Genomic Instability in Exfoliated Buccal Cells among Cement Warehouse Workers

Gaining insight into genotoxicity with the comet assay in inhomogenoeous exposure scenarios: The effects of tritiated steel and cement particles on human lung cells in an inhalation perspective

The comet assay was recently applied for the first time to test the genotoxicity of micrometric stainless steel and cement particles, representative of those produced in the dismantling of nuclear power plants. A large dataset was obtained from in vitro exposure of BEAS-2B lung cells to different concentrations of hydrogenated (non-radiative control) and tritiated particles, to assess the impact of accidental inhalation. Starting from the distributions of the number of nuclei scored at different extent of DNA damage (% tail DNA values), we propose a new comet data treatment designed to consider the inhomogeneity of the action of such particles. Indeed, due to particle behavior in biological media and concentration, a large fraction of cells remains undamaged, and standard averaging of genotoxicity indicators leads to a misinterpretation of experimental results. The analysis we propose reaches the following goals: genotoxicity in human lung cells is assessed for stainless steel and cement microparticles; the role of radiative damage due to tritium is disentangled from particulate stress; the fraction of damaged cells and their average level of DNA damage are assessed separately, which is essential for carcinogenesis implications and sets the basis for a better-informed risk management for human exposure to radioactive particles.

Cyto-Genotoxicity of Tritiated Stainless Steel and Cement Particles in Human Lung Cell Models

During the decommissioning of nuclear facilities, the tritiated materials must be removed. These operations generate tritiated steel and cement particles that could be accidentally inhaled by workers. Thus, the consequences of human exposure by inhalation to these particles in terms of radiotoxicology were investigated. Their cyto-genotoxicity was studied using two human lung models: the BEAS-2B cell line and the 3D MucilAirTM model. Exposures of the BEAS-2B cell line to particles (2 and 24 h) did not induce significant cytotoxicity. Nevertheless, DNA damage occurred upon exposure to tritiated and non-tritiated particles, as observed by alkaline comet assay. Tritiated particles only induced cytostasis; however, both induced a significant increase in centromere negative micronuclei. Particles were also assessed for their effects on epithelial integrity and metabolic activity using the MucilAirTM model in a 14-day kinetic mode. No effect was noted. Tritium transfer through the epithelium was observed without intracellular accumulation. Overall, tritiated and non-tritiated stainless steel and cement particles were associated with moderate toxicity. However, these particles induce DNA lesions and chromosome breakage to which tritium seems to contribute. These data should help in a better management of the risk related to the inhalation of these types of particles.

Cytogenetic features of buccal epithelium under exposure to harmful factors of metallurgical production

At the present stage of development of society, the issues of preserving and strengthening the most important productive force that determine the economic development and national security of the country remain relevant. Metallurgy is one of the basic industries in Russia, which forms up to 20% of GDP. This study assesses the condition of the oral mucosa in workers in the industry. To evaluate the formation of micronuclei in buccal cells as an early biomarker of health disorders as a result of occupational exposure to production factors of a metallurgical plant. Hygienic and clinical laboratory tests were carried out for workers of the metallurgical plant of the Republic of Bashkortostan. Cytological studies of the buccal epithelium were performed. Statistical processing of the results was carried out using the applied programs IBM, SPSS, Statistics, Microsoft Excel. The general assessment of working conditions in accordance with the criteria of R.2.2.2006-05 for workers of the metallurgical plant was established as 3.2-3.3. Analysis of the buccal epithelium revealed the occurrence of cells with cytogenetic disorders in the workers of the main group. Cells with atypical nuclei were identified in workers with a duration of contact with unfavorable factors of production for more than ten years. Signs of nuclear destruction were revealed, characterizing an increase in apoptotic activity in workers with prolonged contact times. Studies have shown that with more than 10 years of work experience, proliferation processes prevail over differentiation processes. The results obtained can be used as diagnostic methods that expand the prospects for identifying pre-pathological and pathological conditions.

