Registration Dossier

Environmental fate & pathways

Phototransformation in air

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
phototransformation in air
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
Atmospheric photo-oxidation potential, mediated by reaction with hydroxyl radicals, was estimated using the submodel, Atmospheric Oxidation Potential for Windows (AOPWIN v.1.91, EPIWIN v3.11, USEPA, 2003). The SAR methods rely on structural features of the subject molecule. The model calculates a second-order half-life with units of cm³/molecules-sec. A pseudo-first order photo-degradation rate is in turn based on the second order rate of reaction (cm³/molecules-sec) with hydroxyl radicals (HO•), assuming first-order kinetics and an HO• concentration of 1.5 E+06 molecules/cm3 and 12 hours of daylight.
Pseudo-first order half-lives (t1/2) were then calculated as follows:
t1/2 = 0.693 / [kphot x HO• x 12-hr / 24-hr].
The EPIWIN model (v 3.11) was run using the following measured physical chemical properties:
Vapor pressure = 4E-020 mm Hg;
Boiling point = 314°C; and
Melting point 187.5°C.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Atmospheric photo-oxidation potential, mediated by reaction with hydroxyl radicals, was estimated using the submodel, Atmospheric Oxidation Potential for Windows. Software used: U.S. EPA (U.S. Environmental Protection Agency). 2003. EPI Suite, Version 3.11; AOPWIN Program, Version 1.91; PC-Computer software developed by EPA’s Office of Pollution Prevention Toxics and Syracuse Research Corporation (SRC)
GLP compliance:
no
Estimation method (if used):
Atmospheric photo-oxidation potential, mediated by reaction with hydroxyl radicals, was estimated using the submodel, Atmospheric Oxidation Potential for Windows (AOPWIN v.1.91, EPIWIN v3.11, USEPA, 2003). The SAR methods rely on structural features of the subject molecule. The model calculates a second-order half-life with units of cm3/molecules-sec. A pseudo-first order photo-degradation rate is in turn based on the second order rate of reaction (cm3/molecules-sec) with hydroxyl radicals (HO•), assuming first-order kinetics and an HO• concentration of 1.5 E+06 molecules/cm3 and 12 hours of daylight.
Pseudo-first order half-lives (t1/2) were then calculated as follows:
t1/2 = 0.693 / [kphot x HO• x 12-hr / 24-hr].
The EPIWIN model (v 3.11) was run using the following measured physical chemical properties:
Vapor pressure = 4E-020 mm Hg;
Boiling point = 314°C; and
Melting point 187.5°C.
Preliminary study:
Overall OH Rate Constant (kphot) =15.9214 E-12 cm³/molecule-sec
Half-life (t1/2) = 8.062 Hrs (12-hour day; 1.5E+06 OH/cm3)
Key result
DT50:
8.062 h
Validity criteria fulfilled:
not applicable
Conclusions:
The calculated half-life of the test material in air is 8.062 h (at 12 -hour daylight).
Executive summary:

The rate of photodegradation in air was calculated by QSAR (US EPA EPISuite) based on reaction with hydroxyl radicals.

Atmospheric photo-oxidation potential, mediated by reaction with hydroxyl radicals, was estimated using the submodel Atmospheric Oxidation Potential for Windows (AOPWIN). A QSAR calculation is considered sufficient as a Tier 1 approach.

The calculated half-life of the test material in air is 8.062 h (at 12 -hour daylight).

Description of key information

The calculated half-life of the test material in air is 8.062 h (at 12 -hour daylight).

Key value for chemical safety assessment

Half-life in air:
8.062 h

Additional information

The rate of photodegradation in air was calculated by QSAR (US EPA EPISuite) based on reaction with hydroxyl radicals. The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

Atmospheric photo-oxidation potential, mediated by reaction with hydroxyl radicals, was estimated using the submodel Atmospheric Oxidation Potential for Windows (AOPWIN). A QSAR calculation is considered sufficient as a Tier 1 approach.

The calculated half-life of the test material in air is 8.062 h (at 12 -hour daylight).