Ethylcyclohexane

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1943

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

The physiological response of animals to cyclohexane, methylcyclohexane, and certain derivatives of these compounds. II Inhalation

Author:

Treon, J. et al.

Year:

1943

Bibliographic source:

J. Indust. Hygiene Toxicol. 25(8), 323-346

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Determination of the minimum lethal concentration after repeated inhalation exposure

GLP compliance:

not specified

Test type:

other: minimum lethal concentration

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Methylcyclohexane

EC Number:

203-624-3

EC Name:

Methylcyclohexane

Cas Number:

108-87-2

Molecular formula:

C7H14

IUPAC Name:

methylcyclohexane

Test material form:

liquid

Specific details on test material used for the study:

Purity: 97%

Test animals

Species:

rabbit

Strain:

not specified

Sex:

not specified

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Details on inhalation exposure:

exposure chamber:
higher concentrations: 223 l metal cage
long-term inhalation at lower concentrations: battery of nine insulated plywood cages, capacity 600 l.
temperature: 23.9 ± 1.7 °C
humidity: <45%
air flow rate: 350 to 800 liters/minute
vapour generator: Bosch fuel injection pump

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

6 h

Remarks on duration:

6 hours per day

Concentrations:

0.948, 1.46,4.57 mg/l: 300 hours
11.35 mg/l: 90 hours
21.90 mg/l: 120 hours
28.75, 39.55 mg/l: 60 hours
59.9 mg/L: 1 1/5 hours

No. of animals per sex per dose:

4

Control animals:

yes

Results and discussion

Effect levels

Effect levels 1

Key result

Sex:

not specified

Dose descriptor:

LC100

Effect level:

59.9 mg/L air

Based on:

test mat.

Exp. duration:

70 min

Effect levels 2

Key result

Sex:

not specified

Dose descriptor:

other: mortality

Effect level:

28.75 - < 39.55 mg/L air

Based on:

test mat.

Exp. duration:

6 h

Effect levels 3

Key result

Sex:

not specified

Dose descriptor:

other: minimum narcotic concentration

Effect level:

21.9 mg/L air

Based on:

test mat.

Exp. duration:

6 h

Mortality:

0.948 - 21.90 mg/L: none
28.75 and 39.55 mg/L: mortality in 1/4 and 4/4 animals, respectively, after 2 weeks of exposure.
59.9 mg/L: mortality in 4/4 within 70 min after exposure initiation

Clinical signs:

other: 0.948 - 11.35 mg/L: no effects 21.90 mg/L: slight lethargy. 28.75 mg/L: lethargy and impaired coordination of legs 39.55 mg/L: convulsions, light narcosis, laboured breathing, salivation, conjunctival congestion 59.55 mg/L: severe convulsions, rapid narco

Body weight:

Animals exposed to non-lethal concentrations gained weight. Mean group body weight gains were:
0.948 mg/L: 752 g (after 10 weeks)
4.57 mg/L: 956g (after 10 weeks)
11.35 mg/L: 328 g (after 3 weeks)
21.90 mg/L: 201 g (after 4 weeks)

Animals exposed to lethal concentrations lost weight. Mean group body weight gains were:
28.75 mg/L: -39 g (after 2 weeks)
39.55 mg/L: -390 g (after 2 weeks)

Gross pathology:

Histopathology: After a 3-week exposure to 11.35 mg/L barely demonstrable evidence of cellular liver and kidney injury was reported.
Potential target organs: CNS at high concentrations

Applicant's summary and conclusion

Interpretation of results:

other: STOT-SE 3 H336 May cause drowsiness and dizziness

Conclusions:

In this rabbit study, all the animals died at 59.9 mg/L within 70 min after exposure initiation. LC50 was considered as between 39.6 and 59.9 mg/L. Signs of toxicity at 59.9 mg/L (70 min exposure) included severe convulsions, rapid narcosis, labored breathing, salivation, and conjunctival congestion.

Executive summary:

In this rabbit study, all the animals died at 59.9 mg/L within 70 min after exposure initiation. LC50 was considered as between 39.6 and 59.9 mg/L. Signs of toxicity at 59.9 mg/L (70 min exposure) included severe convulsions, rapid narcosis, labored breathing, salivation, and conjunctival congestion.

In this study, mortality after single and repeated exposure occurred only at high to very high concentrations of methylcyclohexane, which are above the currently valid LC50 ranges used for classification. Therefore, the study results do not fulfil the classification criteria for acute toxicity by inhalation. Based on the narcotic effects consistently observed at high concentrations in this and further studies (Weight of Evidence), methylcyclohexane fulfils the classification criteria for Specific target organ toxicity-single exposure (STOT-SE) Category 3 (narcotic effects).