We are in the era when disinfection and social distance represent the prerequisite to survival. The realistic requirements ahead focus on problems we haven’t, generally, tackled in the ‘peaceful’ time, such as alternative ways to disinfect the space.
Our grandmothers, mothers, even us (when the air is not polluted) have often put the bed sheets and pillows outside to sunbathe. We believe this custom goes generations and hundreds of years in the past. After staying in the sun and fresh air, the sheets are aerated and have the scent of freshness. This is actually the oldest way to disinfect the objects hard to wash, by using sunlight and fresh breeze.
People have always been fascinated by light, and physicists, within science, have done a great deal on its analysis and better understanding. UV radiation was discovered by a German physicist, chemist and doctor Johann Wilhelm Ritter. In elementary school, we are thought that the light is divided into infrared, visible spectrum and ultraviolet light.
We know today, within the ultraviolet spectrum, of three types of UV rays: UVA, UVB and UVC (the last one includes VUV- Vacuum ultraviolet). The first two types go through Earth’s atmosphere and come to us, so we have SPF UVA + UVB sun creams and sunglasses. The third, so-called germicide UVC, doesn’t reach us because it is withheld by the ozone layer. It is very aggressive to the cells of the eye and skin, since its qualities and intensity dissolve DNA molecules, with the same effect on viruses of type MERS, SARS and COVID. Though UVA and UVB have the power to destroy some pathogen particles, in case of these viruses they have no power to destroy them, only weaken them. This means that natural sunlight doesn’t have the desired disinfecting action in this case.
UV lamps have been used for decades, especially in the hospital environment, for sterilization of rooms, instruments, as well as the popular ‘sunbathing’ of the newborns with physiological jaundice, since it helps in their recovery. UV lamps are also applied in medical diagnostics, in addition to the treatment of pure and residual waters.
Though in use for a long time, the use of UV lamps is limited to professional use, or to use with the necessary training and statement signing. As for quality and performances, there is no universal standard that regulates this area, as this is the case with luminaires for illumination of workspaces- EN 12464 with its versions and annexes.
The International Ultraviolet Association (www.iuva.org) proposes that UV protection (not any kind, but UVC in case of COVID 19) should be only added to physical disinfection consisting of chemical cleaning, and soap and hot water cleaning, in order to cover as many viruses as possible. This approach is the most thorough so far but is still based on assumption since this virus is still much unexplored and the testings have been done only in laboratory conditions.
At the time we are writing this text, the World Health Organization has recommended not to sterilize the hands with UV light.
Therefore, the general recommendation, before you decide to additionally sterilize with UV light, is to get as many information as possible about its advantages and disadvantages.
When purchasing germicide lamps, it is necessary to pay special attention to safety instructions provided by the producer (exposure to radiation can be both direct and indirect, and the consequences are cumulative and risky especially for the eyes and the skin), as well as on the producer’s declaration whether the light source is ozone-free or creates ozone during operation. One of the side effects of UVC and VUV radiation coming from these lamps is the creation of the ozone layer. The ozone is very useful in the higher parts of the atmosphere, while in the immediate proximity it can be dangerous for the elderly and persons with lung problems (such as asthma).
If you have decided to sterilize the space in your factory, apartment or building with additional UVC radiation, please be aware of the dangers of explosion and notify the other employees/tenants of the measures taken and necessary precautions.
Authors: Miroslav Živanović, Gordana Graovčević i Jelena Karalejić