Reproductive toxicity of triethylene glycol and its diacetate and dimethyl ether derivatives in a continuous breeding protocol in Swiss CD-1 mice

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.

A toxicological review of the ethylene glycol series: Commonalities and differences in toxicity and modes of action

This review summarizes the hazards, exposure and risk that are associated with ethylene glycols (EGs) in their intended applications. Ethylene glycol (EG; CAS RN 107-21-1) and its related oligomers include mono-, di-, tri-, tetra-, and penta-EG. All of the EGs are quickly and extensively absorbed following ingestion and inhalation, but not by the dermal route. Metabolism involves oxidation to the mono- and dicarboxylic acids. Elimination is primarily through the urine as the parent compound or the monoacid, and, in the case of EG, also as exhaled carbon dioxide. All EGs exert acute toxicity in a similar manner, characterized by CNS depression and metabolic acidosis in humans and rodents; the larger molecules being proportionally less acutely toxic on a strict mg/kg basis. Species differences exist in the metabolism and distribution of toxic metabolites, particularly with the formation of glycolic acids and oxalates (OX) from EG and diethylene glycol (DEG); OX are not formed to a significant degree in higher ethylene glycols. Among rodents, rats are more sensitive than mice, and males more sensitive than females to the acute and repeated-dose toxicity of EG. The metabolic formation of glycolic acid (GA), diglycolic acid (DGA), and OX are associated with nephrotoxicity in humans and rodents following single and repeated exposures. However, physiological and metabolic differences in the rate of formation of GA, DGA and OX and their distribution result in EG and DEG causing embryotoxicity in rats, but not rabbits. This rodent-specific sensitivity indicates that EG and its higher oligomers are not anticipated to be embryotoxic in humans at environmentally relevant doses. None of the compounds present developmental toxicity concerns at doses that do not also cause significant maternal toxicity, nor do any of the EGs cause adverse effects on fertility. The EGs are neither genotoxic nor carcinogenic. A read-across matrix is presented, which considers the common and distinct toxicological properties of each compound. It is concluded that EGs pose no risk to human health as a result of their intended use patterns.

Triethylene glycol HO(CH2CH2O)3H

TEG is a liquid higher glycol of very low vapor pressure with uses that are primarily industrial. It has a very low order of acute toxicity by i.v., i.p., peroral, percutaneous and inhalation (vapor and aerosol) routes of exposure. It does not produce primary skin irritation. Acute eye contact with the liquid causes mild local transient irritation (conjunctival hyperemia and slight chemosis) but does not induce corneal injury. Animal maximization and human volunteer repeated insult patch tests studies have shown that TEG does not cause skin sensitization. A study with Swiss-Webster mice demonstrated that TEG aerosol has properties of a peripheral chemosensory irritant material and caused a depression of breathing rate with an RD(50) of 5140 mg m(-3). Continuous subchronic peroral dosing of TEG in the diet of rats did not produce any systemic cumulative or long-term toxicity. The effects seen were dose-related increased relative kidney weight, increased urine volume and decreased urine pH, probably a result of the renal excretion of TEG and metabolites following the absorption of large doses of TEG. There was also decreased hemoglobin concentration, decreased hematocrit and increased mean corpuscular volume, probably due to hemodilution following absorption of TEG. The NOAEL was 20 000 ppm TEG in diet. Short-term repeated aerosol exposure studies in the rat demonstrated that, by nose-only exposure, the threshold for effects by respiratory tract exposure was 1036 mg m(-3). Neither high dosage acute nor repeated exposures to TEG produce hepatorenal injury characteristic of that caused by the lower glycol homologues. Elimination studies with acute peroral doses of TEG given to rats and rabbits showed high recoveries (91-98% over 5 days), with the major fraction appearing in urine (84-94%) and only 1% as CO(2). TEG in urine is present in unchanged and oxidized forms, but only negligible amounts as oxalic acid. Developmental toxicity studies with undiluted TEG given by gavage produced maternal toxicity in rats (body weight, food consumption, water consumption, and relative kidney weight) with a NOEL of 1126 mg kg(-1) day(-1), and mice (relative kidney weight) with a NOEL of 5630 mg kg(-1) day(-1). Developmental toxicity, expressed as fetotoxicity, had a NOEL of 5630 mg kg(-1) day(-1) with the rat and 563 mg kg(-1) day(-1) with mice. Neither species showed any evidence of embryotoxicity or teratogenicity. There was no evidence for reproductive toxicity with mice given up to 3% TEG in drinking water in a continuous breeding study. TEG did not produce mutagenic or clastogenic effects in the following in vitro genetic toxicology studies: Salmonella typhimurium reverse mutation test, SOS-chromotest in E. coli, CHO forward gene mutation test (HGPRT locus), CHO sister chromatid exchange test, and a chromosome aberration test with CHO cells. The use patterns suggest that exposure to TEG is mainly occupational, with limited exposures by consumers. Exposure is normally by skin and eye contact. Local and systemic adverse health effects by cutaneous exposure are likely not to occur, and eye contact will produce transient irritation without corneal injury. The very low vapor pressure of TEG makes it unlikely that significant vapor exposure will occur. Aerosol exposure is not a usual exposure mode, and acute aerosol exposures are unlikely to be harmful, although a peripheral sensory irritant effect may develop. However, repeated exposures to a TEG aerosol may result in respiratory tract irritation, with cough, shortness of breath and tightness of the chest. Recommended protective and precautionary measures include protective gloves, goggles or safety glasses and mechanical room ventilation. LC(50) data to various fish, aquatic invertebrates and algae, indicate that TEG is essentially nontoxic to aquatic organisms. Also, sustained exposure studies have demonstrated that TEG is of a low order of chronic aquatic toxicity. The bioconcentration potential, environmental hydrolysis, and photolysis rates are low, and soil mobility high. In the atmosphere TEG is degraded by reacting with photochemically produced hydroxyl radicals. These considerations indicate that the potential for ecotoxicological effects with TEG is low.

