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Diss Factsheets

Environmental fate & pathways

Phototransformation in air

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
supporting study
Study period:
Not applicable
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Qualifier:
no guideline required
GLP compliance:
no
Remarks:
Not applicable
Light source:
other: not applicable
Key result
DT50:
3.4 h
Remarks on result:
not measured/tested
Remarks:
values is calculated based on AOP rate estimation
Key result
DT50:
5 h
Remarks on result:
not measured/tested
Remarks:
Value if calculated based on restrictiverate estimation
Reaction with:
OH radicals
Rate constant:
38.061 cm³ molecule-1 s-1
Remarks on result:
other: Value is calculated based on AOP rate estimation
Reaction with:
OH radicals
Rate constant:
25.467 cm³ molecule-1 s-1
Remarks on result:
other: Value is calculated based on restrictive rate estimation
Transformation products:
not measured

- AOP Rate estimation: Overall OH Rate Constant = 38.0612 E-12 cm3/molecule-sec; Half-life = 0.28 days (12-hr day; 1.5E6 OH/cm3); Half-life = 3.4 Hrs

- Restrictive Rate estimation: The oxidation rate is as following results (calculated with 1.5E6 OH-Radicals/cm3 and a12 hours day): k(min) 25.467 E-12 cm3/molecule-sec; Halflife (max): 5.0 hours

- Rate assessment: The estimated half-life (Atkinson method) of the test substance in the atmosphere (by hydroxyl radical oxidation) is between 3 and 5 hours.

Validity criteria fulfilled:
not applicable
Conclusions:
Based on the results of the AOP and restrictive rate estimation, the estimated half-life (Atkinson method) of the test substance in the atmosphere (by hydroxyl radical oxidation) is between 3 and 5 hours.
Executive summary:

An estimation of the atmospheric oxidization rate based on an AOP rate estimation resulted in an overall OH rate constant of 38.01612E-12 cm3/molecule-sec, with a 0.28 days half-life (equivalent to 3.4 hours). A more restrictive estimation, not accounting for unknown structural elements in the AOP estimation, the recalculated rate constant was at 25.467E-12 cm3/molecule-sec, with a half-life of 5 hours. The rate for photolytic degradation in the atmosphere was estimated with a commercial software using the Atkinson method. Based on the calculations, the estimated half-life of the test substance in the atmosphere (by hydroxyl radical oxidation) was between 3 and 5 hours. A half-life value of 4 hours was used for the CSA. However, both aerial degradation pathways are anticipated not to be relevant under normal environmental conditions due to the very low vapour pressure of the substance.

Description of key information

All available data were assessed and the study representing the worst-case effects is included here. The results can be considered worst-case and are selected for the CSA.


Estimated half-life (Atkinson method) = 4 hours, in the atmosphere by hydroxyl radical oxidation, Stamm 1996

Key value for chemical safety assessment

Half-life in air:
4 h

Additional information

An estimation of the atmospheric oxidization rate based on an AOP rate estimation resulted in an overall OH rate constant of 38.01612E-12 cm3/molecule-sec, with a half-life of 0.28 days (equivalent to 3.4 hours). A more restrictive estimation, not accounting for unknown structural elements in the AOP estimation, provided a recalculated rate constant of 25.467E-12 cm3/molecule-sec, with a half-life of 5 hours. The rate for photolytic degradation in the atmosphere was estimated with a commercial software using the Atkinson method. Based on the calculations, the estimated half-life of the test substance in the atmosphere (by hydroxyl radical oxidation) was between 3 and 5 hours. A half-life value of 4 hours was used for the CSA. However, both aerial degradation pathways are anticipated not to be relevant under normal environmental conditions due to the very low vapour pressure of the substance.