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. The bioaccumulation depends on the physical-chemical properties of individual components in the mixture. 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 bioaccumulation of the substance.

Because the composition of the substance is not easily identifiable, application of read-across in order to evaluate the overall bioaccumulation was regarded as an unsuitable method. The need for further investigations of the substance bioaccumulation was evaluated based on the experimental data on physical-chemical properties performed for the substance ((1) water solubility, (2) vapour pressure, (3) K_ow partition coefficient and (4) hydrolysis). In addition, (5) ready biodegradation screening test results in water, and (6) aquatic toxicity data were used to evaluate the bioaccumulation.

1) 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. Because the water solubility of the constituents differs it might be difficult to maintain exposure concentrations during the BCF testing. Therefore, the BCF test (e.g. OECD 305) might not provide reliable results and testing was considered technically unfeasible.

2) Based on the experimental data, the substance is non volatile at room temperature and 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 substances having potential for bioaccumulation. For complex mixtures (e.g. UVCBs) a single value of K_owwill not be definitive. Therefore, a range of values were given and the study was conducted using the HPLC method. The results of the substance 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. 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.The range of log K_owvalues indicated that there might be constituents present in the mixture having potential for bioaccumulation (log K_owvalues > 3).

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) 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). As a conclusion, the substance might contain more easily biodegradable substances but also constituents that are not readily biodegradable in water. These properties also indicated difficulties that may occur during BCF testing.

6) The substance was not an inhibitory to activated sludge microorganisms at maximum test concentration of 100 mg/L.

Because testing of BCF on fish was considered technically unfeasible the chemical safety assessment leans on the above existing experimental data of the substance. The experimental data on the substance indicates that the substance might contain constituents that have a potential for bioaccumulation. In conclusion, the possibility of the substance having potential for bioaccumulation cannot be neglected when considering the environmental fate and pathways of the substance.