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Short-term toxicity to aquatic invertebrates

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Description of key information

Two standardised test on Al2(SO4)3 and two non standardised tests on (NH4)2SO4 and AlNH4(SO4)2 were performed on the same species (Daphnia magna). The greatest sensitivity was related to aluminium toxicty at pH ranging between 6.5-7.5. The lowest EC50(48h) correspond to 72.2 mg/L of AlNH4(SO4)2.12H2O.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
72.2 mg/L
EC50/LC50 for marine water invertebrates:
72.2 mg/L

Additional information

Aluminium ammonium sulfate is highly soluble in water, dissociating to aluminium sulfate and ammonium sulfate. Therefore, the acute toxicity of the salt on the aquatic invertebrates can be assessed by the effects of its dissociation products.

Two test performed according to OECD 202 guideline and GLP were performed with Al2(SO4)3on Daphnia magna under static and semi static conditions. During the 48h static test no pH adjustment was made and the pH decrease up 4.6. In this test an EC50 (48h) of 0.33 mg/L of Dissolved Al was found corresponding to 72.2 mg/L AlNH4(SO4)2.12H2O at a pH of approximately 6.5-7.5. During the second test under semi-static condition the pH was adjusted between 7.5 and 8.0. No effects were found in this test, therefore, EC50 (48h) greater than 0.176 mg/l Dissolved Al corresponding to 242 mg/L AlNH4(SO4)2.12H2O was determined.

 

An 96h acute toxicity test of (NH4)2SO4to water fleaDaphnia magnaand not performed according to international guidelines was reported in a peer review publication. The methodology was scientifically acceptable and the report well documented however the test was assessed as not assignable because only scarce information is provide on the test substance, no analytical measurement was performed and no replicates were used. Daphnids were exposed under static condition to test chemical at nominal concentration of 0.1, 1, 10 and 100 mg /L. All tests were conducted within the extremes of 6.5 to 8.5 pH units and within a temperature of 20 +/-1 °C. The proportion of Daphnids killed at the highest dose level was less than 50%, therefore the LC50 (96h) value was expressed as greater than 100 mg/L test material corresponding to 172 mg/L AlNH4(SO4)2.12H2O.

 

Another peer review publication reported the toxicity of the salt AlNH4(SO4)2.12H2O to the water fleasDaphnia magnadetermined on the basis of a EC50 by the immobilization test after 48h of exposure. The methodology was scientifically acceptable however the test was assessed as not assignable because no information is provide on the substance purity, the concentrations tested were not reported and the final pH, temperature and oxygen level were not measured. Final concentrations were based on the results of preliminary acute static bioassays and selected on a logarithmic scale but no analysis was performed during the test. The mean temperature was 13°C, the mean pH was 7.6, the mean dissolved oxygen was 5.6 mg/L, the mean total hardness was 240 mg/L as CaCO3 and the mean total alkalinity was 400 mg/L as CaCO3. The EC50 (48h) expressed in metal ion was 59.60 mg/L corresponding to 1001.3 mg/L AlNH4(SO4)2.12H2O.

 

The results show that the greatest sensitivity of Daphnia magna was observed during the 48h static test with Al2(SO4)3and is related to aluminium toxicity at pH of 6.5-7.5. No toxicity of aluminium is observed when the pH is maintained between 7.5 and 8.0 as shown in the semi static test on Al2(SO4)3.By comparison, the toxicity related to ammoniac was less important after 96h exposure to (NH4)2SO4at a pH between 6.5 to 8.5. The result on the toxicity of the salt at pH 7.6 confirm the result on the toxicity of the dissociation products reinforcing the read across approach reliability.