Distillation residue, butyl alcohols production, rectification

Endpoint summary

Additional information

The substance distillation residue, butyl alcohols production, rectification is a UVCB-substance composing of several not easily identifiable substances. Only one of the constituent, 2-ethylhexanol, can be analytically quantified (typical concentration range 20 -30 %).

Due to the complex composition of the substance there are a lot of technical difficulties related to the testing of environmental fate properties. The adsorption potential depends on the physical-chemical properties of the individual components. The different constituents have different physical-chemical properties (e.g. solubility, vapour pressure, octanol/water partition coefficient) that might have an effect on the overall transport and distribution of the substance in the environment. Because the composition of the substance is not easily identifiable, read-across method in order to evaluate the potential for adsorption was also regarded as an unsuitable approach. The need for further investigations of adsorption potential was evaluated based on the available experimental data on physical-chemical properties ((1) water solubility, (2) vapour pressure, (3) K_owpartition coefficient and (4) hydrolysis). In addition, (5) ready biodegradation screening test results were used to evaluate the potential for adsorption/desorption.

The available experimental physico-chemical data indicates that the substance might contain constituents having a potential for adsorption. (1) According to water solubility test, the substance is water soluble (1.8-9 g/L) but most probably also contains constituents having low solubility in water. However, some of the constituents are highly water soluble, and can be expected to be mobile in soil. (2) Based on the experimental data, the substance is non volatile at room temperature and partly volatile at temperature 35 degrees Celsius (7.9 kPa) and 50 degrees Celsius (19.4 kPa).

(3) Based on the experimental data on the octanol-water partition coefficient study (EC 444/2008), the substance might contain consituents having potential for adsorption. For complex mixtures (e.g. UVCBs) a single value of K_owwill not be definitive. The test results indicated peaks corresponding the constituents having log K_owvalues of 1.8 to 5.8, but also constituents corresponding the log K_owvalues of 6.4 up to 7.5. The range of log K_owvalues indicated that there might be constituents present in the mixture having potential for adsorption (log K_owvalues > 3). However, because of the complex and unknown composition, it was not possible to evaluate which were the minor constituents and which were the major constituents representing the measured log K_owvalues.

(4) The substance is hydrolytically stable and the half-life estimated by the preliminary study (OECD 111) at three pH-values is over one year. (5) The substance might contain partly biodegradable constituents. Based on the biodegradation screening test results in water, the substance was inherently biodegradable in water (OECD 301B). Some biodegradation occurred (biodeg-% 49.6) but the criteria for ready biodegradability was not fulfilled (failing 10 day-window).

Because there is no experimental data on the substance adsorption/desorption properties available, and the testing of this kind of complex mixture was considered unfeasible, the chemical safety assessment leans on the above existing experimental data on the physical-chemical and biodegradation studies of the substance. The possibility of the substance having potential for adsorption in soil or sediments cannot be neglected when considering the environmental fate and pathways of the substance.