The intensity of ultra-violet light at Antarctic stations during the time of the ozone hole is not much more than on a tropical beach at midday. This is because in the tropics the light comes straight down through the atmosphere, whereas in the Antarctic the sun is much lower in the sky so that light takes a much longer path through the atmosphere. Nevertheless, it has always been very important to take precautions against sunburn in the Antarctic, because sunlight is also reflected from the snow surface. Recent studies suggest that some skin cancers are caused by a two stage process: sunburn as a child causes a DNA mutation and further sunburn when older activates the cancer, which may appear many years after the original exposure.