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Environmental fate & pathways

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Reaction mass of 2,2'-oxybisbutane (DSBE), DIPE, SBA and 2-methylpropan-2-ol (TBA) consists of moderately volatile organic substances (overall vapour pressure 72 hPa at 20°C, all known constituents in the range of 5 – 250 hPa at 20°C considered as moderately volatile of relatively low molecular weight (average ca. 107 g/mol).

An overall Henry’s law constant (H) calculated from the parameters used for exposure assessment is 163 Pa m3/mol (at 20°C). According to the ECHA TGD IR & CSA, 2008, R7a (p.191), chemicals with H values around 100 Pa m3/mol will tend to partition from water to air at a significant rate. At the same time the reaction mass is soluble in water (solubility of 1 – 10 g/L). Values for individual components vary with DIPE having a higher vapour pressure (199 hPa at 25°C) than the other components and TBA and SBA a higher water solubility (> 100 g/L). DSBE was estimated to be only moderately water soluble (ca. 0.3 g/L) and at the same time has a relatively low vapour pressure (estimated 22 - 30 hPa at 25°C), similar to TBA and SBA. Due to these differences DIPE and DSBE are predicted to volatilze relatively rapidly based on estimated Henry’s law constants and therefore to be present mainly in the air compartment, while TBA and SBA will mainly remain in the water compartment. SBA will be rapidly degraded biotically, while TBA is only inherently biodegradable and may therefore persist in the aquatic compartment. DIPE and DSBE are not readily biodegradable, but will be rapidly oxidized in the atmosphere (estimated atmospheric oxidation half-lives of ca. 4 - 5 hours).

DIPE, TBA and SBA show a low potential for adsorption as log Pow values, based on literature data and a measurement with the reaction mass using the HPLC method, are below 3. Only for DSBE a log Pow between 2.9 – 3.8 and a corresponding log Koc of 2.1 (Koc = 132) that can likely be assigned to DSBE, indicates a moderate potential for adsorption. Chemicals with a Koc value between 150 and 500 are likely to move through the soil at a moderate rate [1]. Strong binding to soil particles is only expected for a log Pow > 5 or log Koc > 4 and adsorption to sediment it not expected below a log Koc of 2.7 - 3 (ECHA, TGD IR & CSA, 2008, R7 p.154). Therefore, DSBE is not predicted to persist in soils. None of the constituents present in the reaction mass are expected to bioaccumulate (see chapter 8).

[1] Swann RL, Laskowshi DA, McCall PJ, Vander-Kuy K and Disburger HJ (1983). A rapid method for the estimation of the environmental parameters octanol/water partition coefficient, soil sorption constant, water to air ratio and water solubility. Residue Reviews 85, 17-28.