Terbium

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

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. In aqueous solution „free“ Terbium metal is converted to Terbiumhydroxide. Terbiumhydroxide is insoluble in water. Since Terbium (and its alloys) are only sparingly soluble in water (in aqueous solution „free“ Terbium metal is converted to Terbiumhydroxide) and crossing of Terbium cations through biological membranes is unlikely (fat barrier) and therefore bioavailability is insignificant. Furthermore the permanent magnets production with Terbium alloys takes place under strictly co ntrolled 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 Terbium in massive form, which would be a prerequisite for toxicological and eco-toxicological studies, is practically not feasible. For this purpose at least Terbium 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” Terbium 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 Terbium metal (powder form) is technically not possible. In aqueous solution „free“ Terbium metal is converted to Terbiumhydroxide. Terbiumhydroxide is insoluble in water as can be shown from the water solubility data in section 4.8. Furthermore the study is scientifically unjustified: Human and/or environmental exposure to elementa l Terbium in massive form can be excluded, since at environmental conditions (presenve 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“ Terbium metal (powder form) is converted to Terbiumhydroxide. Terbiumhydroxide is insoluble in water.

Description of key 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. In aqueous solution „free“ Terbium metal is converted to Terbiumhydroxide. Terbiumhydroxide is insoluble in water. Since Terbium (and its alloys) are only sparingly soluble in water (in aqueous solution „free“ Terbium metal is converted to Terbiumhydroxide) and crossing of Terbium cations through biological membranes is unlikely (fat barrier) and therefore bioavailability is insignificant. Furthermore the permanent magnets production with Terbium alloys takes place under strictly co ntrolled 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 Terbium in massive form, which would be a prerequisite for toxicological and eco-toxicological studies, is practically not feasible. For this purpose at least Terbium 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” Terbium 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 Terbium metal (powder form) is technically not possible. In aqueous solution „free“ Terbium metal is converted to Terbiumhydroxide. Terbiumhydroxide is insoluble in water as can be shown from the water solubility data in section 4.8.

Furthermore the study is scientifically unjustified: Human and/or environmental exposure to elementa l Terbium in massive form can be excluded, since at environmental conditions (presenve 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“ Terbium metal (powder form) is converted to Terbiumhydroxide. Terbiumhydroxide is insoluble in water.