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EC number: 201-193-6 | CAS number: 79-29-8
- 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
Neurotoxicity
Administrative data
Description of key information
NOAEC (sub-chronic, rat, neurological effects) ≥ 31680 mg/m³
Based on available read across data, 2,3-Dimethylbutane is unlikely to present a hazard as a neurotoxicant.
Key value for chemical safety assessment
Effect on neurotoxicity: via oral route
Endpoint conclusion
- Endpoint conclusion:
- no study available
Effect on neurotoxicity: via inhalation route
Link to relevant study records
- Endpoint:
- neurotoxicity: sub-chronic inhalation
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 1989-04-03 to 1989-07-14
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- other: This study is classified as reliable without restrictions because it is well documented and follows OECD Guideline 424.
- Justification for type of information:
- A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.
- Reason / purpose for cross-reference:
- read-across: supporting information
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 424 (Neurotoxicity Study in Rodents)
- Deviations:
- yes
- Remarks:
- On a single occasion a control group female and high exposure female were mis-dosed. Due to it being a single instance, it is not considered to have affected the outcome of the study.
- GLP compliance:
- yes (incl. QA statement)
- Species:
- rat
- Strain:
- Sprague-Dawley
- Sex:
- male/female
- Details on test animals or test system and environmental conditions:
- TEST ANIMALS
- Source: Charles River Canada, Inc.
- Age at study initiation: 7-8 weeks of age
- Weight at study initiation: 233-271 g male, 185-239 g female
- Housing: individually in stainless steel wire mesh cages, identified by ear notching
- Diet (e.g. ad libitum): Purina Rodent Laboratory Chow, ad libitum
- Water (e.g. ad libitum): reverse osmosis sterilized water, ad libitum
- Acclimation period: 2 weeks male, 3 weeks female
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-24
- Humidity (%): 25-79
- Photoperiod (hrs dark / hrs light): 12 hrs light/12 hrs dark
IN-LIFE DATES: From: April 3, 1989 To: July 14, 1989 - Route of administration:
- inhalation: vapour
- Details on exposure:
- GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: cylindrical stainless steel and glass whole-body chambers, 410 l
- Method of holding animals in test chamber: cages
- Method of conditioning air: Test substance was metered into a glass column that was wrapped with a heating element and filled with glass beads. Dry compressed air moved through the column where it mixed with the test substance before entering the exposure chamber.
- Temperature, humidity, pressure in air chamber: 20-24 degree C, 30-70% humidity,
- Air change rate: 12-15 per hour
TEST ATMOSPHERE
- Brief description of analytical method used: pre-study, samples were taken from sampling points in the breathing zone and analyzed using GC. Samples were also analyzed with GC daily during the first exposure week, and weekly thereafter. During exposure, samples were taken every 30 min. and analyzed using an infrared gas analyzer. - Analytical verification of doses or concentrations:
- yes
- Details on analytical verification of doses or concentrations:
- 896 ppm
2,996 ppm
9,006 ppm - Duration of treatment / exposure:
- 13 weeks
- Frequency of treatment:
- 6 hrs/day, 5 days/week
- Remarks:
- Doses / Concentrations:
0, 900, 3000, 9000 ppm
Basis:
nominal conc. - No. of animals per sex per dose:
- 12 male, 12 female
- Control animals:
- yes, sham-exposed
- Observations and clinical examinations performed and frequency:
- CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations: mortality and clinical signs
BODY WEIGHT: Yes
- Time schedule for examinations: weekly, on behavioral testing days
FOOD CONSUMPTION: Yes
Weekly - Neurobehavioural examinations performed and frequency:
- FUNCTIONAL OBSERVATIONAL BATTERY: Yes
- Parameters checked: body position, locomotor activity, bizarre behavior, tremors, piloerection, respiratory rate, defecation, vocalization, pupil size, lacrimation, salivation, urinary staining, diarrhea, body tone, abdominal tone, pinna reflex, extensor thrust, tail pinch, toe pinch, auricular startle, gait, limb rotation, visual placing, air righting reflex, pupillary reflex, positional passivity, urination, grip strength, hindlimb splay,
- Description of procedures:
- Minimization of bias:
- Technicians were blind to treatment status of animals: Yes
- Site of testing: 2' square of plexiglass
- Time schedule for examinations: day 0, 1, 7, 14, 35, 63, and 91
- Description of equipment where required: Both hindlimb and forelimb grip strength was tested using a Chatilon strain gauge.
LOCOMOTOR ACTIVITY: Yes
- Type of equipment used: figure 8 activity monitor
- Length of session, number and length of subsessions: 1 hr, 6 10 min sessions
- Time schedule for examinations: pre-study and days 34, 62, and 90 - Sacrifice and (histo)pathology:
- - Number of animals sacrificed: 8 per group
- Parameters measured:
- Brain weight: yes
- Length and width of brain: yes
- Procedures for perfusion: Ringer's solution with heparin and sodium nitrate, then gluteraldehyde, formaldehyde, calcium chloride, picric acid, and cacodylate buffer.
