Ethers, C5-6-branched alkyl Me

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-compliant guideline study, no restrictions, fully adequate for assessment.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Reference 2

Reference Type:

publication

Title:

Developmental toxicity evaluation of inhaled tertiary amyl methyl ether in mice and rats

Author:

Welsch F, Elswick B, James A, Marr M, Myers C and Tyl R

Year:

2003

Bibliographic source:

Appl Toxicol 23: 387-395.

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)

Version / remarks:

Current study predates the guideline, EPA OPPTS draft testing guidelines 1995b were used.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-methoxy-2-methylbutane

EC Number:

213-611-4

EC Name:

2-methoxy-2-methylbutane

Cas Number:

994-05-8

Molecular formula:

C6H14O

IUPAC Name:

1,1-dimethylpropyl methyl ether

Details on test material:

- Name of test material (as cited in study report): TAME
- Physical state: clear liquid
- Analytical purity: 98.8-98.9%, by GC and NMR
- Purity test date: 01-05-96
- Lot/batch No.: 95-01

Test animals

Species:

mouse

Strain:

CD-1

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories
- Age at study initiation: 10-12 weeks
- Weight at study initiation: 20-35 gram
- Housing: individual
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 65-75°F
- Humidity (%): 40-70
- Airchanges/hour: 12-15
- 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:

TAME exposure concentrations were generated by metering liquid TAME from a stainless steel reservoir into a J-tube generator with an FMI pump. The FMI pump was calibrated and set to the nominal flow rate expected for the target exposure concentration. Nitrogen flowed up through the J-tube at a flow rate of approximately 20 L/min. The TAME was pumped into the upper portion of the J-tube and allowed to flow downward through glass beads, counter-current to the nitrogen flow. A heating jacket warmed the J-tube to approximately 120 to 150 oC. The heat and the increased surface area from the glass beads facilitated the vaporization of the TAME. A sight gauge at the bottom of the J-tube verified total vaporization of the TAME. The vaporized TAME was carried in the nitrogen stream from the top of the J-tube into a 'T" in the 2 inch stainless steel, HEPA-filtered air inlet to the inhalation chambers. The "T" was located approximately three feet upstream of the chamber. The TAME vapor flowed into the "T" and counter-current to the HEPA-filtered chamber air flow to facilitate mixing of the TAME vapor with dilution air. The total chamber air flow through each chamber was maintained at approximately 220 L/min.
Four H-1000 inhalation exposure chambers (Lab Products, Maywood, NJ) were used for these exposures. One H-1000 was used for each target exposure concentration (0, 250, 1500 or 3500 ppm). Each H-1000 was located inside one eight cubic meter Hinners-style stainless steel and class inhalation exposure chamber. The H-1000 is constructed of stainless steel and glass with silicon seals on the doors.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

IR analysis (MIRAN 1A) was used to confirm the exposure concentration.

Details on mating procedure:

For breeding, individual females were placed in the home cage of singly-housed males (i.e., one male and one female). On the following morning and each morning thereafter, the females were examined for the presence of vaginal sperm and/or vaginal or dropped copulation plug. The days on which sperm/plugs were found were designated as gestational day (GD) 0. Sperm/plug-positive females were individually housed until scheduled sacrifice on GD 17. Sperm/plug negative females were retained in the same male's cage and checked for sperm/plug on successive mornings until insemination occurred or the treatment groups were filled, whichever came first. When all treatment groups were filled, remaining sperm/plug-negative females were euthanized by carbon dioxide asphyxiation and discarded, or transferred to other projects, according to CIIT Standard Operating Procedures, with documentation of the fate of all animals in the study records.

Duration of treatment / exposure:

gestation days 6-16

Frequency of treatment:

daily, 6 hours/day

Duration of test:

11 days of exposure

No. of animals per sex per dose:

Twenty-five time pregnant mice per group

Control animals:

yes

Details on study design:

The target exposure concentrations were 0, 250, 1500, and 3500 ppm. The rationale for choosing these exposure concentrations was based on a range-finding study in pregnant mice which employed exposure concentrations of 0, 1000, 4000 and 7000 ppm. With a small number of dams per group, 7000 ppm resulted in excessive maternal mortality,4000 ppm resulted in demonstrable maternal toxicity (including one maternal death) and developmental toxicity, and 1000 ppm resulted in minimal maternal toxicity and no developmental toxicity. The highest exposure concentration level, 3500 ppm, was therefore chosen to induce overt maternal toxicity, but not excessive mortality.

