0 ,CH 3 

I 

CH 2 

1,2=Dimethoxyethane 

CAS Number 110-71-4 

U.S. EPA HPV Challenge Program 

Submission 

December 2001 

Revised August 2002 

Submitted on behalf of 

Ferro Corporation 

Submitted and Prepared by: 

Toxicology and Regulatory Affairs 

1201 Anise Court 

Freeburg IL 62243 

618-539-5280 

----I......,. .---““- __.- . . 
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Table of Contents 

Executive Overview............................................................................................... 4

Testing Plan and Rationale .................................................................................... 5

Testing Plan in Tabular Format .................................................................................... 6 

Introduction................................................................................................................... 7 

Physical-chemical Data ................................................................................................ 8 

Available Information ............................................................................................. 8

Summary and Recommendation for Physical-Chemical Data: .............................. 9

Environmental Fate and Pathways................................................................................ 9 

Biodegradation........................................................................................................ 9

Photodegradation.................................................................................................... 9

Water Stability......................................................................................................... 9

Distribution ............................................................................................................. 9

Summary and Recommendations for Fate ............................................................ 10

Ecotoxicity.................................................................................................................. 10

Aquatic Toxicity .................................................................................................... 10

Summary and Recommendation for Aquatic Toxicity:.......................................... 11

Acute Toxicity ............................................................................................................ 11 

Oral Exposure ....................................................................................................... 11

Inhalation Exposure.............................................................................................. 11

Summary and Recommendation for Acute Toxicity .............................................. 12

Repeat Dose Toxicity ................................................................................................. 12 

Figure 1. Metabolism of 2-Methoxyethanol into Methoxy Acetic Acid. .............. 13

Oral Exposure ....................................................................................................... 14

Figure 2. Major Metabolic Pathways for Monoglyme ........................................ 15

Summary and Recommendations for Repeated-Dose Toxicity ............................. 15

Genetic Toxicity ......................................................................................................... 16 

Genetic Toxicology in vitro................................................................................... 16

Summary of Genetic Toxicology and Recommendations:..................................... 17

Reproductive Toxicity ................................................................................................ 17 

Summary and Recommendation for Reproductive Toxicity.................................. 17

Developmental Toxicity ............................................................................................. 17 

Summary and Recommendation for Developmental Toxicity ............................... 18

Conclusions................................................................................................................. 19 

References................................................................................................................... 19

Robust Summaries ............................................................................................... 22

Physicochemical Properties........................................................................................ 23 

Melting Point......................................................................................................... 23

Boiling Point ......................................................................................................... 24

Vapor Pressure ..................................................................................................... 25

Partition Coefficient, Octanol-Water.................................................................... 26

Water Solubility..................................................................................................... 27

Fate ............................................................................................................................. 28 

Photodegradation.................................................................................................. 28

Water Stability....................................................................................................... 29
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Theoretical Distribution (Fugacity)..................................................................... 31

Biodegradation...................................................................................................... 34

Effects on Environmental Organisms......................................................................... 37 

Acute Toxicity to Fish............................................................................................ 37

Type ............................................................................................................................ 37 

Acute Toxicity to Aquatic Invertebrates................................................................ 43

Acute Toxicity to Aquatic Invertebrates, Supporting Study .................................. 47

Toxicity to Aquatic Plants ..................................................................................... 49

Toxicity to Aquatic Plants (model validation study)............................................. 50

Acute Health Effects................................................................................................... 57 

Acute Oral Toxicity ............................................................................................... 57

Acute Inhalation Toxicity ...................................................................................... 60

Repeated Dose Toxicity,............................................................................................. 64 

Rat Thirteen-Week Drinking Water ...................................................................... 64

Repeated Dose Toxicity, Mouse Thirteen-Week Drinking Water ......................... 68

Genetic Toxicology .................................................................................................... 72 

Chinese Hamster Ovary Cell Mutation Test (HGPRT) ........................................ 72

Sister Chromatid Exchange in Chinese Hamster Ovary Cells (SCE Test) ........... 75

In Vitro Unscheduled DNA Synthesis (UDS) Assay.............................................. 78

Reproductive Toxicology ........................................................................................... 81 

Screening Study in Mice........................................................................................ 81

Developmental Toxicology ........................................................................................ 84 

Developmental Toxicology, Oral .......................................................................... 84

Developmental Toxicology, Oral, Mouse.............................................................. 91
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Executive Overview 

1,2-Dimethoxyethane (CAS Number 110-71-4, Monoglyme) is a stable diether used primarily 

as an industrial solvent, process aid and as a component of lithium batteries. 

