Registration Dossier

Administrative data

Key value for chemical safety assessment

Effects on fertility

Link to relevant study records
Reference
Endpoint:
one-generation reproductive toxicity
Remarks:
based on generations indicated in Effect levels (migrated information)
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1989
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
This was a study carried out to assess whether a recognised protocol for mice could be used with rats. A full and comprehensively documented study report is available. Whilst the study is not documented as compliant with GLP, it has been subject to rigorous QA comparative to the GLP process. The study does omit some aspects of the study that would be included if the toxicity of the substance was unknown, but all the end points likely to be important for this substance were examined.
Qualifier:
according to
Guideline:
other: NTP continuous breeding protocol
Deviations:
yes
Remarks:
rats used instead of mice
Principles of method if other than guideline:
Reproductive assessment by continuous breeding design (RACB). Purpose of study was to develop RACB mouse protocol for use with rats using a known toxicant. Full method described in Chapin (1997) – see reference list. In a modification of the standard protocol, rats were cohabited for ~6 weeks, separated for delivery, nursing and weaning of the second litter for the F2 study, then cohabited for another ~9 weeks to produce a further 3 litters for other activities e.g. cross over mating. Cross over mating was used to determine the affected sex.
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
other: Sprague Dawley VAF Crl:CD
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Portage, MI
- Housing: Two per cage during quarantine and 1 week premating, then breeding pair or individually. Solid bottomed polycarbonate cages. Sani-chip bedding. Cages disinfected weekly.
- Diet: Pelleted rodent lab chow (NIH-07) ad libitum
- Water: deionised, available ad libitum
- One male, one female checked negative for antibodies to 7 rodent viruses, m. pulmonis plus CAR Baccillus.

ENVIRONMENTAL CONDITIONS
- Temperature: 22+/-3
- Photoperiod: 14 hours dark/10 hours light
Route of administration:
oral: drinking water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Mixed with deionised water on a weight/volume basis.
Details on mating procedure:
Males and females cohabited for approximately 6 weeks (a deviation from the standard protocol) to allow delivery, nursing and weaning of the 2nd litter, then re-co-habited for approximately nine more weeks.
M/F ratio: 1 to 1. F1 pairs cohabited for 1 week.
Length of cohabitation: 6 week period then 9 week period to produce 3 more litters.
Otherwise standard RACB protocol.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Bulk solution every 4-6 weeks. Bulk solutions confirmed stable for this period. Dosing solutions prepared at max interval of 3 weeks and stored at room temperature and normal lighting. Doses were in the range 93-103% of target dose.
Duration of treatment / exposure:
Continuous from 1 week before mating through F1 generation.
Remarks:
Doses / Concentrations:
0.01%, 0.03% and 0.1% (F0 average equivalents 11mg/kg, 30mg/kg, 100mg/kg, F1 average equivalents 12mg/kg, 34mg/kg – low and mid dose groups only.)
Basis:

No. of animals per sex per dose:
20 pairs per dose group. 40 in control.
Control animals:
yes
Details on study design:
Dosing for 1 week prior to pairing. F1 pups weaned on postnatal day 21 and weighed weeks 21-23. 2nd generation from 2nd litter of F0 animals.
Dose selection rationale: data from previous studies. Top dose designed.
Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: No data
- Time schedule:

BODY WEIGHT: Yes
- Time schedule for examinations: weeks 1-6, 10, 15, 18 and after every litter. F1 animals at weaning and weeks 31-33.

