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Developmental toxicity / teratogenicity

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developmental toxicity
Type of information:
experimental study
Adequacy of study:
other information
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study. Adopted according to OECD SIDS (public available peer reviewed source). The original source is available and has been reviewed.

Data source

Referenceopen allclose all

Reference Type:
Teratogenic evaluation of 1,4-dichlorobutene-2 in the rat following inhalation exposure.
Kennedy Jr. GL, Culik R, Trochimowicz HJ
Bibliographic source:
Toxicol. Appl. Pharmacol. 64, 125-130.
Reference Type:
secondary source
1,4-Dichlorobut-2-ene - CAS No: 764-41-0
Bibliographic source:
SIDS Initial Assessment Report for 22th SIAM, UNEP Publications

Materials and methods

Test guideline
equivalent or similar to
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
not specified
Limit test:

Test material

Details on test material:
Test substance: other TS: 70% trans, 30% cis 1,4-dichlorobutene-2, < 0.5% 3,4-dichlorobutene-2, < 0.05% trichlorobutene and high boilers

Test animals

other: ChR-CD
Details on test animals and environmental conditions:
- Housing: individually in suspended, stainless-steel wire-mesh cages.
- Diet (e.g. ad libitum): Purina Rat Chow (Ralston Purina Co., St. Louis, Mo.), ad libitum (except during the actual inhalation exposure times).
- Water (e.g. ad libitum): water was available both from an automatic demand-operated valve and from supplemented water bottles attached to each cage.

Administration / exposure

Route of administration:
Type of inhalation exposure (if applicable):
whole body
Details on exposure:
Rats were exposed to 1,4-dichlorobut-2-ene in 600 liter inhalation chambers of the Rochester-type design; controls were exposed to room air only. Chambers temperatures were monitored hourly.
For each exposure, feeders and water bottles were removed randomly transferred (within groups) to the appropriate exposure chamber (high-level first, low-level second, control last) with the loading sequence reversed, at the end of the exposure. A ½ -hr interval from generation system shutdown to rat unloading was allowed to insure that the concentration of 1,4-dichlorobut-2-ene in the test chambers was at background levels.
1,4-dichlorobut-2-ene vapours were delivered through an air intake at the top of each exposure chamber. Vapours were generated by bubbling hydrogen through 1000-mL fritted glass bubblers containing the liquid test material. Air flow was maintained at approximately 0°C to reduce variation in chamber concentration caused by changes in vapour pressure. Bubblers were filled with 1,4-dichlorobut-2-ene before the first exposure and were refilled with fresh material before the sixth exposure.
1,4-dichlorobut-2-ene was analyzed by a chromatograph, using flame ionization detection. The carrier gas helium and sample size of 6 mL were taken in a glass syringe and analyzed every 30 minutes during each 6-hour exposure. Detector conditions of hydrogen, 28 mL/min (13 psi); helium, 55 mL/min (18 psi); air, 230 mL/min (25 psi); and oven, injection port, and detection temperature of 130, 100, and 300 °C, respectively, were used. Gas standards of 0.5, 1.0, 2.2, and 5.0 ppm were prepared fresh daily and chamber concentrations were determined from calibrated standards.
Analytical verification of doses or concentrations:
Details on mating procedure:
- Impregnation procedure: purchased timed pregnant
- Proof of pregnancy: mating was determined by the supplier by finding of sperm in the vaginal smear following overnight cohabitation and that day was considered as Day 1 gestation.
Duration of treatment / exposure:
10 days (day 6-15 of gestation)
Frequency of treatment:
6 h/day
Duration of test:
up to 21st day of gestation
Doses / concentrations
Doses / Concentrations:
0.5, 5 ppm = 0.0026, 0.026 mg/L
nominal conc.
No. of animals per sex per dose:
Control animals:
Details on study design:
Sex: female
Duration of test: up to day 21 of gestation.
Rats were grouped on Gestation Day 3 so that group mean weights were similar. Three groups were formed: Group I (controls-0 ppm); Group II (low level-0.5 ppm), and Group III (high level-5.0 ppm).