The physical-chemical properties of Monoglyme are well defined. It is a volatile liquid at room 

temperature with a vapor pressure of 54 mm Hg. Monoglyme is poorly biodegradable in a waste 

water treatment facility and not considered readily biodegradable. It has high hydrolytic 

stability in water at pH 4 to 9 with an estimated hydrolytic half-life at 25 ̊ C greater than one 

year. Vapors have an estimated photolytic half-life in air of approximately 8 hours, and 

predicted values for fugacity have been calculated with the Mackay Level III model. Based on 

surrogate materials and a validated SAR relationship, fish, daphnia and green algae are 

estimated to be acutely affected by Monoglyme only at concentrations far in excess of 1000 

mg/l. Acute toxicity to mammals has been determined by oral and inhalation routes of 

exposure. Monoglyme demonstrates a low order of toxicity with an oral LD50 of greater than 

4000 mg/kg in rats. Standard repeated-dose studies have not been conducted; however, the 

spectrum of toxicity can be confidently predicted from Monoglyme’s metabolism and studies on 

related compounds by all routes of exposure. Toxic responses include thymic atrophy, bone 

marrow suppression and testicular degeneration. Genotoxicity has been evaluated using 

multiple in vitro experimental procedures covering both mutation and chromosomal aberration. 

Results of genotoxicity studies are mixed. Adverse effects to reproduction are based on 

metabolism of Monoglyme to 2-methoxy acetic acid, a compound that is known to interfere 

with sperm production. Developmental toxicity results are available and, as expected from its 

structure, Monoglyme appears to be a specific developmental toxin in rats and mice. 

With regard to the HPV program, no additional testing is proposed for Monoglyme, as all 

required parameters are sufficiently well characterized by available information. 
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Testing Plan and Rationale 
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Testing Plan in Tabular Format 

(Y = Yes, N = No) 

CAS Number 110-71-4 

1,2-Dimethoxyethane

HPV Endpoint

Physical Chemical

Melting Point Y N N Y N Y N

Boiling Point Y N N Y N Y N

Vapor Pressure Y N N Y N Y N

Partition Coefficient Y N N N Y Y N

Water Solubility Y N N N N Y N

Environmental & Fate

Photo-Degradation Y N N N Y Y N

Water Stability Y N N Y Y Y N

Transport Y N N N Y Y N

Biodegradation Y N N Y N Y N

Ecotoxicity

96-Hour Fish Y N N N Y Y N

48-Hour Invertebrate Y N N N Y Y N

72-Hour Algae Y N N N Y Y N

Toxicity

Acute Y N N Y N Y N

Repeated Dose Y Y YYYYN

Genetic Toxicology in vitro YYNYNYN

Genetic Toxicology in vivo YNNNNYN

Reproductive Y N N Y N Y N

Developmental Y N N Y N Y N
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Introduction 

1,2-Dimethoxyethane, CAS Number 110-71-4 (Monoglyme) is the dimethyl ether of ethylene 

glycol. It is a clear volatile liquid that is miscible with water and most organic solvents. Its 

primary use is as a solvent; the structure is shown below: 

1,2-Dimethoxyethane has been in industrial use for about 40 years it is also known as: 

○ Monoglyme 

○ Glyme 

○ Dimethoxyethane 

○ Dimethyl cellosolve 

○ Ethylene glycol dimethyl ether 

The chemical and physical properties of Monoglyme make it a unique solvent for certain 

applications. (1) It is a preferred solvent in the production of Lithium batteries because of its 

low viscosity and cation solvating property. Likewise as an industrial reaction solvent, it 

facilitates certain reactions including use as a solvent to facilitate formation of alkali metalhydrocarbon adducts; in the Reformatsky reaction with methyl gamma-bromocrotonate (2) 

