ClO2, a radical, undergoes photodecomposition in the stratosphere where
the products of this reaction react with ozone. Since this is a
photochemical reaction it only takes place while the sun is up.
Experiments over Antarctica have shown a direct relation between polar
ozone loss and the increase in halocarbon chemistry, which comes from
anthropogenic sources. Scientist are currently looking at the molecular
behavior of chlorine dioxide in the atmosphere in order to understand its
role in depletion of ozone more thoroughly. [Simon, J. D. and Vaida, V.
The Photoreactivity of Chlorine Dioxide. Science v 268; p. 1443-1448;
1995.]