2-ethylhexane-1,3-diol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Published in a peer-reviewed journal

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1994

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-ethylhexane-1,3-diol

EC Number:

202-377-9

EC Name:

2-ethylhexane-1,3-diol

Cas Number:

94-96-2

Molecular formula:

C8H18O2

IUPAC Name:

2-ethylhexane-1,3-diol

Test material form:

liquid: viscous

Details on test material:

Purity 99%.
Analysis by NMR and GC/MS.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc. Portage, MI, USA
- Age at study initiation:
- Weight at study initiation: 250-300 g (males) and 175-200 g (females)
- Housing: two per cage, in stainless steel wire mesh cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad liitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 68-75 F.
- Humidity (%): 42-65
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

dermal

Vehicle:

unchanged (no vehicle)

Details on exposure:

TEST SITE
- Area of exposure: 1.5 x 1.5 inches
- % coverage:
- Type of wrap if used: occlusive, polyvinyl film over sterilized gauze square. A Lycra-Spandex jacket with Velcro closure covered the dosing site.
- Time intervals for shavings or clipplings: no data, but skin was clipped

REMOVAL OF TEST SUBSTANCE
- Washing (if done): yes, warm water-dampened gauze
- Time after start of exposure: 6 h

TEST MATERIAL
- Amount(s) applied (volume or weight with unit):1.0-4.0 ml/day
- Concentration (if solution): 100%
- Constant volume or concentration used: no

USE OF RESTRAINERS FOR PREVENTING INGESTION: no; applied to dorsal trunk not accessible to mouth

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

No need to assay undiluted EHD

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1/1
- Proof of mating: The presence of a dropped copulation plug was considered evidence of successful mating, and designated as gestation day (gd) 0

Duration of treatment / exposure:

10, days 6-15 inclusive

Frequency of treatment:

once daily, 6 h dermal exposure per day

Duration of test:

21 days after determination of successful mating

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
4.0 ml/kg bw/d
Basis:
other: undiluted test article based on maternal body weight on GD 6. Equivalent to 3768 mg/kg bw/d.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
2.0 ml/kg bw/d
Basis:
other: undiluted test article based on maternal body weight on GD 6, equivalent to 1884 mg/kg bw/d.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
1.0 ml/kg bw/d
Basis:
other: undiluted test article based on maternal body weight on GD 6, equivalent to 942 mg/kg bw/d.

No. of animals per sex per dose:

25 successfully-mated females per dose group

Control animals:

yes, concurrent vehicle

Details on study design:

Controls were animals where 4.0 ml of water was applied under identical occlusive patches
- Dose selection rationale: Doses were those found to include the NOAEL for repeated dose exposure (see Section 7.5.2, Van Miller, 1994)
- Rationale for animal assignment (if not random): randomly assigned by computer-generated procedure.
- Other: Surviving females were sacrificed on GD21 by CO2 asphyxiation.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily, twice daily during the treatment period

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily, twice daily during the treatment period for clinical signs of toxicity or pharmacologic effects and local skin irritation

BODY WEIGHT: Yes
- Time schedule for examinations: on days 0, 6, 9, 12, 15, 18 and 21

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes, over 3-day intervals from GD 0 to 21.
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #21
- Organs examined: gravid uterus, ovaries and ohter pelvic and abdominal visceral were inspected for signs of gross pathology

OTHER:

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other:

Fetal examinations:

- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]
- Head examinations: Yes: [half per litter]

Statistics:

The unit of comparison was the pregnant female or the litter. Quantitative continuous variables were intercompared using Levene's test for equal variances, ANOVA and t-tests with Bonferroni probablilities for pairwise comparisons. When Levene's test indicated heterogeneous variances, all groups were compared by an analysis of variance for unequal variances followed, if necessary, by the separate variance t-test.
Nonparametric data were analyzed statistically by the Kruskal-Wallis test followed by a Mann-Whitney U-test, if appropriate. Incidence data were compared using Fisher's exact test. For all statistical tests, a probability value of p < 0.05 (two-tailed) was used as the criterion for significance.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
No erythema or edema was seen at the dosing site. Exfoliation and crusting, possibly related to drying, were seen in a few animals of the 2.0 and 4.0 ml/kg bw/d groups.

One moribund female of the 4.0 ml/kg bw/d group was sacrificed on GD11. Necropsy showed hydronephrosis and urinary bladder calculi and therefore death was considered not to be related to treatment. Corrected body weight change was slightly but not statistically significantly reduced at the high dose. Although not significant, maternal body weight gains were lower than for controls for the high-dose group over the whole treatment period, particularly during the first 3 days of treatment. There were no significant or dose-related trends for changes in food consumption. There were no treatment-related differences from controls in terminal body weight or gravid uterine weights. Necropsies showed no treatment-related gross pathology in any animal.

There were statistically-significant increases in absolute liver weight at 4.0 ml/kg bw/d, and relative liver weight was increased at all dosages, with mean increases of 15.5% at the high dose, 7.8% at the middle dose, and 7.8% at the low dose.

Effect levels (maternal animals)

Dose descriptor:

NOEL

Effect level:

942 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes. Remark: visceral malformations

Details on embryotoxic / teratogenic effects:
There were no treatment-related effects on the average number of corpora lutea or implantations (total, viable and nonviable), pre- and postimplantation losses. There were no significant differences in fetal body weights or the incidence of external malformations (or variations) or total visceral malformations.

A statistically significant increase in the incidence of unilateral hydroureter, compared with the concurrent controls, was present at the high dose, when analysed on a "per litter" basis. There was no statistically-significant effect when analysed on a "per fetus" basis. There was no apparent predominance associated with the side altered.

Independently, there was a statistically significant increase in the incidence of three variations at the high dose on a "per litter" basis: fetal atelectasis or partial fetal atelectasis, bilateral dilated lateral cerebral ventricle and bilateral dilated ureters. The incidences of dilated lateral ventricle and of bilateral dilated ureter were also significantly increased at the mid dose.

Although statistically there was an increase in the incidence of total skeletal malformations, this was considered not biologically significant because of an absence of a dose-response relationship. Thirteen skeletal variations indicating reduced ossification were statistically increased for several skeletal districts at the high dose. A reduced number of caudal segments was observed at both 4.0 and 2.0 ml/kg bw/d.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Compared with laboratory historical controls, the incidence of unilateral hydroureter at 4.0 ml/kg bw/d in this study was in excess of the upper limit in the historical values. For variants, while 11 of the current incidences fell within the range of the historical controls, six were in excess of the upper limit.

Applicant's summary and conclusion

Conclusions:

EHD, when applied dermally to the skin of pregnant rats, for a duration of 6 h/day on gestational days 6-15, resulted in maternal body weight decreases and liver enlargement. A fetal visceral organ effect was also observed in the high-dose groups as unilateral hydroureter. Variations included dilated lateral cerebral ventricles, bilateral dilated ureter, and decreased ossification and caudal segments. The NOEL is 1.0 ml/kg bw/day or 942 mg/kg bw/day.