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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Entry adopted from the OECD SIAR on sulfur dioxide without modification.Study meets generally accepted scientific principles, sufficiently documented, specific investigation of neurobehavioral changes in F1 generation; investigation of dose-dependcy for 3 test concentrations; acceptable for assessment.

Data source

Reference
Reference Type:
publication
Title:
Prenatal sulfur dioxide exposure induces changes in the behavior of adult male mice during agonistic encounters.
Author:
Fiore, M. et al.
Year:
1998
Bibliographic source:
Neurotox. Teratol. 20: 543-548

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Study only reports on isolated mechanistic investigations:
specific investigation of neurobehavioural changes in F1 generation
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
not specified

Test animals

Species:
mouse
Strain:
CD-1
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River, Calco, Italy
- Weight at study initiation: 27-30 g
- Housing: Upon arrival at the laboratory, animals were housed in same-sex pairs in 33 x 13 x 14 cm Plexiglas boxes with a metal top and sawdust as bedding.
- Diet: Pellet food (Enriched standard diet purchased from Mucedola, Settimo Milanese, Italy) was continuously available.
- Water (e.g. ad libitum): Tap water was continuously available.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 1
- Humidity (%): 60 +/- 10
- Photoperiod (hrs dark / hrs light): Lighting followed a 12L:12D reversed photo period.

No further details are given.

Administration / exposure

Route of administration:
inhalation
Type of inhalation exposure (if applicable):
not specified
Vehicle:
other: air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: The apparatus (custom-made by A. & L. CO. Industries, I-00290 Segrate, Italy) included a control system (with monitoring and recording of concentrations) and four stainless steel exposure chambers (52 x 135 x 113 cm) with a hatch glass in the front door. The chambers were located in an airconditioned room adjacent to the housing room (same temperature and humidity conditions) and were equipped with racks that could hold up to 24 housing boxes.
- System of generating particulates/aerosols: SO2 was delivered from 40-l aluminium bottles. Different SO2 concentrations were obtained by varying the flow and pressure out from the bottles.
- Temperature, humidity, pressure in air chamber: 21 +/- 1°C, 60+/- 10%
- Treatment of exhaust air: The sulphured air passed through appropriate filters before being discharged in the outdoor environment.
No further details are given.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Sulphur dioxide was measured by an ultraviolet (UV) SO2 analyser; periodic calibration of the analyser was performed using permeation tubes that produced known SO2 concentrations.
Duration of treatment / exposure:
from 9 days before breeding until gestation day 14
Frequency of treatment:
This exposure was near-continuous, covering about 90% of the total exposure time.
Doses / concentrationsopen allclose all
Dose / conc.:
0 ppm (nominal)
Dose / conc.:
5 ppm (nominal)
Dose / conc.:
12 ppm (nominal)
Dose / conc.:
30 ppm (nominal)
Control animals:
yes
Details on study design:
Prenatal Treatment: Adult male and female mice were exposed to SO2 starting from 9 days before the formation of breeding pairs up to pregnancy day 14. Litters of SO2 exposed dams were reduced at birth to eight pups (four males and four females) and fostered to unexposed/unhandled dams that had given birth to healthy litters within the same 24 hours. After weaning (PND 21), mice were housed in same-litter, same-sex pairs in cages identical to those described above. On PND 75–80 depending on day of birth, 46 male mice (n: 0 ppm = 12; 5 ppm = 11; 12 ppm = 11; 30 ppm = 12) started a 40-day period of isolation in cages.

Aggressive Behavior Procedures: The fighting pairs were randomly formed by introducing an experimental subject (i.e., a mouse exposed to different
SO2 concentrations during the fetal life, see above) and an opponent mouse into a neutral home box provided with clean sawdust. The opponent animal was an unexposed CD-1 mouse of the same age, body weight, and isolation condition as the experimental subjects. They were weighed and marked on the flanks with a black, odorless, nontoxic ink from a felt pen 30 minutes before testing. Mice were tested for aggressive behavior (single 20-min session) in a quiet experimental room under temperature, relative humidity, and lighting cycle conditions identical to those of the housing room. Aggressive encounters were recorded using a videocamera. The following neurobehavioral responses were recorded: attacking, freezing, tail rattling, offensive postures, defensive postures, fleeing, exploration, rearing, wall rearing, body sniffing, digging.

Examinations

Statistics:
Data were analysed by parametric analysis of variance (ANOVA) considering the exposure conditions as grouping factor and four repeated measures within subjects. Post hoc comparisons were performed using the Tukey’s HSD test.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
The dams of 30 ppm group had a reduction of body weight during pregnancies.

Effect levels (maternal animals)

Dose descriptor:
LOAEC
Effect level:
5 ppm
Based on:
test mat.
Basis for effect level:
body weight and weight gain

Results (fetuses)

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

Effect levels (fetuses)

Dose descriptor:
NOAEL
Remarks on result:
not determinable due to absence of adverse toxic effects

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Any other information on results incl. tables

SO2 exposure did not affect mating, proportion of successful pregnancies, litter size, sex ratio, and neonatal mortality.

The levels of several responses such as tail rattling, freezing, and defensive postures were reduced by the treatment, particularly during the initial period of the agonistic encounter, whereas offensive and attack behaviors were not significantly modified. In addition, rearing and social investigation increased.

Applicant's summary and conclusion

Conclusions:
The investigation of neurobavioral changes after prenatal exposure of mice to sulfur dioxide in concentrations of 5-30 ppm indicated alterations of the social and agonistic behavior. These changes act on the approach phase toward the opponent and suggest changes of the animals capability to cope with threatening dangerous situations.