 Its high solvent power, low viscosity and volatility make it useful in some industrial coating 

applications. Consumer applications of Monoglyme are discouraged because of the known 

reproductive and developmental toxicity of lower molecular weight alkyl glycol ethers such as 

monoglyme. Domestic use of Monoglyme is between one and two million pounds per year and 

worldwide production use could be as high as six million pounds per annum. The manufacturers 

H3C O

CH2

CH2

O CH3
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estimate that 10 to 20 percent of the US production is used in the domestic production of 

Lithium batteries. 

Exposure in these applications is limited by process controls and protective equipment there is 

no occupational exposure level set by governmental agency, except in Russia where there is a 

STEL of 10 mg/m3

. (1) Ferro Corporation recommends a Threshold Limit Value for glycol 

ethers of 5 ppm (TWA) with a Short Term Exposure Limit (STEL) of 25 ppm. The 15-minute 

STEL should not be achieved more than 4 times in 8 hours. For women of child-bearing 

potential, Ferro recommends a TLV of 1 ppm with s STEL of 5 ppm. (3)

Several studies have been conducted on the toxicity of Monoglyme. These studies are briefly 

reviewed in this rationale document describing how they meet the SIDS (Screening Information 

Data Set) end-points of the United States Environmental Protection Agency (USEPA) High 

Production Volume Challenge Program (HPV). Robust summaries have been prepared for key 

studies; supporting studies are referenced in these summaries. Specific additional testing is 

recommended to fill the remaining end-points of the SIDS data set. (or rationale is provided 

why certain end-point do not have to be filled) 

Physical-chemical Data 

Available Information 

Physical-chemical data for Monoglyme are available from the literature and company sources. 

Melting Point 

-58° C (4) 

-69 ̊ C (Ferro book) 

-71 ̊ C (HSDB alternative) 

Boiling Point 85 deg C @ 760 mm Hg (5) 

Vapor Pressure 48 mm Hg @ 20 ̊ C (6) 

54 mm Hg @ 20 ̊ C (1) 

Partition Coefficient Log Ko/w = -0.21 (7) 

Water Solubility Soluble in all proportions (4) 

These properties indicate that Monoglyme is a volatile liquid with high water solubility. The 

value of the partition coefficient suggests that Monoglyme will partition into water and has little 

potential for bioaccumulation. 
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Summary and Recommendation for Physical-Chemical Data: 

All information required by the HPV Program is available. No additional studies are 

recommended. 

Environmental Fate and Pathways 

Biodegradation 

Biodegradation has received limited attention. In a recent publication, Cowan and Kwon (8) 

describe a series of biodegradation studies on several ethylene glycol ethers. Using a high 

concentration of acclimated bacterial, initially obtained from a petroleum refinery wastewater 

treatment plant, they were unable to detect significant biodegradation of Monoglyme. This 

result is supported by three earlier publications that reported Monoglyme was recalcitrant to 

biodegradation, has questionable biodegradation, or is not assimilated as a substrate by bacteria. 

(9,10,11) 

Photodegradation 

Photodegradation was estimated using version 1.90 of the Atmospheric Oxidation Program for 

Microsoft Windows (AOPWIN) that estimates the rate constant for the atmospheric, gas-phase 

reaction between photochemically produced hydroxyl radicals and organic chemicals. The 

estimated rate constant is used to calculate atmospheric half-lives for organic compounds based 

upon average atmospheric concentrations of hydroxyl radical. An experimentally derived rate 

constant is listed in the APOWIN program. Using the default atmospheric hydroxyl radical 

concentration in APOWIN and the measured rate constant for reaction of Monoglyme with 

hydroxyl radical, the estimated half-life of Monoglyme vapor in air is approximately 8 hours 

(12). 

Water Stability 

Ethers are established to be relatively or completely inert in water as are glycols (13). 

