Ozone loss in the Arctic is on a smaller scale than in the Antarctic, where the seasonal `ozone hole' is such a huge environmental concern. But in recent winters that has been changing _ worst of all was the winter of 1995/96, when Arctic ozone fell from about 450 Dobson units to about 300. This change appears to be due to longer stratospheric winters, which allow nitric acid (whose breakdown usually gets in the way of ozone loss) to fall out of the stratosphere on ice particles.
