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EC number: 231-970-5 | CAS number: 7782-91-4
- 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
Basic toxicokinetics
Administrative data
- Endpoint:
- basic toxicokinetics in vitro / ex vivo
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Well documented experimental investigations.
Data source
Reference
- Reference Type:
- study report
- Title:
- Unnamed
- Year:
- 2 009
Materials and methods
- Objective of study:
- other: in vitro bioavailability
Test guideline
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Solubility of test items in artificial biological fluids.
- GLP compliance:
- no
Test material
- Reference substance name:
- molybdenum metal, molybdenum dioxide, molybdenum trioxide, roasted molybdenite concentrate, sodium molybdate dihydrate, ammonium octamolybdate, ferromolybdenum, molybdenum disulfide
- IUPAC Name:
- molybdenum metal, molybdenum dioxide, molybdenum trioxide, roasted molybdenite concentrate, sodium molybdate dihydrate, ammonium octamolybdate, ferromolybdenum, molybdenum disulfide
- Details on test material:
- Several different molybdenum substances, which are within the scope of REACH registrations prepared by the Molybdenum Consortium were tested, as follows: molybdenum metal, molybdenum dioxide, molybdenum trioxide, sodium molybdate dihydrate, ammonium octamolybdate and roasted molybdenite concentrate.
Constituent 1
- Radiolabelling:
- no
Test animals
- Species:
- other: in vitro (simulated human body fluids)
- Details on test animals or test system and environmental conditions:
- The different substances were exposed to five different test media covering relevant pHs ranging from about 1.5 to 7.4. The test media were:
• Phosphate-buffered saline (PBS, pH 7.4), a standard physiological solution that mimics the ion strength of human blood serum. It is generally used within research and medical health care and normally serves as reference test solution for comparison of data under simulated physiological conditions.
• Gamble’s solution (GMB, pH 7.4) mimics interstitial fluid within the deep lung at normal health conditions.
• Artificial sweat (ASW, pH 6.5) which simulates the hypoosmolar fluid, linked to hyponatraemia (loss of Na+ from blood), which is excreted from the body upon sweating.
• Artificial lysosomal fluid (ALF, pH 4.5) simulates interstitial conditions in the lung occurring in conjunction to phagocytosis by cells, which involves relatively aggressive conditions similar to an immunologic reaction of the body.
• Artificial gastric fluid (GST, pH 1.5) mimics the very aggressive digestion milieu of high acidity in the stomach.
The test media where chosen to simulate a relevant inhalation or ingestion scenarios. It should be stressed that the different test media only simulate physiological conditions to a limited extent. The complexity and function of the real body fluids are difficult to simulate, however, in vitro results in synthetic biological media can, in a simple way, provide information that could be relevant for a real situation.
The test solutions were prepared using ultra-pure water and chemicals of analytical grades. The chemical composition (g/L) of ALF and GMB is presented below. The pH of ALF and GMB was adjusted using 50% NaOH and 25% HCl respectively. The pH of PBS was adjusted with 50% NaOH.
Artificial gastric fluid was prepared according to the ASTM standard (ASTM D5517).
Reference: ASTM D5517-03 (2003), ”Standard Test Method for Determining Extractability of Metals from Art Materials”
Administration / exposure
- Details on study design:
- Experimental Procedure
A particle loading of 0.1 g/L was selected since it is experimentally feasible even when low concentrations of released metal are expected. It is also used for testing according to the OECD transformation/dissolution protocol for sparingly soluble metals and metal compounds, which facilitates comparison with other data of metal release/dissolution (OECD, 2001).
The time periods for the exposure were 2 and 24 hours, which were selected to be relevant for a fictitious inhalation and ingestion scenario and to enable comparison with other metal ion release/dissolution data often generated after this time period. The approximate time for digestion is about 2 hours. The 24 hour exposure was selected as a standard time duration that is relatively easy to compare with metal ion release/dissolution data as well as toxicity data for further evaluation of the bioaccessibility of released metals.
Triplicate samples were prepared for exposure to each of the five different test media for two time periods, respectively. In addition, one blank sample containing only the test solution was incubated together with the triplicates for each time period. In each sample vial, 5 ± 0.5 mg of the samples were weighed into a TPX Nalgene® jar. Then, 50 mL of the test solution were added to the powder sample before incubation under gentle bi-lineary shaking (25 cycles per minute) at 37 ± 2 °C. - Details on dosing and sampling:
- After the testing period, the samples were allowed to cool to ambient room temperature before the final pH of the test solution was measured. The test medium was then separated from the powder particles by centrifugation at 3000 rpm for 10 minutes, resulting in a visually clear supernatant. The supernatant solution was decanted into a polypropylene storage flask and acidified to a pH less than 2 (not needed in the case of artificial gastric fluid) with 65% pure HNO3 prior to solution analysis.
Results and discussion
Main ADME resultsopen allclose all
- Type:
- other: Bioavailability based on dissolution in artificial biological fluids
- Results:
- For the purpose of human health risk assessment, the substances sodium molybdate, ammonium octamolybdate, molybdenum trioxide and roasted molybdenum concentrate are considered to be of high bioavailability.
