Registration Dossier
Registration Dossier
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EC number: 500-687-1 | CAS number: 162303-51-7
Toxicity to aquatic algae and cyanobacteria
Administrative data
Link to relevant study record(s)
Description of key information
Testing is not scientifically justified as this substance is hydrolytically unstable. Therefore, the toxicity of the main degradation product n-butanol is used as a key value in CSA.
Key value for chemical safety assessment
- EC50 for freshwater algae:
- 225 mg/L
- EC10 or NOEC for freshwater algae:
- 134 mg/L
Additional information
When this substance comes in contact with water or moisture, a complete hydrolysis will take place with no significant reaction products other than n-butanol and hydrated titanium dioxide (half-life < 2 hours, Brekelmans 2013). The organic decomposition product n-butanol is readily biodegradable and not persistent based on the log Kow value of 0.84. The CSA indicates that toxicity of this substance is similar to the main degradation product n-butanol.
Key studies (short-term toxicity to daphnia and algae) conducted for the analogue category member (titanium tetraisopropanolate CAS 546-68-9) justify that these organometallic titanates hydrolyse during toxicity testing and the aquatic toxicity is similar to the alcohol released in water. These results of the analogue category member of the target substance are included as a part of this weight of evidence approach. Category and read-across justifications are presented in the annexes of the CSR.
Based on these facts toxicity testing on algae is unjustified, and the key value for CSA is obtained from the studies conducted for n-butanol. The OECD 201 guideline study conducted in accordance with GLP reports the 96-h EC50 (growth rate) of 225 mg/l (95% CL: 204 -246 mg/l) to Pseudokirchnerella subcapitata, and the 96-h EC10 of 134 mg/l (95% CKL: 124 -167 mg/l), respectively (UNEP 2004). Another non reliable study presents the 7-d toxicity threshold value of 875 mg/l to Scenedesmus quadricauda (Bringmann &Kuhn 1980).
In conclusion, the results of n-butanol verify that there is no need to classify the target substance as toxic to algae, and the key value for CSA can be obtained from the most reliable guideline study of the degradation product.
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