Non-smoking Chronic Obstructive Pulmonary Disease Attributed to Occupational Exposure to Silica Dust

Occupational exposure to silicon dioxide and prevalence of chronic respiratory symptoms in the cement manufacturing industries: A review

The aim of this review was to assess the association between occupational exposure to silicon dioxide and chronic respiratory symptoms among workers in the cement manufacturing industries. Approximately 60 articles published from 2010 to 2021 were found and four independent reviewers extracted the data from each eligible study using PubMed, Google scholar etc. The following terms were used: exposure to cement dust, exposure to silicon dioxide etc. Inclusion and exclusion criteria were considered while searching for the studies. In this review, a total of 14 articles were included in this study. Chronic cough was the most prevalence exposure symptoms (OR 1.90; CI 9.90, 0.78), with wheezing reported to be the least experienced symptom (OR 1.34; CI 11.5, 0.50). Two studies reported exposure concentration ranging from 0.026 to 0.044 mg/m3, and 0.27 mg/m3 was also reported in one study. The FEV1 and FVC was lower in exposed workers when compared to the control group. Studies reported the crystalline silica quartz to be 21.5% in limestone, 22.5% in bauxite, 21.22% in clinker, and 21.22% in raw cement. Chronic cough, phlegm, wheezing, and shortness of breath or dyspnea was found to be significantly prevalence among workers, particularly cleaning personnel, in the cement manufacturing industries.

Small Airway Susceptibility to Chemical and Particle Injury

Small airways (SA) in humans are commonly defined as those conducting airways <2 mm in diameter. They are susceptible to particle- and chemical-induced injury and play a major role in the development of airway disease such as COPD and asthma. Susceptibility to injury can be attributed in part to structural features including airflow dynamics and tissue architecture, but recent evidence may indicate a more prominent role for cellular composition in directing toxicological responses. Animal studies support the hypothesis that inherent cellular differences across the tracheobronchial tree, including metabolic CYP450 expression in the distal conducting airways, can influence SA susceptibility to injury. Currently, there is insufficient information in humans to make similar conclusions, prompting further necessary work in this area. An understanding of why the SA are more susceptible to certain chemical and particle exposures than other airway regions is fundamental to our ability to identify hazardous materials, their properties, and accompanying exposure scenarios that compromise lung function. It is also important for the ability to develop appropriate models for toxicity testing. Moreover, it is central to our understanding of SA disease aetiology and how interventional strategies for treatment may be developed. In this review, we will document the structural and cellular airway regional differences that are likely to influence airway susceptibility to injury, including the role of secretory club cells. We will also describe recent advances in single-cell sequencing of human airways, which have provided unprecedented details of cell phenotype, likely to impact airway chemical and particle injury.

Pulmonary function and high-resolution computed tomography in outdoor rock drillers exposed to crystalline silica

OBJECTIVES

Chronic obstructive pulmonary disease and silicosis are associated with exposure to crystalline silica. We determined the exposure to respirable crystalline silica and estimated exposure-response relationships between cumulative exposure and pulmonary function in outdoor rock drillers.

METHODS

136 rock drillers and 48 referents were recruited from three heavy construction companies. 98 air samples were collected by personal sampling for determination of respirable particulate matter and crystalline silica. Information about individual job tasks, type of drilling equipment and years of exposure in different job categories was obtained by interview. Cumulative exposure to crystalline silica was calculated for all workers. Pulmonary function was assessed by spirometry. A subgroup of 39 subjects with high cumulative exposure to crystalline silica underwent high-resolution computed tomography (HRCT).

RESULTS

Cumulative exposure (mean (min-max)) to crystalline silica was 0.69 mg٠years m^-3 (0.01-5.89) in the exposed group. Mean time of exposure among rock drillers was 10.7 years (1-42). Compared with referents, the rock drillers had a lower forced expiratory volume in one second/forced vital capacity ratio (79.4 vs 81.4, p<0.05) and maximal mid-expiratory flow% (85.6 vs 93.9, p<0.05). Further, by stratifying the exposed workers into three equally large groups, a dose-response relationship was demonstrated in the highest exposed group, also in never smokers, at a mean cumulative exposure of 21.7 years at 0.08 mg٠m^-3/years. Silicosis was not detected in HRCT, but other patterns of fibrosis and emphysema were seen.

CONCLUSIONS

Outdoor rock drillers exposed to crystalline silica had significantly lower pulmonary function than referents, and signs of airflow obstruction. Silicosis was not detected.

Review of in vitro toxicological research of quantum dot and potentially involved mechanisms

Quantum dots (QDs) are one of emerging engineering nanomaterials (NMs) with advantageous properties which can act as candidates for clinical imaging and diagnosis. Nevertheless, toxicological studies have proved that QDs for better or worse pose threats to diverse systems which are attributed to the release of metal ion and specific characteristics of nanoparticles (NPs), hampering the wide use of QDs to biomedical area. It has been postulated that mechanisms of toxicity evoked by QDs have implications in oxidative stress, reactive oxygen species (ROS), inflammation and release of metal ion. Meanwhile, DNA damage and disturbance of subcellular structures would occur during QDs treatment. This review is intended to conclude the cytotoxicity of QDs in multiple systems, as well as the potential mechanisms on the basis of recent literatures. Finally, toxicity-related factors are clarified, among which chirality seems to be a newly proposed influence factor that determines the destiny of cells in response to QDs. However, details of interaction between QDs and cells have not been well elucidated. Given that molecular mechanisms of QDs-induced toxicity are still not clearly elucidated, further research should be required for this meaningful topic.