Evaluation of Serum and Urinary Neopterin Levels as a Biomarker for Occupational Exposure to Crystalline Silica

Biomonitoring Exposure and Early Diagnosis in Silicosis: A Comprehensive Review of the Current Literature

Silicosis is a particular form of lung fibrosis attributable to occupational exposure to crystalline silica. The occupational exposure to crystalline silica also increases the risk of chronic obstructive pulmonary disease (COPD), cancer and lung infections, especially pulmonary tuberculosis. Silicosis is currently diagnosed in previously exposed workers by standard chest X-ray, when lesions are visible and irreversible. Therefore, it would be necessary to find specific and non-invasive markers that could detect silicosis in earlier stages, before the occurrence of X-ray opacities. In this narrative review, we present several diagnostic, monitoring and predictive biomarkers with high potential in the management of silicosis, such as: pro- and anti-inflammatory cytokines (TNF (Tumour necrosis factor-α), IL-1 (Interleukin-1), IL-6, IL-10), CC16 (Clara cell 16, an indirect marker of epithelial cell destruction), KL-6 (Krebs von den Lungen 6, an indirect marker of alveolar epithelial damage), neopterin (indicator of cellular immunity) and MUC5B gene (Mucin 5B, a gel-forming mucin in mucus). Studies have shown that all the aforementioned markers have a high potential for early diagnosis or evaluation of progression in silicosis and represent promising alternatives to radiology. We consider that a multicentric study is needed to evaluate these biomarkers in correlation with occupational history, histopathological examination, imaging signs and pulmonary functions tests on large groups of subjects to better evaluate the accuracy of the presented biomarkers.

Mercury exposure, neopterin profile, and tryptophan degradation in dental technicians

Amalgam has been widely used as a restorative dental material for over 150 years. Most standard dental amalgam formulations contain approximately 50% elemental mercury in a mixture of copper, tin, silver, and zinc. Mercury is a highly volatile metal, which can easily vaporize to a colorless and odorless gas. It has been demonstrated that mercury is released from dental amalgam, which is increased by chewing, eating, brushing, and drinking hot liquids. Besides this, amalgam is the main occupational exposure source of mercury for dental workers. It is known that mercury exposure causes immune modulation in humans. In this study, it was aimed to evaluate the changes in neopterin levels and tryptophan (Trp) degradation in dental technicians. It was observed that low levels of occupational mercury exposure resulted in decreased neopterin, kynurenine (Kyn), and Kyn/Trp levels. Moreover, mercury and neopterin levels had a significant positive correlation in workers. The lower neopterin levels and Kyn/Trp in dental technicians compared to an unexposed group indicates a possible immune suppression with low level of occupational mercury exposure during amalgam preparation. The relationship between urinary mercury levels as an indicator of occupational mercury exposure and neopterin reminded an effect on T-cell-mediated immune response.

Risk Assessment of Silicosis and Lung Cancer Mortality associated with Occupational Exposure to Crystalline Silica in Iran

BACKGROUND

Exposure to crystalline silica has long been identified to be associated with lung diseases. Therefore, the present study aimed to assess the risk of silicosis and lung cancer associated with occupational exposure to crystalline silica in Iran.

STUDY DESIGN

It is a systematic review study.

METHODS

Different databases were searched, and the Cochrane method was used for the systematic review. Thereafter, cumulative exposure to crystalline silica (mg/m3-y) was calculated in every industry. The relative risk of death from silicosis was performed using Mannetje's method. Based on the geometric mean of exposure, the lung cancer risk of exposure to crystalline silica was also calculated.

RESULTS

As evidenced by the results, worker's exposure to silica ranged from a geometric mean of 0.0212- 0.2689 mg/m3 (Recommended standard by the American Conference of Governmental Industrial Hygienists (ACGIH) was 0.025 mg/m3), which is generally higher than the occupational exposure limit recommended by National Institute for Occupational Safety and Health (NIOSH), ACGIH, and occupational exposure limits. The relative risk of silicosis was in the range of 1 to 14 per 1000 people, and the risk of lung cancer in workers ranged from 13-137 per 1000 people.

CONCLUSION

Since workers are at considerable risk of cancer due to exposure to silica in Iran, exposure control programs need to be implemented in workplaces to decrease the concentration of silica.

Occupational exposure to crystalline silica and peripheral biomarkers: An update

Peripheral biomarkers are important tools for detecting occupational exposures to prevent the onset and/or progression of diseases. Studies that reveal early peripheral biomarkers are highly important to preserve the health of workers and can potentially contribute to diagnosing and/or prognosing occupational pathologies. Exposure to crystalline silica is a problem in several workplaces because it increases the risk of chronic obstructive pulmonary disease (COPD), tuberculosis, cancer, and pulmonary fibrosis, clinically defined as silicosis. Silicosis is diagnosed by chest radiography and/or lung tomography in advanced stages when there is a severe loss of lung function. Peripheral biomarkers can help in diagnosing early changes prior to silicosis and represent a highly important technical-scientific advance that is minimally invasive. This review aimed to investigate the biomarkers studied for evaluating occupational exposure to crystalline silica and to understand the recent advances in this area. Potential oxidative, inflammatory, and immunological biomarkers were reviewed, as well as routine biomarkers such as biochemical parameters. It was found that biomarkers of effect such as serum CC16 and l-selectin levels could represent promising alternatives. Additionally, studies have shown that neopterin levels in urine and serum can be used to monitor worker exposure. However, further studies are needed that include a greater number of participants, different times of exposure to crystalline silica, and a combination of silicosis patients and healthy volunteers. Evaluating the concentration of crystalline silica in occupational environments, its impact on biomarkers of effect, and alterations in lung function could contribute to revealing early health alterations in workers in a more robust manner.