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Environmental fate & pathways

Phototransformation in air

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Description of key information

Calculated photo-oxidation half lives ranging from 5.2 to 6.7 h for dipropylene glycol methyl ethers and 2 h for tripropylene glycol methyl ether are available.  Similarly, the corresponding measured half-life for methanol in the troposphere is 17 to 18 days.

Key value for chemical safety assessment

Half-life in air:
18 d

Additional information

The method of Atkinson (1987) was used with the EPIWIN program to estimate photo-oxidation half-lives based on reaction with hydroxyl radicals. Assuming a concentration of hydroxyl radicals of 1.5 X 10^6 molecules/cm3 and a 12h daylight period, a range of half-lives was calculated.

Half-lives for the di-propylene glycol ethers ranged from 5.2 to 7.6 h, averaging 6.5 h. The half-life for the tripropylene glycol methyl ether component is approximately 2 hours.

For the sodium methanolate component, complete conversion to sodium hydroxide and methanol in the environment is assumed. Methanol is moderately rapidly degraded by reaction with hydroxyl radicals with a measured rate constant of 9.44 x 10^-13 cm3/(molecules-sec). This correspondes to a half-life in the troposphere for methanol of 17 to 18 days.