Acetic anhydride

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: scientifically acceptable, assessed by OECD SIDS

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1994

Report date:

1994

Materials and methods

Principles of method if other than guideline:

This report describes a preliminary study performed to determine appropriate exposure concentrations of the chemical, acetic anhydride, for a subsequent OECD screen, whereby assessment would be made of toxicity to pregnant females. The test substance was administered by the inhalation route, 6 hours per day for days 6 to 15 post coitum for time-mated females at concentrations of 0(Control), 25, 100 and 400 ppm. Five female rats per group were exposed to the vapor of acetic anhydride using whole-body inhalation exposure chambers. Time-mated female rats were exposed on 10 consecutive days, although restricted to only seven occasions for adverse effect of exposure at 100 ppm, due to treatment-related findings. Clinical signs during exposure were recorded as a group response where all visible animals appeared to be responding similarly. For reporting purposes, "day" in relation to clinical signs refers to the day of pregnancy/post coitum for females. Animals were examined at least twice each day and any signs were recorded on the individual sheets. Any animals found dead or dying were examined macroscopically on the day of death and a full spectrum of tissues preserved for further examination. On day 20 of pregnancy, group 1 and 2 animals were killed by CO2 asphyxiation, dissected and examined for congenital abnormalities and macroscopic pathological changes in maternal organs. The ovaries and uteri were examined immediately to determine: the number of corpora lutea, the number and distribution of live young, the number and distribution of embryofetal deaths, the individual and fetal weight from which the litter weight was calculated and fetal abnormalities. Embryofetal deaths were classified as a. early: only placenta visible at termination b. late: both placental and embryonic remnants visible at termination. Uteri without visible implantations were examined for evidence of implantation using a modified Salewski technique. Live young were examined externally, and then discarded. Dams sacrificed on day 13 post coitum (dosage groups 100 and 400 ppm) were examined in a similar manner although embryos were not examined or weighed because they were too immature.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Acetic anhydride

EC Number:

203-564-8

EC Name:

Acetic anhydride

Cas Number:

108-24-7

Molecular formula:

C4H6O3

IUPAC Name:

acetyl acetate

Details on test material:

- Name of test material (as cited in study report): Acetic anhydride
- Physical state: clear, colourless, mobile liquid
- Analytical purity: 99.05%
- Stability under test conditions: adequate for the study
- Storage condition of test material: dry at 4 °C

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK)
- Age at study initiation: 9-11 weeks
- Group mean weight at study initiation: 213 g
- Housing: 5 per sex per cage
- Diet (e.g. ad libitum): SDS Laboratory Animal Diet No. 1
- Water (e.g. ad libitum): tap water


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-24
- Humidity (%): 40-70
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: stainless steel and glass chambers, approximately 0.75 m3 in volume
- The test substance was metered from a polypropylene syringe mounted on an infusion pump to a glass sinter, contained in a glass vessel through which air was passed. Each chamber air supply was pre-warmed by passage through a copper coil immersed in a water bath maintained at 60°C prior to entering the glass vessel. The vapor produced passed out of the vessel and into each chamber via an inlet duct. By varying the liquid feed rate to each vapor generator, it was possible to obtain the desired chamber concentrations.
- Temperature, humidity in air chamber: 22.5-23.2 °C, 23-33 %

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatograph
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on mating procedure:

- time-mated female rats aged approximately 8 to 10 weeks were obtained
- the day of arrival were allocated as Day 1 post coitum

Duration of treatment / exposure:

10 days

Frequency of treatment:

6h/day, daily

Duration of test:

10 days

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 25, 100 ppm
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 24, 103 ppm
Basis:
analytical conc.

Doses / concentrations 3

Remarks:

Doses / Concentrations:
0, 0.10, 0.44 mg/ml
Basis:
other: calculated with conversion factor, 1 ppm = 0.00424 mg/l

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Examinations

Maternal examinations:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: at least twice each day


BODY WEIGHT: Yes
- Time schedule for examinations: all female rats were weighed initially (assumed Day 1 of pregnancy) and on Days 2, 3, 6, 8, 10, 12, 14, 16, 18 and 20) post coitum


FOOD CONSUMPTION:
- Food consumption for each animal determined: Yes, food consumption was measured from weighday to weighday, up to termination.


WATER CONSUMPTION: Yes
- Time schedule for examinations: daily from Day 1 to termination


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: reproductive organs

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: Number and distribution of live young, number and distribution of embryofoetal deaths

Fetal examinations:

- Foetal abnormalities, individual foetal weight from which the litter weight was calculated.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Details on maternal toxic effects:
100 ppm: Although there were no deaths, the severity of the clinical signs and poor condition resulted in termination of this level, females having received 7 exposures. All animals, showed marked weight loss following the first exposure and, thereafter, there was further progressive weight loss for all individuals. This bodyweight loss was severe, considering that the majorities were pregnant and, as such, marked bodyweight gain is usually the norm. As a result of these bodyweight losses, the animals showed markedly lower groups mean bodyweight compared with the respective concurrent controls. After the first exposure, group mean, food and water consumption values were noticeably lower compared with the respective control groups (approximately 40 - 50% for food and 25% for water) and pre-exposure values. Thereafter, there was a further reduction, resulting in values which were approximately 80% lower compared with controls. Comparison was made with the unexposed females also killed at Day 13 post coitum. Four out of five females were pregnant in each group. Two females which received 100 ppm showed total resorption of their litters, compared to none in the concurrent control group. However, the other two pregnant females in this group were supporting live litters of comparable size with those of the unexposed concurrent control group.
25 ppm: The scheduled number of exposures was achieved. All females at this exposure level were pregnant, as were the concurrent controls. Up to Day 8 of pregnancy (after 2 exposures), group mean bodyweight for treated females was similar to the controls. Thereafter, however, to completion of the exposures, group mean bodyweight gain was depressed compared with controls. On cessation of exposure, there was a marked recovery in bodyweight gain, although not of sufficient magnitude to attain parity with the controls in terms of absolute group mean bodyweight at Day 20 of pregnancy. Group mean food and water consumption were, in general, consistently lower compared with the respective concurrent control groups, throughout the exposure periods. A return to parity with controls was seen after cessation of exposures. The extents of differences compared with controls were not comparable with those seen at the higher exposure levels. There were no treatment-related macroscopic abnormalities among females at this exposure level. Organ weights were not recorded. All females at this level had a live litter at termination (Day 20 of pregnancy). The incidence and pattern of embryofetal loss, litter size, litter weight and fetal weight were similar compared with the concurrent controls.

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Details on embryotoxic / teratogenic effects:
100 ppm: Examination of fetuses for visual abnormalities was not fully possible given the age at sacrifice.
25 ppm: fetal weight were similar compared with the concurrent controls and there were no gross fetal abnormalities.

Effect levels (fetuses)

Dose descriptor:

NOAEL

Effect level:

0.1 mg/m³ air

Basis for effect level:

other: teratogenicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

The NOEL for developmental/reproductive effects was considered to be 25 ppm. Although the study is scientifically acceptable, only limited conclusions can be drawn. The number of animals per group (5) is too small and only one group of rats received the full length treatment of 10 days.