Association between occupational exposure to benzene and chromosomal alterations in lymphocytes of Brazilian petrochemical workers removed from exposure

Biomarkers of occupational benzene exposure: A Systematic Review to estimate the exposure levels and individual susceptibility at low doses

Benzene is associated with diverse occupational and public health hazards. It exhibits an ability to rapidly permeate the skin and contaminate water and food sources, leading to dermal and ingestion exposures. Despite numerous studies examining the associations between benzene and various indicators of harm, the findings have yielded inconsistent results. Furthermore, relying solely on air concentration as a measure of benzene exposure is limited, as it fails to account for internal exposure dose and individual susceptibility. This study aimed to conduct a comprehensive review in order to present current knowledge on benzene biomarkers and their significance in evaluating exposure levels and associated health hazards. The search methodology adhered to the PRISMA guidelines and involved the application of specific inclusion and exclusion criteria across multiple databases including PubMed, Embase, and Web of Science. Two researchers independently extracted and evaluated the relevant data based on predetermined criteria. Following the screening process, a total of 80 articles were considered eligible out of the initially retrieved 1053 articles after undergoing screening and assessment for inclusion. As the level of exposure decreased, specific biomarkers demonstrated a gradual increase in limitations, including heightened background concentrations and vulnerability to confounding factors. The advancement of sampling and analysis techniques will yield new biomarkers. Additionally, when conducting practical work, it is crucial to employ a comprehensive utilization of diverse biomarkers while excluding individual metabolic variations and combined exposure factors.

Benzene metabolite hydroquinone enhances self-renewal and proliferation of preleukemic cells through the Ppar-γ pathway

Benzene is a known hematotoxic and leukemogenic chemical. Exposure to benzene cause inhibition of hematopoietic cells. However, the mechanism of how the hematopoietic cells inhibited by benzene undergo malignant proliferation is unknown. The cells carrying leukemia-associated fusion genes are present in healthy individuals and predispose the carriers to the development of leukemia. To identify the effects of benzene on hematopoietic cells, preleukemic bone marrow (PBM) cells derived from transgenic mice carrying the Mll-Af9 fusion gene were treated with benzene metabolite hydroquinone in serial replating of colony-forming unit (CFU) assay. RNA sequencing was further employed to identify the potential key genes that contributed to benzene-initiated self-renewal and proliferation. We found that hydroquinone induced a significant increase in colony formation in PBM cells. Peroxisome proliferator-activated receptor gamma (Ppar-γ) pathway, which plays a critical role in carcinogenesis in multiple tumors, was significantly activated after hydroquinone treatment. Notably, the increased numbers of the CFUs and total PBM cells induced by hydroquinone were significantly reduced by a specific Ppar-γ inhibitor (GW9662). These findings indicated that hydroquinone can enhance self-renewal and proliferation of preleukemic cells by activating the Ppar-γ pathway. Our results provide insight into the missing link between premalignant status and development of benzene-induced leukemia, which can be intervened and prevented.

Brazilian workers occupationally exposed to different toxic agents: A systematic review on DNA damage

The evaluation of genotoxicity in workers exposed to different toxic agents is very important, especially considering the association between these exposures in a chronic context and DNA damage. Assessing biomarkers of exposure and, when possible, early biomarkers of effect, contributes to elucidating the potential toxic mechanisms involved in genotoxicity and its contribution to chronic non-communicable diseases. In Brazil, the biggest country in South America, workers are exposed to hazardous physical and chemical agents. Considering that these exposures occur, in most cases, throughout the worker's whole life, this is an important public health concern in Brazil. Therefore, this systematic review aims to analyze occupational exposure to chemical and physical agents and the association with DNA damage in studies carried out in Brazil from 1980 to 2021. A systematic and comprehensive literature search was performed in different databases based on occupational exposure to chemical and physical agents and DNA damage. Only full articles on studies that investigated experimental evidence on occupational exposure in Brazil and assessed DNA damage were included, amounting to 89 articles. Five main occupational exposure groups were identified: pesticides (36%), organic solvents (20%), dust and particles (16%), metals (11%), and ionizing radiation (6%). Another group called "others" included studies (11%) that did not fall into these main groups. It was found that comet assay and micronucleus tests are the most adopted methods to detect DNA damage. Occupational exposures were most associated with DNA damage. However, further improvements in study design would be needed to better characterize the association between biomonitoring and DNA damage, particularly to account for confounding factors.

A Scoping Review of Technologies and Their Applicability for Exposome-Based Risk Assessment in the Oil and Gas Industry

INTRODUCTION

Oil and gas workers have been shown to be at increased risk of chronic diseases including cancer, asthma, chronic obstructive pulmonary disease, and hearing loss, among others. Technological advances may be used to assess the external (e.g. personal sensors, smartphone apps and online platforms, exposure models) and internal exposome (e.g. physiologically based kinetic modeling (PBK), biomonitoring, omics), offering numerous possibilities for chronic disease prevention strategies and risk management measures. The objective of this study was to review the literature on these technologies, by focusing on: (i) evaluating their applicability for exposome research in the oil and gas industry, and (ii) identifying key challenges that may hamper the successful application of such technologies in the oil and gas industry.

