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Toxicity to aquatic algae and cyanobacteria

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Description of key information

RA_CAS115733-09-0_EPA OTS 797.1050_Selenastrum capricornutum: NOEL: 1000 mg/L WAF, ErL50(72h) > 1000 mg/L. 
RA_CAS61789-86-4_OECD201_Scenedesmus subspicatus: NOEL: 100 mg/L WAF, ErL50(72h) > 100 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
1 000 mg/L
EC10 or NOEC for freshwater algae:
1 000 mg/L

Additional information

General considerations

The toxicity to aquatic algae was investigated for different two different analogue structures of the calcium sulfonate target substance (C15 -C36). For the substance itself, no experimental data are available. Since both substances used belong to the same chemical group, aryl-alkyl sulfonates, the same behaviour and toxicity potential can be expected. Calcium sulfonate read-across substances (CAS 115733-09-0 and CAS 61789-86-4 wre used to fulfil the endpoint of toxicity to algae and cyanobacteria. Investigations concerning toxicity in marine algae were not performed. For the detailed procedure of the read-across principle and justifications, please refer to the separate Read-Across Statement attached to this Chemical Safety Report.

Experimental results -Selenastrum capricornutum

In a key study the calcium sulfonate read-across substance (CAS 115733-09-0) was tested at nominal concentrations of 100, 300 and 1000 mg/L as WAF loading rates under static conditions (Ward, 1994). The study was performed according to US EPA Guideline OTS 797.1050. The algal population grew well during the test, since an average of 1,711,000 cells/mL was recorded in the control group; resulting in a doubling time of 13 h. The test vessels containing 1000 mg/L WAF were slightly cloudy at the start of the test and after 24 h exposure time. After 72 hours, biomass measurements were 80 %, 62 % and 70 % of the control at 100, 300 and 1000 mg/L WAF, respectively. At 96-hours, biomass measurements were 70 %, 66 % and 88 % of the control at 100, 300 and 1000 mg/L WAF, respectively. Based on these findings, the ErL50 (72h), ErL50(96h), EbL50(72h) as well as the EbL50(96h) value are considered to be > 1000 mg/L. The corresponding No Observed Effect Level (NOEL) amounts to 1000 mg/L WAF for each sampling period.

Experimental results -Scenedesmus subspicatus

In a 72 hour key study, the cultures of the green algae (Scenedesmus subspicatus) were exposed to sulphonic acids, petroleum, calcium salts at nominal concentrations of 0 and 100 mg/L nominal WAF loading rate under static conditions (limit test). The test was performed by Mead (2005) in accordance with the OECD Guideline 201 (Alga, Growth Inhibition Test). The EL50 based biomass was > 100 mg/L and the EL50 based on growth rate was > 100 mg/L. There were no compound related phytotoxic effects.