Trichloroethylene

Toxicity to reproduction

Administrative data

Endpoint:

two-generation reproductive toxicity

Remarks:

based on test type (migrated information)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-guideline (NTP protocol) study (GLP status not known), some restrictions, adequate for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1986

Report date:

1986

Materials and methods

Principles of method if other than guideline:

NTP protocol Reproductive Assessment by Continuous Breeding. This system involves four successive tasks. Task 1 is a preliminary 14 day toxicity study, conducted so that appropriate dose levels for the subsequent tasks can be selected. Task 2, the continuous breeding phase, involves a 14 week cohabiting phase during which reproductive performance is monitored. In Task 3, an optional "cross-over" mating trial is conducted; control males are mated with high dose females and high dose males are mated with control females. This is to determine whether any adverse effect seen in Task 2 is mediated through males of females. In Task 4 the reproductive performance of the F1 offspring taken from the Task 2 final litters is assessed. The test substance is administered continuously through Tasks 2, 3 and 4 (except during the Task 3 mating phase).
As an additional task, the open field behaviour of the F1 generation was evaluated at 21 and 45 days of age.

GLP compliance:

not specified

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 (Hi-Tri Purity grade) was obtained by Midwest Research Institute (MRI) as a neat compound from Missouri Solvents (Lot. No. TB-08039AA; MRI Batch No. 04) and in an encapsulated form from Southwest Research Institute (MRI Lot No. S-053084; Batch No. 07). Chemical analysis, dosage formulations and stability analysis were performed by Radian and MRI.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

CDF (COBS(F344)/CrlBr) inbred albino rats were obtained from the Charles River Breeding Laboraties, Inc., Kingston, NY, and were quarantined and examined upon arrival.

Administration / exposure

Route of administration:

oral: feed

Vehicle:

other: microencapsulated in a gelatin/sorbitol shell

Details on exposure:

Data from a two week dose-range-finding study (Task 1) were used to set exposure concentrations for the Task 2 continuous cohabitation study.
Trichloroethylene was microencapsulated in a gelatin/sorbitol shell and administered by incorporation in the diet.

Details on mating procedure:

Task 2: the continuous breeding phase consisted of a 7 days premating exposure, following by a 98 days cohabitation period and a 28 days segregation period.
Task 4: at 81 +/- 10 days of age, a male and a female F1 animal from different litters within the same treatment group were cohabited for 7 days.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analysis of the feed formulations used for the dose-range finding study indicated that these ranged from 96% to 111% of the desired TCE concentrations.
Analysis of the task 2 feed formulatons at 6 weeks intervals indicated that during the course of task 2, there was some variability in the actual concentration of TCE in the feed. For task 2, week 1 samples, the 0.15%, 0.30% and 0.60% formulations assayed at 33%, 66% and 87% of the theoretical concentratrion of TCE. Similarly, during week 6 of task 2, the 0.15%, 0.30% and 0.60% TCE formulation assayed at 27%, 71% and 82% of the theoretical concenctration, respectively. Samples of formulation from each of the dose levels administered during week 12 ad 18 of task 2 assayed at 101-114% of the theorectical concentration.

Duration of treatment / exposure:

administration is continuously through Tasks 2, 3 and 4 (except during the Task 3 mating phase)

Frequency of treatment:

continuously via feed

Details on study schedule:

The protocol consisted of 4 tasks.

Task 1 was a 14-day range-finding study to aid in the selection of dose levels for Task 2 (continuous breeding). 8 males and 8 females (8 weeks of age) per dose group were given TCE (nominal concentrations 0.0, 0.60, 1.20, 2.40, 3.61 and 4.82%) in their feed for 14 days.

Based on the acute toxicity results from Task 1, dietary levels of 0.0, 0.15, 0.30 and 0.60% TCE were selected for the continuous breeding phase (Task 2). The continuous breeding phase consisted of a 7-d premating exposure, following by a 98-d cohabitation period and a 28-d segregation period.

Task 3 utilized the control and high dose parental rats (0.60%) from task 2 in a crossover breeding design in order to determine the affected sex. The following 4 pairs were distinguished (male/female): Control/Control; Control/0.60% TCE; 0.60% TCE/Control; 0.60% TCE/0.60% TCE. Cohabitation for 7 days followed by separation to allow the female to deliver her litter.