METHOD

A scoping review was conducted by identifying peer-reviewed literature with searches in MEDLINE/PubMed and SciVerse Scopus. Two assessors trained on the search strategy screened retrieved articles on title and abstract. The inclusion criteria used for this review were: application of the aforementioned technologies at a workplace in the oil and gas industry or, application of these technologies for an exposure relevant to the oil and gas industry but in another occupational sector, English language and publication period 2005-end of 2019.

RESULTS

In total, 72 articles were included in this scoping review with most articles focused on omics and bioinformatics (N = 22), followed by biomonitoring and biomarkers (N = 20), external exposure modeling (N = 11), PBK modeling (N = 10), and personal sensors (N = 9). Several studies were identified in the oil and gas industry on the application of PBK models and biomarkers, mainly focusing on workers exposed to benzene. The application of personal sensors, new types of exposure models, and omics technology are still in their infancy with respect to the oil and gas industry. Nevertheless, applications of these technologies in other occupational sectors showed the potential for application in this sector.

DISCUSSION AND CONCLUSION

New exposome technologies offer great promise for personal monitoring of workers in the oil and gas industry, but more applied research is needed in collaboration with the industry. Current challenges hindering a successful application of such technologies include (i) the technological readiness of sensors, (ii) the availability of data, (iii) the absence of standardized and validated methods, and (iv) the need for new study designs to study the development of disease during working life.

The association of three DNA repair genes polymorphisms on the frequency of chromosomal alterations detected by fluorescence in situ hybridization

PURPOSE

Gas station workers (GSWs) are exposed to carcinogenic agents. The aim was to study the association of high somatic chromosome alterations (CAs) rates in the blood of GSWs and the polymorphisms of three genes playing a role in DNA double-strand break repair.

METHODS

This is a cross-sectional study with 114 GSWs and 115 age-matched controls. Cytogenetic analyses, blood exams, medical interviews and genotypes for RAD51/G135C (rs1801320), ATM/P1054R (rs1800057) and CHEK2/T470C (rs17879961) genes were performed.

RESULTS

The CA rate in GSWs was 9.8 CAs/1000 metaphases, and 19.1% of the workers had > 10 CAs per 1000 metaphases (group two). GSWs had decreased levels of monocytes (P = 0.024) in their blood exams. The number of variant alleles of the RAD51/G135C polymorphism was higher in GSWs (P = 0.011) compared to the controls, and were associated with enhanced number of CAs per worker (P = 0.008). No allele variant was found for CHEK2/T470C in this study.

CONCLUSION

The RAD51/G135C polymorphism appears to be related to genome instability in gas station workers. Increasing the knowledge of DNA repair gene variations involved in maintaining genomic stability in GSWs may be crucial for future cancer prevention.

Derivation of an occupational exposure limit for benzene using epidemiological study quality assessment tools

This paper derives an occupational exposure limit for benzene using quality assessed data. Seventy-seven genotoxicity and 36 haematotoxicity studies in workers were scored for study quality with an adapted tool based on that of Vlaanderen et al., 2008 (Environ Health. Perspect. 116 1700-5). These endpoints were selected as they are the most sensitive and relevant to the proposed mode of action (MOA) and protecting against these will protect against benzene carcinogenicity. Lowest and No- Adverse Effect Concentrations (LOAECs and NOAECs) were derived from the highest quality studies (i.e. those ranked in the top tertile or top half) and further assessed as being "more certain" or "less certain". Several sensitivity analyses were conducted to assess whether alternative "high quality" constructs affected conclusions. The lowest haematotoxicity LOAECs showed effects near 2 ppm (8 h TWA), and no effects at 0.59 ppm. For genotoxicity, studies also showed effects near 2 ppm and showed no effects at about 0.69 ppm. Several sensitivity analyses supported these observations. These data define a benzene LOAEC of 2 ppm (8 h TWA) and a NOAEC of 0.5 ppm (8 h TWA). Allowing for possible subclinical effects in bone marrow not apparent in studies of peripheral blood endpoints, an OEL of 0.25 ppm (8 h TWA) is proposed.

Micronucleus, Nucleoplasmic Bridge, and Nuclear Budding in Peripheral Blood Cells of Workers Exposed to Low Level Benzene

BACKGROUND

Benzene is one of the important occupational pollutants. There are some reports about the leukemogenic effects related to low-level exposure to benzene.

OBJECTIVE

To study the frequency of micronucleus (MN), nucleoplasmic bridge (NB), and nuclear budding (NBUD) in the peripheral blood lymphocytes of petrochemical workers with low level exposure to benzene.

METHODS

We enrolled 50 workers exposed to low-level benzene and 31 unexposed workers of a petrochemical industry. After exclusion of 3 samples, peripheral blood lymphocytes of the remaining 47 exposed and 31 unexposed workers were analyzed for the frequency of MN, NB, and NBUD by cytochalasin-blocked MN technique.

RESULTS

MN was present in 28 (60%) exposed and 18 (58%) unexposed workers. NB was observed in 6 (13%), and 2 (7%) exposed and unexposed workers, respectively; the frequency for NBUD was 20 (43%), and 13 (42%), respectively. No significant difference was found in the observed frequencies of MN, NB, and NBUD in the peripheral blood lymphocytes between the exposed and unexposed group workers.

CONCLUSION

Occupational exposure to low-level benzene does not increase the frequency of MN, NB, and NBUD in the peripheral blood lymphocytes, biomarkers for DNA damage.