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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption to the solid soil phase is not expected.

Key value for chemical safety assessment

Koc at 20 °C:
38

Additional information

Parent compound 3-chloropropionyl chloride (CAS 625-36-5):

In order to assess the adsorption potential of the parent compound 3-chloropropionyl chloride (CAS 625-36-5), the Koc value was estimated using QSAR models (BASF SE, 2019). According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11 the substance has a Koc of 7 L/kg (log Koc = 0.85). The estimation of the MCI module is more reliable than the log Kow method of KOCWIN v2.00, which estimates the Koc based on the substance’s n-octanol/water partition coefficient (estimated log Kow = 0.27; KOWWIN v1.68, BASF SE, 2019). The latter method resulted in a Koc of 2.75 L/kg (log Koc = 0.44); the substance is within the applicability domain of both estimation models.  

Based on the estimated data, adsorption to the solid soil phase is not to be expected.

However, the parent compound 3-chloropropionyl chloride (CAS 625-36-5) rapidly hydrolyses in contact with water and forms 3-chloropropionic acid (CAS 107-94-8). The adsorption potential will, therefore, be also assessed based on information available for the hydrolysis product 3-chloropropionic acid.

 

Hydrolysis product 3-chloropropionic acid (CAS 107-94-8)

According to Regulation (EC) No 1907/2006, Annex VIII, Section 9.3.1, Column 2, the study on adsorption/desorption screening does not need to be conducted if based on the physicochemical properties the substance can be expected to have a low potential for adsorption (e.g. the substance has a low octanol water partition coefficient), or the substance and its relevant degradation products decompose rapidly.

The substance is readily biodegradable according to OECD criteria (91% DOC removal after 28 days, Trénel J. and Kühn R., 1982). In addition, the substance has a measured log Kow of 0.41 (Gestis Database, see IUCLID Ch. 4.7). Therefore, a study does not need to be conducted.

In addition, the Koc value of 3-chloropropionic acid was estimated using QSAR models. According to the MCI method of the KOCWIN v2.00 module of EPI Suite v4.11, 3-chloropropionic acid has a Koc of 2.62 L/kg and a log Koc of 0.42. The MCI module is more reliable than the log Kow method of KOCWIN v2.00, which estimates the KOC based on the n-octanol/water partition coefficient (log Kow of 0.41; Gestis databank, 2011). The latter method resulted in a Koc of 2.41 L/kg and a log Koc of 0.42. These estimates are representative for uncharged molecules.

At environmentally relevant conditions 3-chloropropionic acid will be present in ionised form (pKa = 4.02; experimental database of SPARC Online calculator, see IUCLID Ch.4.21). Therefore, the adsorption coefficient was calculated according to Franco & Trapp (2008, 2009, 2010) to correct for the charged molecule at pH 5, 7, and 8. This pH range is representative for 98% of the European soils. The model is not yet validated; in addition, the applicability domain is not clearly defined. Nevertheless, the Koc values of the Franco & Trapp method give a good indication on the adsorption potential of a substance depending on the pH conditions of soil. The method is based on the dissociation constant pKa and the log Kow for the uncharged molecule. The resulting Koc:

pH 5 : 1.52L/kg, log Koc: 33.

pH 7 : 1.58L/kg, log Koc: 38.

pH 8 - 9: 1.59L/kg, log Koc: 38.

It can be concluded that adsorption to the solid soil phase is not to be expected. The Koc value at pH 7 will be used as key value, i.e. for PEC and PNEC calculations. Based on the measured and estimated data, adsorption to the solid soil phase is not to be expected.

QSAR-disclaimer

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met.

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

For the assessment of methyl chloroformate (CAS 79-22-1 (Q)SAR results were used for the estimation of the adsorption potential. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.

Therefore, further experimental studies on the adsorption potential are not provided.