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Read across justification for Distilled Tall Oil, Magnesium Salts

Distilled tall oil, magnesium salts is produced by reacting magnesium hydroxide and distilled tall oil. The resulting substance is a UVCB, with the following generic structure:


The R groups are derived from the distilled tall oil starting material, which is a UVCB substance derived from natural sources, with varying composition. Therefore there are a number of different possible combinations for the resulting carboxylic acid groups present in the complex mixture of divalent magnesium salts.

Based on supplier analysis, the distilled tall oil comprises a mixture of unsaturated fatty acids – primarily C18 (~70%) and mixed rosin acids (~30%); typical analysis of a sample of distilled tall oil is presented in Table 1. The variable composition of distilled tall oil means that Distilled tall oil, magnesium salts will comprise a complex mixture of the divalent magnesium salts of both fatty acid and rosin components, in proportion to the ratio of fatty acids:rosin acids found in the starting distilled tall oil. In the absence of data on Distilled tall oil, magnesium salts, the environmental fate, ecotoxicity and toxicology properties are predicted based on read across to related fatty acid and rosin acid salts. Analytical data (Mass Spec., FTIR and NMR) confirm the presence of divalent magnesium carboxylic acid salts and NMR shows the presence of a proportion of cyclic carboxylic acid structures.

No data were identified for magnesium salts of C18 unsaturated fatty acids, which comprises approximately 70% of the registered substance. Data were available however for a similar lithium salt – fatty acids, C18-(unsaturated) lithium salts. Read across to this compound is justified based on the fact that it is also a divalent salt of fatty acids derived from distilled tall oil, which has similar physic-chemical properties. The lithium and magnesium ions present in these salts are not likely to contribute to the toxicity and therefore any effects observed are likely to be due to the fatty acid component.

For the rosin acid salt component (~30%) of Distilled tall oil, magnesium salts, data are read across from a category of substances with similar composition, containing rosin, hydrogenated rosin and rosin acid salts. This category of rosin substances have been registered under REACH using a category approach, and members of this category are considered to be representative of the rosin acid salts found in Distilled tall oil, magnesium salts. The category of rosin substances includes both monovalent and divalent salts of rosin acids, including a magnesium salt. Therefore the rosin acid component of Distilled tall oil, magnesium salts would fit within this category and read across is considered to be appropriate.

Further details are given in the attachment in Section 13.

Environmental Fate summary

Distilled tall oil, magnesium salt is a UVCB with varying components, but comprising fatty acid salts with predominantly C18 carbon chain lengths and rosin acid salts. Experimental environmental fate data is not available for Distilled tall oil, magnesium salt. However, its environmental fate properties can be read across from data on its components. Data have been read across from rosin salts and a C18 fatty acid salt.

Biodegradation data has been read across from other fatty acid and rosin substances. Several reliable biodegradation studies are available for these substances, and based on these, Distilled tall oil, magnesium salt is considered to be readily biodegradable. Due to this the higher tier biodegradation studies in water, sediment and soil have been waived.

No adsorption / desorption data are available for Distilled tall oil, magnesium salt. Calculated Koc values are read across from the rosin and fatty acid components of the substance. Koc values have been calculated for rosin, hydrogenated rosin and rosin salts based on Kow. Calculated Koc values range from 7.514 to 5357 L/kg (log Koc 0.8759 to 3.729). Log Koc values have been calculated for Fatty acids C18 -(unsaturated) lithium salts. Calculated Koc values are in the range 3548 to 11748.98 (log Koc 3.55 to 4.07). Therefore, based on read across, the log Koc value for fatty acids, tall oil, magnesium salts is considered to be in the range 0.87 to 4.07.

Measured BCF values are available for various resin acids and the BCF values range from <25 – 129. Calculated BCF values are also available for rosin and rosin salts and the calculated BCF values range from 3.162 to 56.23 L/kg ww. Calculated BAF values range from 1.47 to 694000 (Oak Ridge National Laboratory, 2010). Based on the measured and calculated BCF values Fatty acids, tall oil, magnesium salts is considered to have a low potential for bioaccumulation.