Induction of DNA damage as a consequence of occupational exposure to crystalline silica: A review and meta-analysis

About 40 million workers are occupationally exposed to crystalline silica (CS) which was classified as a human carcinogen by the IARC. It is assumed that damage of the genetic material via inflammation and reactive oxygen species by CS lead to formation of malignant cells. We conducted a systematic literature search to find out if inhalation of CS containing dusts at workplaces causes damage of the genetic material. Thirteen studies were found eligible for this review, in most of them (n = 9) micronuclei (MN) which reflect structural/numerical chromosomal aberrations were monitored in lymphocytes and/or in exfoliated buccal cells. In 5 investigations DNA damage was measured in blood cells in single cell gel electrophoresis (comet) experiments. Frequently studied groups were potters, stone cutters, miners and construction workers. Results of meta-analyses show that exposure to CS causes formation of MN and DNA breaks, the overall ratio values were in exposed workers 2.06- and 1.96-fold higher than in controls, respectively. Two studies reported increased levels of oxidized guanine, and higher levels of DNA adducts with malondialdehyde indicating that exposure to CS leads to oxidative damage. The exposure of the workers to CS was quantified only in two studies, information concerning the size and chemical structures of the particles is lacking in most investigations. Therefore, it is not possible to use the results to derive occupational exposure limits of workers to CS which vary strongly in different countries. Nevertheless, the evaluation of the current state of knowledge shows that biomonitoring studies in which damage of the genetic material is measured in CS exposed workers can contribute to assess adverse health effects as consequence of DNA instability in specific occupations.

Early genotoxic damage through micronucleus test in exfoliated buccal cells and occupational dust exposure in construction workers: a cross-sectional study in L'Aquila, Italy

AIM

The city of L'Aquila (central Italy) was hit by a strong earthquake in 2009 that caused the collapse of several buildings, deaths and injured people. In the following years, a great number of building sites were activated, building workers resulted intensely exposed and represent a relevant target for research on environmental mutagenesis and epidemiological surveillance. Cells of buccal mucosa are considered an appropriate site for early detecting of cytogenetic damage, since it represents the first barrier in inhalation or ingestion and can metabolize carcinogenic agents into reactive chemicals. Our study is aimed 1) at comparing the early genotoxic damage as measured by the buccal mucosa micronucleus test in two subgroups of workers defined by different occupational exposure and 2) at evaluating possible confounding variables such as lifestyle factors.

METHODS AND RESULTS

A cross-sectional study was conducted in L'Aquila, on 24 outdoor workers (OWs) highly exposed on the construction sites and 26 indoor workers (IWs), all subjected to the compulsory occupational surveillance system, in the period 2017-2018. Buccal cells samples were collected and, based on the Micronucleus test, the exfoliated cells were classified in respect of nuclear changes observed. Moreover, a self-report questionnaire composed of 84 items, was administered to the workers.

RESULTS

Significant differences were observed between Exp⁺ (OWs) and Exp^- (IWs) in the number of the analyzed cells (expressed as mean value out of 1000 cells): respectively 954.46 vs 990.06 normal cells, (p < 0.001); 19.79 vs 4.95 micronucleated cells, as marker of chromosomal damage (p < 0.001); 13.93 vs 8.96 binucleated cells, as marker of failed cytokinesis (p < 0.001); 2.09 vs 1.18 karyolytic cells, as marker of cell death and damaged DNA (p < 0.05). According with a multivariate regression analysis, in addition to the job exposure (OW vs IW, beta = 12.221, p < 0.001), the only variable independently associated with an increase in Micronuclei (MNs) is the smoking habit (OWs vs IWs, beta = 6.683, p < 0.001) which, even if not associated with dust exposure, worsens cell integrity. Moreover, this worsening effect is weaker in workers not exposed to the site dust (moderation effect). Within social demographic factors, the high educational level only apparently seems to affect MNs number: even if unbalanced in favor of IWs vs OWs, this variable resulted a confounder, since its effect disappears when the interaction between these two factors is considered, because it is a covariate of smoking habit as well as of the job condition.

CONCLUSION

Despite some limitation, our findings clearly confirm the role of occupational exposure as a marker of cytogenetic damage associated with MNs number in construction workers. Moreover, smoking status appears as the only other investigated factor independently associated to the outcome. The statistical model, in addition, highlights possible moderation and confounding effects, such as interaction between smoking and occupational exposure and the unbalanced school education level in workers. Micronucleus test in exfoliated buccal cells would be considered a suitable method for studying the early genotoxic damage in the construction occupational setting as well as in evaluating the efficacy of preventive practices.