1,6-dichlorohexane

Bioaccumulation: aquatic / sediment

Description of key information

The study on the bioaccumulation in aquatic species preferably fish was waived as its performance is scientifically not justified. Regulation (EC) No 1907/2006 (Annex IX, sect. 9.3.2, column 2) states as follows: 
"The study need not be conducted if: 
- the substance has a low potential for bioaccumulation (for instance a log Kow <= 3) and/or a low potential to cross biological membranes, or 
- direct and indirect exposure of the aquatic environment is unlikely.” 
Based on RMMs and OCs implemented, exposure of the test item to water is highly unlikely. 
Furthermore, the substance is very volatile. Consequently, the exposure of the test item to water is very low.
Further, using EPIWIN 4.1 software and the ACD/Log D Suite program for 1,6-dichlorohexane a bioconcentration factor (BCF) of 103.3 L/Kg wwt, indicating a low bioaccumulation potential. 
In addition, a Mackay level I calculation gives the general impression of the likely media into which the test substance 1,6-dichlorhexanewill tend to partition and an indication of relative concentrations in each medium and compartment, respectively. Low concentrations in aquatic compartment and also in fish were calculated. Thus, a low bioaccumulation potential of the substance is expected.

Additional information

Using the level I Mackay model the distribution of the substance 1,6-dichlorhexane in the environment at equilibrium between the homogenous compartments air, water, soil and sediment was estimated. As input parameters for this calculation physico-chemical properties of 1,6-dichlorhexane, like its molecular mass, water solubility, vapour pressure and n-octanol/water partition coefficient (log Kow) were used. Based on the physico-chemical properties of 1,6-dichlorhexane, it is assumed that this substance will partition into all compartments and media, respectively (type 1 chemical).On the basis of thermodynamical distribution laws the level 1 Mackay model estimates the concentration of the test substance in each compartment without considering in- or out-flows of the substance or any degradation pathways etc. Additionally this level 1 model assumes a simple environment with defined volumes and densities for the environmental media and compartments, respectively (air, water, soil, sediment, suspended sediment, fish and aerosols).

Considering the total amount/emission of 100000 kg for the test substance 1,6-dichlorhexane its equilibriumconcentration in air, soil, water and

sediment were estimated to be 69.3 % (693 ng/m3), 23.0 % (1.06 ng/g), 7.15 % (35.7 ng/L) and 0.511 % (2.13 ng/g), respectively. Obviously, due to the high volatility of the test substance (vapour pressure: 17.4 Pa) the test substance’s concentration in air is higher than in the other compartments. Since the test substance concentration in water is very low (7.15 %) the concentration of the test substance in suspended sediment and fish were estimated to be also very low (0.0160 % (10.6 ng/g) and 0.0013% (6.49 ng/g), respectively). In this regard the concentration of the test substance in aerosols was estimated to be 0.000479 % (0.00479 ng/m3air). This level I calculation clearly shows that the test substance 1,6-dichlorhexane is predominantly distributed in the compartment air and based on its physico-chemical properties it is not predominantly distributed in water. Thus the exposure to the test substance in the water compartment is very low. Concluding, this level I calculation gives the general impression of the likely media into which the test substance1,6-dichlorhexanewill tend to partition and an indication of relative concentrations in each medium and compartment, respectively. Low concentrations in aquatic compartment and also in fish were calculated. Thus, a low bioaccumulation potential of the substance is expected.