A mixture of: 4-(2,2,3-trimethylcyclopent-3-en-1-yl)-1-methyl-2-oxabicyclo[2.2.2]octane; 1-(2,2,3-trimethylcyclopent-3-en-1-yl)-5-methyl-6-oxabicyclo[3.2.1]octane; spiro[cyclohex-3-en-1-yl-[(4,5,6,6a-tetrahydro-3,6',6',6'a-tetramethyl)-1,3'(3'aH)-[2H]cyclopenta[b]furan]; spiro[cyclohex-3-en-1-yl-[4,5,6,6a-tetrahydro-4,6',6',6'a-tetramethyl)-1,3'(3'aH)-[2H]cyclopenta[b]]furan]

Toxicity to microorganisms

Description of key information

The toxicity of the substance to STP microorganisms was examined in a study according to OECD TG 209 and in compliance with GLP (Huntingdon, 1995). In this study, the substance was inoculated with a mixed population of activated sewage sludge micro-organisms from a sewage treatment plant treating predominantly domestic sewage at nominal concentrations of 0 (control), 10, 18, 32, 56 and 100 mg/L. The test compound was dispersed in 20% Tween 80 acetone to give an initial stock solution of 500 mg/mL and subsequent dilution of this stock with 20% Tween 80 acetone gave a series of stock solutions from which the desired test exposure levels were prepared. No test substance analysis was performed (or required). Oxygen consumption rates were monitored at 30 minutes and 3 hours after exposure, and inhibition of respiration calculated. The validity criteria of the test were met.

At 30 min less than 10% inhibition of respiration was observed at the test concentrations of 10 and 18 mg/L. At test concentrations of 32, 56, and 100 mg/L inhibition of respiration was 23, 37, and 37%, respectively. At 3 hours, inhibition of respiration was 10, 12, 2, 17, and 16% at the test concentrations of 10, 18, 32, 56 and 100 mg/L. Based on these findings the 30 -min and 3 -h EC50 values were determined at >100 mg/L. As after 3 hours exposure a clear concentration effect relationship was not present, the 30 -min NOEC of 18 mg/L is used for the risk characterisation.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

18 mg/L