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Environmental fate & pathways

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Results of the OECD 301B ready biodegradation test indicate that dihydromyrcenol is readily biodegradable: 72% degradation after 28 days. According to the REACH regulation, it was not necessary to conduct the following tests as dihydromyrcenol was determined to be readily biodegradable:

- Hydrolysis test

- Biodegradation in water and sediment: simulation test

- Biodegradation in soil

Adsorption/desorption: the adsorption coefficient of dihydromyrcenol was determined using the HPLC method. Under the conditions of study, the adsorption coefficient of dihydromyrcenol was 177.83 (log Koc = 2.25). This finding suggests that dihydromyrcenol will show limited binding to soil or sediment particulates.

Photodegradation in air: removal from the atmosphere by reaction in sunlight is predicted to be rapid (half-life due to reaction with atmospheric OH radicals or ozone 3.449 hours or 22.92 hours respectively, QSAR estimates)

Although the experimentally determined Log Kow of dihydromyrcenol is slightly greater than 3.0, low BCF (64.8 (L/kg ww or dimensionless) estimated by the BCFBAF v3.00 module of EPISuite v4.0) and rapid biotransformation in fish are predicted by application of the widely accepted EPISuite QSAR model to dihydromyrcenol. The prediction of rapid biotransformation is supported by analogy to mammalian metabolism data. Together, these results lead to low concern for possible bioaccumulation. In addition a similar BCF value can be derived using the BCF model mentioned in REACH guidance R.7.10.3.2, this results in a BCF value of 115 l/kg wwt. This somewhat higher value does not allow for metabolic transformation, which is modelled in the EPISuite QSAR calculation (and mammalian toxicokinetic data in this dossier support a prediction of such biotransformation).