Registration Dossier

Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Data waiving:
other justification
Justification for data waiving:
other:
Justification for type of information:
In accordance with column 2 of REACH Annex VII the study does not need to be conducted if there are mitigating factors indicating that aquatic toxicity is unlikely to occur, for instance if the substance is highly insoluble in water or unlikely to cross biological membranes. Since Dysprosium (and its alloys) are only sparingly soluble in water (in aqueous solution „free“ Dysprosium metal is converted to Dysprosiumhydroxide) and crossing of Dysprosium cations through biological membranes is unlikely (fat barrier) and therefore bioavailability is insignificant.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. 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 REACH 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. Due to its reductive power and vigorous reaction with water appropriate application of Dysprosium metal (powder form) is technically not possible. In aqueous solution „free“ Dysprosium metal is converted to Dysprosiumhydroxide. Dysprosiumhydroxide is insoluble in water.Furthermore the study is scientifically unjustified: Human and/or environmental exposure to elemental Dysprosium in massive form can be excluded, since at environmental conditions (presence of 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.In aqueous solution „free“ Dysprosium metal (powder form) is converted to Dysprosiumhydroxide. Dysprosiumhydroxide is insoluble in water.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 in 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