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EC number: 295-405-4 | CAS number: 92045-23-3 A complex combination of hydrocarbons produced by the distillation of the products of a steam cracking process. It consists predominantly of hydrocarbons having a carbon number of C4, predominantly 1-butene and 2-butene, containing also butane and isobutene and boiling in the range of approximately minus 12°C to 5°C (10.4°F to 41°F).
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
![](https://echa.europa.eu/o/diss-blank-theme/images/factsheets/A-REACH/factsheet/print_toxicological-information.png)
Repeated dose toxicity: oral
Administrative data
- Endpoint:
- short-term repeated dose toxicity: oral
- Type of information:
- migrated information: read-across based on grouping of substances (category approach)
- Adequacy of study:
- key study
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: GLP compliant, near guideline study, available as unpublished report, fully adequate for assessment
Cross-referenceopen allclose all
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to other study
Data source
Reference
- Reference Type:
- study report
- Title:
- Unnamed
- Year:
- 1 986
- Report date:
- 1986
Materials and methods
Test guideline
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)
- Principles of method if other than guideline:
- not applicable
- GLP compliance:
- yes
- Limit test:
- no
Test material
- Reference substance name:
- isobutylene
- IUPAC Name:
- isobutylene
- Reference substance name:
- 2-methylpropene
- EC Number:
- 204-066-3
- EC Name:
- 2-methylpropene
- Cas Number:
- 115-11-7
- Molecular formula:
- C4H8
- IUPAC Name:
- 2-methylprop-1-ene
- Details on test material:
- - Name of test material (as cited in study report): isobutylene
- Lot/batch No.: T101/OH
- Storage condition of test material: in a freezer in a pressurized cylinder
Constituent 1
Constituent 2
Test animals
- Species:
- rat
- Strain:
- Sprague-Dawley
- Sex:
- male/female
- Details on test animals or test system and environmental conditions:
- Animals (CR1:CD SD (BR) supplied by Charles River UK, Margate, Kent, UK. They were obtained as weanlings (about 28d old) and acclimatised for 2 weeks before start of treatment.
Administration / exposure
- Route of administration:
- oral: gavage
- Vehicle:
- corn oil
- Details on oral exposure:
- PREPARATION OF DOSING SOLUTIONS:
VEHICLE: corn oil
- Concentration in vehicle: 0, 0.05, 0.50 and 5.00 % v/v for dose levels of 0, 1.49, 14.86 and 148.55 mg/kg/day respectively
- Amount of vehicle (if gavage): constant volume of 5 mL/kg bodyweight was dosed.
- All preparation was carried out in a freezer then the formulation was slowly allowed to come to room temperature.
- Dosing solutions were prepared fresh each day. - Analytical verification of doses or concentrations:
- yes
- Details on analytical verification of doses or concentrations:
- Samples taken from all dosing formulations prepared in weeks 1 and 4 and analysed in duplicate for achieved concentration. The preparations were in the range 71-134% of nominal and were considered to be acceptable.
- Duration of treatment / exposure:
- 28 days
- Frequency of treatment:
- daily
Doses / concentrations
- Remarks:
- Doses / Concentrations:
0, 1.49, 14.86, 148.55 mg/kg
Basis:
other: nominal
- No. of animals per sex per dose:
- 5
- Control animals:
- yes, concurrent vehicle
- Details on study design:
- - Dose selection rationale: Based on a range-finding study
- Positive control:
- none
Examinations
- Observations and examinations performed and frequency:
- CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
DETAILED CLINICAL OBSERVATIONS: No
BODY WEIGHT: Yes
- Time schedule for examinations: First day , at weekly intervals thereafter and at termination.