WATER CONSUMPTION AND COMPOUND INTAKE: Yes
- Time schedule for examinations: Calculated based on data from weeks when body weight and consumption measured on a per cage (per breeding pair) weekly average.
Oestrous cyclicity (parental animals):
Yes. Relative frequency of oestrus, proestrus, metestrus, diestrus, cycle length.
Sperm parameters (parental animals):
Parameters examined included motility, density, and percent abnormal. Sperm analysis is contained in a separate appended report to the main reference.
Litter observations:
-Drinking water consumption monitored week 21. Body weights. F2 pups monitored for 21 days (on days 0, 4, 7, 14, 21).
- standardization of litters: No
- parameters examined: litters per pair, live pups/litter, proportion of pups born alive, sex ration, live pup weight, (adjusted and unadjusted.)
- Gross examination of dead pups:
Postmortem examinations (parental animals)
- Sacrifice: Male animals: At the end of the crossover examination. Maternal animals: not examined.
- Gross necropsy: Yes
- histopathology/organ weights: liver, kidneys, right testis and epididymis and cauda epididymis, seminal vesicles and prostate, ovary. Histopathology only on males in the control and two lower dose groups as previous data indicated no effects likely on females. 10 randomly selected animals per dose group per generation examined. Livers only examined if gross effects seen.
Postmortem examinations (offspring):
HISTOPATHOLOGY / ORGAN WEIGTHS
F1 animals
Statistics:
Cochran Armitage for dose related trends in fertility. Chi square test for cross over mating. Fisher’s exact test for pairwise comparisons with controls. Kruskal-Wallis (KW) and Jonckheere’s test for fertility parameters. Pairwise comparisons between treatment group means using Wilcox-Mann-Whitney U (WMWU) test. Average pup weight corrected for number of pups per litter using analysis of covariance; organ weights adjusted for total body weight similarly. Unadjusted body/organ weights analysed using KW and WMWU test and dose related trends tested using Jonckheere’s test. Latter also used to check body weight and water consumption data with significance among dose groups assessed using Shirley’s test when a trend in evident or Dunn’s test when one is not.
Reproductive indices:
Yes. Number of litters and live pups per litter, proportion of live pups, sex ratio. Mating index.
Clinical signs:
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Other effects:
effects observed, treatment-related
Reproductive function: oestrous cycle:
not examined
Reproductive function: sperm measures:
effects observed, treatment-related
Reproductive performance:
effects observed, treatment-related
BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS)
Body weights were significantly reduced from week 3 in females and week 6 in males in the high dose group only. Water consumption declined from week2 onwards in both sexes in the high dose group. It was significantly reduced in the mid dose group in week 6 only (4 other measurements not significantly different.)

REPRODUCTIVE FUNCTION: ESTROUS CYCLE (PARENTAL ANIMALS)
No significant effects.

REPRODUCTIVE FUNCTION: SPERM MEASURES (PARENTAL ANIMALS)
Motility and density were decreased in the top dose group. Motility increased marginally but by a statistically significant margin in the mid dose group. All parameters were normal in the low dose group.

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
100% fertility in controls and low dose group, 89% in mid dose group and only 5% (significantly lower – single breeding pair) in the top dose group. Days to litter were similar in the control and low dose group but increased in the mid dose group. (Too few in high dose group.). The number of litters per pair was not affected in the low and mid dose group. But the number of live pups per pair was significantly reduced in the mid dose group.

ORGAN WEIGHTS (PARENTAL ANIMALS)
All significantly reduced in the high dose group. In the mid dose male group adjusted liver seminal vesicle and epididymides weights significantly reduced. In the low dose group, the adjusted prostate weight increased significantly. No changes were seen in the mid dose female group.

HISTOPATHOLOGY (PARENTAL ANIMALS)
Testicular and epididymal lesions seen, but also present in controls. Effects were not attributed to treatment.
Dose descriptor:
NOAEL
Effect level:
0.01 other: % (11mg/kg)
Sex:
male
Basis for effect level:
other: Adverse effects on sperm and male reproductive organs.
Clinical signs:
not specified
Mortality / viability:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Sexual maturation:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
not examined
VIABILITY (OFFSPRING)
Few pups born to high dose animals. Live pups/litter and proportion of live pups/litter decreased significantly in the mid dose group. The proportion of still births, the average postnatal survival were significantly decreased in the mid dose group.

BODY WEIGHT (OFFSPRING)
Mean body weights of mid dose pups were significantly reduced for both sexes at all time points except one. Adjusted live pup weight increased significantly in the low dose group albeit by only around 5%. F1 mature animals showed reduced body weight (-14%) in the mid dose group.

SEXUAL MATURATION (OFFSPRING)
No adverse changes on reproductive performance.

ORGAN WEIGHTS (OFFSPRING)
There was no effect on adjusted organ weight of females. In males, liver, kidney, seminal vesicle, cauda epididymis, right epididymis and prostate all showed lower weights in the mid dose group after adjustment. The low dose group animals were similar to controls

HISTOPATHOLOGY (OFFSPRING)
Only the testes and epididymis were examined. Minimal to mild testicular lesions were seen in 2/10, 7/10, 5/10 animals in the controls/mid/high dose animals respectively. These results suggested a slight effect from treatment but the no clear dose response was evident. Single animals in the mid and high dose animals showed epididymis lesions, which were not attributed to treatment.

