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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

72-h EC50 (growth rate) to Pseudokirchnerella subcapitata  is 20 mg octyl alcohol isomers per litre obtained in the undiluted filtrate prepared at 100 mg Titanium tetra(octanolate), branched and linear per litre as per OECD 201. 
The NOEC for growth rate reduction, 6.7 mg/l based on a TWA concentration of octyl alcohol isomers, which represents 32 % of a filtrate prepared at 100 mg Titanium tetra(octanolate), branched and linear per litre.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
32 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 octyl alcohol isomers (Exxal 8; alcohols, C7-9-iso, C8-rich) and hydrated titanium dioxide (key study on hydrolysis Brekelmans 2013). The key values on toxicity to algae indicates that toxicity of this substance is similar to the main degradation product octyl alcohol isomers (Exxal 8, alcohols C7-9-iso, C8-rich) when these results are compared with the results of the supporting study by Cash G et al (1999). Based on this supporting study, the 96 h EC50 -value of Exxal 8 to green algae is 14.6 mg/l and chronic value 2.2 mg/l, respectively.

The key study was performed in accordance with OECD TG 201 and GLP to assess the effect of the test item on the growth of green algae. The test item hydrolysed in aqueous test media releasing octyl alcohol isomers and hydrated titanium oxide (precipitated form) in water. The final test was performed based on the measured concentrations of the hydrolysis product octyl alcohol isomers. The precipitate, a floating layer of undissolved material (hydrated titanium dioxide) was filtered through a 0.45 µm membrane filter and used as the highest test concentration. The lower test concentrations were prepared by subsequent dilutions of the filtrate in test medium.

Six exponentially growing algal cultures were exposed to a control whereas three replicates per group were exposed to solutions containing 0.1, 0.32, 1.0, 3.2, 10, 32 and 100% of the filtrate prepared at 100 mg/l. Samples for analytical confirmation of the exposure concentrations were taken at the start, 24 hours after start of the test and at the end of the exposure. Concentrations of the hydrolysis products being octyl alcohol isomers were measured. At the start of the test, the mean measured concentrations were 1.96, 7.0, 19 and 57 mg/l in test groups representing 3.2, 10, 32 and 100% of the filtrate, respectively. The mean measured concentrations were at the level of 45 to 95% of initial after 24 hours of exposure. At the end of the test the actual concentrations were below 0.7 mg/l at 3.2 and10 % of the filtrate, below 1.4 mg/l at 32% of the filtrate and below 2.8 mg/l in the undiluted filtrate (note that the concentrations should be considered indicative). The Time Weight Average concentrations were calculated 0.81, 3.3, 6.7 and 20 mg octyl alcohol isomers per litre in test groups representing 3.2, 10, 32 and 100 % of the filtrate, respectively.

Test substance reduced growth rate at a TWA concentration of 20 mg octyl alcohol isomers per litre and inhibited the yield of this fresh water algae species significantly at a TWA concentration of 6.7 mg octyl alcohol isomers per litre.

The EC50 for growth rate reduction (ERC50: 0-72h) was beyond the range tested, i.e. exceeded a TWA concentration of 20 mg octyl alcohol isomers per litre obtained in the undiluted filtrate prepared at 100 mg Titanium tetra(octanolate), branched and linear per litre. The EC50 for yield inhibition (EYC50: 0-72h) was 10 mg/l with a 95 % confidence interval ranging from 2.2 to 46 mg/l.

The NOEC for growth rate reduction was 6.7 mg/l based on a TWA concentration of octyl alcohol isomers, which represents 32 % of a filtrate prepared at 100 mg Titanium tetra(octanolate), branched and linear per litre. The NOEC for yield inhibition was 3.3 mg/l based on a TWA concentration of octyl alcohol isomers which represents 10 % of a filtrate prepared at 100 mg Titanium tetra(octanolate), branched and linear per litre.

Results of this study do not lead to the classification of the substance as toxic to aquatic organisms in accordance with the criteria set out in Directive 67/548/EC and Regulation (EC) 1272/2008. This toxicity study is classified as reliable without restrictions and satisfies the guideline requirements for the aquatic algae study.