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. It is a by-product of butyl alcohols rectification by oxosynthesis manufactured in petrochemical industry. Only one of the substance constituents, 2-ethylhexanol, can be analytically quantified. This constituent is present at a typical concentration range of 20 to 30 % w/w. Some of the other constituents of the substance are also identified but only qualitatively.

Due to the complex composition of the substance there are a lot of technical difficulties related to the testing of environmental fate properties. The fate and pathways of the substance depend on the physical-chemical properties of the individual constituents, which have different physical-chemical properties (e. g. solubility, vapour pressure, octanol/water partition coefficient Kow). Therefore, the overall environmental fate and pathways evaluation was difficult.

Because the composition of the substance is not easily identifiable, application of read-across method in order to evaluate the overall fate and pathways was regarded unsuitable. The need for further investigations of biodegradation in surface waters, sediments and soil as well as bioaccumulation, and potential for adsorption was evaluated based on the existing experimental data on physical-chemical properties (water solubility, vapour pressure, Kow-partition coefficient and hydrolysis).

In addition, ready biodegradation screening test in water, and the acute aquatic toxicity test were used to evaluate the fate and pathways of the substance. The experimental data indicates that the substance might contain constituents that have potential for adsorption and bioaccumulation as well as not being biodegradable in soil or sediments. According to water solubility measurements, the substance is water soluble (1.8-9 g/L) but most probably also contains constituents having low solubility in water. This conclusion is based on the results obtained by the flask method. During the testing two phases were detected, the upper fraction with alcohols and the lower fraction with a clear solution.

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). Based on the experimental data on the Kow-partition coefficient study (EC 444/2008), this substance might contain substances having potential for adsorption and bioaccumulation. For complex mixtures (e. g. UVCBs) a single value of Kow is not definitive. Therefore, a range of values were given and the study was conducted using the HPLC-method, which indicated peaks corresponding the constituents having log Kow of 1.8 to 5.8, but also constituents corresponding the log Kow of 6.4 up to 7.5. 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 Kow values.

The substance was found to be hydrolytically stable, and the half-life estimated by the preliminary study (OECD 111) at three pH-values is over one year. In addition, the biodegradation screening test indicated that 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).

Based on the experimental data, the substance had acute toxicity effects on algae, water fleas and luminescent bacteria at exposure loading rate (EL50) range of 10-100 mg/L. However, there was no inhibitory to activated sludge microorganisms at maximum test concentration of 100 mg/L. Because there is no experimental data available on the substance BCF –values, adsorption/desorption nor biodegradation in soil or sediments, 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.

As a conclusion, the substance might contain more easily biodegradable substances but also constituents that are not easily biodegradable in water. In addition, the range of log Kow values indicated that there might be constituents present in the mixture having potential for adsorption and bioaccumulation (log Kowvalues > 3).

Because the existing data is also indicating the need for the substance to be classified as aquatic chronic category 3, the possibility of the substance having potential for adsorption on soil or sediments, or being bioaccumulative, cannot be neglected when considering the environmental fate and pathways of the substance. Based on the existing data, the chemical safety assessment is indicating the need to investigate further the effects of the substance to terrestrial organisms. The testing according to accepted testing proposals was conducted to study the long-term toxicity of the substance to soil organisms; earthworms and plants. Based on the test results and the exposure assessment and risk characterisation, emissions to soil are adequately controlled. No further investigations are needed.