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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity to aquatic algae for zinc bis(di C8-C10, branched, C9 rich, alkylnaphthalene sulphonate) is determined by a read-cross from testing with the close structural analogue DNNSA (di C8-C10, branched, C9 rich, alkylnaphthalene sulphonic acid). The EC10 for growth rate is 0.70 mg/L and the EC50 for growth reduction is > 1.2 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
1.2 mg/L

Additional information

In view of the similarities of the results found for the daphnia studies performed with DNNSA, BaDNNSA and ZnDNNSA, a read-across is considered appropriate. Therefore the EC50 for the substance will be based on the outcome of the tests on DNNSA.

Under the conditions of the DNNSA study with Pseudokirchneriella subcapitata, reduced growth rate and inhibited the yield of this fresh water algae species significantly at a TWA concentration of 0.27 mg/l and higher. The EC50 for growth rate reduction (ERC50: 0-72h) was beyond the range tested, i.e. exceeded a TWA concentration of 9.6 mg/l. The EC50 for yield inhibition (EYC50: 0-72h) was 2.4 mg/l with a 95% confidence interval ranging from 0.53 to 10 mg/l. The lowest EC10 in this study is for cell number (yield) which is 0.16 mg/L and this is the key value for safety assessment.

In a second study with DNNSA, algae were exposed to 0.019, 0.078, 0.30, 0.57 and 1.2 mg/l (calculated average exposure concentrations for 10, 32 and 100% of WAF prepared at 1.0 mg/l and WAFs prepared at 3.2 and 10 mg/l). The substance reduced growth rate of this fresh water algae species significantly at an average exposure concentration of 1.2 mg/l.

 

The EC50for growth rate reduction (72h-ERC50) was beyond the range tested, i.e. > average exposure concentration of 1.2 mg/l.

The EC50for yield inhibition (72h-EYC50) was 1.2 mg/l with a 95% confidence interval ranging from 0.41 to 3.5 mg/l.

The EC10for growth inhibition was 0.80 mg/l with a 95% confidence interval ranging from 0.29 to 2.2 mg/l.

The EC10value for yield inhibition was 0.20 mg/l with a 95% confidence interval ranging from 0.061 to 0.61 mg/l.