Final report on the safety assessment of Triethylene Glycol and PEG-4

Triethylene Glycol and PEG-4 (polyethylene glycol) are polymers of ethylene oxide alcohol. Triethylene Glycol is a specific three-unit chain, whereas PEG-4 is a polymer with an average of four units, but may contain polymers ranging from two to eight ethylene oxide units. In the same manner, other PEG compounds, e.g., PEG-6, are mixtures and likely contain some Triethylene Glycol and PEG-4. Triethylene Glycol is a fragrance ingredient and viscosity decreasing agent in cosmetic formulations, with a maximum concentration of use of 0.08% in skin-cleansing products. Following oral doses, Triethylene Glycol and its metabolites are excreted primarily in urine, with small amounts released in feces and expired air. With oral LD50 values in rodents from 15 to 22 g/kg, this compound has little acute toxicity. Rats given short term oral doses of 3% in water showed no signs of toxicity, whereas all rats given 10% died by the 12th day of exposure. At levels up to 1 g/m3, rats exposed to aerosolized Triethylene Glycol for 6 h per day for 9 days showed no signs of toxicity. Rats fed a diet containing 4% Triethylene Glycol for 2 years showed no signs of toxicity. There were no treatment-related effects on rats exposed to supersaturated Triethylene Glycol vapor for 13 months nor in rats that consumed 0.533 cc Triethylene Glycol per day in drinking water for 13 months. Triethylene Glycol was not irritating to the skin of rabbits and produced only minimal injury to the eye. In reproductive and developmental toxicity studies in rats and mice, Triethylene Glycol did not produce biologically significant embryotoxicity or teratogenicity. However, some maternal toxicity was seen in dams given 10 ml/kg/day during gestation. Triethylene Glycol was not mutagenic or genotoxic in Ames-type assays, the Chinese hamster ovary mutation assay, and the sister chromatid exchange assays. PEG-4 is a humectant and solvent in cosmetic products, with a maximum concentration of use of 20% in the "other manicuring preparations" product category. This ingredient, with an oral LD50 in rats of 32.77 g/kg, has low acute toxicity. Rats given up to 50,000 ppm PEG-4 in drinking water for 5 days showed no permanent signs of toxicity. Rats given daily oral doses up to 2 g/kg/day of PEG-4 for 33 days showed no signs of toxicity. Undiluted PEG-4 produced only minimal injury to the rabbit eye. PEG-4 was not mutagenic in Ames-type assays, did not induce chromosome aberration in an in vivo bone marrow assay, and was negative for genotoxicity in a dominant lethal assay using rats. Other PEG compounds, which have previously been reviewed by the Cosmetic Ingredient Review (CIR) Expert Panel, e.g., PEG-6, are mixtures that likely include Triethylene Glycol and PEG-4, so these data were also considered. PEG-6 and PEG-8 were not dermal irritants in several rabbit studies. PEG-2 Stearate had a potential for slight irritation in rabbits but was not a sensitizer in guinea pigs. PEG-2 Cocamine was a moderate irritant in rabbits, producing severe erythema. In one dermal study, PEG-2 Cocamine was determined to be corrosive to rabbit skin, causing eschar and necrosis. PEG-6 and PEG-8 caused little to no ocular irritation. PEG-8 was not mutagenic or genotoxic in a Chinese hamster ovary assay, a sister-chromatid exchange assay, and in an unscheduled DNA synthesis assay. In clinical studies on normal skin, PEG-6 and PEG-8 caused mild cases of immediate hypersensitivity; PEG-8 was not a sensitizer; PEG-2 Stearate was not an irritant, a sensitizer, or a photosensitizer; and PEG-6 Stearate was not an irritant or sensitizer. In damaged skin, cases of systemic toxicity and contact dermatitis in burn patients were attributed to a PEG-based topical ointment. The CIR Expert Panel acknowledged the lack of dermal sensitization data for Triethylene Glycol and dermal irritation and sensitization data for PEG-4. That PEG-6, PEG-8, and PEG-2 Stearate were not irritants or sensitizers suggested that Triethylene Glycol and PEG-4 also would not be irritants or sensitizers, and the absence of any reported reactions in the case literature and the professional experience of the Expert Panel further supported the absence of any significant sensitization potential. The need for additional data to demonstrate the safety of PEGs Cocamine was related to the Cocamine moiety and is not relevant here. The Panel reminded formulators of cosmetic products that, as with other PEG compounds, Triethylene Glycol and PEG-4 should not be used on damaged skin because of cases of systemic toxicity and contact dermatitis in burn patients have been attributed to a PEG-based topical ointment. Based on its consideration of the available information, the CIR Expert Panel concluded that Triethylene Glycol and PEG-4 are safe as cosmetic ingredients in the present practices and concentrations of use as described in this safety assessment.