OTHER FINDINGS (OFFSPRING)
Drinking water consumption decreased in the mid dose group from week 21. The estimated daily dose was 9 and 27mg/kg for the low and mid dose group male pups and 15/41mg/kg respectively for females. There was no effect the litter indices of either F1 dose group animals. There were no differences in epididymal sperm morphology or motility among the groups from the F2 generation but there was significantly decreased sperm density in both dose groups (-17% in low dose group, -23% in mid dose group).
Dose descriptor:
NOAEL
Generation:
F1
Effect level:
0.01 other: % (11mg/kg)
Sex:
male/female
Basis for effect level:
other: Reduced number of live pups per litter.
Reproductive effects observed:
not specified
Executive summary:

Methoxyethanol when administered to SD rats over 2 generations and dosed via drinking water was toxic to reproduction.  The top 0.1% dose almost completely inhibited reproduction in the F0 generation and the mid dose 0.03% significantly reduced the number of live pups borne; other adverse changes were seen at this dose on male testes and sperm. The lowest dose 0.01% (equivalent daily dose ~10mg/kg) showed minor changes to sperm density and testicular lesions, but these could not be clearly attributed to treatment with a clear dose response relationship and therefore not considered significant adverse effects.

Effect on fertility: via oral route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEL
11 mg/kg bw/day
Effect on fertility: via inhalation route
Dose descriptor:
NOAEC
316 mg/m³
Effect on fertility: via dermal route
Dose descriptor:
LOAEL
625 mg/kg bw/day
Additional information

RAT


Methoxyethanol when administered to SD rats over 2 generations and dosed via drinking water was toxic to reproduction. The top 0.1% dose almost completely inhibited reproduction in the F0 generation and the mid dose 0.03% significantly reduced the number of live pups borne; other adverse changes were seen at this dose on male testes and sperm. The lowest dose 0.01% (equivalent daily dose ~10mg/kg) showed minor changes to sperm density and testicular lesions, but these could not be clearly attributed to treatment with a clear dose response relationship and therefore not considered significant adverse effects. In a repeat of the experiment which used a different litter to form the parents for the F2 generation (litter 2 versus litter 5), the high dose 0.024%(20mg/kg) significantly reduced the number of pups borne live and the number of male pups borne live. These effects persisted into the second generation. The cross over trial showed that effects were on the males only. The mid dose group 0.012% (11mg/kg)) produced no adverse effects apart from an increase in pup weights, the significance of which was unclear. Many other studies have been performed over short time frames to non-standard methods to further investigate and have confirmed clear effects on males (reduced testes weight, reduced fertility, adverse effects on sperm – multiple abnormal parameters, reduced pregnancy rates, increased post-implantation loss, and fetal death) and females (estrus cycle effects.) Males are clearly more sensitive than females.


When administered to SD rats by inhalation, methoxyethanol was toxic to reproduction at an exposure of 300ppm. Males were more sensitive than females with infertility being caused by testicular atrophy and impairment of sperm production. The NOAEL was 100 (316mg/m3) ppm. In another single generation study, male and female rats exposed to 25ppm exhibited no effects on fertility or overt effects on development. Measurable neurochemical changes were observed in the pups from exposed males but the relevance of these findings to risk assessment is unclear. In a third study where rats (male and female) were administered methoxyethanol by inhalation prior to mating, complete infertility in males resulted following exposure to 300ppm with associated degenerative changes in the testes germinal epithelium of rats. These effects appeared to be substantially, but not completely, reversible following exposure cessation. A similar exposure produced evidence of general toxicity in females but no adverse effects on fertility. Further short term studies in males exposed by inhalation confirmed adverse effects on the testes (weight, sperm damage.)


A single short term study is available for the dermal route of exposure. Methoxyethanol when administered to rats by dermal exposure (occluded and non-occluded) for 7 days was toxic to reproduction. The effects were temporary, at least at the lower doses examined. The effects seen were inhibition of spermatid and spermatozoa production, atrophy of the testes and epididymides and consequential loss in fertility. Effects were seen at the lowest doses tested (625mg/kg/day for the occluded test and 1250mg/kg/day for the non-occluded test. However, the effects seen at this dose were reversible resulting in a NOAEL after 15 weeks recovery time of 625mg/kg/day for occluded animals and 5000mg/kg/day for non-occluded animals.


MICE


Methoxyethanol was administered to 3 different strains of mice (CD1, C57B1/6 and C3H over 2 generations via drinking water. There was clear evidence of toxicity to reproduction in all three strains. The most sensitive effect was a reduction in the number of females becoming pregnant and delivering live pups. The top 0.3% dose was severely toxic in all strains. In the CD1 and C3H mice, the middle dose had few detectable effects on the F0 animals but significantly reduced the reproductive success of the F1 animals. In C57B1/6 mice, the middle dose was toxic, reducing pup numbers and increasing levels of abnormal sperm. The lowest dose 0.03%, equivalent to 53-64mg/kg/day was without adverse effect in all CD1 and C3H and can be regarded as a NOAEL. In the third strain, the lowest dose 0.03%, equivalent to 53mg/kg/day reduced seminal vesicle weights and sperm counts in the F1 generation. However, the effects were not large (~10% change from controls) which suggests that the NOAEL is not much lower than this dose. Other oral studies in mice at higher doses confirmed these effects. No studies have been carried out in mice by other routes of exposure


OTHER SPECIES


Methoxyethanol when administered to male rabbits for 13 weeks via drinking water produced a marked inhibition of normal spermatogenesis. The effect is marked with a NOAEL of 12.5mg/kg and a LOAEL of 25mg/kg. The effect is very specific with no clear effects on sperm morphology and no effect on the ability of the sperm that remain to fertilize a female rabbit. No other adverse effects that could be attributed to treatment were observed at the LOAEL. A gavage study in guinea pigs also confirmed adverse sperm effects at the lowest dose tested of 200mg/kg.




Short description of key information:
RAT-ORAL-Drinking water
- NOAEL: 0.01% -0.012% in drinking water (11mg/kg)
RAT-ORAL-GAVAGE
- LOAEL: 300mg/kg
- LOAEL: 50mg/kg
- LOAEL: 500mg/kg
- LOAEL: 250mg/kg
- NOAEL: 50mg/kg
- LOAEL: 200mg/kg
- NOAEL: 50mg/kg
- LOAEL: 150mg/kg
- LOAEL: 50mg/kg
MOUSE-ORAL-Drinking water
- NOAEL: 0.03% (60mg/kg)
- LOAEL: 0.03% (53mg/kg)
- NOAEL: 0.03% ((64mg/kg)
- LOAEL: <0.1%
MOUSE-ORAL-GAVAGE
- NOAEL: 70mg/kg
- LOAEL: 500mg/kg
RABBIT-ORAL-Drinking water
- NOAEL: 12.5mg/kg/day
GUINEA PIG-ORAL-GAVAGE
- LOAEL=200mg/kg

RAT-INHALATION
- NOAEL=100ppm (316mg/m3)
- NOAEL>25ppm
- NOAEL >25ppm & <500ppm
- LOAEL=7500ppm
- NOAEL=300ppm
- LOAEL=1000ppm
- NOAEL=100ppm

RAT-DERMAL
- LOAEL=625mg/kg

Effects on developmental toxicity

Description of key information

RAT-ORAL-DIET

- NOAEL: 26mg/kg/day

RAT-ORAL-GAVAGE

- NOAEL: 0.01% -0.012% in drinking water (11mg/kg)

- NOAEL: 12mg/kg

- LOAEL: 50mg/kg

- LOAEL: 300mg/kg

- NOAEL: 25mg/kg

- NOAEL: 25mg/kg

- NOAEL: 25mg/kg

- LOAEL: 50mg/kg

- LOAEL: 50mg/kg

- NOAEL: 25mg/kg

- LOAEL: 50mg/kg

- NOAEL: 100mg/kg

- LOAEL: 165mg/kg

MOUSE-ORAL-GAVAGE

- LOAEL: 1400mg/kg

- LOAEL:: 32.5mg/kg

- NOAEL: 70mg/kg

- LOAL: 250mg/kg

- LOAEL: 250mg/kg

- NOAEL: 100mg/kg

- LOAEL: 304mg/kg

- NOAEL: 100mg/kg

MONKEY-ORAL-GAVAGE

- LOAEL: 12.5mg/kg

RAT-INHALATION

- NOAEL: 10ppm (32mg/m3)

- LOAEL: 100ppm

- LOAEL: 25ppm

- NOAEL: 10ppm

- LOAEL: 50ppm

MOUSE-INHALATION

- NOAEL: 10ppm(32mg/m3)

RABBIT-INHALATION

- NOAEL: 10ppm(32mg/m3) (3ppm, 9.5mg/m3)

RAT-DERMAL

- LOAEL=48mg/kg (teratogenicity, NOAEL=48mg/kg (maternal toxicity, fetotoxicity)

