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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

RA_CAS71786-47-5_EPA OTS 797.1050_Selenastrum carpricornutum: NOEL: 1000 mg/L WAF, ErL50 (72h) > 1500 mg/L.
RA_CAS115733-09-0_EPA OTS 797.1050_Selenastrum capricornutum: NOEL: 1000 mg/L WAF, ErL50 (72h) > 1000 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
1 500 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 analogues structures of the magnesium sulfonate target substance (CAS 213297-75-9). For the substance itself, no experimental data are available. Since all substances used belong to the same chemical group, aryl-alkyl sulfonates, the same behaviour and toxicity potential can be expected. The following read-across substances were used to fulfil the endpoint of toxicity to algae and cyanobacteria: Magnesium sulfonate read-across substance (CAS 71786-47-5) and calcium sulfonate read-across substance (CAS 115733-09-0). 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

Selenastrum capricornutum (new name: Pseudokirchneriella subcapitata) was used as test organism in the experiments conducted according to EPA OTS 797.1050 under GLP compliance. Based on the intrinsic properties of the used substances, Water Accommodated Fractions (WAFs) were prepared for testing. The test duration was 96 h. Daily cell counts and cell observations were made visually by means of direct microscopic examination with a haemocytometer. The experiments were conducted under static conditions.

Ward (1994a) used nominal concentrations of 125, 250, 500, 1000 and 1500 mg/L as WAF of the magnesium sulfonate read-across substance (CAS 71786-47-5) for the experiment. Samples were collected from each of the two replicate control and treatment vessels and passed through a 0.45 µm filter prior to analysis. For storage, 125 mL amber glass bottles were used, preserved with sulphuric acid and refrigerated. Total organic carbon (TOC) was analysed by EPA method 415.1 at initial time point (0 hours) high (1500 mg/L), low (125 mg/L) and control test solutions and at test termination (96 hours). No unusual effects were reported. After 72 hours, cell density measurements in the treatments were 97%, 100%, 101%, 95% and 25% of the control at 125, 250, 500, 1000 and 1500 mg/L respectively. At 96 hours, cell density measurements in the treatments were 78%, 61%, 62%, 58% and 31% of the control at 125, 250, 500, 1000 and 1500 mg/L respectively. After 72 hours, specific growth rate measurements were 100%, 100%, 100%, 98% and 75% of the control at 125, 250, 500, 1000 and 1500 mg/L WAF, respectively. At 96 hours, specific growth rate measurements were 95%, 91%, 91%, 89% and 72% of the control at 125, 250, 500, 1000 and 1500 mg/L WAF, respectively. A parametric one-way analysis of variance (ANOVA) and Dunnett's test were used to calculate the no-observed effect level when data were normally distributed and a Kruskal-Wallis test was used when data were not normally distributed. Binomial non-linear interpolation methods were used to calculate EL50 values. 72-hour Effective Loading Rates (EL50) are 1400 mg/L and >1500 mg/L based on cell density and specific growth rate, respectively. 96-hour Effective Loading Rates (EL50) are 1100 mg/L and >1500 mg/L based on cell density and specific growth rate, respectively. The corresponding 72-hour and 96-hour No Observed Effect Loading Rates (NOELR) are 1000 mg/L based on both specific growth rate and cell density.

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, 1994b). 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 is considered to be > 1000 mg/L. A parametric one-way analysis of variance (ANOVA) and Dunnett´s test were used to calculate the corresponding No Observed Effect Level (NOEL), which is reported as 1000 mg/L WAF for each sampling period.