Titanium(4+) ethanolate

Toxicity to aquatic algae and cyanobacteria

Description of key information

Testing is not scientifically justified as this substance is hydrolytically unstable. Therefore, acute toxicity (72-h LCr50 and NOEC/EC10) of the main decomposition product ethanol is used as a key value.

Key value for chemical safety assessment

EC50 for freshwater algae:

275 mg/L

EC50 for marine water algae:

10 940 mg/L

EC10 or NOEC for freshwater algae:

11.5 mg/L

EC10 or NOEC for marine water algae:

3 240 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 ethanol and hydrated titanium dioxide (half-life < 5 minutes, OECD 111). The organic decomposition product ethanol is readily biodegradable having also a low log Kow value (-0.3). The CSA indicates that toxicity of this substance is similar to the main degradation product ethanol. Key studies (short-term toxicity to daphnia and algae, Klimisch score 1) 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. Category and read-across justifications are presented in the annexes of the CSR.

Because of rapid hydrolysis (half-life less than 5 minutes), a toxicity study on algae is unjustified, and the key value for CSA is obtained from the most reliable 72-h EC50 and NOEC- values of ethanol (peer-reviewed secondary source, El Jay 1996 and Cowgill & Milazzo 1989).

According El Jay (1996), the 72 h ECr10-value of ethanol to Chlorella vulgaris is 11.5 mg/l and ECr50 is 275 mg/l, respectively. Studies were based on the nominal test concentrations and followed the OECD 201 guideline. In this same study, the 72 h ECr10-value of ethanol to Selenastrum capricornutum is 440 mg/l and ECr50 is 12 900 mg/l, respectively. In this study which followed the basic principles of a guideline OECD 201, two green algae Chlorella vulgaris and Selenastrum capricornutum were exposed to ethanol at sufficient concentrations to enable EC50 values to be established. Exposure was carried out over 5 days with daily measurements of growth characterised by chlorophyll measurement. The dose response curve obtained was very shallow. The four day data presented showed some evidence that the control had passed the exponential growth phase. Basing the results on the 3 day measurements when exponential growth was still clearly evident, ethanol showed slight toxicity to the Chlorella species but not to the Selenastrum species. Based on the weight of evidence approach, the lowest toxicity values conducted with Chlorella species were used as key value in CSA.

According to Cowgill & Milazzo (1989), the 5-d h NOEC-value of ethanol to Skeletonema costatum is 3240 mg/l and ECr50 is 10 940 mg/l, respectively. Studies were based on the nominal test concentrations in saltwater. This study was considered reliable as it was well reported and gave sufficient amount of data to derive both an EC50 value and a NOEC for CSA in saltwater.