- Number of animals perfused: 8
- Tissues evaluated: peripheral nervous system, sciatic nerve, lumbar dorsal root ganglion, lumbar dorsal root, lumbar ventral root, cervical dorsal root ganglion, cervical dorsal root, cervical ventral root, sural nerve, tibial nerve, Gasserian ganglion, lumbar spinal cord at swelling, cervical spinal cord at swelling, center of cerebrum, midbrain, cerebellum, pons, medulla oblongota
- Type of staining: uranyl acetate
- Methodology of preparation of sections:
- Thickness: 0.5 micron
- Embedding media: epoxy
- Number of animals evaulated from each sex and treatment group: 6 - Statistics:
- Body weights and food consumption were analyzed using Bartlett's test, and the Kruskal-Wallis test if needed. Motor activity testing was analyzed using a repeated measures analysis in Snedecor and Cochran (1980). Two-Way Classifications. In Statistical Methods, Iowa State University Press (14) 255-273.
- 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):
- not examined
- Food efficiency:
- not examined
- Water consumption and compound intake (if drinking water study):
- not examined
- Ophthalmological findings:
- not examined
- Clinical biochemistry findings:
- not examined
- Behaviour (functional findings):
- no effects observed
- Gross pathological findings:
- no effects observed
- Neuropathological findings:
- not examined
- Details on results:
- CLINICAL SIGNS AND MORTALITY
One animal died due to a fracture of the muzzle/nares on day 22. No other animals died during the study. Males and females in treatment groups had more staining of the muzzle/head or periorbital region. No other significant differences between control groups and treatment groups were noted.
BODY WEIGHT AND WEIGHT GAIN
Body weight was unaffected by treatment.
FOOD CONSUMPTION
No adverse effects to food consumption were noted.
NEUROBEHAVIOUR
The motor activity results showed no significant differences between control groups and treatments groups. The results of the hindlimb splay and grip strength studies showed no significant differences between control groups and treatment groups.
GROSS PATHOLOGY
No treatment related effects were found.
NEUROPATHOLOGY
No treatment related finding were noted. - Key result
- Dose descriptor:
- NOAEC
- Effect level:
- 9 000 ppm
- Sex:
- male/female
- Basis for effect level:
- other: Neurotoxicity
- Key result
- Critical effects observed:
- no
- Conclusions:
- Exposure to the test substance had no effect on the behavior of rats. The NOAEC for sub-chronic neurological effects is 9000 ppm in rats.
- Executive summary:
This study examined the neurological effects of inhalation exposure to commercial hexane to rats. Rats were exposed to nominal concentrations of 0, 900, 3000, or 9000 ppm for 6 hrs/day, 5 days/week, for 13 weeks. Rats were tested monthly throughout the exposure for hindlimb splay and grip strength. A functional observational battery was also performed regularly. Animals were also examined for clinical signs, body weight, and food consumption.
Results showed no effects to behavior or evidence of toxicity. The NOAEC for sub-chronic neurological effects in rats is 9000 ppm (31680 mg/m3).
Reference
Endpoint conclusion
- Endpoint conclusion:
- no adverse effect observed
- Dose descriptor:
- NOAEC
- 31 680 mg/m³
- Study duration:
- subchronic
- Species:
- rat
- Quality of whole database:
- 1 key read across study from a structural analogue available for assessment
Effect on neurotoxicity: via dermal route
Endpoint conclusion
- Endpoint conclusion:
- no study available
Additional information
There is no neurotoxicity data available for 2,3-Dimethylbutane. However, sub-chronic neurotoxicity data is available for structural analogue, commercial hexane. This data is read across to based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.
Commercial hexane
In a key study, the neurological effects of inhalation exposure to commercial hexane (53% n-hexane) in rats was examined (API, 1990e; Klimisch score = 2). Rats were exposed to nominal concentrations of 0, 900, 3000, or 9000 ppm for 6 hrs/day, 5 days/week, for 13 weeks. Rats were tested monthly throughout the exposure for hindlimb splay and grip strength. A functional observational battery was also performed regularly. Animals were also examined for clinical signs, body weight, and food consumption. Results showed no effects to behaviour or evidence of toxicity. The NOAEC for sub-chronic neurological effects in rats was 9000 ppm (31680 mg/m3).
This study directly informs the DNEL.
Justification for classification or non-classification
Based on the available read across data from a structural analogue, 2,3-Dimethylbutane does not warrant classification as a neurotoxicant under the new Regulation (EC) 1272/2008 on classification, labeling and packaging of substances and mixtures (CLP).
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