Registration Dossier

Administrative data

Endpoint:
additional toxicological information
Type of information:
other: publication
Adequacy of study:
supporting study
Study period:
2006
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: acceptable method, supporting study

Data source

Reference
Reference Type:
publication
Title:
Dissolution of functional materials and rare earth oxides into pseudo alveolar fluid
Author:
M. Takaya et al.
Year:
2006
Bibliographic source:
Industrial Health, 44, 639-644 (2006)

Materials and methods

Type of study / information:
The dissolution rate of rare earth oxides and rare earth-containing functional materials such as Neodymium-boron-iron magnet alloy (NdBFe) in water and pseudo-alveolar fluid (Gamble's fluid) was determined. The dissolution was evaluated by measuring the concentrations of rare earth elements in the solvent by ICP-MS.
Test guideline
Qualifier:
no guideline followed
Guideline:
other: no guideline available
Deviations:
not applicable
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent

Results and discussion

Any other information on results incl. tables

Very low concentrations of Neodymium were found in the dissolving fluids:

Test material

Time

[d]

Concentration in water

[ppb]

Concentration in Gamble’s solution

[ppb]

Nd2O3

1

7

72.3

0.4

0.7

89.6

NdBFe

1

7

0.22

0.55

0.64

1.06

From these results of above publication the mobilised mass of the Neodymium in Gamble's fluid can be calculated from:

Wi,mob = (ci * V)/ mE with

Wi,mob = mobilised part in the lung in µg/g test item

Ci = measured element concentration in µg/l

V = total volume in l of the aqueous phase (0.04 l)

mE = weight of measured test item (0.5 g)

Bioaccessiblity of the element was calculated from:

Ri = (Wi,mob * 100%)/Wi,total with

Ri = bioaccessible part in %

Wi,mob = mobilised part in the lung in µg/g test item

Wi,total = total part of the element in the test item in µg/g

Following bioaccessiblities were calculated:

Test material

Bioaccessibility Ri in % after 1 day

Bioaccessibility Ri in % after 7 days

Nd2O3

6.610 -6

8.410 -4

NdBFe

7.510 -6

1.210 -5

Assuming a respiratory volume of ca. 10 m3per worker’s shift, a blood volume of ca. 5 l, and an occupational exposure limit (OEL-TWA) of 10 mg/m3 for total (inert) dust (respirable fraction; TRGS 900: Technical Guidance for dangerous substances: Airborne exposure limits), the total mass of Neodymium that may become systemically available in the blood stream after it had been solubilized in the lung after inhalatory uptakewas calculated as:

Test material

Amount of Neodymium solubilized in the blood after inhalatory uptake and its solubilization by lung surfactant in mg/l blood after 1 day

Amount of Neodymium solubilized  

in the blood after inhalatory uptake and its solubilization by lung surfactant

in mg/l blood after 7 days

Nd2O3

1.3210 -6

1.6810 -4

NdBFe

1.510 -6

2.410 -6

The normal serum concentration of Neodymium (background value) in humans is < 0.03 mg/l (R. A. Bulman: Metabolism and toxicity of the lanthanides, in: Metal Ions In Biological Systems (Hrsg. A. Sigel und H. Sigel) Marcel Dekker, Inc., New York,40, 683-708, 2003.

Therefore, it clearly follows that the potential systemic increase of Neodymium from inhalation of Neodymium oxide and Neodymium NdBFe alloy particles is only marginal and obviously without any health relevance since to date measured serum concentrations do not seem to be associated with adverse health effects.

Applicant's summary and conclusion

Conclusions:
The solublity of Nd2O3 and NdBFe in water and Gamble's solution is very low, resulting in concentrations of Nd in the test solutions of the order of ppb. The resulting bioaccessiblity of Neodymium from Nd2O3 and NdBFe alloy in the lung after inhalatory uptake according to inert dust occupational exposure standards is negligible.
Executive summary:

The solublity of Nd2O3 and NdBFe in water and Gamble's solution is very low, resulting in concentrations of Nd in the test solutions of the order of ppb. The resulting bioaccessiblity of Neodymium from Nd2O3 and NdBFe alloy in the lung after inhalatory uptake according to inert dust occupational exposure standards is negligible.