Maternal examinations:
- Time schedule: observation for clinical sings, both during and following exposure, were made daily.

- Time schedule for examinations: rats were weighed eight times during gestation.

- Sacrifice on gestation day 21st
- Organs examined: ovaries and uterus. Other tissues and organs were examined grossly and discarded if found to be normal.

Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
Fetal examinations:
- External examinations: Yes: [all per litter ]
- Soft tissue examinations: Yes: [all per litter]
- Skeletal examinations: Yes: [all per litter ]
- Head examinations: No
The litter was considered the experimental unit of treatment and observation. The Fisher exact probability test was used to evaluate resorptions among litters. Foetal body weights and lengths and maternal body weights were handled by analyses of variance and least significant difference tests. The number of corpora lutea, implantations, and live foetuses per litter was analyzed by the Wilcoxon rank sum test. In all cases, two-tailed significance test were performed and significance tests were performed and significance was judged at the 0.05 probability level.
No further information
Historical control data:

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
No overt outward signs of a response to 1,4-dichlorobut-2-ene were observed either during the exposure or the recovery period (days 16 through 21 of gestation).
The incidence of pregnancy was not affected with 23, 21, and 21 rats out of 26 tested being pregnant in Groups I, II, and III, respectively. The rate of body weight gain of the parental females exposed to 0.5 ppm compared favourably to that of the controls. For the 5.0-ppm group, the rate of weight gain during the exposure period was significantly reduced.
Gross pathological lesions were seen in the lungs of rats, 1 in Groups I and 3 in groups III. The surfaces of all lobes were mottled by small (1-2mm), slightly elevated, red and gray foci.
Histologic examination diagnosed diffuse murine pneumonitis (a latent subclinical form being present in this strain of rat) possibly exacerbated by the exposure and/or pregnancy.
Although the rate of weight gain for rats in the high-level exposure group was reduced, parameters measuring pregnancy outcome and foetal development were not significantly different from those of the control group. The number of implantations, live foetuses, and resorptions per litter and foetal measurements were similar in all groups. Only one litter from a control rat contained a foetus showing late resorption. No litters were totally resorbed and no dead foetuses were observed.

Effect levels (maternal animals)

Dose descriptor:
Effect level:
0.003 mg/L air
Basis for effect level:
other: maternal toxicity

Results (fetuses)

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

Details on embryotoxic / teratogenic effects:
Small subcutaneous hematomas and petechial haemorrhages were equally distributed throughout all the groups. The incidence of runts, umbilical hernias, and oedema was minimal and was unrelated to treatment.
Visceral examination in each group showed a very low incidence of hydronephrosis and hydroureter in control and test groups. One foetus with bilateral anophthalmia was found in the control group. This foetus was also a runt with umbilical hernia. Liver peliosis (extravasation of capillary blood into the surrounding liver tissue) was found in three foetuses from two litters. This is a minor anomaly, observed in both control and test foetuses.
No malformations or minor abnormalities of skeletal system were noted. Unossified sternebrae, bipartite centra, and 14th rudimentary ribs were found to be equally distributed throughout the control and test groups. Asymmetrical and bipartite sternebrae were found only on the control group and affected only one foetus. Likewise, one foetus with a pair of 14th ribs and one foetus with thickened ribs were found in the group exposed to 5.0 ppm.

Effect levels (fetuses)

Dose descriptor:
Effect level:
0.026 mg/L air
Basis for effect level:
other: teratogenicity

Fetal abnormalities

not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

Table 1. Body weight data: rats exposed to 1,4 -dichlorobut-2 -ene during gestation.


1,4 -dichlorobut-2 -ene (ppm)

 No. of pregnant rats   Gestation day          Body weight gain (g) days 7 -15
       7  12  15  21   
                Mean body weight (g)  
 I  0  23  213 ± 10a  268 ± 14   281 ± 15  366± 19 68 
 II  0.5  21  211 ± 12  267 ± 13   282 ± 14  362 ± 22  71
 III  5.0  21  203 ± 13  248* ± 15  258± 17*  346± 26*  55*

a mean ± SD

* Statistically different thancontrol at 0.05 probability.

Applicant's summary and conclusion