Ultraviolet rays

Ultraviolet rays are an integral part of our daily lives. Still not sufficiently well-known to the general public, it is now necessary to learn more about them to understand them better and better protect ourselves.

What are ultraviolet rays?

Ultraviolet (UV) rays are also called “black light” due to the inability of our eyes to see their radiation. Indeed, they are an electromagnetic radiation of a wavelength lower than that of visible light, but much higher than those of X-rays. That is why we can only observe them using fluorescence or specialized detectors.

Just like visible light, the spectrum of UV radiation is divided into three regions: UVAs, UVBs and UVCs. Given that the ozone layer’s role is to absorb UV rays that attempt to enter into the atmosphere, only 95% of the UV light that reaches the Earth’s surface belongs to UVAs.

Indeed, when the sun’s rays pass through the atmosphere, all UVC rays and most UVBs are absorbed by the ozone layer, water vapour, oxygen and carbon dioxide. Only UVAs are not filtered as effectively.

The difference between UVAs, UVBs and UVCs

Only 5% of the Sun’s electromagnetic energy is emitted under UV form. These rays are classified into different categories based on their wavelengths and their power to penetrate the skin:

• UVA
• UVB
• UVC

The longer the wavelength (UVA), the closer it gets to visible light and therefore, the less energy it holds and the less harmful it is to the skin. Conversely, the shorter the wavelength (UVC), the closer it gets to X-rays and therefore, the more energy it holds and the more harmful it is to the skin.

The effects of ultraviolets on health

Depending on their wavelength, ultraviolet rays can be good or harmful to our skin. That is why the protection of the ozone layer as well as skin protection are important issues in our society.

The benefits of ultraviolet rays

UVA rays with a wavelength between 360 and 400 nm help limit the development of myopia in adults.

Although UVB rays are responsible for delayed tanning and infamous sunburns. At moderate doses, UVBs have several benefits:

• They facilitate vitamin D synthesis in our bodies;
• They allow the absorption of calcium by the intestine;
• They help general strengthening of our skeleton.

UVB rays therefore help to fight rickets (due to a severe vitamin D deficiency), and also treat many diseases including psoriasis and eczema.

As for UVC rays, they have long been used in laboratories in the form of germicidal lamps in order to disinfect sensitive areas or professional equipment.

As a result of the global health situation, UVC rays are being used to fight viruses and bacteria on a larger scale. Indeed, they are now very beneficial in the decontamination of larger spaces such as hotels, clinics, or even schools.

The risks of ultraviolet rays

Overly-long or intense exposures to the Sun or to artificial radiation can cause several health complications:

• Dryness of the skin;
• Burns;
• Tumors and cancers. (1)

Indeed, solar radiation itself was classified as a Group 1 carcinogen in 1992 by the International Research Agency.

According to the World Health Organization, 50 to 90% of skin cancers are caused by solar ultraviolet rays, making them the primary risk factor for skin cancers. (2)

What is the link between the destruction of the ozone layer and UV radiation?

The ozone layer plays a fundamental role in the filtration of ultraviolet rays. The destruction of the ozone layer is caused by man-made chemical substances released into the atmosphere. However, as it thins, its filtering properties diminish. The hole in the ozone layer then allows the passage of more intense ultraviolet spectra, such as UVBs.

The consequences can be fatal, such as:

• Increased risks of skin cancer;
• The destruction of more sensitive plants;
• The considerable impact on living beings, such as on penguins in Antarctica.

To learn more about UVC rays and their benefits in the fight against Covid-19.