Benzene, cytochrome, carcinogenesis: A topic in preventive toxicology

Occupational Exposure to Benzene and Risk of Breast Cancer: Systematic Review and Meta-Analysis

INTRODUCTION

Benzene is a recognized carcinogen; however, its association with breast cancer is not well established. Hence, a meta-analysis of cohort and case-control studies was performed to determine the association between occupational benzene exposure and the risk of breast cancer.

METHODS

A systematic literature review identified 7573 publications from which 23 cohort and case-control studies were retained and evaluated using meta-analyses (fixed effects model). PRISMA guidelines were followed. Our protocol was registered in the PROSPERO database (Registration No. CRD42022379720). Study quality was assessed using a modified Newcastle-Ottawa scale (NOS).

RESULTS

The summary relative risk (RR) for ever-benzene exposure was 1.08 (95% CI=1.03-1.14, I2=38.6%, n=23 risk estimates); corresponding RR for cancer incidence and mortality were 1.08 (95% CI=1.02-1.14, I2=56.1%, n=16) and 1.10 (95% CI=0.87-1.37, I2<0.001%, n=10). However, heterogeneity was detected for sex (p-het=0.002), publication year (p-het<0.001), study design (p-het<0.001), study quality (p-het<0.001), and industry of employment (p-het=0.03). The RR for high level of exposure showed positive association with breast cancer 1.35 (95% CI=1.06-1.72, I2 =<0.001%, n=3) and (P-het=0.64). Publication bias was detected (p=0.03).

CONCLUSIONS

The results of our meta-analysis indicate a positive association between occupational benzene exposure and an increased risk of breast cancer, particularly when exposed to higher levels of benzene. However, bias and confounding could not be excluded.

Potential environmental toxicant exposure, metabolizing gene variants and risk of PCOS-A systematic review

Exposure of environmental toxicants such as potentially toxic metals and pesticides have largely been attributed to produce adverse effects on general women's health and to be more precise on the reproductive system. In order to explore exposure of toxicants and metabolizing gene variants as risk factor for polycystic ovarian syndrome (PCOS), literature search was carried out using the databases PubMed, Central Cochrane Library, Google Scholar, Science Direct with appropriate keywords upto 6 December 2020. While most of the studies indicate higher serum Cu concentration and lower concentration of Mn as risk factor, studies also report presence of higher pesticide concentration in PCOS women. Genes such as MTHFR, CYPs participate in the metabolism of toxicants and may show different response due to underlying genetic variants. Thus, toxicant exposure are to some extent responsible for the pathogenesis of syndrome through oxidative stress and endocrine disruption, but the susceptibility may vary due to the underlying genetic polymorphism of the exposed population.

Mitigating biochar phytotoxicity via lanthanum (La) participation in pyrolysis

Biochar (BC) produced from oak sawdust by slow pyrolysis was investigated to check the potential inhibition to early growth of tomato for phytotoxicity assessment. An inverted-U-shaped dose-response relationship between BC dosage and seed germination/seedling growth can be observed. Half maximal effective concentration (EC₅₀), based on the inhibition rate of root and stem length, was 65.7 and 74.0 g kg^-1, respectively. At the highest BC dosage of 80.0 g kg^-1, germination rate, root, and shoot length were notably inhibited by 34.9, 62.3, and 62.2% compared with their corresponding controls (without BC). Fluorescence intensity, indicating reactive oxygen species (ROS) generation in leaf and root, was 177.7 and 344.5% higher than the control. Similar results on H₂O₂ content in leaf and root were observed as well. Besides, membrane leakage from the leaf and root cells was 2.1- and 1.3-fold higher than the corresponding controls. These results proved that BC exhibited significant phytotoxicity in the early growth stage of tomato. Unlike BC, the inhibitions on seed germination and seedling growth, the ROS accumulation, and the plasma membrane damage were not obvious with increasing La-BC dosage. These results indicated that BC phytotoxicity can be greatly mitigated by La involvement in pyrolysis, which was potentially associated with the reduced organic compounds and free radicals in La-BC. Besides, bio-available La in La-BC was partially involved in mitigating the phytotoxicity.

New family of biosensors for monitoring BTX in aquatic and edaphic environments

Benzene, toluene, ethylbenzene and xylenes (BTEX) contamination is a serious threat to public health and the environment, and therefore, there is an urgent need to detect its presence in nature. The use of whole-cell reporters is an efficient, easy-to-use and low-cost approach to detect and follow contaminants outside specialized laboratories; this is especially important in oil spills that are frequent in marine environments. The aim of this study is the construction of a bioreporter system and its comparison and validation for the specific detection of monocyclic aromatic hydrocarbons in different host bacteria and environmental samples. Our bioreporter system is based on the two component regulatory system TodS-TodT of P. putida DOT-T1E, and the PtodX promoter fused to the GFP protein as the reporter protein. For the construction of different biosensors, this bioreporter was transferred into three different bacterial strains isolated from three different environments, and their performance was measured. Validation of the biosensors on water samples spiked with petrol, diesel and crude oil on contaminated waters from oil spills and on contaminated soils demonstrated that they can be used in mapping and monitoring some BTEX compounds (specifically benzene, toluene and two xylene isomers). Validation of biosensors is an important issue for the integration of these devices into pollution-control programmes.