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Environmental fate & pathways

Phototransformation in air

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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 limited documentation / justification
Principles of method if other than guideline:
Calculated with AOP Program v1.92 of EPI-Suite Software. The Atmospheric Oxidation Program (AOPWIN) estimates the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals. The rate constants are then used to calculate atmospheric half-lives for organic compounds based upon average atmospheric concentrations of hydroxyl radicals and ozone.
GLP compliance:
no
Specific details on test material used for the study:
Representaive structure for 2-benzofuran-1,3-dione, addition product with 2-(2-
hydroxyethoxy)ethanol, ethoxylated:
2-[2-(2-hydroxyethoxy)ethoxy]ethyl 2-hydroxyethyl phthalate

Molecular Weight =342.35
Exact Mass =342
Molecular Formula =C16H22O8
Molecular Composition =C 56.14% H 6.48% O 37.39%
Smiles Code for 2-[2-(2-hydroxyethoxy)ethoxy]ethyl 2-hydroxyethyl phthalate:
c1ccc(c(c1)C(=O)OCCO)C(=O)OCCOCCOCCO
Estimation method (if used):
PHOTOCHEMICAL REACTION WITH OH RADICALS
- sensitizer for indirect photolysis: OH radicals
- Concentration of OH radicals: 0.5 E6 OH/cm³, 24 h/d
% Degr.:
50
Sampling time:
0.4 d

Based on average atmospheric concentrations of hydroxyl radicals (0.5 * 106OH/cm3), the atmospheric half -life of the substance (0.399 days) was calculated from rate constant (40.17 * 10-12cm3/(molecule *s)), which was estimated from the chemical structure of the substance.

A 24 -hour day and an OH-radical concentration of 0.5 * 106OH/cm3are assumed for calculation.

Validity criteria fulfilled:
yes
Conclusions:
The calculated atmospheric oxidation rate constant of the test item is 40.17 * 10-12cm3/(molecule *s) and its atmospheric half-life is 0.399 days (Currenta, 2010).
Executive summary:

The calculated atmospheric oxidation rate constant of the test item is 40.17 * 10-12cm3/(molecule *s) and its atmospheric half-life is 0.399 days (Currenta, 2010).

Description of key information

In the atmosphere a half-life of 0.40 days for 2-[2-(2-hydroxyethoxy)ethoxy]ethyl 2-hydroxyethyl phthalate , the representative of this UVCB-substance is estimated due to indirect photolysis with hydroxyl radicals, considering an OH-concentration of 500,000 radicals/cm³ as a 24-h average (Currenta, 2010).

Key value for chemical safety assessment

Half-life in air:
0.4 d

Additional information

As no data on phototransfromation in air are available, the rate constant for the atmospheric gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals is estimated with the Atmospheric Oxidation Program (AOPWIN) of US Environmental Protection Agency. The rate constant is then used to calculate the atmospheric half-life. A 24-hour day and an OH radical conc. of 500,000 OH/cm³ are assumed for calculation. The substance is an UVCB-substance, as representative 2-[2-(2-hydroxyethoxy)ethoxy]ethyl 2-hydroxyethyl phthalate was used for calculation of the phototransformation in air.

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