Biological markers and occupational lung disease: mineral dust-induced respiratory disorders

Adenosine deaminase activity and immunoglobulin levels as potential systemic biomonitors of occupational hazards and health status in municipal solid waste management workers

Immune status of waste management workers (WMW) with underlying systemic inflammation was assessed to identify useful immune-related biomarkers of occupational health and safety. Clinical history of WMW revealed high prevalence of respiratory symptoms alongside gastrointestinal and musculoskeletal complaints relative to control. Systemic inflammation, characterized by significant (p<0.001) elevation of erythrocyte sedimentation rate and C-reactive protein, was associated with marked increase in concentration and prevalence of IgA (p<0.05), IgG (p<0.01) and adenosine deaminase activity (ADA) (p<0.01) in WMW. Haematological changes include significant (p<0.01) increase in lymphocytes, monocytes and total leukocytes. Eosinophils also increased significantly (p<0.001) while haemoglobin, packed cell volume and neutrophil decreased significantly (p<0.05). Receiver operating characteristic curve and multivariate analyses revealed ADA (p<0.002) and IgG (p<0.05) as important immune markers respectively for assessing sub-clinical effects of occupational exposure. Our data suggest ADA and IgG as useful immune health and safety indicators in WMW.

The use of biomarkers in occupational health research, practice, and policy

Biomarkers are potentially useful tools for occupational health and safety research, practice, and policy. However, the full realization of this potential has not been achieved. In this paper, the progress made in these three usage areas is reviewed to identify what efforts can be taken to realize the full promise of biomarkers. Biomarker uses are described by a diverse taxonomy that builds on the categories of exposure, effect and susceptibility, and the continuum between exposure and disease prognosis. The most significant uses of biomarkers in occupational health have been in biological monitoring of workers. Other important uses have been in enhancing research and assessing mechanisms of action of occupational toxicants at low exposures. Seven critical areas will influence the extent to which the potential of biomarkers in occupational health and safety is realized. These include: (1) adequate investment in validation; (2) obtaining international agreement on exposure guidelines; (3) exploring the utility of biomarkers in regulation; (4) applying biomarkers to critical occupational safety and health questions; (5) developing the exposome; (6) utilizing biomarkers to address emerging occupational health issues; and (7) continuing to address the ethical and social justice issues related to biomarkers. Overall, if biomarkers are to make a major contribution to occupational health and safety then a more holistic approach to bringing them from the laboratory to practice will be needed.

Mechanistically identified suitable biomarkers of exposure, effect, and susceptibility for silicosis and coal-worker's pneumoconiosis: a comprehensive review

Clinical detection of silicosis is currently dependent on radiological and lung function abnormalities, both late manifestations of disease. Markers of prediction and early detection of pneumoconiosis are imperative for the implementation of timely intervention strategies. Understanding the underlying mechanisms of the etiology of coal workers pneumoconiosis (CWP) and silicosis was essential in proposing numerous biomarkers that have been evaluated to assess effects following exposure to crystalline silica and/or coal mine dust. Human validation studies have substantiated some of these proposed biomarkers and argued in favor of their use as biomarkers for crystalline silica- and CWP-induced pneumoconiosis. A number of "ideal" biological markers of effect were identified, namely, Clara cell protein-16 (CC16) (serum), tumor necrosis factor-alpha (TNF-alpha) (monocyte release), interleukin-8 (IL-8) (monocyte release), reactive oxygen species (ROS) measurement by chemiluminescence (neutrophil release), 8-isoprostanes (serum), total antioxidant levels measured by total equivalent antioxidant capacity (TEAC), glutathione, glutathione peroxidase activity, glutathione S-transferase activity, and platelet-derived growth factor (PDGF) (serum). TNF-alpha polymorphism (blood cellular DNA) was identified as a biomarker of susceptibility. Further studies are planned to test the validity and feasibility of these biomarkers to detect either high exposure to crystalline silica and early silicosis or susceptibility to silicosis in gold miners in South Africa.

Serum biomarkers in interstitial lung diseases

The use of biomarkers in medicine lies in their ability to detect disease and support diagnostic and therapeutic decisions. New research and novel understanding of the molecular basis of the disease reveals an abundance of exciting new biomarkers who present a promise for use in the everyday clinical practice. The past fifteen years have seen the emergence of numerous clinical applications of several new molecules as biologic markers in the research field relevant to interstitial lung diseases (translational research). The scope of this review is to summarize the current state of knowledge about serum biomarkers in interstitial lung diseases and their potential value as prognostic and diagnostic tools and present some of the future perspectives and challenges.

