4-methyl-3-decen-5-ol

Toxicity to aquatic algae and cyanobacteria

Description of key information

The preferred observational endpoint in the algal inhibition study is growth rate because it is not dependent on the test design (ECHA guidance Chapter R.7b v 4.0 June2017, OECD 201 Guideline). The EU CLP regulation (No 1272/2008 and its adaption 286/2011) also states that classification should be based on the ErC50. Furthermore, the preferred observational endpoint in long-term studies is the EC10 value because it is derived from the dose response curve. In contrast the NOEC strongly depends on the experiment design (e.g. the concentrations used in the test). Thus the EC50 and EC10 based on growth rate are used for classification purposes and derivation of PNEC. Since the 72 hour and 96 hour values are equally acceptable, the lowest values, which are for 72h, have been used for the chemical safety assessment.

Key value for chemical safety assessment

EC50 for freshwater algae:

3.6 mg/L

EC10 or NOEC for freshwater algae:

0.68 mg/L

Additional information

The acute toxicity of the test material to freshwater green algae was investigated in Pseudokirchneriella subcapitata in a GLP study which was conducted in accordance with standardised guidelines OECD 201, EU Method C.3 and EPA OPPTS 850:5400. During the study the algae were exposed to the test material at nominal concentrations of 0, 0.51, 1.3, 3.2, 8.0 and 20 mg/L under static conditions for 96 hours. The geometric mean measured concentrations of the test material were <LOQ, 0.46, 1.3, 2.6, 7.1 and 8.3 mg/L.

After 72 hours, inhibition of cell density was 16-96 % relative to the negative control response. Inhibition of yield was 16-97 % relative to the negative control and inhibition of growth rate at the 0-72 hour interval was 4-68 % relative to the negative control. Reductions in growth rate were statistically significant at 2.6, 7.1 and 8.3 mg/L when compared to the negative control response. Yield and cell density was significantly reduced in all treatment groups at 72 hours of exposure.

After 96 hours, inhibition of cell density was 16-98 % relative to the negative control. Inhibition of yield was 16-99 % relative to the negative control and inhibition of growth rate at the 0-96 hour interval was 4 -80 % relative to the negative control. Reductions in growth rate were statistically significant at 2.6, 7.1 and 8.3 mg/L when compared to the negative control response. Yield and cell density was significantly reduced in all treatment groups at 96 hours of exposure.

After 96 hours of exposure, there were no signs or noticeable aggregation or flocculation in the negative control or in any treatment groups. Cells were observed to be adhering to the test vessels in all experimental groups. Cells in the treatment levels appeared normal when compared to cells present in the negative control.

Under the conditions of the test, the 72-hour EC50, EyC50 and ErC50 values were determined to be 1.4 (C.I. 0.98-2.1), 1.4 (C.I. 1.0-2.1) and 3.6 (C.I. 2.6-5.0) mg/L respectively. The 96 hour EC50, EyC50 and ErC50 of the test material was determined to be 1.8 (C.I. 1.4-2.4), 1.8 (C.I. 1.5-2.3) and 3.8 (C.I. 3.2-4.5) mg/L, respectively. The 72-hour and 96-hour NOEC, based on effects on cell density and yield, were determined to be less than 0.46 mg/L. The 72 and 96-hour NOEC value for growth rate was detemined to be 1.3 mg/L. The 72 and 96-hour EC10 values and their corresponding 95% confidence intervals (CI) for growth rate were calculated as 0.68 (<0.46 to 1.5) mg a.i./L and 1.2 (0.85 to 1.8) mg a.i./L, respectively.

The study was performed in line with GLP and accepted standardised guidelines with a high standard of reporting. The study was assigned a reliability score of 1 in accordance with the principles for assessing data quality as defined in Klimisch (1997).