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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

The short-term toxicity (96 h) of aluminium to fresh water fish (juvenile rainbow trout) has been determined to be between 6.17 and 7.67 mg/L aluminium (depending on water hardness). In another study Atlantic salmon was exposed to aluminium and the resulting LC50 (96 h) values were determined to be between 587 µg/L (pH 5.5) and to 599 µg/L (pH 6.5). The toxicity of ammonia, the other significant degradation product of AlN, was studied at various test conditions towards rainbow trout. The lowest measured LC50 value (96 h) was 11.1 mg/L dissolved total ammonia nitrogen (NH3-N).

Key value for chemical safety assessment

LC50 for freshwater fish:
6.17 mg/L
LC50 for marine water fish:
587 µg/L

Additional information

Three studies have been evaluated to assess the short-term toxicity of aluminium and ammonia, the environmentally relevant degradation products of AlN, to fish. The studies revealed a higher short-term (96 h) toxicity of aluminium to the Atlantic salmon (0.587 -0.599 mg/L, depending on pH) and a lower short-term toxicity to the freshwater fish juvenile rainbow trout (6.17-7.67mg/L, depending on water hardness). The toxicity of ammonia was studied at various test conditions towards rainbow trout (Salmo gairdneri). The lowest measured LC50 (96 h) value was 11.1 mg/L (in terms of total ammonia, i.e. NH3-N).

A general tendency of increased toxicity of aluminium towards marine fish cannot be claimed because only one species was used for each type of habitat. The toxicity of ammonia to fish was expressed in the study as LC50 values related to dissolved ammonium-nitrogen concentration and related to free ammonia (NH3). The LC50 value calculated on the basis of unionised ammonia (NH3) was not used as basis for the risk assessment because this would overestimate the toxicity of ammonium in aqueous solution drastically. If ammonia comes in contact with water it will form an equilibrium between the ionised and the unionised form which is highly on the side of the ionised form, slightly depending on temperature and pH. Nevertheless, the amount of ionised ammonium will be much higher compared to the NH3-form. For this reason the environmental risk characterisation will be performed on the basis of the lowest LC50 value identified for aluminium. The contribution of ammonia to the toxicity against fish, which is significantly lower, can be ignored.