Ethane- 1,2-diol, propoxylated

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Accepted estimation method, as cited in ECHA guidance Chapter R.7.1 (May, 2008)

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Principles of method if other than guideline:

The second-order rate constant for reaction with photochemically-generated hydroxyl radical (indirect photolysis) was estimated using U.S. EPA AOPWIN software v1.92a (June 2008). The associated atmospheric half-life was calculated from an assumed average hydroxyl radical concentration of 500,000 molecules/cm3 and 24 hr. day (ECHA recommended values). Estimates were made for the lowest and highest molecular weight homologues of the UVCB substance. The homologue giving the longest predicted half-life is used in environmental exposure calculations in the chemical safety assessment.

GLP compliance:

no

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Not applicable

Estimation method (if used):

U.S. EPA AOPWIN software v1.92a (June 2008).

Light source:

other: Not applicable

Details on light source:

Not applicable

Details on test conditions:

Half-lives calculated from estimated second-order rate constant, default hydroxyl radical concentration of 500,000 molecules/cm3, and 24-hr. photoday.

Reference substance:

no

Preliminary study:

Not applicable

Test performance:

Not applicable

DT50:

14.3

Test condition:

Lowest molecular homolgue; Estimated half-life for indirect photolysis with hydroxyl radical (500,000 molecules/cm3)

DT50:

3.5

Test condition:

Highest molecular homolgue; Estimated half-life for indirect photolysis with hydroxyl radical (500,000 molecules/cm3)

Results with reference substance:

Not applicable

NLP	Substance Abbreviation	SMILES	MW (g/mole)	Hydroxyl Radical Second-order Rate Constant (cm^3/molecule*sec)	Estimated Half-life (days)*	EstimatedHalf-life (hrs.)*
-	MEG, PO	CC(O)COCCO	120.1	2.70E-11	0.6	14.3
		OC(C)COC(C)COC(C)COCCOCC(C)OCC(C)O	352.5	1.1E-10	0.1	3.5

*Estimated half-life based on hydroxyl radical concentration of 500,000 molecules/cm³and 24 hr. day

The lowest-molecular weight homologues of the UVCB substance are expected to have the longest half-lives in the atmosphere. This is due to relative low molecular weith compared to the highest molecular weight homologue; and the mode of degradation is expected to be the same for all homologues. The estimated half-life for the lowest-molecular weight homologue is used to represent the atmospheric half-life for all components of the UVCB substance in the chemical safety assessment.

Conclusions:

Estimated half-lives for the components of this UVCB substance range from 3.5 to 14.3 hours, based on a default hydroxyl radical concentration of 500,000 molecules/cm3. The longest estimated half-life, associated with the lowest-molecular weight homologue, is used to represent the atmospheric half-life of all homologous components of the UVCB substance in the chemical safety assessment.

Executive summary:

Estimated half-lives for the components of this UVCB substance range from 3.5 to 14.3 hours (Dow, 2010).

Description of key information

Estimated half-lives for the components of this UVCB substance range from 3.5 to 14.3 hours (Dow, 2010).

Additional information

Estimated second-order rate constants for reaction of hydroxyl radical with lowest and highest-molecular weight homologues of the UVCB substance range from 2.7E-11 to 1.1E-10cm3/molecule*sec. Corresponding half-lives range from from 3.5 (higest molecular homolgue) to 14.3 hours (lowest molecular homologue),based on a default hydroxyl radical concentration of 500,000 molecules/cm3. The longest estimated half-life, associated with the lowest-molecular weight homologue, is used to represent the atmospheric half-life of all homologous components of the UVCB substance in the chemical safety assessment.