2-isopropoxyethanol

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

March-April 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OTS 798.4900 (Prenatal Developmental Toxicity Study)

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-isopropoxyethanol

EC Number:

203-685-6

EC Name:

2-isopropoxyethanol

Cas Number:

109-59-1

Molecular formula:

C5H12O2

IUPAC Name:

Propan-2-ol

Test material form:

liquid

Details on test material:

- Lot number: 96 00054592
- Drum labels: T00029 and T00030

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Raleigh, NV, USA.
- Age at study initiation: Males 10 weeks, females 8 weeks (10 on GD0)
- Weight at study initiation: females 217-299 on GD0
- Fasting period before study:
- Housing: single housing during pregnancy period in plastic shoebox cages except during inhalation period
- Diet (ad libitum except during exposure): NIH-7, ex Zeigler brother Inc, Gardners, PA, USA
- Water (ad libitum including during exposure): deionised water
- Acclimation period: 14 day quarantine

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18.3 - 21.2 across all chambers. Average 19.8
- Humidity (%): 35 - 64 across all chambers. Average 48.
- Photoperiod (hrs dark / hrs light):12/12

IN-LIFE DATES: From: To: 10th March to 17th April 1997

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: 1 m3 stainless steel and glass chambers
- Method of holding animals in test chamber: none
- System of generating vapour: liquid EGiPE was vapourised into air carrier gas in a J-tube and then further diluting and mixing it into the incoming chamber airflow. A liquid metering pump was used to meterthe substance from a stainless steel reservoir into a J-shaped stainless steel tube filled with 6 mm glass beads. The tube was warmed to between
125-164°C to aid vaporisation. The system controlled the exposure concentration via a feedback loop.
- Temperature, humidity, pressure in air chamber: - Temperature (°C): 18.3 - 21.2 across all chambers. Average 19.8. - Humidity (%): 35 - 64 across all chambers. Average 48.
- Air change rate: 12-15 ACH

TEST ATMOSPHERE
- Brief description of analytical method used: Gas Chromatograph equipped with a flame ionization detector and a Gas Sampling Valve was used to monitor the exposure chamber concentration and room air.
- Samples taken from breathing zone: No: Concentrations were measured at the center of each chamber during the exposure, The chamber concentration of the test substance was analyzed one to two times per hour in each chamber during each daily exposure period. Prior to the start of the range-finding study, each chamber had been checked and confirmed for uniformity of distribution of test compound by measuring the concentration at nine positions.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Gas Chromatograph validated for the substance and equipped with a flame ionization detector and a Gas Sampling Valve, measured once or twice per hour during exposure periods. A sample of the atmosphere from each chamber was continuously pulled through the sample probe. A stream selector valve was used to conduct the atmosphere from the sample lines one at a time, into the sample loop of the GC.

Details on mating procedure:

- Impregnation procedure: Cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: Each morning following start of cohabitation period and each morning thereafterfemales were examined for the presence of vaginal sperm and/or vaginal or dropped copulation. Sperm-negative females were retained in the same male's cage and checked for sperm on successive mornings until insemination occurred.This process was continued until sufficient pregnant femailes were available (excess animals used).
- Proof of pregnancy: sperm in vaginal smear referred to as GD0

Duration of treatment / exposure:

6 hours per day for 10 consecutive days from GD6 to GD15

Frequency of treatment:

Daily

Duration of test:

10 days exposure

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

99.5 ppm (analytical)

Remarks:

nominal 100

Doses / concentrations 2

Dose / conc.:

299.8 ppm (analytical)

Remarks:

nominal 300

Doses / concentrations 3

Dose / conc.:

599.5 ppm (analytical)

Remarks:

nominal 600

No. of animals per sex per dose:

25

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale: Based on a dose range finder using the same exposures where 600 and 300 ppm resulted in demonstrable maternal toxicity and possible (not statistically significant) developmental toxicity, and I00 ppm resulted in minimal maternal toxicity and no developmental toxicity. The highest exposure concentration level, 600 ppm, was therefore chosen to induce overt maternal toxicity and the lowest no developmental effects.
- Rationale for animal assignment (if not random): stratified randomisation method to provide uniform mean body weights across dose groups.

