1,2,3,4,4a,5,6,7-octahydro-2,5,5-trimethyl-2-naphthol

Toxicity to aquatic algae and cyanobacteria

Description of key information

Ambrinol 95 is tested in an algae toxicity test according to OECD TG 201 and following GLP. Pseudokirchneriella subcapitata was exposed to the test substance at various concentrations (100, 32, 10, 3.2 and 1.0 mg test item/L) for 72 hours under closed conditions. This study encompassed 6 treatment groups (5 dose rates of the test item and a control) with three replicates per test concentration and six replicates for the controls. At test start, 50 mL of the test media were inoculated with nominal 5000 algal cells per mL test medium and defined volumes of the algal suspensions were sampled after 24, 48 and 72 hours for determination of cell densities by spectrophotometric measurement. The measured concentrations were 95 and 88% of the from nominal concentrations for fresh test media and aged test media, respectively. The effect is highest at 24h and algae growth minimally recovered at 32 mg/l and no growth was seen 100 mg/l. The validity criteria were met as the cell density increase in the control was 169.2 fold (should be ≥16-fold), the coefficient of variation of the sectional (daily) growth between control replicates was 7.9% (should be ≤ 35%) and coefficient of variation of average growth between control replicates was 1.1% (should be ≤ 7%). The 72h-ErC50, 72h-ErC10, and 72h-NOEC of the test substance to Pseudokirchneriella subcapitata was 25.3, 9.69, and 1.0 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

25.3 mg/L

EC10 or NOEC for freshwater algae:

9.69 mg/L