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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
see "General Justification for Read-Across" attached to IUCLID section 13

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Mutual read across from the AAPBs to one another is justified:

a) Based on the information given in section 1, it can be concluded that all AAPBs mentioned above are similar in structure, since they are manufactured from similar resp. identical precursors under similar conditions and all contain the same functional groups. Thus a common mode of action can be assumed.
b) The content of minor constituents in all products are comparable and differ to an irrelevant amount.
c) The only deviation within this group of substances is a minor variety in their fatty acid moiety, which is not expected to have a relevant impact on intrinsic toxic or ecotoxic activity and environmental fate. Potential minor impact on specific endpoints will be discussed in the specific endpoint sections.

The read-across hypothesis is based on structural similarity of target and source substances. Based on the available experimental data, including key physico-chemical properties and data from toxicokinetic, acute toxicity, irritation, sensitisation, genotoxicity and repeated dose toxicity studies, the read-across strategy is supported by a quite similar toxicological profile of all five substances.
The respective data are summarised in the data matrix; robust study summaries are included in the Technical Dossier in the respective sections.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
see "General Justification for Read-Across" attached to IUCLID section 13

3. ANALOGUE APPROACH JUSTIFICATION
see "General Justification for Read-Across" attached to IUCLID section 13

4. DATA MATRIX
see "General Justification for Read-Across" attached to IUCLID section 13
Reason / purpose:
read-across: supporting information
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Key result
Type:
Koc
Remarks:
weighted mean
Value:
1 969 L/kg
Temp.:
20 °C
Key result
Type:
log Koc
Remarks:
weighted mean
Value:
3.29 dimensionless
Temp.:
20 °C
Type:
Koc
Remarks:
C12 derivative
Value:
ca. 320 L/kg
Temp.:
20 °C
Type:
log Koc
Remarks:
C12 derivative
Value:
2.5 dimensionless
Temp.:
20 °C
Type:
Koc
Remarks:
C14 derivative
Value:
ca. 3 200 L/kg
Temp.:
20 °C
Type:
log Koc
Remarks:
C14 derivative
Value:
3.5 dimensionless
Temp.:
20 °C
Type:
Koc
Remarks:
calculated range for C8-C18 derivatives
Value:
ca. 89.3 - ca. 56 000 L/kg
Temp.:
25 °C
Conclusions:
Reliable experimental results for Koc are available only for C12 and C14 AAPB from a non-GLP study. Therefore in addition, for all components of C12-18 AAPB soil sorption coefficients were calculated using ACD and EUSES. The weighted mean Koc and log Koc were calculated according to weight fractions of fatty acid chain length distribution, resulting in a weighted mean Koc of 1969 L/kg and a mean log Koc of 3.39.

Description of key information

Reliable experimental results for Koc are available only for C12 and C14 AAPB from a non-GLP study. Therefore in addition, for all components of 
C8-18 and C18 unsatd. AAPB soil sorption coefficients were calculated using ACD and EUSES on the one hand and EPIWIN on the other hand. The weighted mean log Kow was calculated from calculation results, according to weight fractions of fatty acid chain length distribution, resulting in a weighted mean log Kow of 4.2.

Key value for chemical safety assessment

Koc at 20 °C:
1 969

Other adsorption coefficients

Type:
log Kp (solids-water in soil)
Value in L/kg:
1.6
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in sediment)
Value in L/kg:
1.99
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in suspended matter)
Value in L/kg:
2.29
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in raw sewage sludge)
Value in L/kg:
2.77
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in settled sewage sludge)
Value in L/kg:
2.77
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in activated sewage sludge)
Value in L/kg:
2.86
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in effluent sewage sludge)
Value in L/kg:
2.86
at the temperature of:
20 °C

Additional information

A weight of evidence approach was used for evaluation, as the experimental determined values are used as training structure for the ACD calculated values.

In a screening study conducted according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)) the log Koc values of C12 and C14 AAPB were determined. Based on a corrected dead time value, the log Koc of C12 and C14 AAPB were determined to be 2.5 (Koc: ca. 320; C12 derivative) and 3.5 (Koc: ca. 3200; C14 derivative), respectively. Based on these results and taking into account the classification scheme of Blume and Ahlsdorf (1993) a medium (C12 derivative) and high sorption (C14 derivative) onto soil organic matter is to be expected.

Based on the Koc value determined by measurement, C12 AAPB was used as training structure for the ACD software and Kow values were calculated for C8, C10, C14, C16 and C18 AAPB (for this calculation to the IUCLID the following justification documents are attached: QSAR prediction report format (QPRF) and QSAR model reporting format (QMRF)). The soil sorption coefficient of AAPB containing C8-, C10-, C12-, C14-, C16-, and C18 fatty acids was calculated using the guideline conform EUSES algorithm for non hydrophobics. The calculation yielded Koc values of 89.3 (C8 derivative), 303 (C10 derivative), 726 (C12 derivative), 4870 (C14 derivative), 16500 (C16 derivative), and 56000 (C18 derivative). According to the classification scheme of Blume & Ahlsdorf (1993), a low (C8 derivative), medium (C10 derivative), high (C12 and C14 derivatives), and very high (C16 and C18 derivatives) sorption onto soil organic matter is to be expected.

As reported in HERA (2007), the Koc values for AAPB containing C8-, C10-, C12-, C14-, C16-, and C18 fatty acids were calculated using EPIWIN v3.11, PCKOCWIN v1.67. The calculation yielded Koc values of 264.7 (C8 derivative), 900.5 (C10 derivative), 3063 (C12 derivative), 10420 (C14 derivative), 35450 (C16 derivative), and 120600 (C18 derivative). According to the classification scheme of Litz (1990) these values indicate a low to very high sorption potential to the organic matter of soils and sediments depending on the chain length.

Based on the experimental determined Koc values of C12 and C14 AAPB, the Koc values calculated with EPIWIN seem to overestimate soil sorption. The values calculated with ACD/EUSES (reasoned in separate documents (QPRF, QMRF attached to IUCLID)) Koc and Kow values were used for further calculations (environmental exposure and risk assessment).

[LogKoc: 3.29]