Stratospheric ozone layer, photochemical degradation

The Stratospheric Ozone Layer Its Photochemical Formation and Degradation... 

Photochemical stability also can play an important role in solvent selection. Ethers are for instance easily attacked by UV light, to form in the presence of oxygen explosive peroxides a well-known industrial hazard. Fully halogenated solvents are on the other hand so stable, that, once evaporated, they remain a long time in the atmosphere without being degraded by sunlight. In this way they indirectly, finally affect the stratosphere ozone layer around the earth. 

Depletion of Stratospheric Ozone Layer from Photochemical Degradation... 

Because of their extreme stability against all kinds of aggressive chemical agent, for example radicals, perfluorocarbons and halofluorocarbons are not degraded in the lower layers of the atmosphere as are other pollutants. After several years, or even decades, they finally reach the stratosphere at altitudes of 20 to 40 km [26, 27]. In this layer, under the influence of short-wave UV irradiation, ozone is formed continuously (Scheme 1.2). This stratospheric ozone plays an essential role in preserving life on earth by absorbing the short-wavelength UV which would otherwise lead to an increase of photochemically induced mutations in most life-forms. For humans, over-exposure to short-wave UV irradiation results in a dramatically increased risk of skin cancer. Many crops and other plants also react rather sensitively towards an increase of UV exposure. 

---