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THE RADIATION
UV
The sun boosts morale and promotes the production of vitamin D, yes! But we sometimes forget that it can also present risks. In metropolitan France, the sun's rays are most intense between May and August, so all your outdoor activities, whether you are in your garden, on a café terrace, at the beach, in the mountains or in the countryside, when you play sports or simply when you go for a walk.... Protect yourself so that the sun remains a pleasure!
The Ministry of Health and Sports.
Everyone is exposed to UV radiation, both from the sun and from many artificial sources used in industry, commerce and recreation. The sun emits light, heat and UV radiation.
The ultraviolet region of the solar spectrum corresponds to the wavelengths 100-400nm; it is divided into three bands (attached).
When passing through the atmosphere all UVC and nearly 90% of UVB are absorbed by ozone, water vapor, oxygen and carbon dioxide. UVA radiation is less modified by the atmosphere.
HEIGHT OF THE SUN
The higher the sun is in the sky, the greater the UV radiation. Therefore, UV radiation varies with the time of day and the month of the year. Outside of the tropical zone, radiation is highest when the sun is at its highest, in the time slot around noon during the summer months.
NEBULOSITY
UV radiation is at its highest when there is no cloud cover, but can be significant despite the clouds. Scattering can have the same effect as reflection from different surfaces and therefore increases the total UV radiation.
ALTITUDE
With increasing altitude, the atmospheric layer absorbs less UV radiation because it is thinner. For an increase of 1000 meters in altitude, the UV radiation increases by 10 to 12%.
LATITUDE
The closer you get to the equatorial regions, the more UV radiation is important.
OZONE
Ozone absorbs part of the UV radiation, preventing it from reaching the earth's surface in its entirety. The thickness of the ozone layer varies with the time of year, and even during the day.
REFLECTION BY THE EARTH'S SURFACE
UV radiation is more or less reflected or diffused depending on the surface: fresh snow can reflect up to 80% of UV radiation, dry beach sand about 15% and sea foam on the ocean surface about 25%.
According to the Ministry of Health and Sports, ultraviolet rays can cause irreversible damage, and in the most serious cases, death.
At too high a dose, exposure to UV rays causes burns, which is called sunburn. The skin is red and painful. Afterwards, it peels, signalling the death of millions of cells.
The deeper the layers of the skin are affected, the more severe the sunburn.
At the same time, repeated sunburns strongly increase the risk of skin cancer, especially if they occurred during childhood.
CHILDHOOD VIGILANCE
With skin that is thinner than that of adults and not prepared for the sun, children must be the focus of our attention.
At birth, each individual has a sun capital that will help him or her fight against a certain amount of UV rays. When this capital is exhausted, the body is no longer able to repair the damage caused by the sun. The earlier a child is exposed to the sun, the more his or her sun capital is depleted. To save this reserve, the only solution is to adopt effective protection from a very young age.
THE RISKS
- On the skin: sunburn, premature aging, allergies, cancers (melanoma and carcinoma).
- For the eyes: serious lesions can appear in the short term like ophthalmia (sunburn of the eye) or in the long term like cataract or retinal degeneration.
To communicate the level of risk from exposure to the sun, the World Meteorological Organization and the World Health Organization recommend using a universal scale called the UV Index.
This numerical index (from 1 to 11+, i.e. 11 and above) reflects the intensity of ultraviolet radiation and its health impact on the skin.
It is quite easy to calculate the number of minutes you can safely stay in the sun. Below is a UV index number for each phototype. This is the only number to remember.
You divide this number by the UV index level and you have the number of minutes you are protected.
Example:
You are type 3, so your UV index number is 200. When the UV index is level 7, you divide 200 by 7. This means you can safely stay in the sun for about 30 minutes. If you want/need to stay in the sun longer, you need to protect yourself from UV rays properly.
According to the Cancer Federation.