Butan-2-ol

Toxicity to aquatic algae and cyanobacteria

Description of key information

The substance was not toxic to algae when tested according to OECD guideline 201 (Alga, Growth Inhibition Test), the substance is predicted to possess a 96-hour EC50 values of 2029 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

2 029 mg/L

EC10 or NOEC for freshwater algae:

1 240 mg/L

Additional information

Three studies addressing toxicity to aquatic algae and cyanobacteria are presented in the dossier. The study selected as key was carried out on the read-across substance,methyl ethyl ketone (CAS No. 78-93-3) being the first oxidation product of s-buthanol. Thus methyl ethyl ketone may be used as an appropriate surrogate for s-buthanol. The results are in line with supportive studies performed with s-buthanol that did not derive an EC50 value but only addressed an LC3 endpoint after 7 respectively 8 days of exposure.

RA Toxicity to aquatic algae and cyanobacteria. 001 – Selenastrum – 1998 – Key: Acute toxicity of the read-across substance, methyl ethyl ketone (CAS No. 78-93-3), to Pseudokirchneriella subcapitata (previously known as Selenastrum capricornutum) was assessed according to OECD guideline 201 (Alga, Growth Inhibition Test), and in compliance with OECD GLP. Algae were exposed to the substance at a nominal concentrations of 313, 625, 1250, 2500, and 5000 mg/L in the culture medium. The study was performed using 250 mL glass Erlenmeyer flasks, stoppered with foam, containing 1000 mL of test solution inoculated with an algal suspension such that the initial cell concentration was 1x10⁶ cells/mL. Test flasks were incubated at 23.9-25.8°C and constantly exposed to a light intensity of 3870-4730 lux. Analytical chemistry and physico-chemical measurements were carried out at the beginning and the end of the test. An electronic particle counter was used to determine the cell concentrations. During the test, the control pH ranged between 7.3 and 7.8. The following validity criteria were met: exponential growth in the control was observed. The concentrations of the test substance at the beginning of the test were approximately 94 to 104% of nominal. All test concentrations dropped below 70% of nominal at exposure termination, the test results were calculated based on the day 0 measured concentrations. No abnormalities of algae were observed during the test and the 96 hour No Observed Effect Concentration (NOEC), was determined to be 1240 mg/L based on growth rate. The 96 hour EC50 was determined to be 2029 mg/L which also was based on growth rate.

Toxicity to aquatic algae and cyanobacteria.002-Scenedesmus – 1980: Acute toxicity to Scenedesmus quadricauda was assessed; however, no guideline was followed. The algae were exposed to the substance under static conditions for 7 days. The toxicity threshold was determined to be 95 mg/L based on mean extinction value. This toxicity threshold, approximately equivalent to the LC3, over a longer exposure period is in keeping with the result of the key study.

Toxicity to aquatic algae and cyanobacteria.003-Scenedesmus – 1977: Acute toxicity to Scenedesmus quadricauda was assessed; however, no guideline was followed. The algae were exposed to the substance under static conditions for 8 days. The toxicity threshold was determined to be 95 mg/L based on growth inhibition. This toxicity threshold, approximately equivalent to the LC3, over a longer exposure period is in keeping with the result of the key study.