Developmental toxicity study with triethylene glycol given by gavage to CD rats and CD-1 mice

Triethylene glycol (TEG) is a liquid industrial chemical with a potential for human exposure. The likelihood for developmental toxicity was investigated in two species. Timed-pregnant CD rats and CD-1 mice were dosed daily by gavage with undiluted TEG over gestational days (gd) 5-15 at 0.0 (water control), 1126, 5630 or 11,260 mg kg(-1) day(-1) with rats and 0.0, 563, 5630 or 11,260 mg kg(-1) day(-1) with mice. They were examined daily, and gestational body weights and food and water consumption measured throughout gestation. At necropsy on gd 21 (rats) or gd 18 (mice) dams were examined for body, gravid uterine, liver and kidney weights, and implantation sites. Maternal kidneys were examined histologically. Fetuses were weighed, sex determined, and examined for external, soft tissue and skeletal variations and malformations. Rat dams had reduced body weights, body weight gains, and food consumption, and increased water consumption and relative kidney weights at 11,260 mg kg(-1) day(-1). They also had reduced body weight and increased water consumption at 5630 mg kg(-1) day(-1). Mice had clinical signs and increased relative kidney weight at 11,260 mg kg(-1) day(-1). Renal histology was normal in both species. Neither species had treatment-related effects on corpora lutea or implantations. Fetal body weights were reduced at 11,260 mg kg(-1) day(-1) (both species) and 5630 mg kg(-1) day(-1) (mice). In rat fetuses there was a pattern of delayed ossification in the thoracic region at 11,260 mg kg(-1) day(-1). Mouse fetuses had delayed ossification in the frontal and supraoccipital bones, cervical region, hindlimb proximal phalanges and reduced caudal segments at 11,260 mg kg(-1) day(-1), and in the skull bones at 5630 mg kg(-1) day(-1). These patterns of delayed ossification are consistent with reduced fetal body weights. No biologically significant embryotoxicity or teratogenicity was observed at any dosage in either species. The NOEL for TEG given by gavage over the period of organogenesis was 1126 mg kg(-1) day(-1) in the rat and 5630 mg kg(-1) day(-1) in the mouse for maternal toxicity, and 5630 mg kg(-1) day(-1) (rat) and 563 mg kg(-1) day(-1) (mouse) for developmental toxicology.