Registration Dossier

Toxicological information

Developmental toxicity / teratogenicity

Currently viewing:

Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
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

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
2001
Report date:
2001
Reference Type:
publication
Title:
Unnamed
Year:
2006

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)
Qualifier:
according to guideline
Guideline:
other: Directive 87/302/EEC: Teratogenicity Test – Rodent and Non-Rodent Species
Qualifier:
according to guideline
Guideline:
other: s Japan MAFF Toxicity Testing Guidelines for Teratogenicity Studies
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Trichloroethylene
EC Number:
201-167-4
EC Name:
Trichloroethylene
Cas Number:
79-01-6
Molecular formula:
C2HCl3
IUPAC Name:
1,1,2-trichloroethene
Constituent 2
Reference substance name:
Trichloroethene
IUPAC Name:
Trichloroethene
Details on test material:
Trichloroethylene was obtained from the Dow Chemical Company (Freeport, TX). A purity of 99.0 +/- 0.05% was established via an area gas chromatographic procedure. Infrared spectroscopy, mass spectroscopy, and nuclear magnetic resonance spectroscopy confirmed the structure and chemical identity.

Test animals

Species:
rat
Strain:
Crj: CD(SD)
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories
- Housing: mated females were housed singly in stainless-steel wire mesh cages
- Diet: ad libitum
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 40-60
- Air changes (per hr): 12-15
- 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:
Animals were exposed in 2-cubic-meter stainless steel and glass Rochester-style exposure chambers under dynamic airflow conditions. Chamber airflow was maintained at approximately 450 liters per minute (L/min), which was sufficient to provide 12-15 air changes per hour and thus maintain normal concentrations of oxygen. The various concentrations of TCE were generated using a glass J-tube method (Miller et al., 1980). Compressed air and TCE vapors were diluted and mixed with room air.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The concentrations TCE were measured twice per hour with a Miran 1A infrared spectrometer (Foxboro/Wilks, South Norwalk, CT) at a wavelength of 11.85 micrometer. A PC-based data acquisition and control system was used (CAMILE TG, Camile products, LLD, Indianapolis, IN) to calculate and store the TCE chamber concentrations.
Details on mating procedure:
Virgin female rats were mated overnight at the supplier with male rats (one female to one male). The day on which evidence of positive copulation was established was documented as GD 0.
Duration of treatment / exposure:
day 6-20 of gestation
Frequency of treatment:
6 hours/day, 7 days/week
Duration of test:
21 days
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
50, 150 and 600 ppm
Basis:
other: target concentrations
Remarks:
Doses / Concentrations:
49.9 +/- 1.4, 150 +/- 4.1, and 600 +/- 10.0 ppm
Basis:
analytical conc.
No. of animals per sex per dose:
27
Control animals:
yes

Examinations

Maternal examinations:
Maternal necropsies were performed on GD 21. Dams were evaluated for clinical signs, body weight and feed consumption. Liver and kidney weights were measured.
Ovaries and uterine content:
On the scheduled day of euthanasia each surviving female underwent a gross necropsy where gravid uterine weights were recorded, along with the number of corpora lutea, uterine implantations, resorptions, and live/dead fetuses.
Fetal examinations:
All fetuses were weighed, sexed, and examined for external alterations. Fetuses were examined under blind conditions. Approximately one half of the fetuses were examined for visceral alterations, which were done using the fresh in situ examination ("Staple's") technique (Staples, 1974; Stuckhardt and Poppe, 1984). The study also employed free-hand sectioning of the fetal head as part of the visceral examination. Skeletal examinations were conducted on the remaining fetuses in each litter following staining with Alizarin Red Sand Alcian Blue for identification of bone and cartilage, respectively (McLeod, 1980; Kimmel and Trammel, 1981; Webb and Byrd, 1994).
Statistics:
The litter was used as the statistical unit for analysis for litter/fetal data. Continuous data were tested in both studies for homogeneity of variance using Bartlett's test at alpha = 0.01 (Bartlett, 1937). In this study, the raw data were tested. Based on the results of Bartlett'stest, data were analyzed using either parametric or nonparametric tests. Analysis of variance was used, followed by a Dunnett's test (Winer, 1971), or followed by a Bonferroni corrected Wilcoxon Rank Sum test (Miller, 1966). For the TCE study, frequency of pre-implantation loss, resorptions per litter, resorptions per fetal population, and fetal variations and malformations were analyzed using a censored Wilcoxon test with Bonferroni's correction. In addition, pregnancy rates were analyzed using the Fisher's exact probability test (Siegel, 1956) with Bonferroni's correction. Fetal sex ratios were analyzed using a binomial distribution test (Steel and Torrie, 1960).

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
All rats survived to scheduled maternal necropsy, no clinical observations were noted that could be attributed to treatment.

No statistically significant differences in mean body weight or feed consumption were noted between the treated groups and the control. At 600 ppm, mean body weight gain was reduced by 22% during the first 3 days of dosing (GD 6-9) and found to be statistically significant. No other significant body weight changes were noted at 600 ppm, or the remaining dose levels (50 and 150 ppm) of TCE. No statistically identified differences in feed consumption were found for any TCE treatment group, as compared to the control. Anatomic pathology revealed slightly increased relative kidney weight (~6% increase at 0.521 and 0.525 g/100, respectively) at 50 and 600 ppm TCE, which was statistically identified; however, these changes were not considered treatment related as they were within the historical control range (0.458-0.530 g/100) and lacked a dose-response relationship. A slight (~6%) increase in relative liver weight at 600 ppm. TCE was statistically identified, with the value just barely outside the historical control range (3.455-3.872g/100). As liver weights at the low dose were higher than at the middle dose, the degree of change at the high dose was small, and in consideration of previous toxicity data, this change was most likely spurious.

At necropsy no gross maternal observations were noted in any of the TCE treatment groups. No significant differences were observed for pregnancy rates, number of corpora lutea, implantations, viable fetuses per litter, percent pre- and post-implantation loss, resorption rates, fetal sex ratios, or gravid uterine weights in rats exposed to any dose level of TCE. An increase in mean male fetal body weight at 150 ppm was noted and statistically identified, but this was not considered test article related, as no such effect was observed at the high-dose level (600 ppm) of TCE.

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEC
Effect level:
150 ppm
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEC
Effect level:
600 ppm
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
There were no statistically identified differences in the incidence of fetal malformations or variations in any of the TCE treatment groups, as compared to the control. One control fetus showed multiple cardiac malformations, consisting of a right-sided arotic arch, along with missing carotid and subclavian arteries. No fetal malformations were identified at 50 ppm. At 150 ppm, there was one fetus with dilated cerebral ventricles, without atrophy of brain tissue. At 600 ppm, one fetus was identified with cutis laxa (a condition of redundant, loosely adherent skin; also called cutis laxis) and another fetus was identified with unilateral anophthalmia. As these alterations occurred in single fetuses, without a clearly defined dose-response relationship, they were not considered toxicologically meaningful.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion