2-chlorobuta-1,3-diene

Toxicity to reproduction: other studies

Administrative data

Endpoint:

toxicity to reproduction: other studies

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 December 1977 to 2 August 1978

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Although pre-dating GLP and test guideline publications the study was conducted according to a protocol design that meets the study objectives and provides much of the information required by subsequent published test guidance.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1979

Report date:

1979

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

A one generaton study was conducted in rats exposed to chloroprene via inhalation. The F0 and F1 generations were exposed to atmospheres at nominal concentrations of 0, 10, 33 or 100 ppm (0, 9.8, 32.6 and 100.01 ppm for F0 and 0, 9.85, 32.99 and 100.58ppm for F1 analytically).
The F0 animals were exposed for 6 hours per day, 5 days per week for a period of 13 weeks and then mated with untreated rats. The F1 rats were exposed for 6 hours per day, 5 days /week but for a period of 10 weeks only.
Various fertility maturation and pathological parameters were investigated to determine the reproductive toxicity potential for chloroprene.
The animals were all subject to gross and microcopic examination but no differences bewteen test and controls were found.

GLP compliance:

no

Type of method:

in vivo

Test material

Test material information

Constituent 1

Reference substance name:

ß-chloroprene

IUPAC Name:

ß-chloroprene

Details on test material:

- Name of test material (as cited in study report): ß-chloroprene

- Physical state: Liquid - 200 ml freshly purified
- Analytical purity: No data
:
- Purity test date: No data
- Lot/batch No.: No data
- Expiration date of the lot/batch: No data

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Central Institute for the Breeding of Laboratory Animals, TNO, Zeist, The Netherlands. Cpb:Wu Wistar Random strain. Received on 13 December 1977. Weight on arrival circa 50 g
- Age at study initiation: No data for parental generation
- Weight at study initiation: Group means were in range of (F0) Males: 92-94 g; Females: 82-85g; (F1) Males: 119-129 g; Females: 99-108 g
- Fasting period before study: Fasting only during exposure period
- Housing: Housed in the exposure chamber for exposure period and between exposures. During mating phase one male and one female pair housed in suspended stainless steel cages on a rack in the exposure room

- Diet (e.g. ad libitum): ad libitum access to Muracon I stock diet except during exposure period
- Water (e.g. ad libitum): ad libitum access to unfluoridated tap water via water bottles
- Acclimation period: 4 days for P generation


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22°C
- Humidity (%): 45-60%RH
- Air changes (per hr): Not stated. Air flow rate was 40 m3/h during aexposure and 60 m3/h during non-exposure
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 17 December 1977 for P generation for 13 weeks - last exposure on 17 march 1978 and F1 generation exposure commenced on 22 May 1978 for 10 weeks - last exposure on 2 August 1978

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

other: filtered and dried nitrogen flow passed over ß-chloroprene and the saturated nitrogen was fed into chamber and mixed with incoming ambient air.

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: stainless steel cylindrical chamber with glass door for observations. 2.5 m3 capacity
- Method of holding animals in test chamber: wire mesh cages on a heptagonal frame holding 6 layers and seven vertical rows of cages, 42 cages per exposure chanber housing a single rat in each cage.
- Source and rate of air: test material saturated nitrogen mixed with room air 40 m3/h during exposure period
- Method of conditioning air: ß-chloroprene was evaporated by passing filtered dried nitrogen through a glass evaporator containing liquid chloroprene at 0°C. The chloroprene saturated nitrogen flow was mixed with the air flow entering the inhalation chamber to achieve the required atmosphereconcentration.

- Temperature, humidity, pressure in air chamber: The exposure chambers were maintained at 1-2 mmH20 negative pressure relative to the room. Temperature was 22°C ±1°C and 45-60% RH
- Air flow rate: 40 m3/h during exposure periods and 60m3/h during non-exposure period

- Treatment of exhaust air: No details provided


TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatography - Intersmat GC 120 with flame ionisation detector
- Samples taken from breathing zone: yes. ß-chloroprene concentration monitored in each generated atmosphere. Samples taken at regular intervals via a sampling tube and sample loop and 7-port gas sampling valve

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

gas chromatography - Intersmat GC 120 with flame ionisation detector, ß-chloroprene concentration monitored in each generated atmosphere. The mean achieved concentrations were almost identical to the intended nominal atmosphere concentrations.
F0 nominal - 10, 33, 100 ppm achieved concentration = 9.8, 32.6, 100.01
F1 nominal - 10, 33, 100 ppm achieved concentration = 9.85, 32.99, 100.58

Duration of treatment / exposure:

Parental generation exposed daily for 13 weeks prior to mating
F1 generation exposed for 10 weeks
6 hours exposure per day for fivedays per week

Frequency of treatment:

Daily (5 days per week)

Duration of test:

two generation study. first generation exposed for 13 weeks and second generation for ten weeks with mating, gestation and lactation in between

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 10, 33 and 100 ppm
Basis:
nominal conc.

No. of animals per sex per dose:

25 males and 25 females for P generation
40 males and 40 females for F1 generation

Control animals:

yes, sham-exposed

Details on study design:

Groups of 25 males and 25 females were exposed to concentrations of 0, 10, 33 or 100 ppm chloroprene for 13 weeks. The animals were checked daily for clinical condition, behavioural changes or mortality. Bodyweights were recorded at weekly intervals. After 13 weeks the treated rats were mated for 20 days. The chloroprene treated males were mated (1:1) with untreated stock females and the treated females were similarly mated with untreated stock males. Following the mating period the females were allowed to wean their litters. Records of the numbers of pups born per litter and the total numbers of surviving pups at days 1, 3, 14 and 28 were maintained. Total litter weights were recorded at days 1, 3, 14 and 28 and male/female pup ratios confirmed. Litters with more than 8 pups were randomly culled to a litter size of 8 on day 4.

From the F1 litters, 20 males and 20 females were randomly selected from each mating group, one week after weaning, to provide a total of 160 males and 160 females for allocation to the F1 treatment groups - each consisting of 40 rats/sex. These were exposed to chloroprene for a further 10 weeks

Statistics:

Bodyweights and relative organ weights analysed using Student's t-test. Haematology data analysed using Wilcoxon's test

Results and discussion

Effect levels

Dose descriptor:

NOAEC

Effect level:

> 100 ppm (nominal)

Sex:

male/female

Observed effects

The mean analytical exposure concentrations for the Fo and F1 atmospheres were all close to the niminal values of 0, 10, 33 or 100 ppm.
The F0 rats showed no clinical or behavioural changes indicating a reaction to treatment.
The F0 high dose animals had lower bodyweight gains than controls, noted throughout the exposure period for the females and in the first 8 weeks for males.
The reproductive performance of the F0 rats was evaluated using various parameters. From the results it was apparent that the percentage of females pregnant and producing a litter was high in all groups. There were no indications of reduced fertility in any treatment group. The numbers of young born per litter showed no treatment-related effect. While there was some variation in the male/female ratios within litters, there was no apparent dose-relationship and no treatment effect was indicated. Mortalities also varied within the groups but again there were no indications of a treatment or dose relationship. The index for resorptions was similar in all groups, indicating no increase in foetal mortality as a result of parental exposure to chloroprene vapour.
For the offspring of the mating between treated females and untreated males, bodyweights were significantly lower in the 100 ppm group than in the controls. The effect was apparent at birth and during lactation.
For the F1 generation, the general condition and behaviour showed no adverse treatment related effects. Bodyweight gains were lower among groups dosed at 33 or 100 ppm, for both sexes.
Haemoglobin levels were checked and found to be similar in all treated and control groups. The clinical condition alopecia was evident in a number of rats in treated and control groups but there was no evidence that chloroprene exposure had either reduced or increased the incidence.
Several differences in relative organ weight were noted, probably reflecting the lower bodyweight gains in the high and mid dose groups rather than any effect of chloroprene directly. The relative liver weight for the high dose females was increased in comparison with controls but the relative lung weight in this group was decreased. The relative ovary weight in the high dose group was increased in comparison with control. Relative testes weight was increased in all treated groups but witout any dose relationship and this was considered to reflect the variation in bodyweight rather than any direct effect of exposure to chloroprene.
No abnormalities considered attributable to exposue to chloroprene were apparent at necropsy of either the F0 or F1 rats.
Microscopic examination of the testes of the F0 rats revealed no abnormalities attributable to exposure to chloroprene. In the F1 rats the histopathological changes were limited to common background finding s forthe strain of rat used and occurred at similar incidence in test and control groups. TThere were no treatment related histopathology changes that could be associated with the increased relative liver and ovary weights in the high dose group

Applicant's summary and conclusion

Conclusions:

The conclusion based on the limited non-adverse findings from the one generation study was that exposure to chloroprene had no adverse effect on the reproductive performance of rats at concentrations of up to 100 ppm.

Executive summary:

In a one generation reproductive toxicity study, rats (F0 and F1) were exposed for 6 hours per day for 5 days per week for 13 or 10 weeks respectively to atmospheres containing ß-chloroprene at nominal concentrations of 0, 10, 33 or 100 ppm.

The treated rats of the F0 generation were mated with untreated males or females after the last exposure period.

Analysis of the generated atmospheres indicated the mean chamber concentrations for both treatment phases were close to the nominal values in all treatment groups.

General clinical condition and appearance, male and female fertility, the number of live pups born per litter, male/female ratio of pups in litter and pup mortality were not adversely affected by inhalation exposure to ß-chloroprene. Intra-uterine mortality was also not increased as a result of exposure to chloroprene.

Reduced bodyweight gains were recorded for the F0 generation exposed to 100 ppm, the highest concentration, and also for rats in the F1 generation exposed to 100 or 33 ppm.

For the high dose F1 females (offspring of treated males and untreated females in F0) relative liver and ovary weights were significantly higher than the controls.

No gross or microscopic pathology changes indicative of treatment-related effects were apparent.

The conclusion based on the limited non-adverse findings from the one generation study was that exposure to chloroprene had no adverse effect on the reproductive performance of rats at concentrations of up to 100 ppm.