- LOAEL: 50mg/kg

- NOAEL: 250mg/kg

- LOAEL: 2000mg/kg

- NOAEL: 3% solution

Effect on developmental toxicity: via oral route
Dose descriptor:
NOAEL
11 mg/kg bw/day
Effect on developmental toxicity: via inhalation route
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEC
9.76 mg/m³
Species:
rabbit
Effect on developmental toxicity: via dermal route
Dose descriptor:
LOAEL
48 mg/kg bw/day
Additional information

RAT (ORAL)

Methoxyethanol when administered in a liquid diet to pregnant female rats during GD7-18 produced both teratogenic and embryotoxic effects. The most sensitive effect being embryotoxicity, manifest as a slight but significant reduction in pup weight of 12-15% at the lowest dose tested of 0.006% (equivalent to 26mg/kg/day.)  The no effect level for teratogenic effects was 0.006% and for maternal toxicity 0.025% (73mg/kg/day). This study was used as the key study as the route of exposure is more relevant than gavage.

Methoxyethanol when administered by gavage to pregnant female rats during GD6-15 produced embryotoxic, manifest as a slight but significant reduction in the number of live pups per litter.  The no effect level was 12.5mg/kg.  At higher dose, more severe effects were seen with total resorptions occurring at 100mg/kg.

A study specifically designed to assess the developmental effects of methoxyethanol in the heart showed no adverse effects on this organ when given to pregnant rats over two different parts of the organogenesis period.  A slight prolongation of gestation was observed at the dose used (25mg/kg) and a slight change in a biomarker for cellular growth was seen but the biological significance of this, particularly for risk assessment, is unclear. A similar study confirmed the severe developmental effects of methoxyethanol in the absence of maternal toxicity.  The most sensitive effects were offspring viability (manifest as no litters) and reduced pup body weight.  Pregnancy length also increased.  The inhibition of Orthinine Decarboxylase (ODC) activity in the heart was found to be closely associated with the developmental effects, and whilst there is no evidence to suggest causality, this was proposed by the study authors as a biomarker for developmental effects. In another study focussing on the heart, doses which produced adverse changes to litter parameters such as pup body weight, also produced teratogenic effects with heart defects the most sensitive effect.  The clear no effect level for developmental effects was 25mg/kg although it could be argued that this is a LOAEL because of the incidence of hydronephrosis at this level.  There were also clear reprotoxic effects at 50mg/kg and evidence of biological if not statistically significant effects at 25mg/kg.  Overall, whilst effects remained small, there was multiple evidence to suggest that the no effect level for reprotoxic and possibly developmental effects was below the lowest level tested of 25mg/kg. In the final study of this type, severe effects on reproductive outcome in the absence of maternal toxicity were again demonstrated.  In addition to producing physical abnormalities, reduced litter sizes and reduced survival rates, offspring surviving to 8 weeks of age showed a persistent intraventricular delay cardiac abnormality, albeit in the absence of any visible morphological changes; the consequences of this aberration are unknown and the implications unclear.  A no effect level was not established as effects were seen at the lowest dose tested (50mg/kg).

A study specifically designed to assess certain serum chemistry parameters relevant to development confirmed the marked developmental and reprotoxic effects of methoxyethanol in the absence of maternal toxicity.  At a dose which produced adverse changes to litter parameters such as survival and pup body weight, there is also evidence for teratogenic effects with heart defects the most sensitive effect.  The clear no effect level for maternal toxicity was 50mg/kg whilst developmental effects developmental effects were seen at this dose (NOAEL50mg/kg).  Changes were observed in the serum levels of calcium and vitamin D that could be attributed to treatment but these changes were considered secondary to the loss of litters.

A single dose of methoxyethanol given by gavage to pregnant female rats on GD13 was capable of inducing digit malformation and dismorphogenesis of limb bud developments as well as depressing fetal body weight growth.  Lower doses which caused dismorphogenesis soon after treatment did not result in visible malformations at the end of term suggesting that recovery could result from these lower insult levels.  The biologically and statistically significant no effect level was less than 50mg/kg.

RAT (INHALATION)

Methoxyethanol when inhaled at 25ppm by pregnant female rats caused overt effects on development.  However, a measurable deficit was recorded in one of six behavioural tests and neurochemical changes were observed for pups from exposed females.  The relevance of these findings, particularly the neurochemical changes, to risk assessment is unclear.

