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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1984
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Remarks:
Well documented publication which meets basic scientific principles and based on a GLP study.
Cross-reference
Reason / purpose for cross-reference:
reference to other study

Data source

Reference
Reference Type:
publication
Title:
Teratogenic evaluation of ethylene glycol monobutyl ether in Fischer 344 rats and new zealand white rabbits following inhalation exposure.
Author:
Tyl RW, Millicovsky G, Dodd DE, Pritts I, France KA and Fisher LC
Year:
1984
Bibliographic source:
Env. Health Perspect., 57, p47-68.

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Deviations:
not specified
GLP compliance:
not specified
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
2-butoxyethanol
EC Number:
203-905-0
EC Name:
2-butoxyethanol
Cas Number:
111-76-2
Molecular formula:
C6H14O2
IUPAC Name:
2-butoxyethanol
Details on test material:
- Name of test material (as cited in study report):
- Source: Union Carbide Corporation
- Lot #45-235
- Analytical purity: 99.6 %, verified.

Test animals

Species:
rat
Strain:
Fischer 344
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Hilltop Lab Animals Inc, Scottdale, PA
- Age at study initiation: 100 days on arrival
- Weight at study initiation: 185-203g
- Housing: stainless steel wire mesh cages
- Diet (ad libitum except during exposure): Ground rodent lab chow, certified, Ralston Purina Mills, RIchmond, IN
- Water (ad libitum except during exposure): tap
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature, Humidity, Air changes: recorded in source but not reported except for during exposures (see later)
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
unchanged (no vehicle)
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Glass and stainless steel 2.1x1x2.1(h)m, volume 4350l.
- Method of holding animals in test chamber: no restraint
- Air change rate: 14/hr
- Temperature, humidity, pressure in air chamber: measured 4x per exposure: temp 75.7-80.9F, humidity 33.9-49%
- System of generating vapour: Liquid metered from a piston pump into a heated glass evaporator. Temperature maintained at minimum required to vapourise liquid. Vapour carried to exposure chamber by conditioned air. Expected chamber concentration reached within 20mins of start of experiment.
- Treatment of exhaust air: filtered.

TEST ATMOSPHERE
- Brief description of analytical method used: GC with FID calibrated over expected concentration range. Sampling once per hour.
- Samples taken from breathing zone: yes. Vapour concentrations in breathing zone found variation of 1%
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
GC FID, once per hour during exposure period.
Details on mating procedure:
- Impregnation procedure: cohoused.
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: checked 2x day for copulation plugs
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy
Duration of treatment / exposure:
GD 6-15.
Frequency of treatment:
6hrs/day
Duration of test:
to GD 21
Doses / concentrationsopen allclose all
Dose / conc.:
25 ppm (nominal)
Remarks:
121mg/m3. 24-26ppm (analytical)
Dose / conc.:
50 ppm (nominal)
Remarks:
242mg/m3. 49-51ppm (analytical)
Dose / conc.:
100 ppm (nominal)
Remarks:
483mg/m3. 96-100ppm (analytical)
Dose / conc.:
200 ppm (nominal)
Remarks:
966mg/m3. 195-207ppm (analytical)
No. of animals per sex per dose:
36 per dose group.
Control animals:
yes, sham-exposed
Details on study design:
no further information

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS, DETAILED CLINICAL OBSERVATIONS: No data

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

FOOD CONSUMPTION and WATER CONSUMPTION: Yes
- days 0-3, 3-6, 6-9, 9-12, 12-15, 15-18, 18-21

POST-MORTEM EXAMINATIONS: Yes / No / No data
- Sacrifice on gestation day 21
- Organs examined: liver, kidney, thymus, spleen, uterus.
- haematologic analysis also carried out for erythrocyte count, haemoglobin and hematocrit.
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 resorptions: Yes
Fetal examinations:
- External examinations: Yes
- Soft tissue examinations: Yes
- Skeletal examinations: Yes
- Head examinations: Yes
Statistics:
For continuous variables: comparison with control by Levene's test for equal variances, ANOVA and t test with Bonferroni probabilities. Non-parametric data compared using Kruskal-Wallis test followed by Mann-Whitney U test when appropriate. Incidence data compared using Fisher's exact test. Significance level of 0.05 used for all assessments.
Indices:
no data
Historical control data:
no data

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
The following were not seen in controls or low dose groups but were in >75% of dams at 200ppm: cold and pale extremities; tail tip discoloured, ulcerated missing.
The following were not seen in controls or low dose groups but were in up to 25% of dams at 100ppm and >75% of dams at 200ppm: stained urogenical area, fluid on tray (positive for occult blood), red fluid on tray.
The following was not seen in controls but with increasing incidence with dose: perioccular wetness.
The following was seen in controls but with increasing incidence at 100/200ppm: perinasal encrustation, urogenital wetness and encrustation, fur stained red
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Dose-dependent maternal weight loss was observed at 200 ppm (GD 6-15) and 100 ppm (GD 6-9). Statistically significantly reduced weight gain was seen at 200ppm (GD 6-21) and 100ppm (GD6-15). Overall weight of the 100ppm dams was similar at the end of the study to controls but in the high dose animals was reduced by 11%. These reductions co-incided with the start of treatment.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Dose-dependent reduction of food consumption was observed at 200 ppm and 100 ppm (both GD 6-12). The GD 6-9 reduction at 200ppm was 80% with the animals almost stopping eating. The reduction at 100ppm over the same period was 25%. These reductions co-incided with the start of treatment. Overall food consumption during the treatment period was signficantly reduced by 43% at 200ppm and 13% at 100ppm compared to controls.
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Description (incidence and severity):
Dose-dependent reduction of water consumption was observed at 200 ppm, primarily over the period GD6-9, where it reduced by 66%. These reductions co-incided with the start of treatment. Overall water consumption during the treatment period was signficantly reduced by 14% compared to controls.
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
Haematological findings from blood samples taken at necropsy on GD21 (six days after the last exposure) showed signs of haemolytic anaemia for treatment with 100 ppm 2-butoxyethanol and higher. At 200ppm there was a significant reduction in RBC (-8%) and an significant increase in hemoglobin (+14%) and hematocrit (+20%.) RBC was also reduced at 100ppm (-9%). Mean corpuscular volume was significantly enlarged at 100 and 200ppm (+11 % and +30% respectively), hemoglobin per cell was increased (+11% at 100ppm, +25% at 200ppm) and mean corpuscular hemoglobin content also increased at both dose levels relative to controls by a small (<5%) but significant amount.
Description (incidence and severity):
Evidence of haematuria from 100 ppm
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Absolute and relative organ weight reductions were seen at 200ppm. Absolute and relative spleen weight increased (+19% and +24% respectively) and relative kidney weight increase (+9%) compared to controls. Gravid uterine weight was significantly reduced (-43%)
Gross pathological findings:
not examined