- Type:
- other: Bioavailability based on dissolution in artificial biological fluids
- Results:
- For the purpose of human health risk assessment, the substances molybdenum (metal), ferromolybdenum, molybdenum dioxide and molybdenum disulfide are considered to be of negligible bioavailability.
Any other information on results incl. tables
Results and discussion:
Specific surface area (m²/g)
Test items |
Mo (1) |
FeMo (2) |
MoO2(3) |
MoO3(4) |
Na2MoO4∙2H2O(5) |
(NH4)4Mo8O26(6) |
MoS2(7) |
MoO3‐a (8) |
RMC (9) |
BET area |
0.23 |
0.11 |
1.18 |
2.97 |
1.15 |
1.82 |
4.15 |
4.59 |
0.32 |
SEM images
See attached graphs.
Surface composition (XPS analysis)
For the substances molybdenum (1) and ferromolybdenum (2) approximately 1/3 of the surface atoms were oxygen, indicating the expected presence of an oxide layer on these metallic materials. All other test item showed the expected elemental surface composition, in accordance with their chemical nature.
Bioaccessibility data / dissolution in synthetic biological fluids
The measured molybdenum concentrations in the various media and after two time points were used to calculate the fraction of the sample that has dissolved. The results are presented in the table below (variability omitted here for reasons of clarity). All samples were introduced into the media at a loading of 0.1 g/L, with the exception of sample (4), MoO3, which was tested at a loading of 1 g/L.
Table: Fraction of material dissolved (%)
(Test item) Material |
Exposure period |
GMB pH 7.4 |
PBS pH 7.2 |
ASW pH 6.5 |
ALF pH 4.5 |
GST pH 1.6 |
(1) Mo |
2h 24h |
0.17 0.17 |
0.32 6.1 |
0.32 2.4 |
0.21 0.58 |
0.44 0.50 |
(2) FeMo |
2h 24h |
0.44 0.64 |
0.58 2.2 |
1.8 12.7 |
0.27 2.5 |
0.16 0.85 |
(3) MoO2 |
2h 24h |
0.16 0.25 |
0.18 0.48 |
0.14 0.93 |
0.17 0.25 |
0.28 0.08 |
(4) MoO3 |
2h 24h |
26.7 95.3 |
42.5 95.1 |
42.0 106 |
7.8 77.2 |
2.1 10.4 |
(5)Na2MoO4.H2O |
2h 24h |
78.7 89.4 |
85.2 80.2 |
80.8 82.0 |
47.1 58.2 |
84.8 83.2 |
(6)(NH4)4Mo8O26 |
2h 24h |
78.9 67.8 |
81.5 86.5 |
56.0 88.0 |
36.6 66.7 |
64.1 94.0 |
(7) MoS2 |
2h 24h |
0.007 0.04 |
0.001 0.007 |
0.008 0.02 |
< DL 0.002 |
0.006 0.004 |
(8) MoO3‐a |
2h 24h |
100.6 98.6 |
91.9 94.2 |
n/a
|
48.2 51.1 |
41.9 71.0 |
(9) RMC |
2h 24h |
36.5 114.5 |
50.3 101.6 |
n/a |
28.2 55.6 |
6.6 24.8 |
Discussion:
The tested substances can be divided into two groups:
A) The molybdates sodium molybdate (5) and ammonium octamolybdate (5), as well as molybdenum trioxide (samples 4 and 8) dissolved completely or almost completely already after 2 hours in solution or after 24 hours at the latest. Into the same group falls roasted molybdenite concentrate, which - from a chemical standpoint - is essentially molybdenum trioxide. The dissolution of the oxides in artificial gastric juice is less than in other media, as a result of the low pH of the medium. The dissolution of MoO3in aqueous media is in fact a chemical reaction which liberates protons. This reaction is therefore considerably restricted in acidic solutions such as artificial gastric juice (which is essentially 0.1% hydrochloric acid).For the purpose of human health risk assessment, the substances sodium molybdate, ammonium octamolybdate, molybdenum trioxide and roeasted molybdenum concentrate are considered to be of high bioavailability.
B) Dissolution of the other substances is considerably less.
Molybdenum disulfide (7) hardly dissolved at all. Less than 0.04% of the added MoS2material dissolved, independently of medium or exposure time. Less than 1% of molybdenum dioxide (3) dissolved after 24h in all media. Molybdenum metal and ferromolybdenum, in which the metals are in their elemental form (oxidations state zero), show similar dissolution behaviour. For these two substances the dissolved molybdenum and iron is derived from the surface layer of oxides on these materials (existence of this oxide layer shown by XPS surface analysis). The dissolved concentrations will depend on the extent of the layer and how strongly it adheres to the substrate (the underlying compound). Once the oxide layer is dissolved, molybdenum metal and ferromolybdenum are considered to be inert. Even the exposure to artificial gastric juice (which is essentially 0.1% hydrochloric acid) does not lead to a significant dissolution of these metallic materials.
For the purpose of human health risk assessment, the substances molybdenum (metal), ferromolybdenum, molybdenum dioxide and molybdenum disulfide are considered to be of negligible bioavailability.
Applicant's summary and conclusion
- Conclusions:
- For the purpose of human health risk assessment and regarding systemic bioavailability, molybdenum substances can be grouped into high or negligible bioavailability.
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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