Examinations

Maternal examinations:

Maternal body weights were measured on GD 0, 6, 9, 12, 15, and 17. The feed consumption was measured during intervals 0-6, 6-9, 9-12, 12-15 and 15-17.

Ovaries and uterine content:

Ovarian corpora lutea were counted and the number of implantation sites was recorded.

Fetal examinations:

All foetuses were dissected from the uterus, counted, weighed, sexed and examined for external abnormalities, fixed and stained. Half of the litter from each exposure group was examined for visceral malformations and variations. The other half, which did not go to visceral examination, was examined for skeletal malformations and variations.

Statistics:

Statistical analysis used either the pregnant female or the litter as the unit of comparison. Appropriate parametric- or non-parametric tests were applied to the data after initial analysis using Bartlett's test for homogeneity of variances.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Maternal toxicity
Four dams of the 3500 ppm group died. The deaths occurred on gestation days 6, 7, 8 and 9. One female at 3500 ppm died before the start of exposure. No abortions occurred. One dam of the 250 ppm group delivered early. Maternal feed consumption for GD 0-6 prior to the exposure period was unexpectedly significantly increased at 3500 ppm (as glday and g/kg/day). Maternal feed consumption in g/day was significantly reduced at 3500 ppm for GD 9-12, 12-15, 15-17, and 6-17 (exposure period). Maternal feed consumption for the gestational period, GD 0-17, was unaffected across groups. At 1500 ppm, feed consumption was significantly reduced only for GD 6-9 (g/day). When the data were expressed as g/kg/day, maternal feed consumption at 3500 ppm was reduced only for GD 9-12. At 1500 ppm, feed consumption as g/kg/day was unaffected. There were no effects of treatment on maternal feed consumption at 250 ppm. There were no effects related to treatment in gestational parameters. Maternal body weight was significantly decreased only at 3500 ppm for GD 15 and 17. Maternal weight change was significantly reduced at 3,500 ppm on GD 9-12, 12-15, 15-17, 6-17 (exposure period), and 0-17 (gestation period). The 250 and 1500 ppm dose groups had no significant changes in weight development. Treatment-related clinical observations included ataxia, prone positioning, lethargy, head tremors, eye squinted, gasping and slow respiration at 3500 ppm. Head tremors and eye(s) half closed were also seen at 1500 ppm, but only in one mouse on one gestation day (10). Maternal absolute and relative liver weights increased at 1500 and 3500 ppm. The absolute liver weight was significantly increased at 1500 ppm but not at 3500 ppm. The absolute liver weights were as follows: 0 ppm: 2.72 ± 0.06, 250 ppm: 2.81 ± 0.06, 1500 ppm: 2.96 ± 0.06* and 3500 ppm: 2.86 ± 0.06. When measured relative to the sacrificed body weight the following figures were reported: 0 ppm: 5.78 ± 0.12, 250 ppm: 5.61 ± 0.05, 1500 ppm: 6.41 ± 0.13**, 3500 ppm: 6.91 ± 0.12** (*p 0.05, **p 0.01).

Effect levels (maternal animals)

Dose descriptor:

NOAEC

Effect level:

250 ppm

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Developmental toxicity
All pregnant animals had one or more foetuses (the pregnancy rates were high and approximately equivalent across all groups (87.5-96.0%)); the numbers of litters (foetuses) examined were: 0 ppm: 23 (252), 250 ppm: 21 (258), 1500 ppm: 22 (244), 3500 ppm: 19 (193).
In the 3500 ppm group, the increase of incidence of litters late foetal deaths was significantly increased (control: 8.7%, 3500 ppm: 36.8%) and foetal weight per litter weight decreased (-40%) compared to control group.
Malformations and variations included increased incidence of cleft palate and enlarged lateral ventricles. The incidence of cleft palate at 3500 ppm was 11 foetuses in 6 litters and at 1500 ppm 3 foetuses in 3 litters. The incidence of enlarged lateral ventricles was as follows: at 0 ppm 8 foetuses/8 litters, at 250 ppm 6 foetuses/4 litters, 1500 ppm 7 foetuses/7 litters and at 3500 ppm 38 foetuses affected in 16 litters. The occurrence of other visceral and skeletal malformations and variations was comparable in control and treated groups.

Effect levels (fetuses)

Dose descriptor:

NOAEC

Effect level:

250 ppm

Basis for effect level:

other: developmental toxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified