Trichloroethylene

Developmental toxicity / teratogenicity

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

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

2006

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: Directive 87/302/EEC: Teratogenicity Test – Rodent and Non-Rodent Species

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: s Japan MAFF Toxicity Testing Guidelines for Teratogenicity Studies

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

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.

Specific details on test material used for the study:

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 / concentrations

Doses / concentrations 1

Dose / conc.:

50 ppm (nominal)

Doses / concentrations 2

Dose / conc.:

150 ppm (nominal)

Doses / concentrations 3

Dose / conc.:

600 ppm (nominal)

No. of animals per sex per dose:

27

Control animals:

yes

Details on study design:

- Dose selection rationale: maternal toxicity at highest dose,
- Rationale for animal assignment (if not random): Random assignment to groups
-

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.

Blood sampling:

Not examined

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

General toxicity (maternal animals)

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

22% decrease in body weight gain in the first 3 days of exposure at 600 ppm

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

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:

no effects observed

Description (incidence and severity):

Observed differences between groups were minor, not beyond historical control, and/or not dose responsive.

Gross pathological findings:

no effects observed

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

not examined

Details on results:

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.

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

no effects observed

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

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)

Key result

Dose descriptor:

NOAEL

Effect level:

150 ppm (nominal)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

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:

no effects observed

Changes in postnatal survival:

no effects observed

External malformations:

no effects observed

Skeletal malformations:

no effects observed

Visceral malformations:

no effects observed

Other effects:

not examined

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.

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

600 ppm (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

reduction in number of live offspring

changes in sex ratio

fetal/pup body weight changes

changes in litter size and weights

changes in postnatal survival

external malformations

skeletal malformations

visceral malformations

Fetal abnormalities

1

Abnormalities:

not specified

2

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

no

Lowest effective dose / conc.:

600 ppm (nominal)

Treatment related:

no

Applicant's summary and conclusion

Conclusions:

Maternal Toxicity was reflected in a 22% lower body weight gain see in the first 3 days of exposure to 600 ppm.
There were no signs of developmental toxicity among any treatment group.

Executive summary:

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. 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.