Experience with Monoglyme in various aqueous preparations supports its resistance to 

hydrolysis under conditions that would occur in the environment. 

Distribution 

Theoretical Distribution (Fugacity) of Monoglyme in the environment was estimated using the 

Mackay Level III model with measured values for physical and fate constants were available 
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and standard defaults in EPIWIN v 3.05 (14). The results for distribution using a model 

calculated Ko/c (adsorption coefficient based on organic carbon content) of 0.253 are: 

o Air 0.91 % 

o Water 61 % 

o Soil 38 % 

o Sediment 0.1 % 

Summary and Recommendations for Fate 

Monoglyme is resistant to hydrolysis and biodegradation by acclimated bacteria. The EQC 

Level III model suggests it will distribute primarily to water. Environmental degradation to 

carbon dioxide will likely occur by a combination of slow biodegradation and reaction with 

atmospheric hydroxyl radicals after volatilization. All fate parameters have adequate 

information to fulfill the HPV Program requirements. No further testing is recommended. 

Ecotoxicity 

Aquatic Toxicity 

No studies of aquatic toxicology were found. EPIWIN estimates, using the neutral organic 

model are given in the table below. 

EPIWIN Aquatic Toxicity Estimates, Monoglyme (15) 

Fish, 96 hour LC50 7984 mg/L 

Daphnia, 48 hour EC50 7344 mg/L 

Algae, 96 hour EC50 4042 mg/L 

These estimates are supported by fish and invertebrate data for Diglyme that reveals LC50 and 

EC50 values in the same range as that predicted for Monoglyme by the modeling program (16). 

Other surrogate chemicals, 1,3-Dioxolane for fish and daphnids (17) and 2-Methoxyethanol for 

daphnids (18), also demonstrate acute toxicity in this same range providing support for the 

estimated values for Monoglyme. The data from Diglyme for acute fish toxicity LC50 > 2000 

mg/L, which has terminal methoxy groups similar to the structure of Monoglyme, indicate that 

the methoxy groups are not specifically toxic toward fish. 
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The algae ESOSAR result of 4042 mg/L is considered satisfactory for the HPV program since 

the model has been validated by a high-reliability study on a similar compound. The validation 

(surrogate) study is presented it the attached robust summary for this endpoint. 

Summary and Recommendation for Aquatic Toxicity: 

Modeling and comparison with related compounds indicate that Monoglyme is of low concern 

to aquatic environmental species. Given that the estimates and surrogate compounds show acute 

toxicity parameters several fold the OECD recommended maximum concentration for these 

studies, there is a high degree of confidence that Monoglyme is of similar low hazard. Modeling 

results of algae data based on the ECOSAR mode are sufficient for the purpose of the HPV 

program. No further testing is recommended. 

Acute Toxicity 

Oral Exposure 

The acute oral LD50 for rats has been determined in at least two studies. The critical study 

chosen for preparing a robust summary gives the LD50 as > 4000 mg/kg and is based on a four 

dose study using four animals per group (19). This is supported by an industrial toxicology 

report that states the oral rat LD50 is >3200 mg/kg (20). Although these studies do not meet the 

current OECD guidelines, the quality is sufficient to provide a good estimate of the acute oral 

toxicity of Monoglyme. In addition, the result is in accord with data for many other similar 

glycol ethers that are known to have low acute toxicity. 

Inhalation Exposure 

The acute inhalation toxicity of Monoglyme was determined in a two-dose study in which the 

six-hour inhalation LC50 was found to be between 20 and 63 mg/L. The vapors produced some 

irritation and anesthesia at the high level. All high dose animals survived the exposure but died 

within 72 hours post-exposure (21). 
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Summary and Recommendation for Acute Toxicity

The oral and inhalation acute toxicity of Monoglyme are satisfactorily established to meet the 

requirements of the HPV Challenge Program. No additional testing is recommended. 

Repeat Dose Toxicity 

Information on the repeated-dose effects of Monoglyme is derived from an understanding of the 

metabolic conversion of Monoglyme to metabolites in test animals. Although direct chemical 

evidence identifying the primary and secondary metabolites of Monoglyme was not found, the 

metabolic pathways for this class of chemicals are well known. Additionally, there is very 

strong biological evidence linking adverse effects of Monoglyme with a common active 

metabolite of methoxy glycol ethers. 

It has been demonstrated that most of the toxic effects of the monoalkyl glycol ethers arise as a 

result of the metabolic conversion of the glycol ether into a substituted acetic acid derivative. In 

Figure 1, this pathway is shown for the prototype, and most toxic, of the family members 2-

methoxyethanol. Upon absorption, at least three paths compete for the test material. Excretion 

by the lungs or kidneys accounts for a small portion of the absorbed dose. Demethylation by 

mixed-function oxidases, a relatively slow reaction, accounts for some metabolic conversion to 

ethylene glycol which is converted to oxalate. Dehydrongenase enzymes initially convert the 

free alcohol to the aldehyde and then the carboxylic acid (22). This is a very rapid conversion 

(as indicated by the size of the arrows) and it is known that a teratogenic dose of 2-

methoxyethanol is completely oxidized in a period of one-hour in rats (ref, Sheets). The 

competing reaction, demethylation of -ME to ethylene glycol is comparatively slow as it is 

accomplished by the mixed-function oxidase system. The pharmacokinetics of these 

transformations have been determined in the rat and the approximate ratio of production for 2-

methoxyacetic acid:ethylene is 5:1. The relative first-order rate constants have been determined 

to be 31 L/h/kg liver for conversion of 2-ME to 2-methoxyacetic acid and 5.6 L/h/kg liver for 

conversion of 2-ME to ethylene glycol (23). There is some question as to what is the active 

form of 2-methoxyacetic acid that interferes with metabolism, but there is general agreement 

that 2-methoxyacetic acid is the proximate toxin. It is also established the clearance of 2-

methoxyacetic acid is relatively slow as compared to its formation and the clearance in man 

may be much longer than in rats (24). 
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H O CH H3C O CH2 COOH 2 CH2 OH

Ethylene glycol Methoxy acetic acid

HOOC COOH

Oxalic acid

TOXIC METABOLITE

CH3 O CH2 CH2 O H

2-Methoxyethanol

Lung & Kidney

Excretion

Slow Excretion

Figure 1. Metabolism of 2-Methoxyethanol into Methoxy Acetic Acid. 

The anticipated metabolic pathway for Monoglyme is shown in Figure 1. Although definitive 

chemical evidence for the metabolism of Monoglyme to 2-ME was not found in the open 

literature, the biological evidence for this conversion is strong. One study of pregnant mice in 

particular compared four glycol ethers at a dose of 4 mmol/kg: ethylene glycol monomethyl 

ether (2-ME 304 mg/kg), ethylene glycol dimethyl ether (Monoglyme, 361 mg/kg), diethylene 

glycol dimethyl ether (537 mg/kg), and triethylene glycol dimethyl ether (713 mg/kg). Fetuses 

were collected on gestation day 18 and examined. There were no signs of maternal toxicity, and 

intrauterine survival was unaffected by glycol ether treatments. Fetal body weights were 

significantly reduced only in litters treated with Monoglyme. There was no treatment-related 

pattern of gross external malformations other than paw defects. Paw defects were present in 

87.5% of 2-ME-treated litters (68.5% of fetuses) and 86.7% of Monoglyme-treated litters 

(33.8% of fetuses). Hindpaw defects predominated over forepaw, with syndactyly the most 

common malformation. The incidences of oligodactyly and short digits were also significantly 

increased. The similarity of malformations produced by these methyl-substituted glycol ethers is 

proposed to be attributable to in vivo conversion to a common teratogen, methoxyacetic acid. 

(25) 

Additional evidence for a mixed-function oxidase production of 2-ME from Monoglyme comes 

from an in vitro study of microsomal oxidation of Diglyme in which it was demonstrated that 

microsomal cytochrome P-450 oxidizes Diglyme to 2-ME and 2-(2-methoxyethoxy)ethanol. 
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Both human and rat liver microsomes were demonstrated to catalyze the oxidation of Diglyme 

(26). 

This information about the metabolic pathways and nearly identical developmental effects at 

similar dose levels indicates that the repeated-dose, reproductive, and developmental toxicity of 

Monoglyme can be ascertained from the results of these studies on 2-ME in the appropriate 

protocol. A slight adjustment for dose due to molecular weight and pulmonary/kidney may be 

necessary but the spectrum of effects and dose-response should be similar. The presence of 

excess Monoglyme in the body is also expected to inhibit the conversion of 2-ME to ethylene 

glycol, a process that could increase the relative yield of 2-methoxyacetic acid from 

Monoglyme. Although the relative pharmokinetics of metabolism are somewhat speculative, the 

similarity in effects and dose levels for the Chernoff-Kavlock screen, the paw defects in mice, 

and the perinatal toxicity in rats (27) strongly argue that 2-ME is an excellent surrogate for 

repeated dose toxic effects of Monoglyme. 

Oral Exposure 

A great deal of information is available on the repeated-dose toxicity of the biologically 

indicated metabolite of Monoglyme, 2-methoxyethanol (2ME). One of the more definitive 

repeated dose studies was conducted on rats and mice by the National Toxicology Program 

using the drinking water route and reported in 1993 (28). In this study testicular degeneration 

was a prominent finding in rats even at the lowest dose tested (750 ppm, about 70 mg/kg/day) 

and in females, at this level, thymic atrophy was a finding. Thus, a NOEL was not found for 

rats of either sex. In the case of mice, the NOAEL for testicular degeneration and increased 

hematopoiesis in the spleen was 2000 ppm in males. A NOAEL was not reached for female 

mice since adrenal gland hypertrophy and increased hematopoiesis in the spleen occurred at the 

lowest concentration administered (2000 ppm, about 300 mg/kg/day). 

Repeated dose exposure in the drinking water was also associated with progressive anemia in 

rats and mice and increased mortality in rats at the two highest doses. The target organs can be 

identified as testes, bone marrow, spleen (hematopoiesis), thymus and adrenal. In general, the 

testes is considered a sensitive, if no the most sensitive, target organ. 

Regarding extrapolation to man, the standard use of the safety-factor approach is somewhat 

confounded by the differences in pharmacokinetics (especially the long excretion half-life of 2-

methoxyacetic acid in man) and the seriousness of the most sensitive target tissue. There is, 

however, a more definitive manner to assess human exposure and potential risk using the 

biological indicator approach. It is established that 2-methoxyacetic acid is the defining toxic 

metabolite and studies have shown that the level of 2-methoxyacetic acid in urine is an excellent 
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marker for exposure. The reference value for this metabolite has not been firmly set; however, 

the BEI reference level for Monoglyme should be as protective as the reference level for 2-ME. 

CH3 O CH2 CH2 O CH3

H3C O CH2 COOH

H O CH2 CH2 OH

Ethylene glycol

Methoxy acetic acid

HOOC COOH

Oxalic acid

TOXIC METABOLITE

CH3 O CH2 CH2 O H

2-Methoxyethanol

Monoglyme

Lung

Excretion

Kidney

Excretion

Lung & Kidney

Excretion

Slow Excretion

Inhibition by Monoglyme ?

Figure 2. Major Metabolic Pathways for Monoglyme 

Summary and Recommendations for Repeated-Dose Toxicity 

Based on common metabolites and biological indications of similar mechanism-specific adverse 

effects, the repeated dose toxicity of Monoglyme is approximated quantitatively and 

qualitatively by the studies on 2-methoxyethanol. 2-ME and hence Monoglyme, are potent 

testicular toxins, adversely affect the bone marrow, cause thymic atrophy and affect the 

adrenals. No additional testing is recommended as the target organs are understood on the basis 

of the metabolic product 2-methoxyacetic acid. Exposures and relative risk to humans may also 

be determined by using the Biological Exposure Indicator 2-methoxyacetic acid that can be 

used with the same reference range as for 2-ME. 
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Genetic Toxicity 

The SIDS/HPV requirement for genetic toxicity screening is for two end-points: generally one 

sensitive to point mutation and one sensitive to chromosomal aberrations. In the case of this 

material, these requirements are basically fulfilled by OECD guideline-like studies. The data 

indicate genotoxic activity in vitro and suggest the potential for in vivo genotoxic activity. 

Genetic Toxicology in vitro

A S. typhimurium reverse mutation assay is cited by the National Toxicology Program as 

“positive” no other information is available in the open literature for this study result (29). In 

the NTP Results report (12-2001 version) ethylene glycol diethyl ether is also listed as positive 

in the Ames test. Monoglyme is known to be cytotoxic to Salmonella typhimurium (30) at 

concentrations as low as 500 microliters per plate. McGregor also notes in this paper that most 

glycol ethers have low activity in the Ames test. 

Mammalian cell point mutation activity was assessed using the HGPRT assay in CHO cells. In 

this study Monoglyme produced no evidence of genotoxicity in the presence or absence of S9 

metabolic activation (31, robust summary attached). Although no guideline was specified, the 

study was conducted in accord with OECD 476 In Vitro Mammalian Cell Gene Mutation (32). 

Clastogenic activity was assessed in vitro using the Sister Chromatid Exchange in Chinese 

Hamster Ovary Cells Test (SCE). In this test, the material produced numerous indications of 

statistically significant effects on the frequency of SCE over the range of concentrations tested 

with and without addition of an active S9 metabolic system. A high number of cells were also 

observed with significant types of chromosomal aberrations suggesting that material was a 

clastogenic agent, especially in the presence of S9 activation (33, robust summary attached). 

No specific guideline was specified for the study; however, it was conducted in accord with 

OECD 479 "Genetic Toxicology: In vitro Sister Chromatid Exchange Assay in Mammalian 

Cells" (34). 

DNA damage was assessed using an in vitro unscheduled DNA synthesis (UDS) Assay. In this 

assay, rat hepatocytes were treated with a wide range of concentration of Monoglyme up to 

concentrations demonstrating cytotoxicity in the assay system. Treatment did not produce either 

statistically significant or dose-related increases in the amount of UDS activity as measured by 

radioactive thymidine uptake. Activity was measured by liquid scintillation counting of nuclear 

preparations and also by counting of nuclear DNA (35, robust summary attached). The protocol 

was conducted in accord with OECD 482 guidelines (36) with regard to most experimental 

parameters. The number of replicates was fewer than recommended by the guideline and there 
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was no independent repeat; however, more concentration levels were tested than typical and 

there was an independent radioactivity determination of nuclear DNA. 

Summary of Genetic Toxicology and Recommendations: 

Strictly speaking, the SIDS requirement for genetic testing has been met as both a point 

mutation and an assay sensitive to clastogenic effects have been conducted using an acceptable 

protocol. This also is in accord with the more recent guidance from the EPA concerning the 

HPV Program genotoxicity guidelines encouraging reduction in live animal use (October 14, 

1999 letter from EPA to sponsors). In the case of Monoglyme, the results have been mixed 

using several in vitro studies. Sufficient information is available for Monoglyme for the 

purposes of the HPV Challenge Program. No further testing is recommended. 

Reproductive Toxicity 

Monoglyme is considered to be a reproductive toxin based on its metabolism to 2-

methocyacetic acid which is an established testicular toxin (see repeated dose section). Adverse 

effects on the conceptus, including embryo lethality are also caused by this metabolite. Direct 

specific effects on female reproduction are not known to result from 2-methoxyacetic acid and 

thus are not expected from Monoglyme exposure 

Summary and Recommendation for Reproductive Toxicity 

The extensive literature on 2-methoxyethanol (2-ME) and the metabolic data indicating that 

Monoglyme’s oxidative metabolism to 2-methoxyacetic acid indicates a clear and significant 

repeoductive hazard from overexposure to Monoglyme. The available information is sufficient 

for the purposes of the EPA HPV Challenge Program. No additional testing is recommended. 

