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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

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:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Qualifier:
no guideline followed
Principles of method if other than guideline:
An estimation of the atmospheric oxidization rate of the test substance was performed using the Atkinson method.
GLP compliance:
no
Remarks:
Not applicable
Key result
DT50:
14 h
Remarks on result:
other: Calculated based on restrictive rate estimation
DT50:
3.4 h
Remarks on result:
other: Calculated based on AOP rate estimation
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 s-1
Remarks on result:
other: Restrictive rate calculation
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 s-1
Remarks on result:
other: AOP rate estimation

Based on AOP rate estimation, assuming a constant concentration of 1.5E+06 OH-radical/cm3 and a 12 hours day, the total rate constant and the half-life period was calculated to be 37.776E-12 cm3/molecule/sec and 3.40 hours, respectively.


Based on restrictive rate estimation, assuming a constant concentration of 1.5E+06 OH-radical/cm3 and a 12 hours day, the total rate constant and the half-life period was calculated to be 9.176E-12 cm3/molecule/sec (Kmin) and 14.0 hours (max), respectively.

Validity criteria fulfilled:
not applicable
Conclusions:
The estimated half-life (Atkinson method) of the test substance in the atmosphere (by hydroxyl radical oxidation) is between 3.4 and 14 hours.
Executive summary:

The rate of photolytic degradation of the test substance in the atmosphere was estimated in the AOP program V1.51 (1993) using the Atkinson method. It was assumed that the OH radical concentration was 1.5E+06 OH radicals/cm3 and the OH timeframe was 12 hours/day. Based on AOP rate estimation, the overall OH rate constant was calculated to be 37.776E-12 cm3/molecule/sec, with a 3.40 hours half-life. Based on a more restrictive estimation, supposing that the values taken to represent the triazole/dioxolane group in the estimation calculation show a too fast reactivity against an OH radical reaction, the recalculated rate constant was at 9.176E-12 cm3/molecule/sec, with a half-life of 14.0 hours. Therefore, the estimated half-life of the test substance in the atmosphere (by hydroxyl radical oxidation) was between 3.4 and 14.0 hours. A half-life value of 14 hours was used for the CSA.

Description of key information

Estimated half-life (Atkinson method) = 3.4 - 14.0 hours, in the atmosphere by hydroxyl radical oxidation, Stamm 1994. A half-life of 14 h was used for the CSA as it can be considered worst-case.

Key value for chemical safety assessment

Half-life in air:
14 h
Degradation rate constant with OH radicals:
0 cm³ molecule-1 s-1

Additional information

There is one calculation available for this endpoint. The calculation was performed in the AOP program V1.51 (1993) using the Atkinson method. It was assumed that the OH radical concentration was 1.5E+06 OH radicals/cm3 and the OH timeframe was 12 hours/day. Based on AOP rate estimation, the overall OH rate constant was calculated to be 37.776E-12 cm3/molecule/sec, with a 3.40 hours half-life. Based on a more restrictive estimation, the recalculated rate constant was at 9.176E-12 cm3/molecule/sec, with a half-life of 14.0 hours. The recalculated half-life was used for the CSA, assuming the worst case.