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Environmental fate & pathways

Biodegradation in water: screening tests

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Biodegradation in water:
readily biodegradable but failing 10-day window

Additional information

Jasmonyl is a multi-constituent substance composed of 3-pentyltetrahydro-2H-pyran-4-yl acetate (main component, approximately 60%) and nonane-1,3-diyl diacetate (2nd main component, approximately 25%).

 

Standard biodegradation tests are not ideally suited to mixtures because they measure ultimate biodegradation as a function of either the CO2 evolved or O2 consumed and as such do not provide information on the biodegradability of individual constituents. Thus the ready biodegradability study on Jasmonyl (Givaudan Study No 99-E20) has been assessed in conjunction with data on the ready biodegradability of Jasmopyrane Forte, which contains approximately 80% of 3-pentyltetrahydro-2H-pyran-4-yl acetate (the main component in Jasmonyl) and predicted biodegradation for the nonane-1,3-diyl diacetate (2ndmain component in Jasmonyl). This additional information is provided in the ready biodegradation endpoint record for Jasmonyl as “background material”.

 

In the Ready Biodegradability study performed on JASMONYL, 44% biodegradation was observed after 14 days. After this time the two replicates behaved differently. In one flask, after a short biodegradation plateau of approximately 4 days, biodegradation restarts to reach a level of 77% after 28 days. In the other flask the biodegradation level remained at 43-46% for a significantly longer period with biodegradation starting again around day 30 (See Appendix 2 in full study report. The different behaviour between the two flasks is probably due to some heterogeneity in the inoculum leading to different microorganism population growth and diversity (i.e. one or more competent microorganism(s) required for the biodegradation to continue were either not introduced into the second flask or had not established themselves to a sufficient concentration for metabolism to be observed). However, the level of 77% biodegradation achieved in one replicate indicates that one or both components of JASMONYL are biodegraded.

 

The two stages of biodegradation observed (i.e. approximately 44% up to day 14, then up to 77% after 28 days in one replicate) may be related to the multi-component nature of JASMONYL (i.e. one component more easily degraded than the other) or to rapid partial degradation for one or more of the component(s) to transient metabolites which are then subsequently degraded.

 

The latter scenario is supported by tests performed on JASMOPYRANE FORTE. Two ready biodegradability studies are available; a 301F and sealed CO2 test. In both studies the replicates behaved similarly. A first biodegradation step starts immediately and reaches 43% on day 18 (301F) or 41% on day 14 (sealed CO2). Then a second step starts and reaches 71% (301F) to 71.5% (Sealed CO2) after 28 days. Given the chemical structure of 3-pentyltetrahydro-2H-pyran-4-yl acetate, it is likely that the first stage of biodegradation represents breakdown of the first 4 carbon atoms in the pentyl side chain and the acetate moiety (see Figure 1 in endpoint record). This represents 6 of the 12 carbon atoms present in the molecule (i.e. 50% of the carbon present) and thus roughly equates to the 43% biodegradation measured based on BOD. The second stage of biodegradation is probably ring opening of a transient “pyrane” metabolite followed by subsequent breakdown. Based on the result of this test, JASMOPYRANE FORTE (and hence the 3-pentyltetrahydro-2H-pyran-4-yl acetate component of JASMONYL) can be considered as readily biodegradable but failing the 10 day window.

 

The second main component of JASMONYL, nonane-1,3-diyl diacetate, is a linear diester. Based on its chemical structure, this component would be expected to be more readily degraded than the cyclic component. Indeed, BIOWIN predicts that this component would be readily biodegradable.

 

In summary, the main component of Jasmonyl (3-pentyltetrahydro-2H-pyran-4-yl acetate, approximately 60%) is considered to be readily biodegradable but failing the 10 day window (based on study for JASMOPYRANE FORTE) and the second component of Jasmonyl (nonane-1,3-diyl diacetate, approximately 25%) is predicted to be readily biodegradable. Thus, based on the component data it is reasonably to conclude that JASMONYL is readily biodegradable but failing the 10 day window for the purposes of classification and labelling. This is supported by the test data on Jasmonyl itself, where the results for one replicate (77% after 28 days, flask 2) and the mean results (62% after 28 days), exceed the pass criterion of > 60%.

The fact that both components are expected to be completely mineralised under environmentally relevant conditions, is supported by the high % BOD obtained in a 302C inherent test (96% after 28 days).