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Environmental fate & pathways

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Description of key information

Based on its physical and chemical properties, the Level III fugacity model has been used to predict the environmental partitioning for methyl eugenol, with consideration of the half-lives in air (estimated as 5 hours, HSDB 1983-2009), water (measured as 8 days, CHRIP c2008), soil (8 days estimated as the same as half-life in water), and sediments (32 days estimated as four times the half-life in water). The results from the modelling suggest that methyl eugenol is expected to mainly reside in the environmental compartment to which it is released.

Environmental Persistence

Both empirical and modelled data is available to determine the environmental persistence and bioaccumulation potential of the substance. In the atmosphere, methyl eugenol is not expected to undergo photolysis due to the lack of absorption in the environmental UV spectrum (>298 nm) (Meylan and Howard 1993). If released to air, the substance will degrade by reaction with photochemically-produced hydroxyl radicals. The half-life for this reaction in air is estimated to be 5 hours (HSDB 1983-2009).

In water, methyl eugenol is not expected to undergo hydrolysis in the environment due to the lack of hydrolysable functional groups.

The test data from the biodegradation study show that there is approximately 92.11% ultimate biodegradation over 28 days and passing the 10 -day window for ready biodegradability with over 60% degradation in 10 days, using a domestic sewage inoculum in a ready-biodegradation test for methyl eugenol. Furthermore the empirical data from a biodegradation study (HSDB 1983-2009) show that there is approximately 90% ultimate biodegradation over 28 days using an activated sludge inoculum. The rapid degradation observed in the test can be translated into a half-life of approximately 8 days in water, assuming first order degradation kinetics. The substance is therefore not expected to persist in water. Shaver and Bull (1980) identified a dissipation half-life of 34 hours in water and 16 hours in soil. Although they did not determine a mechanism for the dissipation, they speculated that the losses were mostly a result of evaporation.

The Danish QSAR database was used to support the empirical biodegradation results, which show ready biodegradability. According to the report from the Danish QSAR database the Biowin 5 and Biowin 6 models both have am estimated value of over 0.5, which means that the prediction is in line with the biodegradability values.

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