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Diss Factsheets

Administrative data

Description of key information

The acute toxicity data on isoprene are limited.   Using a weight-of-evidence approach, the available data suggest that isoprene has a low order of acute toxicity in animals by the oral, dermal and inhalation routes of exposure.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records
Reference
Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Predates GLP and OECD guidelines, but otherwise sufficient for assessment.
Principles of method if other than guideline:
15 male Wistar rats were administered single doses of isoprene in oil by stomach tube. LD50 was calculated according to Litchfield & Wilcoxon (1949).
GLP compliance:
not specified
Test type:
other: unknown
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals or test system and environmental conditions:
160-210 g
Route of administration:
other: by stomach tube
Vehicle:
other: plant oil
Doses:
unknown
No. of animals per sex per dose:
250, 500, 1000, 2000, 2150, 2250 and 2500 mg/kg
Control animals:
not specified
Sex:
male
Dose descriptor:
LD50
Effect level:
2 125 mg/kg bw
Remarks on result:
other: 2043 - 2210 mg/kg
Mortality:
There were no deaths up to and including 1000 mg/kg.
There were 4, 8, 11 and 15 mortalities at 2000, 2150, 2250 and 2500 mg/kg respectively, with first deaths reported after 1 day of exposure.
Clinical signs:
other: At >= 500 mg/kg animals showed signs of sedation and had breathing difficulties after 1 hour's exposure. These observations were reported up to 7 days.
Interpretation of results:
Category 5 based on GHS criteria
Conclusions:
15 male Wistar rats were administered single doses of isoprene in oil by stomach tube. LD50 was concluded to be 2043 - 2210 mg/kg bw
Executive summary:

In a Key pre-guideline study, 15 male Wistar rats were administered isoprene in oil by stomach tube at single doses of 250, 500, 1000, 2000, 2150, 2250 and 2500 mg/Kg.

No mortality was observed at doses up to and including 1000 mg/kg. There were 4, 8, 11, and 15 mortalities observed at 2000, 2150, 2250, and 2500 mg/Kg doses, respectively, with first deaths reported post day 1 of exposure. At =500 mg/Kg, animals showed signs of sedation and had breathing difficulties after 1 hour's exposure. These observations were reported up to 7 days.

The acute oral LD50 was concluded to be 2043 - 2210 mg/Kg bw in male Wistar rats.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Acute toxicity: via inhalation route

Link to relevant study records
Reference
Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Lethality study only; insufficient experimental detail to assess quality.
Qualifier:
no guideline followed
GLP compliance:
no
Species:
mouse
Route of administration:
inhalation
Duration of exposure:
4 h
Dose descriptor:
LC50
Effect level:
214 000 mg/m³ air
Exp. duration:
4 h
Clinical signs:
other:
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Acute toxicity: via dermal route

Link to relevant study records
Reference
Endpoint:
acute toxicity: dermal
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Insufficient experimental detail to assess quality.
Principles of method if other than guideline:
5 rats received single application of 1 mL/kg isoprene each on their back skin (animals had been shaved the day before application). The substance was not removed for 7 days.
GLP compliance:
no
Test type:
fixed dose procedure
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals or test system and environmental conditions:
weight 160-210 g
Key result
Sex:
male
Dose descriptor:
LD50
Effect level:
> 1 mL/kg bw
Remarks on result:
other: >679 mg/kg bw
Interpretation of results:
other: Not classified
Conclusions:
An acute dermal LD50 of >1 mL/kg bw was established.
Executive summary:

5 rats received single application of 1 mL isoprene each on their back skin (animals had been shaved the day before application). The substance was not removed for 7 days.

An acute dermal LD50 of >1 mL/kg bw (>679 mg/Kg bw) was established.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Additional information

The oral LD50 of isoprene is reported as 2125 mg/kg (range of 2,043 to 2,210 mg/kg) and the 4-hour inhalation LC50 in rat is 180,000 mg/m3 and 2-hour LC50 in the mouse is 157,000 mg/m3.

The dermal LD50 of isoprene is >679 mg/kg (> 1mL/kg). Considering read-across from 2 -methyl-2 -butene (structurally similar to isoprene), it is considered that weight of evidence suggest an LD50 in excess of 2000 mg/kg.

Justification for classification or non-classification

No classification for acute toxicity is warranted under CLP since the oral and dermal LD50 values are >2000 mg/kg and the inhalation LC50 exceeds 20,000 mg/m3.