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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC30 (72-h) values (Al3+) ranged from 70 nM (pH 6.0) to 10 µM (pH 4.5). The influence of aluminium on the growth of the alga Chlorella pyrenoidosa was expressed as EC30, increasing markedly from 3 µg/L to 50 µg/L as the pH is decreased from 6 to 5.
The following inhibitory concentrations were determined describing adverse effects of aluminium against Desmodesmus subspicatus (test duration 72h): Algal growth rate ErC50 = 10.90 mg/L; biomass integral of the growth curve EbC50 = 10.02 mg/L; endpoint measurement EeC50 = 12.87 mg/L.
The 21-d LOEC value of ammonia against Chlorella vulgaris was found to be ≥ 500 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
10.9 mg/L

Additional information

The 21d study by Tam et al. was performed to determine the effects of ammonium on the unicellular green alga Chlorella vulgaris. The study revealed that within the tested ammonia concentration range no EC50 value could be determined because the effect was not strong enough within the tested concentration range to inhibit the growth rate by 50 %. Statistically significant adverse effects on the growth rate were observed at 500 mg NH3-N per litre.

The 72h study by Eisenträger et al. was performed to measure algal growth-inhibition with Desmodesmus subspicatus in photometric and fluorometric assays for several metals including aluminium. The following results were obtained: Algal growth rate ErC50 = 10.90 mg/L; biomass integral of the growth curve EbC50 = 10.02 mg/L; endpoint measurement EeC50 = 12.87 mg/L.

The 96h study by Parent et al. measured the influence of aluminium on the growth of the alga Chlorella pyrenoidosa. Effects were reported as 30 % inhibitory concentrations (EC30) and values for aluminium increased markedly from 3 µg/L to 50 µg/L as the pH is decreased from 6 to 5. The study revealed that the observed adverse effect (growth inhibition) depends on the pH value of the growth media. EC30 values for aluminium (Al3+) values ranged over more than two orders of magnitude from 70 nM (pH 6.0) to 10 µM (pH 4.5).

The presented studies show that adverse effects on algae are much lower for ammonia than for aluminium. The aluminium component of aluminium nitride is mainly responsible for adverse effects. For this reason the risk assessment will be performed only for aluminium and not for ammonia/ammonium. Additionally, aluminium toxicity strongly depends on pH and temperature.

The effect values reported by Eisenträger et al. will be forwarded to the risk assessment as these are the only "standard values" regarding exposure duration (72h) and effect level (ErC50) available.