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EC number: 231-166-4 | CAS number: 7440-58-6
- 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
Additional information
In aqueous solution, hafnium is always quadrivalent and precipitates as the Hf(OH)4. Hf(OH)22+ is the hydrated form of HfO2, and is the only species present in solution in the absence of other stabilising ligands. This complex is very stable and resistant to protonation (Hagfeldt et al. 2004). Complexes with sulphates, fluorides and chlorides may be poorly soluble in aqueous solution, but complexation with natural organic materials may increase the concentrations of Hf in natural freshwater.
Studies suggest that when hafnium is detected in surface water samples it is associated with particles in the water column (Tanisaki et al. (1992); Taylor et al. (1990)).
Due to this behaviour of Hf in aquatic compartment, all tests required have been carried out on the hydrated form HfO2 (asHf(OH)22+). (Acute toxicity to aquatic invertebrates, algae and fish).
Aquatic compartment:
Three studies with aquatic invertebrates, algae and fish were carried out with HfO2 at saturated concentrations.
The first one assessed the acute toxicity to Zebrafish (Brachydanio rerio), over an exposure period of 96 hours in flow through conditions.
The second one was performed on Daphnia magna, over an exposure period of 48 hours in a semi-static system.
And the third assessed the effect of HfO2 on algal growth using the unicellular green alga Pseudokirchneriella subcapitata (Selenastrum capricornutum), over an exposure period of 72 hours.
One concentration at the solubility limit of the test item in the test medium (100 % v/v saturated solution) plus an untreated control were tested in limit tests.
In the conditions of these three tests, Hafnium dioxide had no toxic effect at water solubility limit (<0,008 mg Hf/L) on fish, invertebrate and algae; the LC50 results and the NOEC are higher than the solubility limit of the test item in the test medium.
These three tests showed no hazard to these three trophic levels due to short term exposure of HfO2. Consequently, there is no need to derive any aquatic PNEC.
Microorganisms/ sewage treatment plant:
The extremely low water solubility of Hf and its affinity to form complexes with organic molecules in water (see explanation for Kd values just above), makes it not bioavailable to aquatic organisms. Moreover, the nature of the substance (inorganic), suggests that no biological treatment is expected for this substance. But in case a WWTP with several treatment steps exists on site, Hf will then be removed in the primary settling tank, due to adsorption on particulate matter and exposure of micro-organisms is unlikely. For these reasons, no PNEC was derived for STP.
Sediment organisms:
There is no data for sediment species, but considering the very low water solubility of Hf, it is not expected that it is present in the pore water of sediment, where sediment-dwelling organisms can be found. It is furthermore assumed that due to complexation reactions, Hf will not be bioavailable to benthic organisms. In addition, no effects have been observed in aquatic organisms (daphnia and fish) in acute tests with HfO2 used for read across. In conclusion, it can be reasonably assumed that Hf concentrations will not reach sufficiently high levels to be able to exert toxic effects to benthic organisms.
Moreover, due to tonnage band, the potential hazard assessment to sediment is not mandatory.
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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