4,4'-cyclohexylidenedi-o-cresol

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

no guideline followed

Principles of method if other than guideline:

KOCWIN Program (v2.00), found in EPI Suite, was used to estimate the organic-carbon normalised adsorption coefficient. Experimentally-determined input parameters for melting point, boiling point, water solubility, vapor pressure and log Kow were manually entered into the model.

GLP compliance:

no

Type of method:

other: estimated by calculation

Computational methods:

The following input parameters were manually populated with experimentally determined values:
- Melting point: 190 °C
- Boiling point: 336.2 °C
- Water solubility (at 20 °C): 1.26 mg/L
- Vapour pressure: 3.6e-11 mmHg (based on value of 0.00000000485 Pa)
- Log Kow: 3.1

Type:

Koc

Value:

ca. 940.8

Remarks on result:

other: log Koc = 2.97

Validity criteria fulfilled:

yes

Conclusions:

The Koc was estimated to be 940.8 L/kg (log Koc = 2.97).

Executive summary:

KOCWIN Program (v2.00), found in EPI Suite, was used to estimate the organic-carbon normalised adsorption coefficient. Experimentally-determined input parameters for melting point, boiling point, water solubility, vapor pressure and log Kow were manually entered into the model.

The Koc estimated by calculation using KOCWIN Program (v2.00) was found to be 940.8 L/kg (log Koc = 2.97).

Reference 2

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

other: Gerstl Z. 1990. Estimation of organic chemical sorption by soils. J. Contaminant Hydrology, 6, 357-75.

Principles of method if other than guideline:

As recommended in ECHA REACH Guidance Document R.7a, the Koc was calculated using the Gerstl correlation (Gerstl, 1990).

GLP compliance:

no

Type of method:

other: calculation

Computational methods:

The Gerstl correlation was used to calculated the log Koc:
Log Koc = 0.679 log Kow + 0.094

For the log Kow, the experimentally-determined log Kow of 3.1 is used:
Log Koc = 0.679 (3.1) + 0.094
Log Koc = 2.1 + 0.094
Log Koc = 2.2 (Koc = 158 L/kg)

Type:

log Koc

Value:

2.2

Temp.:

25 °C

Remarks on result:

other: calculated using the Gerstl correlation

Conclusions:

A log Koc of 2.2 was calculated using the Gerstl correlation.

Executive summary:

As recommended in ECHA REACH Guidance Document R.7a, Koc was calculated using the Gerstl correlation (Gerstl, 1990).

The Gerstl correlation was used to calculate the log Koc using the experimentally determined log Kow of 3.1:

Log Koc = 0.679 log Kow + 0.094

Log Koc = 2.2 (Koc = 158 L/kg)

Reference 3

Endpoint:

adsorption / desorption: screening

Remarks:

Further information on adsorption/ desorption - information requirement 9.3.3

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the physicochemical properties of the substance indicate that it can be expected to have a low potential for adsorption

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
In accordance with section 9.3.3 of Column 2 of Annex IX, the further information on adsorption/desorption study 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). DMBPC has a log Kow of 3.1, indicating a low potential for adsorption. It is therefore considered to be justified to omit this study.

Furthermore, the study is waived on the basis of exposure-based waiving. More specifically - in accordance with Section 3 of REACH Annex XI, testing in accordance with Annex IX and X may be omitted on the basis of substance-tailored exposure-driven testing.
Exposure-based waiving is considered justified based on the following rationale:
• The registrant does not supply the substance (as a reacted monomer in polymers) to the EU and has never supplied the substance in unreacted form to the EU. Furthermore, there are no co-registrants and hence there is currently no substance supply to the EU;
• Previously, the registrant has only ever supplied the substance to the EU in the form of the substance being a reacted monomer in imported polymers. In this historic case, the substance was permanently embedded within the polymer matrix throughout its entire life cycle. Hence, there was no substance release (either to man or the environment) during its past life cycle. Indeed, it would not have been reasonable to expect that there would have been any substance exposure to workers, the general public or the environment following normal and reasonably foreseeable conditions of use. Furthermore, when the substance was previously supplied as a reacted monomer in polymers, the relevant polymers were handled according to the conditions set out in Article 18(4)(a) to (f) during all manufacturing and production stages including the waste management of the substance during these stages;
• The likelihood of depolymerization (and back-formation) of the polymer to the substance monomer is negligible;
• A hypothetical, worst-case exposure based on previous EU use of the polymer demonstrates the absence of or no significant exposure to the registered substance throughout the lifecycle of the polymer. This exposure assessment has been conducted even though the EU supply level for the substance is zero, even though the substance has only ever been supplied as a reacted monomer in previously imported polymers, and even though analysis of residual levels in the previously imported polymer have been determined to be below 0.1 %.
• There have never been any professional or consumer uses of the substance.

