2-tert-pentylcyclohexyl acetate

Biodegradation in water: screening tests

Description of key information

Coniferan biodegrades up to 12% in an OECD TG 310 study and is considered non-readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Additional information

The key study is a screening study according to OECD TG 310 (Headspace Test) and in compliance with GLP criteria (WIL, 2012). In this study an amount of 20 mg/L test substance (expressed as TOC) was inoculated with non-adapted activated sludge from a domestic sewage treatment plant for 28 days. CO2 evolution from the ultimate aerobic biodegradation of the test substance is determined by measuring the inorganic carbon (IC) produced in the test bottles over that produced in the blank control bottles. The amount of IC produced by the test substance (corrected for that evolved by the controls and the amount added by basification, where applicable) is expressed as a percentage of the theoretical amount of IC (ThIC) that could have been produced if complete biodegradation of the test substance occurred. The study contained two tests. The initial test was a standard ready biodegradability test conducted according to OECD 310 Guidelines. The second test was an enhanced biodegradation screening test, also based upon OECD 310 Guidelines. The enhancements included low-level pre-adaptation, by utilization of inoculum pre-exposed to the test substance concurrently with the conduct of the first test and by extending the test duration to 60 days. Each test contained a blank control group, two reference groups and a treatment group. The blank controls were used to measure the background IC production of the inoculum medium and were not dosed with a carbon source. The reference chambers were dosed with either rapeseed oil or 1 -Octanol, substances known to be biodegradable, at a nominal concentration of 20 mg C/L. The results indicated that the activated sludge inoculum was active, degrading the reference substances rapeseed oil and 1 -Octanol respectively 81.5% and 74.2% in the initial test with a 28-day duration and 61.6% and 72.3% by day 28 in the second test with a 60-day duration. The average cumulative percent biodegradation for the test substance was 12.4% in the initial test and 17.1% in the second test.

In a supporting study, the non ready biodegradability is confirmed. In this study, also a headspace test performed according to OECD TG 310, Coniferan was biodegradaded 3% after 28 days and 1% after 56 days inoculation (van Ginkel and Geerts, 2008). The study report provides a bit less detail on study results but is nonetheless considered to be reliability 2 and thus adequate to support the key value for chemical safety assessment.