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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Exposure of Pseudokirchneriella subcapitata to the test item gave ErL50 (72 h) greater than 160 mg/L loading rate WAF. However, it was not possible to calculate 95 % confidence limits for the ErL50 value as no loading rate tested resulted in greater than 50 % inhibition of growth rate. The No Observed Effect Loading Rate (NOEL) based on growth rate was 40 mg/L loading rate WAF and the Lowest Observed Effect Loading Rate (LOEL) based on growth rate was 80 mg/L loading rate WAF (OECD 201 and EU Method C.3).
 
Exposure of Pseudokirchneriella subcapitata to the test item gave EyL50 (72 h) 150 mg/L loading rate WAF. The No Observed Effect Loading Rate (NOEL) based on yield was 40 mg/L loading rate WAF and the Lowest Observed Effect Loading Rate (LOEL) based on yield was 80 mg/L loading rate WAF (OECD 201 and EU Method C.3).

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Additional information

GUIDELINE

A study was performed to assess the effect of the test item on the growth of the green algaPseudokirchneriella subcapitata. The method was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) 761/2009.

METHODS

Due to the low aqueous solubility and complex nature of the test item, a Water Accommodated Fraction (WAF) was prepared.

Following a preliminary range-finding test,Pseudokirchneriella subcapitatawas exposed to Water Accommodated Fractions (WAFs) of the test item over a range of nominal loading rates of 10, 20, 40, 80 and 160 mg/L (three replicates per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group using a Coulter multisizer particle counter.

RESULTS

Analysis of the test preparations at 0 hours showed that measured test concentrations ranged from 0.035 to 0.24 mg/L. A decline in measured concentration was observed at 72 hours to less than the limit of quantification (LOQ) of the analytical method employed, which was determined to be 0.0015 mg/L, indicating that the test item was unstable over the test duration.

Given that the toxicity cannot be attributed to a single component or a mixture of components but to the test item as a whole, the results were based on nominal loading rates only.

CONCLUSION

Exposure of Pseudokirchneriella subcapitata to the test item gave ErL50 (72 h) greater than 160 mg/L loading rate WAF. However, it was not possible to calculate 95 % confidence limits for the ErL50 value as no loading rate tested resulted in greater than 50 % inhibition of growth rate. The No Observed Effect Loading Rate (NOEL) based on growth rate was 40 mg/L loading rate WAF and the Lowest Observed Effect Loading Rate (LOEL) based on growth rate was 80 mg/L loading rate WAF.

 

Exposure of Pseudokirchneriella subcapitata to the test item gave EyL50 (72 h) 150 mg/L loading rate WAF. The No Observed Effect Loading Rate (NOEL) based on yield was 40 mg/L loading rate WAF and the Lowest Observed Effect Loading Rate (LOEL) based on yield was 80 mg/L loading rate WAF.