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Long-term toxicity to aquatic invertebrates

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Description of key information

pH and Water Hardness play an important role in the toxicity of soluble aluminium salts. The 21-d nominal EC50 for reproduction of Daphnia magna exposed to Aluminium was calculated as 986.5 μg/L at pH 6.3, hardness of 140 mg/L, and 2 mg/L DOC. The chronic (6 day) NOEC for C. dubia exposed to aluminium chloride ranged from 1.02 to 0.34 mg/L in water with hardness from 25 mg/L to 200 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
1.43 mg/L

Additional information

 

The substance is a ceramic . In contact with water the substance is hardening within minutes integrating most of the soluble fraction into the solid formed. Nevertheless to assess the toxicity of the substance, the worst case scenario for solubility has been applied:

In the absence of organic matter, Al3+ is the predominant aluminium species at low pH (less than 5.5). As pH increases above 5.5, aluminium-hydroxide complexes formed by hydrolysis become increasingly important and dominate aqueous aluminium speciation . Al3+, depending on the composition of the medium and pH, may form Al(OH)3 or AlCl or AlNO3 or AlSO4. According to the long term solubility calculation:

-         At long term, if we consider the substance as a 100% CaAl2O4component:

o  1µg of ground substance if completely dissolved will provide 0.341µg of total Aluminium (34.1%) until Al(OH)3saturation.

Knowing that maximum CaAl2O4content is 70% , the ratio between substance and Aluminium equivalent Al(OH)3 is 0.7 x 0.341 = 0,238. or 1g of Aluminium equivalent Al(OH)3 is 4.2g of substance.

A read-across was made with all relevant soluble aluminium salts . An assessement factor of 4.2 is applied for the calculation of the substance long term NOEC.

In a long-term reliable chronic toxicity study with AlCl3 to C.Dubia, identified as acceptable from the published literature, the NOEC (6 days) values are ranged from 0.34 mg/L to 1.02 mg/L.

Other two supporting studies on aluminium nitrate and aluminium sulfate may be used to assess the low toxicity of the soluble fraction of the substance.

Hence the calculated NOEC could be from 1.43 mg/L to 4.28 mg/L.

Literature Review: 

Six long-term chronic toxicity studies to two species of aquatic invertebrates(Ceriodaphnia dubia and Daphnia magna) were identified as acceptable studies. ECr10s were calculated using raw data provided from each study using the statistical program Toxicity Relationship Analysis Program (TRAP) version 1.10 from the US EPA National Health an Environmental Effects Research Laboratory (NHEERL). All other endpoints were as reported in each study. NOECs and EC10s ranged from 0.076 to 4.9 mg Al/L and 0.021 to 0.997 mg Al/L, respectively. Water quality data for these studies suggest a direct relationship between toxicity and pH, hardness, and DOC. For studies that experimentally manipulated water quality (e.g., CIMM 2009 and 2010a ), toxicity decreased with increasing pH, hardness, and DOC.

Recent studies conducted by the Chilean Mining and Metallurgy Research Center (CIMM) tested aluminium toxicity to C. dubia and D. magna (one data point) across a range of pH, DOC, and hardness values. These results demonstrated that increasing DOC concentration has a protective effect on aluminium LC50s for invertebrates. Increasing water hardness also had a protective effect. Aluminium toxicity was reduced at high pH, but a larger reduction was observed when changing pH from 6 to 7 than from 7 to 8. 

Two additional LC50 values that are not included in this comparison were reported for pH 7 and pH 8 in filtered test media (i. e., filtered before organisms were exposed). The filtered test media were approximately 5-fold less toxic, meaning that their LC50s were approximately 5-fold higher than the results from exposure to unfiltered media. Therefore, toxicity was largely a function of exposure to aluminium hydroxides, which are removed by filtration through these types of filters.