Task 4 evaluated fertility and reproductive performance in the F1 offspring from the final Task 2 litters of the control group and all three dose groups.

As an additional task, the open field behaviour of the F1 generation was evaluated at 21 and 45 days of age.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0.15%, 0.30% and 0.60%
Basis:
nominal in diet

Doses / concentrations 2

Remarks:

Doses / Concentrations:
75, 150 and 300 mg/kg bw/day
Basis:
nominal in diet

No. of animals per sex per dose:

Task 1: 8/sex/dose
Task 2: 20 pairs/dose
Task 4: 20 male and 20 female F1 generation offspring from the control and high dose groups

Control animals:

yes

Details on study design:

Selected F1 offspring were evaluated for open field behavior at 21 and 45 days of age, prior to the conduct of task 4.

Examinations

Parental animals: Observations and examinations:

In the F0 and F1 males the following parameters were evaluated:
-liver weight
-kidneys/adrenals weight
-left testis/epididymis weight
-right testis weight
-right epididymis weight
-number of cauda epididymal sperm per mg cauda tissue
-sperm motility and morphology.

The prostate, seminal vesicles/coagulating glands, a portion of the median lobe of the liver, kidneys/adrenals, and the remaining carcass (with top of cranium removed) were preserved in neutral-buffered 10% formalin. The left testis/epididymis and testis were fixed for 24 h in Bouin's solution and then transferred to 70% ethanol, the right epididymis (cauda) was used for sperm analysis.

In the F0 and F1 females the following parameters were evaluated:
-liver weight
-kidneys/adrenals weight.

The ovaries and oviducts were removed and preserved for 24 hours in Bouin's solution and then transferred to 70% ethanol. The uterus and the upper half of vagina were excised and preserved in 10% formalin. A portion of the median lobe of the liver, the kidneys with attached adrenals and the carcass (with top of cranium removed) also were preserved in 10% formalin. Histopathological evaluation of the preserved excised tissues was performed for the control group and the highest dose group evaluated for the F0 males and females, and the control/low/mid and high dose groups for the F1 males/females.

Oestrous cyclicity (parental animals):

In the F0 and F1 females the following parameters were evaluated:
the ovaries and oviducts were removed and preserved for 24 hours in Bouin's solution and then transferred to 70% ethanol. The uterus and the upper half of vagina were excised and preserved in 10% formalin.

Sperm parameters (parental animals):

In the F0 and F1 males the following parameters were evaluated:
-left testis/epididymis weight
-right testis weight
-right epididymis weight
-number of cauda epididymal sperm per mg cauda tissue
-sperm motility and morphology.

The prostate and seminal vesicles/coagulating glands were preserved in neutral-buffered 10% formalin. The left testis/epididymis and testis were fixed for 24 h in Bouin's solution and then transferred to 70% ethanol, the right epididymis (cauda) was used for sperm analysis.

Litter observations:

litter size, proportion of live pups, litter weight and sex ratio of the pups

Postmortem examinations (parental animals):

See above

Postmortem examinations (offspring):

See above

Statistics:

not specified in the available report

Reproductive indices:

Reproductive performance was monitored by counting the number of F1 generation litters produced by each breeding pair and recording on the day of birth the litter size, proportion of live pups, litter weight and sex ratio of the pups.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

not specified

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not specified

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

effects observed, treatment-related

Details on results (P0)

No clinical signs of toxicity were observed at any dose level of TCE during Task 2. Continuous exposure of F344 rats (11 weeks of age at outset) up to 0.60% in the feed had no effect on the proportion of breeding pairs able to produce at least one litter. All treated F0 generation animals were fertile. However, there was a slight, but statistically significant, reduction in the number of litters produced by high dose F0 pairs (mean 2.90 ± SD 0.22 compared with 3.49 ± 0.15 for control) and a decrease in the litter size in the middle and high dose groups (9.39 ± 0.35 and 8.66 ± 0.64, respectively compared with 10.36 ± 0.36 for the control).
During the crossover mating trial (Task 3), the proportion of detected matings was significantly depressed in the mating pairs with treated partners compared to the control pairs. However, the fertility and reproductive performance of breeding pairs containing one TCE-treated partner was not different form control breeding pairs. Specifically, TCE exposure of either the male or the female partner had no significant effect on the number of pairs able to produce a live litter, the number of live pups per litter, the proportion of pups born alive, the sex of pups born alive, absolute live pup weight, or adjusted live pup weight.
The postpartum weight of 0.60% TCE-treated dams was significantly reduced compared to control dams.