Examinations

Maternal examinations:

CLINICAL OBSERVATIONS: Yes
- Time schedule: During exposure period: twice, immediately before and after exposures. Once per day at other times.

BODY WEIGHT: Yes / No / No data
- Time schedule for examinations:DG 0, 6, 9, 12, 15, 18, 20 (day of sacrifice)

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
- Food consumption for each animal determined and mean diet consumption calculated as g food/kg body weight/day: Yes, over periods GD 0-6, 6-9, 9-12, 12-15, 15-18, 18-20.

POST-MORTEM EXAMINATIONS: Yes / No / No data
- Sacrifice on gestation day # 20
- Organs examined: liver, spleen, thymus and uterus

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
- Other: Number of live/dead fetuses.

Blood sampling:

- Plasma: No
- Serum: No

Fetal examinations:

- External examinations: Yes, all
- Soft tissue examinations: Yes, half per litter
- Skeletal examinations: Yes, half per litter
- Head examinations: Yes, half per litter
- Anogenital distance of all live rodent pups: not specified
- All fetuses were confirmed for sex.

Statistics:

The unit of comparison was the pregnant female or the litter. Quantitative continuous data were compared among the three treatment groups against the one air only control group by the use of Bartlett's test for homogeneity of variances. If Bartlett's test indicated lack of homogeneity of variances, then nonparametric statistical tests were employed for the continuous variables. If Bartlett's test indicated homogeneous variances (i.e., p>0.001) , then parametric statistical tests were employed for the continuous variables.

Historical control data:

Data available and include with main report.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

300 and 600ppm: Blood in bedding, on tail and fur after exposures on gd 6 and 7 with a concentration-related incidence, and more severe on gd 6. General clinical observations (not assigned to specific dams) also indicated blood in catch pans (under the cages in the cage racks in the inhalation chamber and immediately after exposure) over a 4 day period which corresponded to the first through the last gd 6 and possibly through gd 9 (last date corresponds to gd 9 for dams with the earliest gd 6 date). Rust-colored fur on head and neck (probably from chromodacryorrhea from the Harderian glands behind the eyes groomed onto the head and/or neck) was observed gd 7-1 2,. Piloerection was observed at 600 pprn on gd 7-1 3 and 16 (1 -14 dams) and at 300 ppm on gd 9-13, and 15 (1-4 dams).

Rust-colored fur was also observed on the neck of control animals gd 9 and 13.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Clinical weight loss (>5.0 g within a weigh period) was observed in ten dams at 600 ppm, three dams at 300 ppm, and one dam at 100 ppm on gd 9 (for interval gd 6-9), and in one control dam on gd 12 (for interval gd 9-12). Based on means, the difference was greatest GD 6-9 (~ -7% at 600ppm) It was only statistically significant GD 6-15 @ 600ppm and only GD6-9 @ 300ppm.) GD6-9 there was a clear dose response.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

When the data were expressed as glkglday, maternal feed consumption at 600 ppm was reduced for gd 6-9 and 6-15. GD 6-9 was most marked at -34%. At 300 ppm, feed consumption as glkglday was significantly reduced only for gd 6-9 and significantly increased for gd 12-15. At 100 ppm, maternal feed consumption as glkglday was significantly reduced only for gd 6-9. Over the whole exposure period, there was no significant reduction.

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Maternal spleen weights, absolute and relative to terminal body weight, were significantly increased at 600 pprn. (30% increase in relative spleen weight). Maternal absolute thymus weight was significantly reduced at 300 pprn but not at 600 ppm, and maternal relative thymus weight was unchanged across groups. This was not regarded as treatment related.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

one dam at 300 pprn exhibited pale kidney but this was not seen in any other dose group.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

effects observed, treatment-related

Description (incidence and severity):

Whilst the absolute number of adversely affected implants per litter was not statistically significantly elevated, in the top dose this was statistically significantly increased from 3.8%in controls to 7.6% in the top dose group.

