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Environmental fate & pathways

Phototransformation in water

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Description of key information

The available weight of evidence demonstrates that Hydrocarbons, C14-C20, aliphatics, ≤2% aromatics do not absorb light within a range of 290 to 750 nm, the range in which photolysis occurs. Therefore, direct photolysis will not contribute to the degradation of these substances in the aquatic environment. Further testing is not required under Annex XI, section 1.2.

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Additional information

The direct photolysis of an organic molecule occurs when it absorbs sufficient light energy to result in a structural transformation. The absorption of light in the ultra violet (UV) -visible range, 110-750 nm, can result in the electronic excitation of an organic molecule. The stratospheric ozone layer prevents UV light of less than 290 nm from reaching the earth's surface. Therefore, only light at wavelengths between 290 and 750 nm can result in photochemical transformations in the environment.

 

A conservative approach to estimating a photochemical degradation rate is to assume that degradation will occur in proportion to the amount of light wavelengths >290 nm absorbed by the molecule. Hydrocarbons, C14-C20, aliphatics, ≤2% aromatics contain hydrocarbon molecules that absorb UV light below 290 nm, a range of UV light that does not reach the earth's surface. Therefore, Hydrocarbons, C14-C20, aliphatics, ≤2% aromatics do not have the potential to undergo photolysis in water and soil, and this fate process will not contribute to a measurable degradative loss of these substances from the environment.