Lymphocyte DNA damage in Turkish asphalt workers detected by the comet assay

The Comet Assay as a Tool in Human Biomonitoring Studies of Environmental and Occupational Exposure to Chemicals-A Systematic Scoping Review

Biomonitoring of human populations exposed to chemical substances that can act as potential mutagens or carcinogens, may enable the detection of damage and early disease prevention. In recent years, the comet assay has become an important tool for assessing DNA damage, both in environmental and occupational exposure contexts. To evidence the role of the comet assay in human biomonitoring, we have analysed original research studies of environmental or occupational exposure that used the comet assay in their assessments, following the PRISMA-ScR method (preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews). Groups of chemicals were designated according to a broad classification, and the results obtained from over 300 original studies (n = 123 on air pollutants, n = 14 on anaesthetics, n = 18 on antineoplastic drugs, n = 57 on heavy metals, n = 59 on pesticides, and n = 49 on solvents) showed overall higher values of DNA strand breaks in the exposed subjects in comparison with the unexposed. In summary, our systematic scoping review strengthens the relevance of the use of the comet assay in assessing DNA damage in human biomonitoring studies.

Evaluating the relationship between the respiratory exposure to the benzene with the primary damages of deoxyribonucleic acid and total antioxidant capacity in one of the oil companies in Iran

Benzene is a carcinogenic chemical substance which causes the injuries and damages through producing the free radicals in DNA (deoxyribonucleic acid) and the antioxidants are the agents which reduce the impacts of DNA damages by inhibiting the free radicals. This study was conducted aiming at determination of primary damages of DNA and level of plasma oxidative stress markers resulting from the respiratory exposure to the benzene found in petroleum compounds among the workers at loading platforms of a petroleum products distribution center. This study was an analytical (case control) research conducted among the workers in a working shift serving at the loading platforms of petroleum products. The exposure group included the workers with a history of contact with benzene and the control group was composed of the persons with no history of exposure to benzene. To investigate the level of the personnel's exposure to benzene, NIOSH-1501 method was utilized; to analyze the samples taken from the air, GC mass (gas chromatography-mass spectrometry) was applied; and to determine the average of DNA primary damages, comet assay was used. Total antioxidant capacity was determined by a photometric method. Results indicated that tail length (TL), tail density (TD), tail momentum (TM), percentage of tail in the DNA (%DNA), and %TAC in control group were 78.59, 8.35, 1.20, 10.05, and 25.58 and in the exposure group were 59.21, 75.74, 57.74, 3.5, and 16.58, respectively. The previously mentioned results showed a decrease in the TL, %DNA, and %TAC values among the workers already exposed to benzene while an increase in the TD and TM values of the same group compared to the control non-exposed group. In comparing the averages between two studied groups, all study variables had statistically meaningful difference (p < 0.05). More studies are recommended to be conducted on using the methods which identify the special places of breakage and damage in DNA chain due to the exposure to benzene and consequently prevent the complications and consequences.

The modulation of oxidative stress and DNA damage to radiology technicians by repair enzymes XRCC1 and XRCC3 The association of oxidative stress and DNA damage with XRCC1 and XRCC3 polymorphisms in radiology technicians

Ionizing radiation has widespread use in medicine in the diagnosis and treatment of many medical conditions. Radiology technicians are one group that is occupationally exposed to low doses of radiation. There are questions regarding whether low dose exposure to radiation could have long-term health consequences. Assessing the effect of radiation on genetic material is essential for appraising long-term health results. Hereditary variations in DNA repair genes cause differentiation in individual responses to radiation related health effects. This study aimed to determine oxidative stress and DNA damage, and their relationship to XRCC1 (Arg399Gln) and XRCC3 (Thr241Met) polymorphisms in radiology technicians occupationally exposed to low dose radiation. Peripheral blood samples were collected from 45 radiology technicians and age-matched with 40 healthy control individuals working in office environments. Our results showed that radiology technicians had significantly greater oxidative stress and DNA damage than the control group, and women appeared more susceptible to occupational radiation exposure than men. Individuals with wild-type genotypes for XRCC1 (Arg/Arg) and XRCC3 (Thr/Thr) had less DNA damage. Lower DNA damage levels could be explained by the enhanced capacity to repair low dose radiation induced DNA damage. Further studies are needed to evaluate the role of DNA repair genes in individuals that are occupationally exposed to low dose radiation.

