The urinary metabolic profile of diethylene glycol methyl ether and triethylene glycol methyl ether in Sprague-Dawley rats and the role of the metabolite methoxyacetic acid in their toxicity

New insights into the oxidative and cytogenotoxic effects of Tetraglyme on human peripheral blood cells

The present study investigated the oxidative and cytogenotoxic potential of Tetraethylene glycol dimethyl ether (known as Tetraglyme) on healthy human peripheral blood lymphocytes, widely used as an in vitro model for assessing the human health risk posed by different chemical compounds. In a first step, Nuclear Magnetic Resonance (1H NMR) spectroscopy, and Ultra-High Performance Liquid Chromatography-Mass Spectrometry (UHPLC-MS) were employed to estimate Tetraglyme's stability under a wide range of pH values (4-12), and thus to identify potential by-products. Thereafter, isolated lymphocytes were treated with different concentrations of Tetraglyme (0.02-20 mg L-1) for assessing its oxidative (using the DCFH-DA staining), and cytogenotoxic potential (using the trypan blue exclusion test for estimating cell viability, Comet assay, as well as the cytokinesis-block micronucleus assay, with or without the addition of S9 metabolic activation system). According to the results, Tetraglyme remains stable at pH 4, but two additional derivatives (i.e. 1-[2-(2-ethoxyethoxy)ethoxy]-2-methoxyethane [C9H20O4] and 1-ethoxy-2-(2-ethoxyethoxy)ethane (Diethylene glycol diethyl ether) [C8H18O3]) were found in traces, under alkaline conditions (pH ≥7). Moreover, although Tetraglyme (and/or its derivatives) showed negligible alterations of cell viability (>92 %) in all cases, the pronounced ROS formation, DNA damage, cell proliferation arrest, and MN frequencies in challenged cells are indicative of its oxidative and cytogenotoxic potential. The significant alterations of Cytokinesis-Block Proliferation Index (CBPI) and Micronucleus (MN) frequencies in S9 challenged cells give further evidence for the potential involvement of Tetraglyme's metabolites in the observed cytogenotoxic mode of action. Although not conclusive, the present findings give rise to further research, utilizing different cell types and biological models, for elucidating Tetraglyme's toxic mode of action, as well as its environmental and human risk.

Reaction Thermodynamic and Kinetics for Esterification of 1-Methoxy-2-Propanol and Acetic Acid over Ion-Exchange Resin

The esterification of 1-methoxy-2-propanol (PM) and acetic acid (AA) is an important reaction for the production of 1-methoxy-2-propyl acetate (PMA). Herein, we used the macroporous ion-exchange resin Amberlyst-35 as a catalyst to explore the effects of reaction conditions on the reaction rate and equilibrium yield of PMA. Under the optimized conditions of a reaction temperature of 353 K, using the initial reactant PM/AA with a molar ratio of 1:3, and a catalyst loading of 10 wt%, the PMA equilibrium yield reached 78%, which is the highest equilibrium yield so far. The reaction equilibrium constants and activity coefficients were estimated to obtain reaction thermodynamic properties, indicating the exothermicity of the reaction. Furthermore, pseudo-homogeneous (PH), Eley-Rideal (ER), and Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic models were fitted based on experimental reaction kinetic data. The results demonstrate that the LHHW model is the most consistent with experimental data, indicating a surface reaction-controlled process and exhibiting an apparent activation energy of 62.0 ± 0.2 kJ/mol. This work represents a valuable example of calculating reaction thermodynamics and kinetics, which are particularly essential for promising industrial reactor designs.

Ethylene oxide derived glycol ethers: A review of the alkyl glycol ethers potential to cause endocrine disruption

The 'ethylene glycol ethers' (EGE) are a broad family of solvents and hydraulic fluids produced through the reaction of ethylene oxide and a monoalcohol. Certain EGE derived from methanol and ethanol are well known to cause toxicity to the testes and fetotoxicity and that this is caused by the common metabolites methoxy and ethoxyacetic acid, respectively. There have been numerous published claims that EGE fall into the category of 'endocrine disruptors' often without substantiated evidence. This review systematically evaluates all of the available and relevant in vitro and in vivo data across this family of substances using an approach based around the EFSA/ECHA 2018 guidance for the identification of endocrine disruptors. The conclusion reached is that there is no significant evidence to show that EGE target any endocrine organs or perturb endocrine pathways and that any toxicity that is seen occurs by non-endocrine modes of action.

Novel sampling strategy for alive animal volatolome extraction combined with GC-MS based untargeted metabolomics: Identifying mouse pup pheromones

In this study, we identify 11 mouse pup volatiles putatively involved in maternal care induction in adult females. For this purpose, we have adapted the dynamic headspace methodology to extract the volatolome of whole alive animals. Untargeted metabolomic methodology was used to compare the volatolome of neonatal (4-6 days) with elder pups until the age of weaning (21-23 days old). Pup volatolome was analyzed by gas chromatography (GC) coupled to single quadrupole mass spectrometry (MS) using automated thermal desorption for sample introduction. After data processing and multivariate statistical analysis, comparison with NIST spectral library allowed identifying compounds secreted preferentially by neonatal pups: di(propylen glycol) methyl ether, 4-nonenal, di(ethylene glycol) monobutyl ether, 2-phenoxyethanol, isomethyl ionone, tridecanal, 1,3-diethylbenzene, 1,2,4,5-tetramethylbenzene, 2-ethyl-p-xylene and tri(propylene glycol) methyl ether. Palmitic acid was enriched in the volatolome of fourth week youngsters compared to neonatal pups. The results demonstrated the great potential of the new sampling procedure combined with GC-MS based untargeted volatolomics to identify volatile pheromones in mammals.

Exposure to glycol ethers among 6-year-old children in France

Glycol ethers are an oxygenated solvent family widely present in consumer products. Some of them are recognized reproductive, developmental or hematological toxicants. Although several glycol ether biomonitoring studies have been performed on adults from working or general populations, no studies have hitherto been carried out on children. The aim of our study was to explore the detection of glycol ether metabolites in the urinary samples of 6-year-old children, and if any were found, to describe them. The PELAGIE mother-child cohort included 3421 pregnant women from the general population of Brittany, France, between 2002 and 2006. Our biomonitoring study included a random sample of 110 children from the PELAGIE cohort who had participated in a neurodevelopment evaluation at the age of six. First morning voids were collected from all of the children. Eight urinary glycol ether metabolites were measured using gas chromatography with mass spectrometry. The limit of detection was 0.003 mg/L for all metabolites. Glycol ether metabolites were detected at rates varying from 33.5% of samples for propoxyacetic acid to 100% of samples for phenoxyacetic acid and methoxyacetic acid. The highest median concentration observed was for phenoxyacetic acid (0.141 mg/l). Our study reported the ubiquitous presence of glycol ether metabolites in children's urinary samples. These results call for larger biomonitoring surveys of the general population and study of the potential sources and determinants of these exposures.