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Environmental fate & pathways

Phototransformation in air

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Description of key information

Key value for chemical safety assessment

Half-life in air:
9.7 yr

Additional information

The atmospheric degradation of HFC-134a occurs mainly in the troposphere, initiated by reaction with naturally occurring hydroxyl radicals (photo-oxidation), and in the stratosphere through photolysis and reaction with O(1D) and OH. Both tropospheric and stratospheric degradation processes were taken into account to calculate an overall atmospheric lifetime of 14 years (IPCC, 1994), corresponding to a half-life of 9.7 years. More recent estimations remained very close to this value, i.e. 13.6 years (WMO, 1998), 13.8 years (IPCC, 2001) or 14.0 years (WMO, 2002). The atmospheric lifetime of HFC-134a is much longer than either the intra- or inter-hemispheric mixing times. As a consequence, HFC-134a will become more or less uniformly distributed in the atmosphere on a global scale (Franklin, 1993). This conclusion is supported by atmospheric measurements.