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EC number: 240-347-7 | CAS number: 16219-75-3
- 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
Endpoint summary
Administrative data
Description of key information
Based on the 14-wk inhalation study, the NOAEL for repeated inhalation toxicity in the rat is 24.8 ppm (122 mg/m3). These values are based on systemic effects other than thyroid and kidney that are not considered relevant to humans (IARC, 1998).
Key value for chemical safety assessment
Repeated dose toxicity: via oral route - systemic effects
Endpoint conclusion
- Endpoint conclusion:
- adverse effect observed
- Dose descriptor:
- NOAEL
- 20 mg/kg bw/day
- Study duration:
- subacute
- Species:
- rat
Repeated dose toxicity: inhalation - systemic effects
Endpoint conclusion
- Endpoint conclusion:
- adverse effect observed
- Dose descriptor:
- NOAEC
- 122 mg/m³
- Study duration:
- subchronic
- Species:
- rat
Additional information
There are no sub-chronic repeat dose studies available by the oral route of exposure. There is a sub-acute 28-day repeated oral dose toxicity test available. Sprague-Dawley rats received doses of 0, 4, 20 and 100 mg/kg/day for 28-d by oral gavage.
In the 100 mg/kg group females the mean body weight was significantly reduced at dosage termination but not in the recovery group. Food consumption was not affected. Urinalysis revealed an increase in the number of animals with protein-positive urine and a decrease in water consumption in males given 100 mg/kg. These changes were not found at the end of recovery period. In the hematological examination, no effect was observed after administration of ENB. In the blood biochemical examination, 20 and 100 mg/kg group males showed a decrease in alpha-1 globulin level. However, these changes were not found at the end of the recovery period. In high dose males there was increased brain/body wt ratio and increased kidney/body wt ratio; both effects were absent in recovery males. At autopsy, pale discoloration of the kidneys was observed in males given 100 mg/kg, and histopathology showed increased hyaline droplets in renal tubule epithelium of all male rats in the 20 and 100 mg/kg groups. Histopathological examination of the thyroid indicated hypertrophy of follicular epithelium, as well as decrease in colloid or irregular shape of follicles in males given 4 mg/kg or more. Hypertrophy of follicular epithelium and decrease in colloid were also observed in females given 100 mg/kg. There were no effects on the testes. The NOAEL of ENB for repeated dose toxicity was reported to be less than 4 mg/kg/day for males (based on thyroid effects at 4 mg/kg and kidney effects at 20 mg/kg) and 20 mg/kg/day for females (based on thyroid effects at 100 mg/kg). However, the male rat kidney effects are consistent with alpha-2u-globulin nephropathy and are not considered to be relevant to humans (IARC, 1998). The thyroid effects are also likely to be a species specific effect not relevant to humans (IARC, 1998). For these reasons, the oral NOAEL based on systemic effects other than thyroid and kidney is 20 mg/kg/d, based on reduced body weight of females in the 100 mg/kg/d group.
There are no repeat dose studies available by the dermal route of exposure.
There are four inhalation repeated dose toxicity studies of ENB. One study was of less than 2 wk duration and served as a range finding study for a subchronic study. The early studies, with limited monitoring, showed that exposure to high concentrations (e.g., 237 ppm) of ENB vapor produced liver, kidney, and testicular injury in the rat accompanied by a high incidence of mortality, and liver and testicular injury in the dog (Kinkead, E. et al., 1971). In the more recent rat studies where the purity of the ENB was measured and exposure concentrations maintained at or below 149 ppm, there is no biochemical or histologic evidence for testicular effects, minor adaptive and reversible changes in the liver, and male-rat specific kidney effects (Ballantyne, B. et al., US, 1997b). Thyroid effects were evaluated in the rat oral 28-d study (MHLW,, 2001) and the rat inhalation 14-wk study (Ballantyne, B. et al, US, 1997b). These two were selected as key studies and considered to be the most reliable because they were conducted under well-designed protocols, reported analytical purity of the test material, and providedetailed information. An observation common to these two studies are thyroid changes which are considered likely to be a species specific effect not relevant to humans.
The NOAEL for repeated oral dose toxicity in rats is considered to be 20 mg/kg/day for male and female rats, based on the 28-d oral toxicity study. Based on the 14-wk inhalation study, the NOAEL for repeated inhalation toxicity in the rat is 24.8 ppm (122 mg/m3). These values are based on systemic effects other than thyroid and kidney, which are not relevant to humans (IARC, 1998).
Justification for classification or non-classification
Under regulation 1272/2008, a classification for STOT (RE) category 2 could be considered appropriate as a LOAEL of 0.75mg/l (150ppm) was established in a sub-chronic study. However, the only effects seen were increases in liver and kidney weight without associated changes to histopathology and changes to urinary parameters of unknown toxicological significance. Other effects noted at this or lower concentrations (e.g. on the thyroid) were established as reversible. Therefore no 'significant' toxic effects were seen and therefore classification under 1272/2008 is not warranted based on this study. However, the data from older studies reported adverse findings (LOAEL) of 61ppm (0.305mg/l) in both rats and dogs. These changes were associated with adverse histopathology as well. These findings could be considered 'significant' and therefore, on a precautionary basis, a STOT classification (category 2) would appear warranted.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
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