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

no effects observed

Changes in number of pregnant:

no effects observed

Other effects:

no effects observed

Description (incidence and severity):

Corpora lutea per dam

Effect levels (maternal animals)

1

Dose descriptor:

NOAEC

Effect level:

300 ppm (analytical)

Based on:

test mat.

Basis for effect level:

pre and post implantation loss

2

Dose descriptor:

NOAEC

Effect level:

100 ppm (analytical)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

clinical signs

food consumption and compound intake

Maternal abnormalities

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

no effects observed

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Anogenital distance of all rodent fetuses:

not examined

Changes in postnatal survival:

not examined

External malformations:

effects observed, non-treatment-related

Description (incidence and severity):

One fetus at 600 ppm exhibited cleft palate. One fetus at 300 ppm exhibited three external malformations: cleft palate, anasarca (whole body edema) and
micromelia (short limbs). One fetus at 100 ppm exhibited short, thread-like tail. Fetal external variations were limited to one fetus at 0 pprn (dam no. 80, fetus no. 11, female) with a hematoma on the neck.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Only one fetal skeletal malformation was observed; one fetus at 300 ppm, the same fetus with multiple external malformations, exhibited cartilage of sternum split (a finding present in the historical control dataset). Fetal skeletal variations included misaligned sternebrae and changes in cartilage and bone in the thoracic centra, and predominantly extra rib (full or rudimentary) on Lumbar I, and short rib). These are common fetal findings and were distributed across all dose groups examined.

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Fetal visceral malformations were almost exclusively limited to hydronephrosis and hydroureter distributed across all groups. This is a very common finding in term rodent fetuses. One fetus from the control group exhibited kidneys fused with one ureter. Fetal visceral variations were distributed across all groups with no treatment- or exposure-related pattern; they included predominantly enlarged lateral ventricles of the cerebrum, and distended ureters, both common findings in term fetuses

Effect levels (fetuses)

Dose descriptor:

NOAEC

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Fetal abnormalities

Abnormalities:

no effects observed

Overall developmental toxicity

Developmental effects observed:

no

Any other information on results incl. tables

Developmental toxicity was seen at 600 ppm but only as a small but significant increase in adversely affected implants per litter. However, there were no significant increases in any other developmental parameters. There was no evidence of treatment-related teratogenicity at any exposure concentration evaluated. There were no significant embryolfetal effects observed at 300 or I00 ppm. All of the fetal malformation and variation findings in this study were those commonly observed in historical control C rat fetuses in the performing laboratory.

Applicant's summary and conclusion

Executive summary:

Groups of 25 pregnant female SD rats were exposed in a guideline developmental toxicity study by inhalation to vapour concentrations of 100, 300 and 600ppm of ethylene glycol isopropyl ether (EGiPE) 6hrs/day over the period GD6 -15. Animals were sacrificed on GD20 for a detailed examination of the parent animals and pups.

Pregnancy rates were high and approximately equivalent across all groups. No dams died, aborted, delivered early, or were removed from study. Maternal body weights were significantly reduced at 600 ppm (whole exposure period) and at 300 pprn on gd 9; maternal weight change was significantly reduced at 300 and 600 pprn for gd 6-9 and at 600 pprn for the whole exposure period. Maternal spleen weights, absolute and relative, were significantly increased at 600 ppm. Maternal feed consumption in was significantly reduced in g/kgbw/day at 600 pprn during the exposure period. Treatment-related clinical observations at 300 and 600 pprn included blood in urine early in the exposure period (gd 6-7) and piloerection at 600 ppm. There were no treatment-related effects on gestational parameters, iother than a slightly adversely affected implants per litter (which encompassed resorptions, dead fetuses, and malformed fetuses) was significantly increased at 600 pprn in the absence of any increased incidences of the component parameters. There were no treatment-related statistically or biologically significant changes in the incidence of external, visceral, skeletal, or total fetal malformations or variations.

In conclusion, EGiPE administered by inhalation of the vapor during major organogenesis in CD rats resulted in maternal toxicity at 300 and 600 ppm, and developmental toxicity at 600 ppm. There was no evidence for teratogenicity at any concentration tested. The NOAEL for maternal toxicity was at or about 100 pprn and for developmental toxicity was 300 ppm