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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1988
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study design appears to follow latest OECD guideline Test Guideline 403 (2009) with deviations (younger rats tested, oxygen and carbon dioxide concentrations were not provided; and no individual data for clinical examination results).

Data source

Reference
Reference Type:
review article or handbook
Title:
Acute inhalation toxicity of eugenol in rats
Author:
Clark G.C.
Year:
1988
Bibliographic source:
Archives of Toxicology. 1988; Volume 62: 381-386

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 403 (Acute Inhalation Toxicity)
Deviations:
yes
Remarks:
younger rats tested, oxygen and carbon dioxide concentrations were not provided; and no individual data for clinical examination results
Principles of method if other than guideline:
The acute toxicity of inhaled eugenol was assessed by exposure of three groups of five male and five female rats to a submicron aerosol of eugenol for 4h followed by a 14 days observation period. An aerosol generator was used for production of a submicron aerosol.
GLP compliance:
not specified
Test type:
standard acute method
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Eugenol
EC Number:
202-589-1
EC Name:
Eugenol
Cas Number:
97-53-0
Molecular formula:
C10H12O2
IUPAC Name:
4-allyl-2-methoxyphenol
Details on test material:
- Name of test material (as cited in study report): eugenol
- Storage condition of test material: Stored in dark-brown glass bottle at room temperature.

Eugenol 500g (purity 99%) was purchased from the Aldrich Chemical Co. Ltd, England.
The identity and purity of the chemical were established by comparison of the IR spectrum with published data and by GLC.
Further details not reported.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River UK Ltd, margate, Kent, England.
- Age at study initiation: 6-8 weeks old
- Weight at study initiation: males 156 ± 10g, females 171 ± 10g
- Housing: The rats were housed in polypropylene-walled cages with 5 animals of the same sex/group in each cage. The rats remained in a holding room for the 4h exposure and a port-exposure period of approximately 18h were kept in a ventilated cabinet to allow dispersal of any residual test substance. The whole-body exposure chambers are divided by wire mesh partitions to provide 10 separate animal compartments.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 3°C
- Humidity (%): 55 ± 15%
- Photoperiod (hrs dark / hrs light): 12h fluorescent white light-dark cycle
Further details not reported.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
air
Details on inhalation exposure:
Exposures were made at three levels, low, medium and high.
Three groups of 10 rats (5 male and 5 female) were exposed continuously for 4 hours to test atmospheres containing eugenol in the form of respirable droplets. A fourth group of ten rats (5 male and 5 female) was exposed to air alone using the same type of exposure system.
Analytical verification of test atmosphere concentrations:
yes
Remarks:
GLC
Duration of exposure:
4 h
Concentrations:
A concentration of 2.58 mg/L was the highest concentration of eugenol in the exposure chamber. The animals were also exposed at concentrations of 1.37 mg/L and 0.77 mg/L.
No. of animals per sex per dose:
10 animals (5 male and 5 female)/group
Control animals:
yes
Details on study design:
The acute toxicity of eugenol was assessed by exposure of three groups of 5 male and 5 female rats to submicron aerosol of eugenol for 4 hours followed by a 14-day observation period.
Statistics:
no data

Results and discussion

Preliminary study:
Not applicable
Effect levelsopen allclose all
Sex:
male
Dose descriptor:
other: LD50
Effect level:
> 2.6 mg/L air (nominal)
Based on:
test mat.
Exp. duration:
4 h
Sex:
female
Dose descriptor:
other: LD50
Effect level:
> 2.6 mg/L air (nominal)
Based on:
test mat.
Exp. duration:
4 h
Mortality:
No rats died during the course of the study.
Clinical signs:
other: The appearance and behaviour of the control and low dose animals was normal throughout exposure. High dose rats, observed during exposure, had increased salivation and restlessness, some gasping also was noted. With the exception of restlessness, clinic
Body weight:
Both male and female rats exposed to eugenol lost weight overnight following exposures. The weight loss (ca 7%) was not related to the concentration of eugenol to which the animals had been exposed. Subsequently, the weight gain of the eugenol exposed groups was similar to or greater than that of the control group such that, the body weights of all groups were similar by the end of the 14-day observation period.
Gross pathology:
Macroscopic pathology: macroscopic abnormalities consisting of dark red slightly raised areas, were detected in the lungs only of two animals in the highest and lowest eugenol concentrations.
Other findings:
Microscopic pathology: There were no significant histophathological findings in the lungs of individual animals. No treatment-related changes were detected. A few incidental lesions described in the individual animal reports were considered spontaneous in origin and therefore of no toxicological importance.

Applicant's summary and conclusion

Interpretation of results:
not classified
Remarks:
Migrated information Criteria used for interpretation of results: EU
Conclusions:
Temporary, readily reversible signs of toxicity were noted, including irregular breathing (gasping), lethargy, overnight weight loss and overnight reduced food and water intake, after inhalation of eugenol at a concentration of 2.58 mg/L; however, there were no deaths and no evidence of blood in the respiratory tract. The acute LD50 was reported to be >2.6 mg eugenol/L air. Low dose and control rats showed no changes in appearance and behavior, indicating a lack of effects. The rats were normal in all respects within 48h. Histophathological examination of the lungs after the 14-day observation period was normal. These findings suggest that eugenol would have a 4-hour LC50 of greater than 5 mg/L.
Executive summary:

The acute toxicity of inhaled eugenol was investigated in groups of five male and five female rats per test concentration of 0, 0.77, 1.37, or 2.58 mg/L for 4 hours in an exposure chamber, followed by 14 days of observation. Control and low dose rats showed no changes. Some intermediate-dose rats showed temporary wet snouts and red-brown staining of the fur immediately after dosing. Temporary, readily reversible signs of toxicity were noted, including irregular breathing (gasping), lethargy, overnight weight loss and overnight reduced food and water intake, after inhalation of eugenol at a concentration of 2.58 mg/L; however, there were no deaths and no evidence of blood in the respiratory tract. The rats were normal in all respects within 48h. Histophathological examination of the lungs after the 14-day observation period was normal. The acute LD50 was reported to be >2.6 mg eugenol/L air. Taken altogether, these findings suggest that eugenol would have a 4-hour LC50 of greater than 5 mg/L.

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