Propylidynetrimethanol, propoxylated

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Study period:

2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Use of validated QSAR, which is described extensively in peer-reveiwed literature. The substance falls within the application domain.

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Reason / purpose for cross-reference:

reference to same 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: sunlight irradience producing default tropospheric hydroxyl radical concentration of 500,000 molecules/cm3

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

DT50:

>= 2.5 - <= 11.9 h

Test condition:

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.)*
4	TMP + PO	CC(O)COCC(CO)(CC)CO	192.3	3.2E-11	0.50	11.9
		OC(C)COC(C)COC(C)COCC(CC)(COCC(C)OCC(C)O)COCC(C)OCC(C)O	540.7	1.6E-10	0.10	2.5
		OC(C)COCC(COCC(C)O)(CC)COCC(C)O	308.4	6.9E-11	0.23	5.6

*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 weigth 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 2.5 to 11.9 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.

Description of key information

Estimated half-lives for the components of this UVCB substance range from 2.5 to 11.9 hours.

Key value for chemical safety assessment

Half-life in air:

11.9 h

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 3.2E-11 to 1.6E-10 cm³/molecule*sec. Corresponding half-lives range from 2.5 to 11.9 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.