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Environmental fate & pathways

Phototransformation in air

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Description of key information

Dichloromethane undergoes reactions with hydroxyl radicals in the atmosphere. The half life of dichloromethane due to this reaction, based on a 12-hr day with a OH radical concentration of 1.5E6 OH/cm3 is 107 days.

Key value for chemical safety assessment

Half-life in air:
107 d

Additional information

Since dichloromethane does not absorb light above 290 nm, it will not degrade by direct photolysis in the troposphere. In the troposphere dichloromethane is photochemically oxidized by hydroxyl radicals abstracting H atoms. The calculated half life of dichloromethane due to this reaction is 107 days using an OH radical concentration of 1.5E6 OH/cm3 (AOPWIN, 2000), the corresponding OH-rate constant is 1.0 +/- 0.1 E-13 cm3/molecule.sec at 298 K, based on preferred values from IUPAC.