F0 male and female rats used in the mating trials were weighed and necropsied at the completion of Task 3. There was some evidence of generalised toxicity in the F0 generation, observed as a slight reduction in bodyweight gain for both males and females at all treatment levels, although for males a clear dose-response relationship was not apparent. Mean absolute body weight of the males exposed to 0.60% TCE was significantly depressed compared to control males. Absolute liver and kidney/adrenal weight were significantly elevated for the TCE-treated males compared to controls. This pattern held true when male organ weights were adjusted for body weight at necropsy. In addition, combined left testes/epididymis mean weight was increased (by about 3%) in the high dose group. However, sperm assessment indicated no significant effect of TCE treatment on sperm motility, concentration or morphology. Furthermore, no treatment related histopathological effects were observed in the male reproductive organs. For female rats, mean absolute body weight in the 0.60% TCE-treated group was significantly depressed compared to the control group. Mean absolute liver and kidney/adrenal weight were unaffected by treatment. When female organ weights were adjusted for body weight at necropsy, both liver and kidney/adrenal weight in the treated group were significantly elevated compared to the combined control group.

No significant treatment-related gross or histological lesions were noted in any tissues examined microscopically from male or female rate exposed to 0.60% TCE in the feed, compared to vehicle-treated control rats. Evaluation of the vaginal mocusa indicated there were no consistent treatment-related changes in vaginal cyclicity. Histopathological changes observed but not associated with treatment included bile duct proliferation in the hepatic portal regions of both male and female rats, minimal to slight focal hepatocellular necrosis in male rats, and focal accumulations of macrophages in the hepatic parenchyma of female rats. Tubular regeneration and tubular casts were observed in the kidneys of rats of both sexes.

Effect levels (P0)

1

Key result

Dose descriptor:

LOAEL

Remarks:

parental toxicity

Effect level:

75 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: reduced body weight gain, increased relative liver weight, depressed postpartum dam weights

Remarks on result:

other: Generation: P and F1 (migrated information)

2

Key result

Dose descriptor:

NOAEL

Remarks:

effects on fertility

Effect level:

75 mg/kg bw/day

Sex:

male/female

Basis for effect level:

other: reductions in the number of litters born to continuously bred animals at 300 mg/kg/day and in the litter size at 150 and 300 mg/kg/day, dose levels at which other toxic effects were elicited

Remarks on result:

other: Generation: P and F1 (migrated information)

Results: P1 (second parental generation)

Effect levels (P1)

Key result

Dose descriptor:

NOAEC

Effect level:

75 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

other: reduced liter size at 150 and 300 mg/kg

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

no effects observed

Histopathological findings:

no effects observed

Details on results (F1)

In order to assess the reproductive and behavioral effects of TCE on the F1 generation, an open field behavioral assessment and Task 4 were conducted. In the present study, final task 2 litters from the 0.0, 0.15, 0.30 and 0.60% TCE groups were raised to sexual maturity. For the treated groups, there were only 6-8 litters per group available for rearing, due to the reduction in the number of pairs producing final live litters. Birth weights for male and female rats in the TCE groups were not significantly different from the control group. On day 4 and 14 however, male and female pup weights in the 0.60% TCE group were significantly depressed compared to the controls. At weaning, pup weights for both males and females in each TCE-treated group were significantly depressed compared to controls. Continuous exposure of F1 rats to TCE in the feed via their mother and from birth to 21 days of age did not appear to affect perinatal survival. A tendency towards decreased survival for day 21-81 was observed for F1 pups exposed to 0.15 and 0.60% TCE.

