Cyclododeca-1,5,9-triene

Biodegradation in water: screening tests

Description of key information

Not readily biodegradable according to OECD criteria.

Key value for chemical safety assessment

Type of water:

freshwater

Additional information

Experimental data are available on the biodegradability of 1,5,9-Cyclododecatriene (CAS 4904-61-4).

A study by Hüls (199, report no. GF-190) was selected as key study. The closed-bottle test was conducted according to the EU Method C.4-E under GLP with sewage from a wastewater treatment plant treating predominantly domestic sewage was used. No biodegradation of the test substance was observed after 28 days based on the biological oxygen demand (0% BOD). 

This result is supported in a modified MITI (I) test according to OECD 301C under GLP. The test conditions were improved for volatile substances. A mixed inoculum according to the guideline was used. No biodegradation was observed based on dissolved organic carbon (DOC) and chemical analysis by gas chromatography (0% removal after 14 days; J-CHECK, 2018).

In contrast to the previous studies, the substance was biodegradable in a modified Ready Biodegradation test (based OECD 301B). The test material was radiolabelled (t,t,t-[14C]CDT); therefore, it was possible to use lower test concentrations by monitoring the formation of 14CO2. The lag phase was less than 7 days. After 63 days, the t,t,t-[14C]CDT concentrations in the 0.2 mg/L vessels decreased to approximately 8% of the originally applied concentration in the viable test mixtures, compared to approximately 96% for the corresponding abiotic controls (i.e., biologically inhibited). For test mixtures amended with 1 mg/L of the test compound, the t,t,t-[14C]CDT concentrations in the viable test mixtures decreased to non-detectable levels (i.e., < 0.8%) after 77 days, compared to approximately 97% remaining in the corresponding abiotic controls. After 63-77 days, 14CO2 production ranged from approximately 50-68% in the viable mixtures compared to approximately 1-2% in the abiotic controls. Taken together these results indicate that t,t,t-[14C]CDT was mineralized to 14CO2 by the activated sludge inoculum.

In a similar study without radiolabelling of the test substance, 1,5,9-Cyclododecatriene was biodegradable as well. The modified Ready Biodegradation test (based on OECD 301F) was initiated to examine the aerobic biodegradation of trans, trans, trans, 1,5,9-cyclododecatriene (t,t,t-CDT). Biodegradation of t,t,t -CDT was observed following a lag phase of approximately 14 days. After 42 days, the t,t,t-CDT concentrations in the viable mixtures amended with 1 mg/L t,t,t -CDT decreased to less than 7% of the initial dose applied, compared to 95% remaining in the corresponding abiotic controls ( i.e. biologically inhibited test mixtures). After 60 days, the t,t,t-CDT concentrations in the viable mixtures amended with 10 mg/L t,t,t-CDT decreased to 38% of the initial dose applied, compared to 87% remaining for the corresponding abiotic controls. The water controls containing 1 mg/L t,t,t -CDT in mineral medium alone showed no change in concentration of the test material beyond the experimental variability through 42 days, confirming that the experimental design and analytical procedures minimized any losses of t,t,t-CDT from the test system. The delayed degradation (i.e. extended lag phase) at 10 mg/L is in agreement with some inhibition of the inoculum at this test compound level as revealed by the toxicity controls. Due to a significant contribution of endogenous respiration in the formation of inorganic carbon, no conclusive interpretation regarding the mineralization of t,t,t-CDT was possible.

It can be concluded that 1,5,9-Cyclododecatriene is biodegradable, not meeting the criteria for ready biodegradability according to OECD.