Developmental Toxicity 

Studies of the developmental toxicity and perinatal effects of Monoglyme are available from the 

open literature. In a study conducted by oral gavage at 0, 30, 60, 120, 250 or 1000 mg/kg, 

groups of pregnant female rats were treated from day 8 to 18 of gestation (37). The results show 

that 120 mg/kg/day or more was associated with 100% fetal death and doses of 30 or 60 mg/kg 

were fetotoxic but did not produce major malformations (see robust summary for details). This 

study suggests that Monoglyme is a specific developmental toxin as would be anticipated based 

on its metabolism to 2-methoxy acetic acid. 
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This result in rats is strikingly similar to the results Stenger et al. (38) reported in 1971 for 2-

ethoxyethanol. In this study of 2-ethoxyethanol, groups of 20 pregnant rats were treated orally 

at 0, 11, 23, 46.5, 93, 186, or 372 mg/kg per day from gd 1 through gd 21. A significant increase 

in embryonic and fetal deaths occurred in rats treated at 46.5 mg/kg per day and higher, at oral 

doses of 93 to 372 mg/kg per day, the incidence of skeletal aberrations increased in a dose 

related pattern (no statistical treatment given). Complete resorption occurred at 372 mg/kg. No 

comparable rat gavage studies could be found for 2-ME. 2-Ethoxyethanol is known to be very 

similar in its effects but less potent than 2-ME (39); thus, the similarity of the effects of 

Monoglyme and 2-ethoxyethanol add strength to the argument that Monoglyme is metabolized 

to 2-methoxyacetic acid. The relative potencies (Monoglyme caused 100% fetal death at 120 

mg/kg/day while 2-ethoxyethanol caused 100% death at 372 mg/kg/day) support the 

metabolism of Monoglyme to 2-methoxyacetic acid which is known to be more potent than 2-

ethoxyacetic acid (the active metabolite of 2-ethoxyethanol)(39). 

A mouse teratology study with oral doses of 0, 250, 350, or 490 mg/kg on days 7 to 10 of 

gestation produced results indicating teratogenicity and fetotoxicity (40). In this study, there 

was an increased incidence of major malformations including exencephaly, open eye, and tail 

defects at the two highest doses (see robust summary for details). Clear evidence showing lack 

of maternal toxicity is not presented in the publication. 

The mouse teratology result is similar to the results Nagano et al. reported in 1981 for 2-ME 

after oral gavage in the mouse (41). In this study of 2-ME, 1000 mg/kg produced total 

resorptions, 250 or 500 mg/kg produced increased fetal deaths, 125 or 250 mg/kg was 

associated with gross fetal abnormalities and skeletal malformations, 62.5 mg/kg produced only 

skeletal malformations and 31.25 mg/kg was fetotoxic with retarded ossification. Thus it 

appears that Monoglyme is a less potent developmental toxin in the mouse than 2-ME, which is 

the predicted result based on the metabolic pathway and slow conversion of Monoglyme to 2-

ME competing with excretion. 

The lower potency of Monoglyme as compared to 2-ME in producing paw defects was also 

demonstrated in a study discussed earlier, in which pregnant mice dosed at 4 mmol/kg 2-ME or 

Monoglyme showed paw defects in 87.5% of 2-ME-treated litters (68.5% of fetuses) and 86.7% 

of Monoglyme-treated litters (33.8% of fetuses) indicating a lower potency for Monoglyme 

(25). 

Summary and Recommendation for Developmental Toxicity

Rat and mouse developmental toxicity studies of Monoglyme indicate that is has the potential to 

be teratogenic and fetotoxic and may cause delayed partition. Although the studies available are 

not GLP and do not clearly establish the A/D ratio, they show a dose-response relationship and 
1,2-Dimethoxyethane U.S. EPA HPV Submission 

 

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indicate the potency range for Monoglyme as a developmental toxin in rats and mice. Sufficient 

information is available for Monoglyme for the purposes of the HPV Challenge Program. No 

further testing is recommended. 

Conclusions 

With regard to the parameters specified in the EPA HPV Challenge program, the available 

information from laboratory experiments, surrogate chemicals and modeling efforts fill all of 

the HPV Program requirements for chemical parameters and toxicity information. 

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