3.9, 95% CI: 1.2, 12.7); and vegetable dust/animal dust (OR = 4.7, 95% CI: 2.1, 10.4). Interaction was detected between smoking and exposure to livestock (p = 0.06) and farming (p = 0.08). Results confirm previous studies showing increased risk associated with dusty environments.

An investigation of occupational metal exposure in thermal spraying processes

A cross-sectional study of 34 workers engaged in thermal spraying at six worksites was undertaken in order to determine levels of exposure to and uptake of metals during different metal spraying activities. Levels of exposure to cobalt, chromium and nickel were highest in plasma sprayers and, on occasions exceeded UK Occupational Exposure Limits. Exposure to metals during detonation gun and electric arc spraying was better controlled and levels remained below the relevant Occupational Exposure Limits throughout the study period. Urinary levels of cobalt and nickel mirrored the airborne concentrations and the highest urine concentrations were again found in plasma sprayers. Urinary chromium levels were highest in electric arc sprayers, which may also reflect an increased body burden in this group due to a longer history of exposure. The findings clearly indicate that exposure to and uptake of metals may exceed UK Occupational Limits or Standards when spraying is performed manually or semi-automatically and where control relies on local exhaust ventilation (LEV) and personal respiratory protective equipment (RPE).

Hard metal lung disorders: analysis of a group of exposed workers

The experience gained during the last 5 years in the study of 36 male workers exposed to hard metal dusts (10 engaged in mixing, 12 in presintering, three in sintering and 11 in grinding) is presented. The mean age was 33.2 years (S.D., 11.8) and the mean number of years of exposure was 9.4 (S.D., 7.6). All subjects received a physical examination, chest X-rays, pulmonary function test (VC, FEV1, expiratory flows, RV, DLCO, and metacholine bronchial provocation test), skin tests, bronchoalveolar lavage (BAL) and determination of trace metals in BAL, blood, urine, pubic hair and toe nails. Two cases of bronchial asthma, six cases of interstitial lung disease and one case with both disorders were identified; eight of these cases presented at BAL signs of alveolitis with different cytologic features. Among the other 27 asymptomatic subjects, two showed an aspecific bronchial hyperreactivity, four showed a reduced DLCO, 12 showed an inverted ratio of CD4/CD8 lymphocytes in BAL without signs of alveolitis while one subject presented both an aspecific bronchial reactivity and a reduced DLCO. The presence of aspecific bronchial hyperreactivity in asymptomatic subjects might represent a preclinical indicator of a possible evolution towards bronchial asthma. An altered DLCO, alone or associated with an inverted CD4/CD8 ratio of BAL lymphocytes, might constitute an early sign of a possible evolution towards interstitial lung disease. The association of aspecific bronchial reactivity and reduced DLCO might indicate the possible evolution towards a mixed form.(ABSTRACT TRUNCATED AT 250 WORDS)