Methoxyethanol when administered by inhalation to pregnant female rats during GD6-15 was not teratogenic but produced slight fetotoxicity or variations in the highest dose group, manifest as a slight but significant increase in skeletal variations.  Slight effects were seen on dam erythrocyte parameters, but the biological significance of these was questionable.  A clear no effect level for developmental effects was observed at a dose of 10ppm and below.

RAT (DERMAL)

In an OECD guideline and GLP prenatal toxicity study, 2-Methoxyethanol was applied dermally (6hrs/day) to pregnant Wistar rats in doses of 0.05; 0.1 and 0.3 ml/kg body weight/day to the intact shaven dorsal skin using an occlusive dressing on GD6-15. Control animals were treated with water. The two higher doses elicited clear signs of maternal toxicity (reduced food consumption, impaired body weight gain (corrected), although the lower dose induced no signs of maternal toxicity. Severe Embryo-/fetotoxicity was demonstrated in the intermediate and high dose group manifest by increased postimplantation losses and at all three dose levels by reduced fetal weights. A clearly increased incidence of different soft tissue variations, retardations and unclassified observations were also seen in the mid and high dose groups, although observations in the latter were greatly restricted by the very small number of offspring produced at this dose. Teratogenic effects were seen at all three doses, manifest through increased incidence of various malformations. NOAEL (maternal effects) 0.05ml/kg. NOAEL (teratogenicity) <0.05ml/kg

Methoxyethanol when administered by occluded dermal application to pregnant female rats showed teratogenic potential according to the criteria of the screening study used.  The no effect level was 3% in 10ml physiological saline and a clear dose response relationship was seen. In a separate study, when administered as a single unoccluded dermal application to pregnant female rats on GD12 showed clear teratogenic and embryotoxic effects with multiple malformations in fetuses and a reduction in fetal body weight observed.  The clear no effect level seen was a dose of 250mg/kg.

Methoxyethanol when administered as a single unoccluded dermal application of 2000mg/kg to pregnant female rats on showed clear teratogenic effects with multiple malformations in fetuses and a reduction in fetal body weight observed.  Administration over a window of .GD10-14 produced these anomalies, although GD14 was the least sensitive and GD12-13 the most sensitive.  Treatment on GD11-12 produced predominantly soft tissue anomalies whilst treatment on GD12-13 produced predominantly external and skeletal malformations.

Values obtained by the dermal route do not establish the true NOAEL and a route to route extrapolation is therefore preferred to derive the DNEL.

RABBIT

Methoxyethanol when administered by inhalation to pregnant female rabbits during GD6-18 produced severe and extensive teratogenity at an exposure of 50ppm.  Significant but not severe maternal toxicity was also seen, manifest as a decrease in body weight gain but this is unlikely to be a primary cause of the malformations seen.  An increase in resorptions was seen at 10ppm relative to concurrent controls, but as these were within the range of historic controls, they were not attributed to treatment.  No other effects were seen at this exposure, hence the NOAEL was 10ppm. However, a conservative interpretation based on concurrent controls is a NOAEL of 3ppm.

MONKEY

Methoxyethanol when administered by gavage to pregnant female monkeys during GD20-45 produced embryotoxicity, manifest as an increase in the number of abortions seen.  Treatment at the lowest dose tested of 12mg/kg was attributed by the authors to cause death of primate embryos at a rate of 23% of total pregnancies and 100% at 36mg/kg.  The embryonic death rate should be treated semi-quantitatively however as the small number of animals used precluded meaningful statistical treatment of the results. The results cannot unequivocally be related to treatment.

MOUSE

Methoxyethanol when administered by gavage to pregnant female mice during GD7-14 results in toxicity and teratogenicity in the absence of marked maternal toxicity.  The most sensitive effects were skeletal variations and retardation of ossification, which was seen at the lowest dose tested of 32.5mg/kg. A single dose of methoxyethanol given by gavage to pregnant female mice on GD11 was capable of inducing digit malformations.  The biological and statistically significant no effect level was 100mg/kg.

Methoxyethanol when administered by inhalation to pregnant female mice during GD6-15 was not teratogenic but produced slight fetotoxicity or variations in the highest dose group, manifest as a slight but significant increase in skeletal extra lumbar ribs and unilateral testicular hyperplasia.  No effects were observed at a dose of 10ppm.

Justification for classification or non-classification

There is clear evidence in animals of adverse effects on fertility. There is clear evidence in animals of developmental toxicity effects in the absence of maternal toxicity. Classification for both end points is warranted.