Registration Dossier

Toxicological information

Acute Toxicity: inhalation

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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study with acceptable restrictions.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1972
Report Date:
1972

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
Deviations:
yes
Remarks:
- unusual exposure time: 10 min every 30 min (20 min interval); only 5 animals were tested
Principles of method if other than guideline:
Study was performed before actual guideline was established.
GLP compliance:
no
Test type:
standard acute method
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): MRD-72-4
- Analytical purity: 100% pure commercial product

Test animals

Species:
rat
Strain:
other: albino
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., North Wilmington, Mass. USA
- Weight at study initiation: males: 120-220 g; females: 190-220 g
- Housing: The animals were housed individually in stock cages.
- Diet: Wayne Lab Blox, Allied Mills, Inc. Chicago, USA; ad libitum, except during inhalation exposure
- Water: ad libitum, except during inhalation exposure
- Other: All animals had been under observation for at least five days to insure thier general health and suitability for testing.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: specially constructed Plexiglas inhalation chamber
- Exposure chamber volume: 700 L
- Method of holding animals in test chamber: The chamber was designed so that the animals could be introduced to the test atmosphere after the maximum aerosol concentration was established and removed quickly after 10 min of exposure. Each animals was caged separately during exposure.
- System of generating aerosols: An aerosol of the undiluted test material was generated with an Ohio Ball-Jet Nebulizer (Ohio Chemical and Surgical Equipment Co., Madison, Wisc., USA). A stream of clean dry air (-40 °C dewpoint) was passed through the Nebulizer. The resulting aerosol stream was mixed with additonal clean air.
- Temperature, pressure in air chamber: 26 °C, 741 mm Hg

TEST ATMOSPHERE
- Air flow rate through the nebulizer (4.5 L/min at 760 mm Hg and 25 °C) was measured with a rotameter connected upstream of the nebulizer. Diluent air flow (40 L/min) was measured with a calibrated hot wire anemometer.


Analytical verification of test atmosphere concentrations:
yes
Duration of exposure:
4 h
Remarks on duration:
10 min every 30 min (20 min interval)
Concentrations:
9.4 mg/L air
No. of animals per sex per dose:
5
Control animals:
yes
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of weighing: prior to inhalation exposure and for each surviving animal after 7 and 14 days
- Necropsy of survivors performed: yes
- Other examinations performed: body weight, histopathology, behavioural reactions

Results and discussion

Effect levels
Sex:
male/female
Dose descriptor:
LC50
Effect level:
> 9.4 mg/L air
Exp. duration:
4 h
Remarks on result:
other: exposure time: 10 min every 30 min (20 min interval)
Mortality:
No deaths were observed during the exposures or during the 14-day observation period which followed.
Body weight:
No adverse effects on body weight were noted.
Gross pathology:
Necropsy of all animals sacrificed at the end of the exposure period or following the 14-day observation period revealed no gross pathologic differences between test and control animal.
Other findings:
- Histopathology: Histopathological examinations of all animals sacrificed at the end of the exposure period or following the 14-day observation period showed no differences between test and control animals.
- Other observations: No untoward behavioral reactions were observed among any experimental animals during the exposures or during the 14-day observation period which followed.

Applicant's summary and conclusion

Interpretation of results:
other: Not classified
Remarks:
Criteria used for interpretation of results: other: GHS EU, 2007
Conclusions:
An LC50 of >9.4 mg/L was determined in this study. Therefore the test substance, hydrocarbons, C7-C9, isoalkanes, needs not to be classified.
Executive summary:

No data is available for 2,2,3-trimethylbutane. However, data is available for hydrocarbons, C7-C9, isoalkanes and is being read across to using the category approach explained in the category justification document attached to Section 13 of the dossier.

An LC50 of >9.4 mg/L was determined in this study. Therefore the test substance, hydrocarbons, C7 -C9, isoalkanes, needs not to be classified.