Platinum levels in nasal lavage fluid as a biomarker for traffic-related exposure and inflammation in children

Platinum (Pt) is a well-known constituent of particles emitted by catalytic converters during car operation. To evaluate Pt as a potential marker for traffic related particle exposure, we investigated Pt content along with metals vanadium (V) and chromium (Cr) in coarse and fine particulate matter (PM), sampled in four areas with different traffic density, as well as in the nasal lavage (NAL) of 67 children (average age: 6 years) living in these areas. The different sites were characterised by significant differences in air pollutants including PM, NO, NO(2), CO and Cr, but differences in V or Pt were absent. No significant differences in neutrophil and epithelial cell counts or concentrations of the neutrophil chemoattractant interleukin-8 (IL-8) were found in the NAL of children living in the different areas. In addition, the concentrations of V, Cr and Pt, which were detectable in 64%, 73% and 93% of the individuals, respectively, did not differ between the different locations. However, in the NAL of the children, a significant correlation between Pt and the number of neutrophils/ml (r=0.40, p<0.001) as well as of epithelial cells/ml (r=0.41, p<0.001) was found. No relation was present between nasal inflammation and nasal Cr levels, whereas a relatively weak association was observed between V and epithelial cells counts (r=0.30, p=0.018). In conclusion, our data suggests a role for nasal lavage Pt as a candidate biomarker for traffic-related PM, which is able to induce inflammation in the upper respiratory tract.

Serum beta-glucuronidase activity in a population of ex-coalminers

BACKGROUND

The aim of this study was to investigate whether BGD activity is of additional value in the assessment of pulmonary inflammation caused by coal dust exposure.

DESIGN AND METHODS

Ex-coalminers were included in this study. Forty-eight healthy male subjects, without a relevant medical history, were used as controls.

RESULTS

In ex-coalminers serum BGD activity was higher compared to the control group. Moreover, ex-coalminers with a normal chest radiograph and normal serum LDH demonstrated elevated serum BGD compared to the control group. However, no relation was found in the total group of ex-coalminers between serum BGD activity and pulmonary function parameters.

CONCLUSIONS

Our study adds in vivo human evidence to the already existing animal data that BGD is a potential biomarker useful in monitoring pulmonary inflammation caused by coal dust exposure.

NR8383 alveolar macrophage toxic growth arrest by hydrogen peroxide is associated with induction of growth-arrest and DNA damage-inducible genes GADD45 and GADD153

Breathing air exposes humans and other mammals to various toxic agents including oxidative contaminants associated with fine particles of less than 2.5 micron which may be deposited in the deep lung and have been implicated in the increased morbidity and mortality correlated with air pollution. Oxidative damage from inhaled particles may include damage to DNA, thereby adversely affecting the immunosurveillance provided by alveolar macrophages. Using the rat alveolar macrophage cell line NR8383, we demonstrated that cell proliferation was inhibited by exogenous hydrogen peroxide, an oxidant naturally produced in cellular respiration and phagocytosis. Mercaptosuccinate, a specific inhibitor of the antioxidant enzyme glutathione peroxidase, also inhibited cell growth. Genes known to be coordinatively regulated in response to growth arrest and DNA damage, GADD45 and GADD153, were induced compared to the housekeeping gene beta-ACTIN by equitoxic doses of hydrogen peroxide and mercaptosuccinate. Hydrogen peroxide treatment of cells in which glutathione peroxidase was inhibited by mercaptosuccinate resulted in even greater induction of both GADD genes. This approach using the NR8383 alveolar macrophage cell line provides a model for studying genotoxicity at the mechanistic level at which stress-responsive genes involved in growth arrest and DNA-damage response are modulated.

Risk of gastric cancer in pneumoconiotic coal miners and the effect of respiratory impairment

OBJECTIVES

This study was carried out to investigate the mortality patterns in a group of 3790 coal miners. The study population had abnormal chest x ray films at a routine medical examination that was performed in the 1950s.

