Teratology study of diethylene glycol mono-n-butyl ether in rats

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.

Triethylene Glycol Ethers: Evaluations of In Vitro Absorption Through Human Epidermis, 21-Day Dermal Toxicity in Rabbits, and a Developmental Toxicity Screen in Rats

The methyl, ethyl, and butyl ethers of triethylene glycol (TM, TE, and TB, respectively) were evaluated in three screening studies to assess their potential hazards to humans. The assessments included (1) an in vitro procedure to determine the ability of the materials to penetrate human skin, (2) a 21-day dermal limit test in rabbits to determine potential systemic toxicities, and (3) a screening procedure to evaluate the chemicals' potentials to induce developmental toxicity. In the in vitro dermal absorption procedure, the three test materials crossed human epidermis at molar rates 170-330 times more slowly than the lower molecular weight homolog ethylene glycol methyl ether (EM), a chemical known to induce systemic effects following skin application. In the 21-day dermal study, daily applications of 1000 mg/kg TM, TE, or TB did not produce systemic toxicity in male or female rabbits, including hematologic or testicular effects. The low dermal penetration rate of the triethylene glycol ethers may have played a role in this outcome. In the developmental toxicity screening test, oral doses of 1000 mg/kg given on Days 6-15 of gestation did not produce maternal toxicity in rats and had no effect on viability or growth of offspring, pre-or postnatally, indicating low developmental toxic potential for these compounds. The results of these studies indicate that triethylene glycol methyl, ethyl, and butyl ethers have very low capacities to be absorbed through the skin of exposed individuals, low potentials to produce systemic toxicity following oral or dermal exposures, and do not appear to be selectively toxic to the developing conceptus. The data clearly indicate that triethylene glycol ethers do not exhibit toxicologic profiles comparable to those of the methyl and ethyl ethers of ethylene glycol.

Toxicology of Diethylene Glycol Butyl Ether 4. Dermal Subchronic/Reproduction Study in Rats

The subchronic and reproductive toxicity of diethylene glycol butyl ether (DGBE) by the dermal route was evaluated in Sprague-Dawley rats using a novel combined protocol. DGBE was administered dermally at 10 or 30% v/v in aqueous solutions or undiluted (100%) for 13 weeks under occlusion, 6 hr/day, 5 days/week at a maximum attainable volume of 2 mL/kg. Satellite groups of male and female rats were treated with the top dose of DGBE for 13 weeks, mated, and the females were treated through day 20 of gestation and allowed to deliver and nurse their offspring through day 21 of lactation (weaning). DGBE produced dermal irritation, which was dependent on concentration in incidence, severity, and time of onset and was more severe in females than in males. No corresponding histopathology was evident. The only suggestion of a systemic effect was a slightly increased incidence of urinary occult blood at study termination in the females receiving the 30% or 100% DGBE dose. There was no evidence of histopathologic changes in the testes, and vaginal cytology indicated no adverse effect on estrous cycling. There were no effects on reproductive performance of the DGBE-treated males and females. Litters delivered by treated females contained the same number of live pups as control litters and the growth and survival of pups within the treated litters was comparable to control. No reproductive or systemic toxicity was observed at the highest dose tested—2 g/kg/day.

Toxicology of Diethylene Glycol Butyl Ether 1. Exposure and Risk Assessment

Diethylene glycol mono-n-butyl ether (DGBE) is a glycol ether solvent used in many consumer products including hard-surface cleaners and paints; its acetate ester (DGBA) is also used in paints. The highest consumer exposure to DGBE was estimated to be about 0.06 mg/kg/day from use in cleaners, and to DGBA was 0.19 mg/kg/day by inhalation from use in paints. DGBA was shown to be rapidly metabolized to DGBE, and its systemic toxicity was considered to be similar to DGBE. Prior toxicology studies and those required by a 1988 TSCA Final Test Rule, detailed in the following four papers, confirm that DGBE (and by implication DGBA): (1) can be absorbed dermally, (2) is not genotoxic in a battery of assays, (3) is not a systemic nor a reproductive toxicant by the dermal route in rats, and (4) is not neurotoxic by the dermal route in rats. There is an adequate margin of safety between the no observed adverse effect level in the animal studies and the estimated human exposure levels, confirming that there is no risk of systemic toxicity from the use of DGBE or DGBA in consumer products.

Fertility and developmental toxicity studies of diethylene glycol monobutyl ether (DGBE) in rats

OBJECTIVES

The solvent, dimethylene glycol monobutyl ether (DGBE), is a component of latex paints, inks; it is used as a degreasing agent, industrial detergent. The aim of the study was evaluating the effects of DGBE administered by gavage on the estrous cycle and given with drinking water on fertility in rats and early development of their progeny.

MATERIALS AND METHODS

Female rats were exposed to DGBE by gavage during 8 weeks at 250, 500 or 1000 mg/kg/day. Vaginal smears were collected during the exposure and 4 weeks after its cessation. Fertility studies were performed in male and female animals exposed to in drinking water. Males were exposed for 10 weeks and then mated with females exposed before mating, during pregnancy and lactation. Young animals were observed during 3 weeks after birth.

RESULTS

DGBE does not cause disturbances of the menstrual cycle in females. Parameters used to assess the general toxicity indicate that males receiving DGBE in drinking water are more sensitive to this compound than females: significantly greater, dose-dependent relative spleen weight, significant decrease in hematological parameters from 8% to 15% depending on the dose, were observed. Clinical chemistry parameters (HDL-cholesterol, BUN) and some markers of oxidative stress differ between the exposed groups and the control one, but without adverse health effect. The microscopic examination of internal organs did not reveal morphological changes in male and female rats.

CONCLUSION

The results of our study on the impact of exposure to DGBE on fertility in rats indicate that the substance administered for 9-10 weeks to females and males at a limit dose of 1000 mg/kg did not impair fertility or viability of their offspring during the first three weeks of life.