3,7-dimethylocta-2,6-dienyl acetate

Endpoint summary

Description of key information

Abiotic degradation:

Air: No experimental data on the phototransformation of the substance in air are available. Based on estimation with the QSAR model AopWin (v1.92), in air the substance undergoes rapid degradation after reaction with hydroxyl radicals with a DT50 value of 0.06 days for all constituents. Degradation after reaction with ozone radicals is also rapid with a DT50 -value of 0.013 days for all constituents. This indicates that the substance is not a long-range transported chemical in air according to the UNECE criteria (http://www.unece.org/fileadmin/DAM/env/documents/2000/ece/eb/ece%20eb%20air.60.e.pdf). These half-lives will not be used for the CSA because these are calculated and not experimental values. Furthermore, the substance does not have an ozone depletion potential because it does not contain halogens and does not have the potential to reach the stratosphere (EU CLP (EC No. 1272/2008 and its updates).

Water: The hydrolysis endpoint is waived as the substance is qualified as readily biodegradable. Some hydrolysis can be expected based on the substance’s ester functionality. To be conservative a hydrolysis half-life of 1 year is used.

Biotic degradation:

The biodegradability is assessed based on read-across from the close structural analogue Geranyl acetate, which is tested in an OECD TG 301F study in which the substance qualified as readily biodegradable at an exposure concentration of 100 mg/l.

Bioaccumulation:

Bioaccumulation in aquatic and terrestrial species is based on the available information (log Kow (4.6) and calculated BCF values). The BCFs for aquatic and terrestrial organisms were calculated using QSARs of Veith et al. (1979) and Jager (1998), both incorporated in the EUSES model, and yielded values of 1620 and 479 L/kg ww, respectively. This are conservative values because (acetate) esters are known to cleaved readily by carboxyl esterases.

Transport and distribution:

The absorption / desorption (Koc) is calculated to be 2010 L/kg based on the Koc-QSAR for esters incorporated in EUSES, with the log Kow of 4.6 as input.

The Henry's law constant is calculated using the equation from EUSES. Using a molecular weight of 196 g/mole, and the experimentally determined vapour pressure of 2.12 Pa (at 24 °C) and water solubility of 28.8 mg/L (at 24 °C), the Henry's Law constant at environmental temperature (12 °C) is calculated to be 7.29 Pa·m³/mol. The substance is not expected to volatilise from water to a significant extent.

Based on Level III environmental distribution modelling using EPISUITE for all constituents (assuming equal and continuous releases to air, water and soil), using the EPISuite default physico-chemical parameters for each constituent as input, it is estimated that the majority of the constituents released to the environment will partition mainly into soil (ca. 79.3%) and water (ca. 20.2%) with minor amounts to sediment (ca. 0.4%) and air (0.05%).

The SimpleTreat model, which is incorporated in EUSES, simulates the distribution of the substance in a Sewage Treatment Plant (STP). Model calculations show that 72.6% of the substance will be degraded and that 15.0%, 10.3% and 2.1% will partition to sewage sludge, water and air, respectively.