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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, non-guideline animal experimental study, published in peer reviewed literature, limitations in design but contributing to a weight of evidence.

Data source

Reference
Reference Type:
publication
Title:
Postnatal development and behaviour of Wistar rats after prenatal toluene exposure
Author:
Thiel R and Chahoud I
Year:
1997
Bibliographic source:
Arch Toxicol (1997) 71, 258-265

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Pregnant rats exposed to toluene by whole body inhalation from day 9-21 of pregnancy. Rats were allowed to litter and offspring assessed for range of developmental effects including learning ability and fertility.
GLP compliance:
not specified
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Toluene was supplied by Merck (No. 8323), Darmstadt, Germany and had a purity of 99%

Test animals

Species:
rat
Strain:
other: Wistar (Bor: Wisw/spf, TNO)
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Winkelmann (Borchen, Germany)
- Age at study initiation: not reported
- Weight on arrival: 180 to 270 g
- Housing: after mating, the females were kept individually caged
- Diet: standard pellet feed (Altromin 1324; Altromin, Lage, Germany), ad libitum
- Water: ad libitum
- Acclimation period: 3 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 21 ± 1 °C
- Humidity: 50 ± 5%
- Photoperiod: 12hrs dark / 12hrs light

IN-LIFE DATES: not reported

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 1m^3 inhalation chamber and an aerosol-generating system (compressor, pump with calibrated syringe, nozzle). The inhalation conditions were controlled by a Multi-Function Unit (TSE), registering temperature (°C), humidity (%), pressure (mBar), oxygen (%) and flow rate (m^3/h) throughout the exposure period. Controls were placed in the same chamber and inhaled fresh air only.

Samples of the gas mixture in the chamber were taken twice daily and the concentrations were determined by headspace gas chromatography.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Achieved exposure concentrations were within 10% of target
Details on mating procedure:
One male was mated with three female animals from 6:30 to 9:00 a.m.; the following 24 h was designated day 0 of pregnancy if sperm were detected in the vaginal smears. After mating, the females were kept individually caged and were allowed to deliver to term.
Duration of treatment / exposure:
6h/day
Frequency of treatment:
day 9-21 of pregnancy
Duration of test:
Day 0 of pregnancy to delivery and then approximately 90 days after delivery
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0, 300, 600, 1000, 1200 ppm
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
0, 1131, 2261, 3768, 4522 mg/m3
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
0, 271, 628, 951, 1167 ppm
Basis:
analytical conc.
No. of animals per sex per dose:
38, 23, 23, 29 and 24 for the 0, 300, 600, 1000 and 1200 ppm groups respectively
Control animals:
yes, sham-exposed
Details on study design:
Measurement of toluene blood concentrations: Blood samples were taken from the tail vein on day 20 of pregnancy immediately at the end of exposure from the 300 and 1200 ppm groups. The concentrations of toluene in blood plasma were measured by headspace gas chromatography.

Examinations

Maternal examinations:
CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes (no details recorded)

POST-MORTEM EXAMINATIONS: No data
Fetal examinations:
As soon as possible after birth the number of viable and dead newborn were counted in each litter, the litter weight was measured and the mean pup weight per litter was calculated.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
Toluene exposures of 1000 and 1200 ppm resulted in a reduced body weight of rat dams

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEC
Effect level:
1 200 ppm
Basis for effect level:
other: other:
Dose descriptor:
NOAEC
Effect level:
4 522 mg/m³ air (nominal)
Basis for effect level:
other: other:
Dose descriptor:
NOAEC
Effect level:
600 ppm
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEC
Effect level:
2 261 mg/m³ air (nominal)
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEC
Effect level:
600 ppm
Basis for effect level:
other: developmental toxicity
Dose descriptor:
NOAEC
Effect level:
2 261 mg/m³ air (nominal)
Basis for effect level:
other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Toluene exposures of 1200 ppm resulted in lower body weight of offspring at birth and on day 7 and a higher mortality until weaning. Incisor eruption and vaginal opening were also delayed. At 1000 ppm body weight at birth was low and vaginal opening was delayed.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

Pregnancy data: The duration of pregnancy was identical in all groups.

 

Litter data: No significant effects on litter size. The mean body weight of offspring of dams exposed to 1000 and 1200 ppm toluene was significantly lower at birth. The reduction of the offspring mean body weight remained until postnatal day 7 in the 1200 ppm group. There was a significantly higher mortality prior to weaning in the 1200 ppm group (7% v. 2.6%).

 

Postnatal development: Incisor eruption and vaginal opening were delayed at 1200 ppm. Vaginal opening was also delayed at 1000 ppm.

 

Fertility: No treatment-related effects.

 

Development of reflexes:There were no differences in the development of reflexes, rota rod performance and locomotor activity between the offspring of animals exposed to toluene and the controls.

 

Locomotor activity:There were no differences in locomotor activity between the offspring of animals exposed to toluene and the controls.

 

Discrimination learning: No concentration-dependent adverse effects were detected.

 

Applicant's summary and conclusion

Conclusions:
Toluene exposures up to 1200 ppm do not induce adverse effects on the behaviour of rat offspring exposed during late embryonic and foetal development. The NOAEC for offspring behaviour is 1200 ppm (4522 mg/m3). The NOAECs for maternal toxicity and developmental toxicity are 600 ppm (2261 mg/m3).
Executive summary:

Developmental toxicity and post-natal development were assessed in groups of >20 pregnant female rats exposed to toluene via inhalation 6 h/day during gestation (days 9 -21). Exposure concentrations were 0, 300, 600, 1000 or 1200 ppm. A detailed evaluation of physical development of offspring was conducted and the following tests performed: fore-limb grasp reflex, righting reflex, cliff-drop aversion reflex, maintenance of balance on a rotating rod, locomotor activity, learning ability in a discrimination learning test.

Maternal toluene exposures of 1200 ppm resulted in a reduced body weight gain of rat dams and offspring had lower body weight at birth and day 7 and a higher mortality until weaning. Some developmental landmarks (incisor eruption and vaginal opening) were delayed in this group and are likely to be secondary to the effect on body weight. At 1000 ppm maternal body weight gain was low and offspring had low body weight at birth and delayed vaginal opening. 600 ppm (2261 mg/m3) is the NOAEC for both maternal toxicity and developmental toxicity.

There were no differences in the development of reflexes, rota rod performance and locomotor activity that were attributable to treatment with toluene and no effects were found on learning ability in the operant conditioning task. There were no differences in mating, fertility and pregnancy indexes in the F1-generation. 1200 ppm (4522 mg/m3) is the NOAEC for effects on offspring behaviour.