Maternal developmental toxicity

Pre- and post-implantation loss:
effects observed, treatment-related
Description (incidence and severity):
Significant reduction in the number of viable implants in 200ppm dose group only (reduced by half compared to other dose groups and control) Pre-implantation loss was elevated but not significantly.
Total litter losses by resorption:
effects observed, treatment-related
Description (incidence and severity):
Significant increase in number of litters totally resorbed in highest dose group (9 versus none in controls and 100ppm dose group)
Early or late resorptions:
effects observed, treatment-related
Description (incidence and severity):
Significant number of embryonic resorptions at 200ppm (2.8 versus effectively zero in all other groups including control)
Dead fetuses:
effects observed, treatment-related
Description (incidence and severity):
Significant increase at 200ppm only. (50% versus ~5% rate in all other dose groups and control).
Changes in pregnancy duration:
no effects observed
Changes in number of pregnant:
no effects observed
Details on maternal toxic effects:
Maternal toxicity was observed in a dose-related incidence during the exposure period,

Effect levels (maternal animals)

Dose descriptor:
NOAEL
Effect level:
50 ppm
Basis for effect level:
body weight and weight gain
clinical signs
food consumption and compound intake
haematology

Maternal abnormalities

Abnormalities:
no effects observed

Results (fetuses)

Fetal body weight changes:
no effects observed
Reduction in number of live offspring:
effects observed, treatment-related
Description (incidence and severity):
Reduction by approaching 50% at 200ppm compared to other dose levels and controls
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
not examined
External malformations:
no effects observed
Description (incidence and severity):
Total number of malformations: control 0, 25ppm 1, 50ppm 1, 100ppm 0, 200ppm 0.
Skeletal malformations:
no effects observed
Description (incidence and severity):
Total number of malformations: control 0, 25ppm 3, 50ppm 0, 100ppm 0, 200ppm 1.
Evidence for retarded skeletal ossifications were seen at 100ppm and 200ppm. Exposure to 200 ppm was also associated with a significant increase in the number of litters with one or more foetuses with unossified skeletal elements and poorly ossified skeletal elements (anterior arch of atlas, cervical centra 5 and 6 and forelimb proximal phalanges) and poorly ossified skeletal elements (cervical arches and sternebrae 1, 3, 4 and 6). Primarily because the skeletal elements were poorly ossified there was a decreased incidence of bilobed cervical centra 5 and 6 and bilobed thoracic centra 9 and 13. There was also a decreased incidence of poorly ossified hindlimb proximal phalanges. At 100 ppm, the number of litters with one or more foetuses with unossified cervical centrum 6 was significantly increased and, because fewer also showed ossification of cervical centrum 5, the number bilobed was significantly decreased. No significant differences were observed for other aspects of skeletal ossification.
Visceral malformations:
no effects observed
Description (incidence and severity):
Total number of malformations: control 1, 25ppm 1, 50ppm 2, 100ppm 2, 200ppm 3.
Details on embryotoxic / teratogenic effects:
There were no statistical significant increases in incidences of external, visceral, skeletal, or total malformations associated with exposure to 2-butoxyethanol.

Effect levels (fetuses)

Dose descriptor:
NOAEC
Effect level:
50 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: delayed ossification
Remarks on result:
other: delay likely to be secondary to maternal toxicity

Fetal abnormalities

Abnormalities:
no effects observed

Overall developmental toxicity

Developmental effects observed:
yes
Lowest effective dose / conc.:
100 ppm (nominal)
Treatment related:
yes
Relation to maternal toxicity:
developmental effects as a secondary non-specific consequence of maternal toxicity effects
Dose response relationship:
yes
Relevant for humans:
no

Any other information on results incl. tables

No adverse reproductive or developmental effects were observed in animals exposed to 25 ppm or 50 ppm.

Applicant's summary and conclusion

Conclusions:
2-butoxyethanol is not a developmental toxicant. Developmental effects seen are secondary to maternal toxicity.
Executive summary:

In a GLP developmental toxicity study, pregnant rats were exposed to 2 -butoxyethanol vapour at concentrations up to 200ppm during GD6 -15. The results indicated that exposures from 100ppm upwards caused marked maternal toxicity, manifest by haemotoxicity and erduced body weight gain and food consumption. Exposures of 200ppm produced embryotoxicity, manifest as as increased resorptions and decreased viable implants per litter) and fetotoxicity (retardations in skeletal ossification). There was no evidence of teratogenicity. The developmental effects appear to be secondary to maternal toxicity.

Synopsis

NOAEC (maternal) =50ppm

NOAEC (ebryotoxicity, fetotoxicity) =100ppm