FOOD CONSUMPTION: Yes
- Time schedule: weekly
WATER CONSUMPTION: No
OPHTHALMOSCOPIC EXAMINATION: No
HAEMATOLOGY: Yes
- Time schedule for collection of blood: During week 4
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes
- How many animals: All
- Parameters examined: Haemoglobin, mean cell volume, red blood cell count, mean cell haemoglobin, packed cell volume, mean cell haemoglobin concentration, total and differential white cell count, platelet count.
CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: During week 4
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes
- How many animals: All
- Parameters examined: glutamate oxaloacetic transaminase, glutamate pyruvate transaminase, alkaline phosphatase, blood urea nitrogen, glucose, sodium, potassium, calcium, inorganic phosphorus, chloride, creatinine, total protein, albumin, albumin/globulin ratio, bilirubin
URINALYSIS: No
NEUROBEHAVIOURAL EXAMINATION: No - Sacrifice and pathology:
- GROSS PATHOLOGY: Yes
ORGAN WEIGHTS: YES (adrenals, liver, kidneys, testes form all animals)
HISTOPATHOLOGY: Yes (All of the following from the controls and 148.55 mg/kg groups): adrenals, colon, caecum, duodenum, heart, ileum, jejunum, kidneys, liver, oesophagus, rectum, spleen, stomach, gross lesions - Other examinations:
- none
- Statistics:
- group mean values and standard deviations where appropriate
Results and discussion
Results of examinations
- Clinical signs:
- no effects observed
- Mortality:
- no mortality observed
- Body weight and weight changes:
- no effects observed
- Food consumption and compound intake (if feeding study):
- no effects observed
- Food efficiency:
- not specified
- Water consumption and compound intake (if drinking water study):
- not examined
- Ophthalmological findings:
- not examined
- Haematological findings:
- effects observed, treatment-related
- Clinical biochemistry findings:
- effects observed, treatment-related
- Urinalysis findings:
- not examined
- Behaviour (functional findings):
- not examined
- Organ weight findings including organ / body weight ratios:
- effects observed, treatment-related
- Gross pathological findings:
- no effects observed
- Histopathological findings: non-neoplastic:
- no effects observed
- Histopathological findings: neoplastic:
- no effects observed
- Details on results:
- CLINICAL SIGNS AND MORTALITY: No mortalities or treatment-related effects
BODY WEIGHT AND WEIGHT GAIN: No treatment-related effects
FOOD CONSUMPTION: No treatment-related effects
HAEMATOLOGY: Stat sig treatment-related decrease in white blood cell counts of females dosed with 148.55 mg/kg/day compared to controls. However, values were within the background range.
CLINICAL CHEMISTRY: Slight treatment-related increases in blood urea nitrogen in males and in glucose levels in females compared to controls. However, values were within the background range.
ORGAN WEIGHTS: Relative liver and kidney weights were increased by approximately 5% in females dosed at 148.55 mg/kg/day. However, values were within the background range.
GROSS PATHOLOGY: No treatment-related effects
HISTOPATHOLOGY: No treatment-related effects
Effect levels
- Dose descriptor:
- NOAEL
- Effect level:
- 148.6 mg/kg bw/day (nominal)
- Sex:
- male/female
- Basis for effect level:
- other: there were no mortalities or adverse treatment-related effects
Target system / organ toxicity
- Critical effects observed:
- not specified
Any other information on results incl. tables
none
Applicant's summary and conclusion
- Conclusions:
- No toxicologically significant changes were observed at dose levels up to 148.6 mg isobutylene/kg/day administered orally to rats over 28 days. Oral administration is an unusual route for a gaseous substance but the analytical results indicate that the gas remained dissolved and the target concentration was achieved.
- Executive summary:
No toxicologically significant changes were observed at dose levels up to 148.6 mg isobutylene/kg/day administered orally to rats over 28 days. There were no treatment-related changes in viability, clinical condition, body weight, food consumption and gross pathology or histopathology. Slight changes in haematology and clinical chemistry and organ weights were observed, but the values remained within what was considered the normal range. A NOAEL of 148.55 mg/kg/day was established.
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