The Tour of Mont-Blanc

Solar radiation

UVA and UVB rays and hazards for the excursionist


We tend to underestimate just how harmful the sun's rays can be, especially ultraviolet radiation.  They can alter the DNA of our skin cells and induce skin tumors (e.g., melanoma) and other dermatological diseases as well as problems related to the eyes, such as conjunctivitis, snow blindness, corneal burns, heavy tearing and photosensitivity.

The highest risk time time slot is during midday (from 11 am to 2 pm) around the summer solstice (June 21st).  At this time at our latitudes, the sun's rays strike the earth at an angle of nearly 90°, which means the distance they travel through the atmosphere is at its shortest and has less of a filtering effect. In addition, the intensity of radiation increases by 7% for every 1000 meters in altitude, thanks to the increasing thinness of the air. In the mountains, therefore, conditions can vary considerably through the course of a single day.

Another factor to keep in mind is how snow and ice on the ground can increase the intensity of radiation by as much as 100%, thanks to their reflective capacity.

What to do:

  • Wear UV filter sunglasses;
  • Always use high protection sunblock;
  • Avoid prolonged direct exposure of the skin to the sun (do not take naps in the sun or lay out to work on your tan);
  • Take care of particularly exposed body zones (face, ears, neck, scalp, hands).