On day 21, 10 F1 litters from the 0% TCE group and the surviving F1 litters in the 0.15, 0.30 and 0.60% TCE group were selected for weaning and rearing to sexual maturity. At 21 days of age, 6 animals were randomly selected from each litter for behavioral assessment by open field activity. Equal representation of males and females within each litter was obtained whenever possible. On the afternoon of day 21, the pups were brought to the behavioral testing room with their dams in their home cages, and habitated to the testing environment for at least 30 minutes. The pups were then tested individually in the open field. The open field test consisted of a three-minute trial period during which the following measures were recorded: 1) latency to traverse the first grid; 2) total number of traverses, 3) rearing, 4) grooming, and 5) defecation and urination. Continuous exposure to TCE upto 0.60% in the feed via the mother (in utero) and throughout lactation to day 21 resulted in a significant dose-related trend toward an increase in the time required for males and females (sexes combined) to traverse the first grid, but had no significant effect on any other measure open field evaluation. No effect of treatment was noted for locomotor activity or miscellaneous behavior when the animals were retested at 45 days of age. Therefore, TCE appeared to have only a slight effect on the ability of 21 day old F1 offspring to react to a novel environment, which was not evident at 45 days of age.

After the behavioral evaluation, all F1 offspring were separated from their mothers. F1 offspring were housed by sex in groups of two or three rats and maintained on the same feed level of TCE as their Task 2 parents. At 81 +/- 10 days of age, a male and female from different litters within the same treatment group were cohabited for 7 days. The pairs were then separated and the females allowed to deliver their litters. Continuous exposure to the F1 rats to TCE in the feed via their mothers and from birth to 81 +/- 10 days of age had no significant effect on indices of mating or fertility or any measure of reproductive performance including live litter size, proportion of pups born alive, sex of pups born alive, or absolute or adjusted live pup weight. The postpartum weights of the F1 dams were significantly decreased compared to controls in all TCE treatment groups.

A reduction in bodyweight gain, which followed a clear dose-related pattern, was seen in the retained F1 generation animals of both sexes at all treatment levels. The F1 rats were necropsied 4 weeks after the 7-day cohabitation period. Mean male body weight and absolute right testis weight were significantly depressed in the treated groups compared to controls. Combined mean kidney/-adrenal weight for 0.15% TCE-treated males was significantly decreased, left testis/epididymis weight was significantly depressed in the 0.60% group, and prostate weight was significantly depressed in the 0.30% group. There were no significant differences between control and TCE-treated males for mean absolute liver, right epididymis, or seminal vesicle weight. When F1 male organ weights were adjusted for body weight at necropsy, increased bodyweight-related liver weight in males at all treatment levels (by 16% at the highest dose) and in females in the middle and high dose groups (by about 10% at the highest dose) and seminal weight was elevated in the 0.30% TCE group compared to controls. There were no other significant differences among the control and treatment groups for any other mean adjusted organ weight.

Sperm assessment for the F1 males indicated that continuous exposure to TCE in the feed via their mothers and throughout lactation and weaning to day 81 +/- 10 resulted in a significant increase in the percent abnormal sperm in the 0.30% TCE group, but no other adverse effects on sperm motility, concentration, or sperm morphology. F1 female body weights at necropsy were significantly depressed below controls in all TCE treatments groups. Mean absolute liver weight was unaffected by TCE treatment, and combined kidney/adrenal weights were significantly depressed below control only in the 0.15% TCE group. When F1 female organ weight were adjusted for body weight at necropsy, adjusted mean liver weight was significantly elevated over controls in the 0.30% and 0.60% TCE groups, but adjusted kidney/adrenal weight was not significantly affected by TCE treatment.

Histopathological examination of tissues from F1 male and female rats revealed no treatment-related lesions in any of the tissues of either sex. Microscopic changes in the kidney that were noted but not considered to be treatment-related were similar to those observed in the F0 rats, and included evidence of chronic progressive nephropathy. In addition, prostatitis was observed in a few male rats in each treatment group.

Effect levels (F1)

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

75 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Litter size decreases at 150 and 300 mg/kg

Overall reproductive toxicity

Reproductive effects observed:

not specified