(2H)chloroform

Toxicity to reproduction

Administrative data

Endpoint:

two-generation reproductive toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1997

Materials and methods

Principles of method if other than guideline:

Reproductive Assessment by Continuous Breeding (RACB) protocol of the US National Toxicology Program (NTP) according to Lamb (1985), J. Amer. Coll. Toxicol. 4, 163-171 and Reel et al. (1985), J. Amer. Coll. Toxicol. 4, 147-162

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Chloroform

EC Number:

200-663-8

EC Name:

Chloroform

Cas Number:

67-66-3

Molecular formula:

CHCl3

IUPAC Name:

chloroform

Test material form:

liquid

Test animals

Species:

mouse

Strain:

other: CD-1 (ICR)BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS- Source: Charles River Breeding Laboratories Inc., Kingston, New York- Age at study initiation: 11 weeks- Weight at study initiation: (P) Males: 31.96-38.92 g; Females: 23.18-29.66 g; (F1) Males: 32.68 +/- 0.52 g; Females: 26.56 +/- 0.55 g- Housing: 2 per cage by sex during quarantine and the 1-week pre-mating using solid bottom polycarbonate cages with stainless steel wire lids; animals were subsequently housed as breeding pairs or individually- Diet (e.g. ad libitum): NIH-07 diet ad libitum- Water (e.g. ad libitum): ad libitum- Acclimation period: 2 weeks of quarantine, 1 week of acclimationENVIRONMENTAL CONDITIONS- Temperature (°C): 18 to 26- Humidity (%): no data- Air changes (per hr): no data- Photoperiod (hrs dark / hrs light): 14 hours light/10 hours darkness

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

Animals were treated with 8, 20 or 50 mg/kg body weight/day by gavage. The test chemical was mixed with Mazola corn oil on a weight to volume basis. Corn oil was tested for peroxide content prior to formulation and discarded if peroxide level was greater 10 meq. Each dose level was independently formulated. The concentration of chloroform was adjusted so that all doses were administered in 10 mL/kg body weight. Dose formulations were prepared at minimum every three weeks and aliquotted at the time of formulation into vials for daily use. Aliquots were stored at approximately 4 °C until use.

Details on mating procedure:

continuous cohabitation phase (14 weeks)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

An aliquot of each formulation, the control and the bulk chemical were sent to Research Triangle Institute for reference analysis during weeks 1, 6, 10 and 14 of the F1 study. Dosage formulation studies performed by Research Triangle Institute indicated no problems with the preparation of corn oil solutions at the 40 mg/mL level. Stability studies on corn oil solutions of chloroform (5 mg/mL level) indicated no significant loss of chemical after three weeks storage in sealed glass bottles in the dark at room temperature. Analysis of dosing solutions by gas chromatography showed that the actual doses administered to the animals were closer to 6.6, 15.9 and 41.2 mg/kg body weight/day.

Duration of treatment / exposure:

Continuous for 18 weeks (1 week prior to cohabitation, 14 weeks of cohabitation 3 weeks therefater) : Treatment of F0 and F1 generations

Frequency of treatment:

daily

Details on study schedule:

At the end of the dosing phase, the last litter from all dose groups was reared by the dam until weaning. At weaning, the F0 animals were killed. The pubs from the low and middle dose groups were killed and the pubs from the control and high dose groups were reared and dosed through the mating period (at approximately postnatal day 74) until necropsy.

Doses / concentrations

Remarks:

Doses / Concentrations:0, 6.6, 15.9 and 41.2 mg/kg body weight/dayBasis:analytical conc.

No. of animals per sex per dose:

20 breeding pairs for dose groups, 40 breeding pairs for control

Control animals:

yes, concurrent vehicle

Details on study design:

-Dose selection rationale: Data on body weights, clinical signs, and food and water consumption from a 2-week dose-range-finding study.

Examinations

Parental animals: Observations and examinations:

Clinical signs, parental body weight and average consumption of drinking water during representative weeks

Oestrous cyclicity (parental animals):

As monitored by vaginal lavage for the 12 days preceding necropsy

Sperm parameters (parental animals):

Epididymal sperm motility, sperm morphology, sperm count

Litter observations:

Litters per pair, live pups per litter, proportion of pups born alive, sex of live pups and the pup body weights

Postmortem examinations (parental animals):

Selected organs: testes, epididymides and ovaries

Statistics:

The Cochran-Armitage test (Armitage 1971, Statistical Methods in Medical Research, John Wiley & Sons, New York) was used to tes for a dose-related trend in fertility. Dose group means for the number of litters, the number of live pups per litter, the proportion of live pups (number of pups born alive divided by the total number of pups produced by each pair), and the sex ratio (total number of male pups born alive out of the total number of live pups born to each fertile pair) were tested for overall differences using the Kruskal-Wallis test and for ordered differences using Jonckheere's test. Pairwise comparisons of treatment group means were performed by applying the Wilcox-Mann-Whitney U test. To remove the potential effect of the number of pups per litter on the average pup weight, an analysis of covariance (Neter and Wasserman 1974, Applied Linear Statistical Models) was performed. Least squares estimates of dose group means, adjusted for litter size, were computed and tested for overall equality using an F-test and pairwise equality using a t-test (carried out for males, females and both sexes combined). An analysis of covariance was used to adjust organ weights for total body weight. Unadjusted body and organ weights were analysed using the Kruskal-Wallis and Wilcox-Mann-Whitney U tests. Dose-related trends were tested for by Jonckheere's test.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Organ weight findings including organ / body weight ratios:

not examined

Histopathological findings: non-neoplastic:

not examined

Other effects:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

no effects observed

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

no effects observed

Details on results (P0)

Five animals died during the dosing phase; these deaths were scattered throughout the dose groups and were not judged related to treatment. Food and water consumption was not affected by treatment; group mean body weights during the dosing phase differed by no more than 2 %. There were no treatment-related changes in any endpoint related to reproductive function. All F0 mice were killed at weaning.

Effect levels (P0)

Key result

Dose descriptor:

NOAEL

Effect level:

41.2 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings:

effects observed, treatment-related

Details on results (F1)

Number of litters and number of pub per litter were all unchanged. There were no treatment-related alterations in pub-viability or increase in body weight.Female body weight-adjusted liver weight was elevated by 14 % compared to the control group in the F1 treated group (dose of 41.2 mg/kg body weight/day). Vaginal cytology was not evaluated in these animals. In males, the only difference between the control and treated groups was a 7 % increase in relative epididymis weight. There were no differences between the groups in epididymal sperm measures. All treated females showed some degree of hepatocellular degeneration. Treatment-related histologic alterations in males included hepatitis and hepatocellular degeneration (1 case each). No changes were seen in lung, thyroid, spleen, esophagus, or the accessory sex organs.

Effect levels (F1)

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

15.9 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: Based on increased fertility index, relative epididymis weight and liver weight

Overall reproductive toxicity

Key result

Reproductive effects observed:

no

Any other information on results incl. tables

Table 1: Reproductive toxicity of chloroform in Swiss mice

Reproductive toxicity in F0 generation	7 mg/kg Male, female	16 mg/kg Male, female	41 mg/kg Male, female
Average # litters/pair	No change	No change	No change
# live pubs/litter; pub weight/litter	No change	No change	No change
Cumulative days to litter	No change	No change	No change
Absolute testis, epididymis weight a)	No observation	No observation	No observation
Sex accessory gland weight a) (prostate, seminal vesicle)	No observation	No observation	No observation
Epidid. Sperm parameters (#, motility, morphology)	No observation	No observation	No observation
Estrous cycle length	No observation	No observation	No observation
Reproductive toxicity in F1 generation	7 mg/kg Male, female	16 mg/kg Male, female	41 mg/kg Male, female
Fertility index	No observation	No observation	Increase b)
# live pubs/litter; pub weight/litter	No observation	No observation	Increase b), No change
Absolute testis, epididymis weight a)	No observation	No observation	No change, Increase (b)
Sex accessory gland weight a) (prostate, seminal vesicle)	No observation	No observation	No change
Epidid. Sperm parameters (#, motility, morphology)	No observation	No observation	No change
Estrous cycle length	No observation	No observation	No observation

a) adjusted to bodyweight; b) statistically significant change (p 0.05)

Table 2: General toxicity of chloroform in Swiss mice

General toxicity in the F0 generation	7 mg/kg Male, female	16 mg/kg Male, female	41 mg/kg Male, female
Body weight	No change	No change	No change
Kidney weigh a)	No observation	No observation	No observation
Liver weight a)	No observation	No observation	No observation
Mortality	No change	No change	No change
Feed consumption	No observation	No observation	No observation
Water consumption	No change	No change	No change
Clinical signs	No change	No change	No change
General toxicity in the F1 generation	7 mg/kg Male, female	16 mg/kg Male, female	41 mg/kg Male, female
Pub growth to weaning	No observation	No observation	No change
Mortality	No observation	No observation	No change
Adult body weight	No observation	No observation	No change
Kidney weight a)	No observation	No observation	No change
Liver weight a)	No observation	No observation	No change, Increase b)
Feed consumption	No observation	No observation	No observation
Water consumption	No observation	No observation	No change
Clinical signs	No observation	No observation	No change

a) adjusted to bodyweight; b) statistically significant change (p 0.05)

Applicant's summary and conclusion

Executive summary:

A two-generation reproductive toxicity test was carried out with chloroform using Swiss mice according to the Reproductive Assessment by Continuous Breeding (RACB) protocol. Chloroform was administered by oral gavage at actual doses of 0, 6.6, 15.9 and 41.2 mg/kg bodyweight/day.

The second generation reproductive assessments were conducted using pups from the control and high dose (41.2 mg) groups only. Of the 20 cohabited control pairs, 14 delivered live pups, while 19 of 20 high dose pairs delivered live pups. The controls delivered 10 pups per litter, the treated groups 12 pups. There were no other differences between the groups.

The necropsy of the F1 parent generation showed that there was no difference in female body weights, while female body weight-adjusted liver weight was elevated by 14 % in the treated group. All females showed some degree of hepatocellular degeneration. In males, the only difference between the control and the high dose groups was a 7 % increase in relative epididymis weight of the treated animals. There were no differences in epididymal sperm measures.

In summary, based on the findings, the NOAEL of the study for the reproduction functions was 15.9 mg/kg body weight/day.