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Endpoint:
adsorption / desorption: screening
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:
Endpoint:
adsorption / desorption
Remarks:
other: (Q)SAR calculated endpoint
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
28 June 2020
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
Estimation Programme Interface (EPI) Suite programme for Microsoft Windows v4.11.


2. MODEL (incl. version number)
KOCWIN v2.00


3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
SMILES: O=C(O)c(ccc(c1)C(=O)O)c1


4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
Please refer to attached justification.


5. APPLICABILITY DOMAIN
Please refer to attached justification.


6. ADEQUACY OF THE RESULT
Please refer to attached justification.
Guideline:
other: ECHA's Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals
Version / remarks:
May 2008
Principles of method if other than guideline:
The prediction of Koc for terephthalic acid was performed using the model KOCWIN v.2.00 (September 2008). The KOCWIN program estimates the organic carbon-normalised sorption coefficient for soil and sediment using two different models: the first based on the Sabljic molecular connectivity index and the second a QSAR applied to a measured log Kow value for TPA (attributed to Hansch et al., 1995) held in the KOWWIN database.

- Software tool(s) used including version:
Estimation Programme Interface (EPI) Suite programme for Microsoft Windows v4.11.

- Model(s) used:
KOCWIN v2.00
GLP compliance:
no
Remarks:
not relevant
Specific details on test material used for the study:
SMILES: O=C(O)c(ccc(c1)C(=O)O)c1
Key result
Type:
Koc
Value:
18.28 L/kg
Remarks on result:
other: QSAR
Remarks:
based on KOCWIN v2.00 log KOW method: see QPRF for justification as key value.
Type:
Koc
Value:
79.24 L/kg
Remarks on result:
other: QSAR
Remarks:
based on KOCWIN v2.00 MCI method.

Table 1: KOC predictions for terephthalic acid obtained with KOCWIN v.2.00

KOCWIN v2.00

1,4-benzenedicarboxylic acid; SMILES: O=C(O)c(ccc(c1)C(=O)O)c1

Method 1: Sabljic molecular connectivity index

KOC(L/kg):

79.24

Method 2: Calculated from measured log Kow held in KOWWIN data base

KOC(L/kg):

18.28

Note: KOCmay vary significantly with pH. 

 

Conclusions:
KOCWIN predicts a KOC value of 79.24 L/kg for terephthalic acid, based on the first-order Sabljic molecular connectivity index (MCI), and a figure of 18.28 L/kg derived from an experimentally determined log Kow measurement.  KOC may vary significantly with pH.
Executive summary:

The adsorption coefficient (KOC) of terephthalic acid was estimated using the KOCWIN v2.00 QSAR model available from the US EPA. The estimated adsorption coefficient of terephthalic acid, based on the first-order Sablljic molecular connectivity index is 79.24 L/kg.

Additionally, KOCWIN provides a value of 18.28 L/kg, calculated from a measured log Kow value for terephthalic acid that is contained in the data base of experimental results used to construct the QSAR model.

Description of key information

In accordance with the Column 2 adaptation statements of REACH Annex VIII and IX, information requirements 9.3.1 and 9.3.3 respectively; adsorption/desorption screening and further studies on adsorption/desorption may be omitted since the log Kow value for the substance is < 3.0 and has low potential for adsorption (CSR section 1.3). (Q)SAR-modelled KOC values for terephthalic acid range from 18.28 to 79.24 L/kg.

Key value for chemical safety assessment

Koc at 20 °C:
18.28

Additional information

(Q)SAR-modelled Koc values for terephthalic acid (obtained with the KOCWIN v2.00 model of the US EPA) range from 18.28 to 79.24 L/kg. Based on these values, terephthalic acid is classed as moderately mobile to mobile and is expected to have a low tendency to adsorb to soils and sediments. KOC may be influenced by and vary significantly in response to pH. Under alkaline conditions, terephthalic acid will rapidly be converted to salts whose KOC may be expected to be lower (therefore, mobility would be higher) than that of the free acid.


 


The low Koc values modelled for terephthalic acid also imply a low tendency to associate with sludge solids during the primary settlement and secondary biological stages of waste water treatment. The majority of the TPA load contained in a treatment plant influent load may therefore be expected partition to the aqueous phase and to be routed toward aerobic biological treatment. Since process effluents discharged to treatment facilities are typically neutralised to protect both the plant hardware (concrete and metalwork) from corrosion and the biological treatment process from pH-shock effects, TPA is likely to be discharged in the form of salts that are more highly water-soluble and have a correspondingly lower Koc than the parent acid. Salts formed by the pre-treatment neutralisation step are likely to have an even lower tendency than that of free terephthalic acid to bind to sludge solids.