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Environmental fate & pathways

Phototransformation in air

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Description of key information

Calculation with AOPWIN v1.92 (EPIWIN software by US-EPA), 12-hr day with OH concentration of 1.5E6 OH/cm³ at 25 °C:
Component with chlorine: overall gas-phase reaction constant: 57.52 E-12 cm³/molecules-sec (= 0.00000497 cm³/molecules-day), with a half-life of 2.23 hours
Component without chlorine: overall gas-phase reaction constant: 54.44 E-12 cm³/molecules-sec (= 0.00000470 cm³/molecules-day) with a half-life of 2.36 hours

Key value for chemical safety assessment

Additional information

The phototransformation in air of the test substance was determined by the computer program AOPWIN v1.92 (EPIWIN software) by US-EPA (Chemservice S.A., 2012). This tool estimates the gas-phase reaction rate for the reaction between the most prevalent atmospheric oxidant (hydroxyl radicals) and a substance. For olefins and acetylenes the gas-phase ozone radical reaction rates are estimated as well. Additional information is given by the program if nitrate radical reaction will be important. The assumed average hydroxyl radical and ozone concentration are automatically used to calculate the atmospheric half-live for the chemical of interest.

For the test substance the results differ only a little depending if chlorine belongs to the main component or not.With chlorine,an overall OH rate constant (gas-phase reaction constant) of 57.52 E-12 cm3/molecules-sec and a half-life of 0.19 days (2.23 hours) were calculated, assuming a 12-hr day with an OH concentration of 1.5 E6 OH/cm3. No ozone reaction as well as no nitrate radical reaction is estimated for the compound. “Hydrogen Abstraction” (57.38 E-12 cm3/molecule-sec) and “Reaction with N, S and –OH” (0.14 E-12 cm3/molecule-sec) were detected for the substance.Without chlorine, the overall OH rate constant results in 54.44 E-12. The half-life will be also in the same magnitude with 0.20 days (2.36 hours), assuming the same OH rate constant for a 12-hr day. In this case “Hydrogen Abstraction” gives a value of 54.44 E-12 cm3/molecule-sec.All calculations were performed supposing a surrounding temperature of 25 °C.

No GLP criteria are applicable for the usage of this tool, but due to the fact that this is a scientifically accepted calculation method the estimation performed is reliable with restrictions and can be used for the chemical safety assessment.