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Environmental fate & pathways

Phototransformation in air

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phototransformation in air
Type of information:
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source
The applicability domain of the AOPWIN (v.1.92a) modul is not defined finally. Nevertheless, structural fragments of Benzotriazole as well as other chemical substances with compareable molecular weight have been considered in the model. In addition, the group of Benzotriazoles have been explicitly listed in the substances group within range of the model.
other: REACH Guidance on QSARs R.6, May 2008
Principles of method if other than guideline:
AOPWIN estimates the rate constant for the atmospheric, gas-phase reaction between naturally occurring hydroxyl radicals and organic chemicals.
Reference substance:
not specified
10.7 d
Test condition:
12-hr day, 1.5E6 OH/cm3, 25 °C
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 d-1
Transformation products:
not specified
Validity criteria fulfilled:
not applicable
Based on the calculations with AOPWIN 1.92a the half-life of atmospheric 1H-Benzotriazole was estimated to be about 10.7 days.
Executive summary:

In absence of experimental data a QSAR estimation for the atmospheric phototransformation of 1H-Benzotriazole was performed by using AOPWIN 1.92a to calculate the gas-phase reaction with natural occurring hydroxyl radicals. The estimation methods of this software are based primarily on the work of Atkinson and co-workers in 1995. Based on the given conditions a half-life of 10.7 days was estimated.

Description of key information

Key values were estimated by AOPwin v1.92.

Key value for chemical safety assessment

Half-life in air:
10.7 d
Degradation rate constant with OH radicals:
0 cm³ molecule-1 d-1

Additional information

Based on the estimation by AOPwin v1.92 the theoretical half-life of the substance is 10.7 days assuming degradation by reaction with atmospheric hydroxyl radicals. Due to the low volatility of the substance, this reaction plays only a minor role in the environmental fate of Benzotriazole.

As this study is not a standard information requirement in REACH and there is no indication from the CSA on the need to further investigate the fate and behaviour of the substance, no further testing is considered necessary.