Genotoxic effect of exposure to polycyclic aromatic hydrocarbons (PAHs) in asphalt workers

Asphalt workers are at risk due to exposure to asphalt fumes containing polycyclic aromatic hydrocarbons (PAHs). The main purpose of this study was to measure the urinary metabolite of PAHs and to determine its effect on micronucleus (MN) formation as an indicator of genotoxic damage. In this cross-sectional study, the MN frequency in 48 male asphalt workers exposed to PAHs was measured and compared with 48 male non-exposed employees. PAHs exposure was evaluated by determining urinary 1-Hydroxypyrene (1-OHP). The mean concentrations of 1-OHP in the exposed and non-exposed groups were 0.58 ± 0.41 μmol/mol creatinine and 0.38 ± 0.25 μmol/mol creatinine, respectively. 1-OHP concentration was significantly higher in smokers compared with non-smokers in both exposed and non-exposed groups. Moreover, the mean MN frequency in the exposed group was significantly higher than in the non-exposed group. The MN frequency was significantly higher in asphalt workers with a work history of ≥ 15 years compared to workers with lower work history. In a fully adjusted model, there was a statistically significant association between exposure to PAHs, with MN and 1-OHP concentration, and between smoking status with 1-OHP. The findings of the present study indicated that occupational exposure to PAHs was associated with increased urinary 1-OHP as well as DNA damage in the asphalt workers.

Evaluation of telomere length and genotoxicity among asphalt associated workers

There are contradictory reports about bitumen exposure and malignancy risk worldwide. Also, the evidence for genotoxicity risk among workers occupationally exposed to asphalt is insufficient. The study intended to evaluate particulate matter 10 (PM₁₀) at the workplace and biomarkers of genotoxicity effects among a group of asphalt workers in and around Bangalore, India. This study involved a total of 107 participants (54 exposed group and 53 unexposed control group). To evaluate the genotoxicity, the urinary 8-OHdG and relative telomere length as oxidative damage while micronucleus (MN) assay for cytogenetic damage was carried out during the study. The majority of workers have reported health complaints and 57.4% of them were not using any personal protective equipments (PPE's). The level of PM₁₀ detected was 104 ± 9.5 μg/m³ and 619 ± 22.7 μg/m³ in the road paving and asphalt mixing sites respectively. The biomonitoring study observed a highly significant (p = <0.001) increase in the level of 8-hydroxy-2-deoxyguanosine (8-OHdG) in the exposed group (23.17 ± 8.65 ng/mg creatinine) compared to the control (13.6 ± 7.12 ng/mg creatinine), revealed age significant associated and non-smoking borderline significant associated for oxidative stress. The relative telomere length (TL) analysis revealed its highly significant (p = 0.004) reduction in the exposed group, adjusted mean 0.95 (95% CI 0.83-1.07) compared to the control 1.06 (95% CI 0.91-1.26). The job category (p = 0.028), non-smoking (p = 0.026), and tobacco chewing (p = 0.013) were associated with reduced relative TL in the asphalt exposed group. In cytogenotoxicity analysis, the mean micronucleus (MN) frequency per 100 cells in the exposed group (26.46 ± 19.8) was significantly (p = <0.001) increased over the control group (8.56 ± 7.18). Neither smoking habit nor age appeared to influence the MN frequencies in either group. In the present study, we have demonstrated genetic damage in workers occupationally exposed to asphalt and particulate matter, raising concern for an increased risk of malignancy in these workers.

Assessment of chromosome stability in boars

Chromosome instability adversely affects animal fertility and reproduction. Analysis of instability can be a valuable diagnostic tool. Helpful tests for assessment of instabilities include the sister chromatid exchange assay, identification of fragile sites, the bleomycin assay and the comet assay. These techniques can be used to assess and compare the chromosome stability of individual breeds of animals. The aim of the study was to assess chromosome stability in boars: Duroc, Duroc x Pietrain and Pietrain x Duroc crossbreds, Polish Large White, and the Neckar, P76 and PIC lines. The study assessed the chromosome stability of boars. The distribution of instabilities in individual breeds was varied. The average frequency of chromatid exchange was 4.8 ± 1.5, while that of fragile sites was 3.9 ± 1.4. The mean level of DNA damage (% tail DNA) was 9.4 ± 8.3, while in the bleomycin assay b/c and %AM were 0.6 ± 0.7 and 44.4 ± 4.1. A higher rate of instability was found in older individuals than in younger ones. The cytogenetic assays used to identify various forms of chromosome instability can be used to evaluate boars intended for breeding.

Analysis of chromatin instability of somatic cells in sheep

Cytogenetic tests are highly reliable, sensitive indicators of the early effects of genomic instability. Their results provide information on the organism’s susceptibility to exogenous and endogenous factors and are measures of the degree of repair of DNA damage. Our study assessed spontaneously occurring damage in following four breeds of sheep: Polish Heath, Polish Lowland (Zelazna variety), Polish Blackhead, and Berrichon du Cher. Instability was identified using the following three different tests: a sister chromatid exchange (SCE) assay, identification of fragile sites, and the comet assay. The distribution of instabilities varied depending on the breed. The mean frequency of SCEs was 5.13 ± 1.58, whereas that of fragile sites was 3.30 ± 1.24. The mean level of DNA damage (% head DNA) was 96.52 ± 6.59. The most damage to genetic material was observed in the Berrichon du Cher sheep, and the least in the Polish Heath sheep. The tests used are reliable biomarkers of genome stability in animal breeds, as well as in individuals within breeds.