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EC number: 404-450-2 | CAS number: 118685-34-0 COBRATEC 435
Toxicity to aquatic algae and cyanobacteria
Administrative data
Link to relevant study record(s)
Description of key information
Under the conditions of the present study with Pseudokirchneriella subcapitata, BUTYL BZT powder, 5-butyl-1H-benzotriazole, sodium salt inhibited growth rate significantly at 0.27 mg a.i./l. The inhibition was below 10% and therefore considered biologically irrelevant. Yield was significantly inhibited at a concentration of 0.27 mg a.i./l.
The EC50 for growth rate inhibition (72h-ERC50) was 5.7 mg a.i./l with a 95% confidence interval ranging from 4.9 to 6.4 mg a.i./l, based on TWA concentrations.
The EC50 for yield inhibition (72h-EYC50) was 0.91 mg a.i./l with a 95% confidence interval ranging from 0.76 to 1.1 mg a.i./l, based on TWA concentrations.
The 72h-NOEC for growth rate inhibition was 0.27 mg a.i./l. The 72h-NOEC for yield inhibition was 0.084 mg a.i./l.
The study procedures described in this report were based on the Organization for Economic Co-operation and Development (OECD), OECD guidelines for Testing of Chemicals, guideline No. 201: "Freshwater Alga and Cyanobacteria, Growth Inhibition Test", Adopted March 23, 2006; Annex 5 corrected 28 July 2011.
Key value for chemical safety assessment
- EC50 for freshwater algae:
- 5.7 mg/L
- EC10 or NOEC for freshwater algae:
- 0.27 mg/L
Additional information
The inhibition of the growth rates increased with increasing concentration and was significantly reduced from a TWA concentration of 0.27 mg a.i./l. However, the effect at 0.27 mg a.i./l was below 10% and therefore considered biologically irrelevant. Therefore, the NOEC was determined to be 0.27 mg a.i./l, corresponding with 1.1 mg/l.
Inhibition of yield increased with increasing TWA concentration of BUTYL BZT powder, 5-butyl-1H-benzotriazole, sodium salt from 0.27 mg a.i./l upwards resulting in 100% inhibition at 30 mg a.i./l. Statistically significant inhibition of yield was found at test concentration of 0.27 mg a.i./l and higher. This corresponds to a NOEC of 0.084 mg a.i./l corresponding to 0.34 mg/l.
Microscopic observations at the end of the test revealed a normal and healthy appearance at a TWA concentration of 0.81 mg a.i./l of the exposed cells when compared to the control.
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