Registration Dossier

Diss Factsheets

Administrative data

Endpoint:
acute toxicity: dermal
Data waiving:
other justification
Justification for data waiving:
other:
Justification for type of information:
Human and/or environmental exposure to elemental Dysprosium in massive form can be excluded, since at environmental conditions (air/humidity) practically insoluble substances (oxides, hydroxides) are formed immediately on the surface: Any respective investigations would be of no additional merit for the relevant scientific knowledge with regard to human and/or environmental protection.The skin provides a sturdy, flexible, and self-repairing barrier to the exterior environment, protecting the internal body organs and fluids from external influences. The major barrier to permeation within the skin is the Stratum corneum, the outermost cornified layer, consisting of corneocytes. These corneo-cytes comprise mainly scleroprotein keratin. Permeation of a chemical through the Stratum corneum is basically a diffusion process in which active transport plays no role. The layer with the highest resistance to diffusion is the rate-limiting membrane. For many compounds, the lipophilic Stratum corneum is the primary or rate-limiting barrier.Dysprosium metal is insoluble in water and not fat soluble, consequently Dysprosium is not expected to be absorbed through the skin.In particular also Dysprosium cations will not be absorbed dermally.Furthermore the permanent magnets production with Dysprosium alloys takes place under strictly controlled conditions (vacuum, inert gas; see technological process) in order to ensure the high quality of the permanent magnets. Therefore exposure of humans during production of the magnets is unlikely to occur. In addition the study is technically not feasible: Application of Dysprosium in massive form, which would be a prerequisite for toxicological and eco-toxicological studies, is practically not feasible. For this purpose at least Dysprosium powder would be required (see Annex XI (2)).The Lanthanide elements own a very high affinity for oxygen; they exhibit the highest free energy for oxide formation of all elements in the periodic table, accounting for the exceptional thermodynamic stability of the oxides. In consequence the metals will react with air, building up an oxide layer on the surface. This implies the technical unfeasibility of exposure to “free” Dysprosium metal (powder form), which is a prerequisite for the requested biological tests. Appropriate application of „free“ Dysprosium metal is not possible since the particles would react in contact with water and air. Insoluble Dysprosium hydroxides are formed in contact with skin humidity.Furthermore according to REACH annex V, section 1 "substances which result from a chemical reaction that occurs incidental to exposure of another substance or article to environmental factors such as air, moisture, microbial organisms or sunlight" are exempted from the obligation to register. The ignoble metal Dysprosium is due to its high reactivity (high reduction potential) with water and air not existent at ambient conditions. In air Dysprosium metal is converted to Dysprosium oxide. In contact with water Dysprosium hydroxide is immediately formed. These reaction products are exempted from REACH registration obligations.

Data source

Materials and methods

Results and discussion

Applicant's summary and conclusion