A more detailed justification of these points is included in the attached justification document. Please also refer to the various assessment reports as included in section 13.2.

Overall, it is therefore considered justified to omit a study to obtain further information on adsorption/desorption as included under section 9.3.3. of REACH Annex IX.

Description of key information

The organic carbon normalised adsorption coefficient (Koc) was estimated by calculation using KOCWIN Program (v2.00) found in EPI Suite and was found to be 940.8 L/kg (log Koc = 2.97). The Koc was also estimated using the Gerstl correlation, as reported in ECHA REACH Guidance Document R.7a, and found to be 158 L/kg at 25 °C. The geometric mean of 941 and 158 L/kg is 386 L/kg (log Koc = 2.59) at 25 °C and this value used for the chemical safety assessment.

No data on desorption are available.

Key value for chemical safety assessment

Koc at 20 °C:

386

Additional information

ECHA Guidance Document R.7a indicates that "Estimation methods for Koc are not appropriate for surface active or ionisable (at environmentally relevant pH) substances." Therefore, a screening level estimation of Koc for the test substance is appropriate if it can be shown that the substance will not ionise at environmental pH. For ionisable substances, the adsorption coefficient will be highly dependent on the acid dissociation constants of the hydrolysable protons. For the test substance, the SPARC Performs Automated Reasoning in Chemistry (SPARC) Program estimates pKa1 and pKa2 values of 10.5 and 10.7, respectively for the two phenolic hydrogen atoms. Using the Henderson-Hasselbalch equation, it can be shown that > 99 % of the test substance will exist in the non-ionised form at environmental pH of 7:

pH = pKa + log ([A-]/[HA])

7 = 10.5 + log ([A-]/[HA])

-3.5 = log ([A-]/[HA])

[A-]/[HA] = 0.00032

[A-] = 0.00032[HA]

0.00032[HA] + [HA] = 1

[HA] > 0.99

Based on this result (>99 % non-ionised at environmental pH), the use of calculations to estimate the Koc is scientifically acceptable. KOCWIN, found in EPI Suite, estimates a Koc of 940.8 L/kg (log Koc = 2.97) for DMBPC at 25 °C. ECHA REACH Guidance Document R.7a (ECHA, 2008) indicates that the Gerstl correlation (Gerstl, 1990) is an acceptable method of estimation for non-ionised substances. The Gerstl correlation estimates a Koc of 158 L/kg for DMBPC.

ECHA REACH Guidance Document R.7a (ECHA, 2008) specifies that the geometric mean of multiple estimations should be taken as the key value for the chemical safety assessment. The geometric mean of 941 and 158 L/kg is 386 L/kg (log Koc = 2.59) at 25 °C. This value cannot be extrapolated to 20 °C; therefore, it will be used for the chemical safety assessment.

In accordance with section 9.3.3 of Column 2 of Annex IX, the further information on adsorption/desorption study 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). DMBPC has a log Kow of 3.1, indicating a low potential for adsorption. It is therefore considered to be justified to omit this study.

Furthermore, this substance is not manufactured or imported as such on the EEA market, but is only available as a reacted monomer in an imported polymer with residual levels below 0.1 %. Consequently the exposure and emissions to the environment are considered to be negligible. Therefore, this testing is not required.

References

European Chemicals Agency (ECHA). 2008. Guidance on information requirements and chemical safety assessment, Chapter R.7a: Endpoint specific guidance. May 2008.

Gerstl Z. 1990. Estimation of organic chemical sorption by soils. J. Contaminant Hydrology, 6, 357-75, as cited in: European Chemicals Agency (ECHA). 2008. Guidance on information requirements and chemical safety assessment, Chapter R.7a: Endpoint specific guidance. May 2008.

SPARC Performs Automated Reasoning in Chemistry (SPARC). October 2011 release w4.6.1691-s4.6.1687. Available at: http://archemcalc.com/sparc/test/login.cfm?CFID=148855&CFTOKEN=98109949. Accessed on: 09.02.2012.

[LogKoc: 2.59]