METHODS

The total group of 3790 coal miners were followed up for mortality up to 1 January 1992. Causes of death, determined and coded at time of death, were traced with help from the Central Bureau of Statistics.

RESULTS

Total mortality in this group of coal miners with abnormal chest x ray films was significantly higher than expected (SMR 127.1, 95% CI 122.5-131.6), mainly a reflection of the increase in mortality from non-malignant respiratory disease (SMR 411.0, 95% CI 382.3-441.3). Mortality from gastric cancer was also significantly increased (SMR 147.5, 95% CI 122.3-176.3). This risk of mortality from gastric cancer was confined to workers with no pneumoconiosis or only a mild form. Despite the strong relation to duration of employment and pneumoconiosis the group of workers with more severe manifestations of pneumoconiosis did not experience an excess in mortality from gastric cancer.

CONCLUSION

This study confirms the earlier reported risk of gastric cancer in coal miners. Also it confirms the hypothesis that this risk of gastric cancer is limited to workers with a mild degree of pneumoconiosis or none. In workers with severe forms of pneumoconiosis the pulmonary clearance system is impaired in such a way that the inhaled coal dust does not reach the digestive tract.

Evaluation of serum type III procollagen peptide as an exposure marker in retired coal workers

Serum type III procollagen peptide (PIIIP), a degradation product of the type III collagen precursor, has been put forward as an exposure marker for mineral dust. We evaluated PIIIP levels as a marker of exposure to and effects of coal dust in retired coal miners (n = 104). To this end: (a) the individual cumulative dust exposure was calculated from job-exposure matrices, and (b) in addition to routine chest radiography (CR) of all miners according to the criteria of the International Labour Organisation (ILO), a subgroup (n = 46) was screened by high-resolution computed tomography (HRCT). Profusion score (CR and HRCT) tended to increase with cumulative dust exposure, even in the absence of CR evidence for pneumoconiosis (i.e. CR < or = 0/1, n = 35). In contrast to our previous findings in active miners, PIIIP levels were not increased in miners as compared with non-dust-exposed controls (n = 29), and no differences were observed between miners without (ILO = 0/0) and miners with coal workers' pneumoconiosis (CWP; ILO > or = 0/1). No trend in PIIIP versus pneumoconiosis stage was present, either by CR or by the more sensitive HRCT score. PIIIP was also unrelated to any lung function parameter (FEV1, FVC, impedance, diffusion capacity). Age, medication, medical history and smoking habits had no significant effect on PIIIP levels. In the miners with CWP (i.e. ILO > 0/0, n = 28) a significant negative correlation was present between PIIIP values and (log) cumulative dust exposure. This decrease in serum PIIIP levels with increasing cumulative exposure may be due to chronic adaptive changes in type III collagen deposition and/or breakdown. Other relations between exposure and PIIIP were not observed. In conclusion, the present findings do not support the use of serum type III procollagen peptide as a marker of exposure to and (early) interstitial or respiratory effects of coal dust.

Oxidative DNA damage in peripheral blood lymphocytes of coal workers

Reactive oxygen species are important mediators of both mineral dust-induced (malignant) lung disease and in vitro DNA damage. Therefore, we studied in vivo oxidative DNA damage in coal workers who had been chronically exposed to silica-containing dust. In peripheral blood lymphocytes of 38 retired coal miners (eight with coal workers pneumoconiosis, 30 references) and 24 age-matched, non-dust-exposed controls 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG) was determined by reversed phase high-performance liquid chromatography with electrochemical detection. The ratio of 8-oxodG residues to deoxyguanosine (dG) was related to individual cumulative dust exposure estimates and pneumoconiotic stage as established by chest radiography. The ratio of 8-oxodG to dG(x 10(-5)) in lymphocytes did not differ between miners with coal workers' pneumoconiosis (2.61 +/- 0.44) and miners without coal workers' pneumoconiosis (2.96 +/- 1.86). However, oxidative DNA damage in all miners was higher than in the non-dust-exposed controls (1.67 +/- 1.31). 8-oxodG/dG ratio was not related to individual cumulative coal dust exposure, age or smoking (pack years) when evaluated by multiple linear regression. We suggest that oxidative damage to the DNA of peripheral blood lymphocytes may be introduced by increased oxidative stress responses in subjects chronically exposed to mineral dusts. Whether this is an important pathway in the suggested carcinogenicity of silica is still an open question.