UV rays: what they are and effects

UV rays: what they are and effects

UV rays are allies of the body, but if precautions are not taken they can cause damage to the skin and eyes. Here's what UV rays are and what effects they cause

The sun is a source of life and heat. It puts you in a good mood, it is the undisputed star of hot summer days, it plays a key role in some physiological processes of the body, but it is also a source of UV rays. These have the ability to penetrate through sun exposure but, without the necessary precautions, can cause damage over time. For this reason, experts recommend – especially in summer – to avoid exposure to the sun during the hottest hours of the day and to protect the skin by applying adequate protection.

However, UV rays (in particular UV-C) are being heard more and more in recent months in correlation with the spread of Covid-19. In fact, masks and cleansing gels are essential to reduce the infection, but UV-C ray lamps can also provide valuable help. The reason? UV-C rays, according to the findings of various studies, have a germicidal action on viruses and bacteria.

So let's see what UV rays are, what the effects on humans and viruses can be, but above all what is the correlation between UV-C lamps and Coronavirus.


  • What are
    • UV-A rays
    • UV-B rays
    • UV-C rays
  • Effects
  • What damage they can cause
  • UV-C and Coronavirus lamps

What are

UV rays, as indicated by the World Health Organization, are ultraviolet radiation coming mostly from the sun, but also from artificial sources such as those used in the commercial, industrial and leisure fields. With a wavelength ranging from 100 to 400 nanometers (nm), ultraviolet radiation is divided into three bands:

  • UV-A rays (315-400 nm);
  • UV-B rays (280-315 nm);
  • UV-C rays (100-280 nm).

To reach the earth, ultraviolet rays must pass through the atmosphere and in this passage UV-C rays and about 90% of UV-B rays are absorbed, so they are mostly UV-A rays and a part of the UV-B rays reaching the earth's surface.

But the amount of UV radiation that reaches the earth also depends on other (countless) factors such as:

  • the height of the sun in the sky (lower in the hottest months, especially around noon in the summer months);
  • the altitude (every 1,000 meters, UV levels increase by 10-12%);
  • latitude;
  • the reflection on the ground (sand reflects about 15% of UV radiation, while snow reflects about 80%);
  • the thickness of the ozone layer (the reduction of the ozone layer due to pollution facilitates the passage of UV-A and UV-B rays on the earth);
  • cloudiness.

Let's see specifically the types of UV rays.

UV-A rays

UV-A rays are able to cross the atmosphere and reach (all) the earth, but they are also among the most dangerous as they can penetrate well beyond the epidermis. They operate all year round and pass through clouds and glass, so it is important to protect the skin and eyes with the necessary precautions.

UV-B rays

Unlike UV-A rays, only a small fraction of UV-B rays make it to earth. These affect the surface layer of the epidermis causing burns and redness typical of unprotected exposure. UV-B radiation is present at all altitudes, but in this case windows and clouds act as an effective barrier.

UV-C rays

UV-C rays are the most dangerous for human health. While not reaching the earth's surface, they can be produced by lamps or devices that use this radiation to disinfect surfaces and environments such as public places and hospitals. As also indicated in the Report of the Higher Institute of Health, in fact, UV-C rays perform a germicidal action on viruses and bacteria thanks to their ability to modify the DNA and RNA of microorganisms, preventing their reproduction. These radiations cannot be perceived by humans as they are not visible and do not generate heat / cold, however they can cause serious damage to the eyes and skin.


With effects that can occur in the long or short term, UV rays can cause harmful effects on human health, such as melanoma, sunburn, erythema, premature aging of the skin. On the other hand, however, they represent indispensable allies for the psychophysical well-being of the organism: in addition to promoting the production of serotonin (the so-called "happiness hormone"), sun exposure, if carried out correctly and consciously, is in fact, the main means of promoting the synthesis of vitamin D, essential to counter the development of diseases such as osteoporosis. Correct doses of UV radiation are also used as a therapy for the treatment of skin diseases such as psoriasis, vitiligo, atopic dermatitis. Therefore we must not avoid the sun but rather protect ourselves in order to avoid the negative effects of ultraviolet radiation.

What damage they can cause

Different parts of the body such as the skin, blood vessels and eyes are involved in the possible damage from exposure to UV rays. Burns, erythema and burning can, for example, occur due to the action of UV-B rays, while UV-A rays that penetrate deeper can accelerate the skin aging process with the consequent appearance of unsightly wrinkles. In this case, the damage is not immediate, but we can see the effects over time.

The eyes can also be damaged by ultraviolet radiation and favor the appearance of phototraumatic maculopathy or even cataracts. But that's not all, because the diseases related to exposure to UV rays and identified by the World Health Organization itself include:

  • keratosis (chronic skin disease);
  • skin melanoma (malignant tumor);
  • squamous skin carcinoma (a malignant tumor with a slower evolution than skin melanoma);
  • reactivation of cold sores;
  • squamous carcinoma of the cornea (eye cancer of rare frequency).

UV-C and Coronavirus lamps

UV-C lamps have already been used for some time in numerous contexts to disinfect air, water and food. The already known bactericidal and virucidal action of UV-C rays has also been confirmed with regard to the Coronavirus Sars-Cov-2: specifically, an experimental study has verified that even a small dose of UV-C rays, such as that supplied by a UV-C lamp for a few seconds and a few centimeters from the subject is sufficient to prevent the reproduction of the virus, regardless of its concentration.

These disinfectant effects are valid and safe as long as the UV-C ray lamps comply with European regulations, developed precisely to avoid any damage to health: as reported in the RAPEX report of 10 July 2020 by the Community rapid information system on in fact, on the market you can not only come across UV-C lamps that do not emit this radiation (therefore they do not kill viruses and bacteria), but also lamps that emit doses of UV-A, UV-B and UV-C not compliant with European safety regulations: it follows that users of these types of products, even more so if exposed to radiation without adequate protection, can not only increase the risk of incurring serious injuries to the skin and eyes but also experiencing a false sense of security, potentially dangerous.

On the contrary, the use of UV-C lamps compliant with European legislation could instead be indicated for the disinfection of surfaces and environments (especially those with a high probability of transmission of pathogens by air, such as hospitals and laboratories), always putting in place the appropriate safety measures.

However, it should be borne in mind that the ability of the UV-C lamp to sterilize the environment or surfaces decreases both in the presence of dust and dirt on the lamp or in the environment, and after a certain period of time has elapsed. For these reasons, the germicidal lamp should only be used after thorough cleaning of the same and the premises (always in the absence of people), and carefully following the instructions provided by the manufacturer. Finally, once its function is exhausted, proper disposal of the product is essential, which must be treated as special waste due to the presence of mercury, highly toxic to both man and the environment: also in this case, it is necessary then follow the disposal procedures indicated by the manufacturer.

Category: Health
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