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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity of tert-butyl peroxypivalate to algae was assessed according to OECD guideline 201, EU method C.3 and OPPTS 850.5400. The 72-h EC50 value based on growth rate was determined as 1.417 mg/L and based on yield was determined as 0.422 mg/L. The 72-h EC10 value based on growth rate was determined as 0.293 mg/L and based on yield was determined as 0.119 mg/L. The overall NOEC was determined to be 0.096 mg/L. The results are based on the measured geometric mean concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:
1.417 mg/L
EC10 or NOEC for freshwater algae:
0.293 mg/L

Additional information

The toxicity of tert-butyl peroxypivalate to algae was assessed according to OECD guideline 201, EU method C.3 and OPPTS 850.5400. Exponentially growing cultures of Pseudokirchneriella subcapitata were exposed to various concentrations of the test item over several generations under defined conditions. The algal growth in relation to a control culture was determined over a fixed test period of 72 hours and thus, over several algal generations. Test concentrations were prepared by appropriate diluting of a stock solution. Based upon the results from the preliminary experiment, nominal concentrations of 0.8; 1.8; 4.1; 9.5; 21.7 and 50.0 mg/L were investigated in the main study. Because significant toxic effect was observed in the lowest tested concentration, influence of the test item was further investigated in a complementary experiment at the following nominal concentrations: 0.07, 0.15, 0.35 and 0.80 mg/L. The measured concentrations deviated more than 20 % from the nominal during the experiments therefore the geometric mean of the measured concentrations were calculated in order to determine exposure concentrations. The corresponding calculated geometric mean concentrations were the followings: Experiment I: 0.414, 0.779, 2.383, 5.471, 12.301 and 26.531 mg/L;

Experiment II: 0.053, 0.096, 0.189 and 0.462 mg/L.

For the determination of the LOEC and NOEC, the calculated mean growth rates and yield at the test concentrations were tested on significant differences to the control values by Bonferroni t-Test using TOXSTAT software. The test item had a statistically significant inhibitory effect on the growth based on the average specific growth rate and yield of Pseudokirchneriella subcapitata after the exposure period of 72 hours in the concentration range of 0.189 – 26.531 mg/L (Bonferroni t-Test, α=0.05). Accordingly the 72-hour overall NOEC was determined as 0.096 mg/L. The ErCx and EyCx values of the test item and their confidence limits were calculated using Probit analysis by SPSS PC+ software. The 72-h ErC10 was determined as 0.293 mg/L and the 72-h ErC50 was determined as 1.417 mg/L. The 72-h EyC10 was determined as 0.119 mg/L and the 72-h EyC50 was determined as 0.422 mg/L.