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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Description of key information

The 48-h EC50 for freshwater invertebrates ( 6840 mg pigment/L) was observed for the effect on mortality of Daphnia magna in hard water (Weyand, 2000; Klimisch 2).

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
6 840 mg/L

Additional information

Read-across approach:

 

Zircon, cadmium yellow is a zircon-type oxide/pigment with the main structural element ZrSiO4 (Zr in an dodecahedral O environment) which forms a strong and inert matrix. Zr and Si are the main components with percentages of ~46% w/w and 15% w/w respectively. The amount of Cd as component is about 2% w/w.

 

The read-across substanceSilicic acid, zirconium salt, cadmium pigment encapsulated is a zircon-type pigment as well with an identical crystallographic structure and a very similar composition. Zr content is ~46% w/w and the Si content is ca. 14% w/w. Cd is present in about 4.7% w/w. Minor amounts of Se and S (1.53 and 1.04% w/w, respectively) are present as well.

 

Besides the obvious structural analogy the solubility of both pigments in aqueous and physilogical media are as follows (determination of Zr and Cd):

 

Solubility of Cd from the pigment Zircon, cadmium yellow in physiological media was in a range of 0.180µg/L (PBS) and 0.398 µg/L (ALF) after 2 hours. After 24 hours a dissolution range from 0.140 µg/L (GMB) - 0.722 µg/L (GST) was measured.

 

Solubility of Zr from the pigment Zircon, cadmium yellow in physiological media was in a range of below LODand 0.812 µg/L (ALF) after 2 hours. After 24 hours a dissolution range from below LOD (ASW) - 1.44 µg/L (ALF) was measured.

 

The read-across substance Silicic acid, zirconium salt, cadmium pigment encapsulated afforded after 2 hours a solubility for the element Cd in range of 0.07 µg/L (GMB) 2.58 µg/L (GST) and after 24 hours a solubility of 0.07 µg/L (GMB) to 6.13 µg/L (GST).

 

Solubility of Zr from the pigmentSilicic acid, zirconium salt, cadmium pigment encapsulatedin physiological media was in a range of below LODand 0.52 µg/L (ALF) after 2 hours. After 24 hours a dissolution range from below LOD - 1.25 µg/L (ALF) was measured.

 

T/D testing of the pigment Zircon, cadmium yellowafforded the following solubility at 1mg loading after 28 days:

Cadmium: below LOD (<0.0048) and 0.2077 ± 0.0993μg/L at pH 8 and pH 6, respectively

Zirconium: <LOD (0.0017μg/L) and 0.9241 ± 0.4349 at pH 8 and pH 6, respectively

 

T/D testing of the read-across substance Silicic acid, zirconium salt, cadmium pigment encapsulated afforded the following solubility at 1mg loading after 28 days:

Cadmium: 0.34 ± 0.09μg/L and 0.86 ± 0.39μg/L at pH 8 and pH 6, respectively

Zirconium: <LOQ (0.001μg/L) and <LOD at pH 8 and pH 6, respectively

 

In sum, the two zircon type pigments are structurally identical with very similar composition and both show a very low solubility in different artificial and aqueous media. In fact, the read-across substanceSilicic acid, zirconium salt, cadmium pigment encapsulated shows slightly higher dissolution and bioaccessibility without showing any signs of systemic or local toxicity in various studies (acute inhalation, skin/eye irritation, sensitisation). No toxicity on algae, fish and invertebrates could be observed in respective studies.

Hence, read-across to Silicic acid, zirconium salt, cadmium pigment encapsulated is fully justified.

One reliable study (Klimisch 2) is available for the acute toxicity of the test item on Daphia magna. The value for mortality and immobilisation was determined to be 6840 mg pigment/L.