Ultraviolet (UV) radiations make a part of the solar radiations spectrum and SUN is a major natural source of these radiations. Naturally designed and developed Ozone layer in the stratospheric region of the Earth’s atmosphere acts a shield by absorbing most of the UV radiations to protect not only human beings but all sensitive biotic system of earth due to deadly affect of UV radiations. Ultraviolet (UV) radiation covers the wavelength range of 100–400 nm, which is a higher frequency and lower wavelength than visible light. UV radiation comes naturally from the sun, but it can also be created by artificial sources used in industry, commerce and recreation.
The UV region covers the wavelength range 100-400 nm and is divided into three bands: UV-A (315-400 nm); UV-B (280-315 nm) and UV-C (100-280 nm). As sunlight passes through the atmosphere, all UV-C and approximately 90% of UV-B radiation is absorbed by ozone, water vapour, oxygen and carbon dioxide. UV-A radiation is less affected by the atmosphere. Therefore, the UV radiation reaching the Earth’s surface is largely composed of UV-A with a small UV-B component. The amount of UV radiation from the sun that hits the Earth’s surface depends on several factors, including the sun’s height in the sky, latitude, cloud cover, altitude, the thickness of the ozone layer and ground reflection. Reductions in the ozone layer due to human-created pollution increase the amount of UV-A and UV-B that reaches the surface. This can impact human health, animals, marine organisms and plant life. In humans, increased UV exposure can cause skin cancers, cataracts and immune system damage.
Role in disinfestations
Disinfection by way of UV light is nothing new as it's been a useful technology for over 40 years, contributing to clean water and clean air. Many consumer devices also use UV light to disinfect things, such as self-cleaning UV light water bottles and UV-emitting cases that clean your dirty phone. In the recent times of corona virus pandemic (COVID-19) UV radiations/light has attracted great significance due to its energy being used to kill or disinfect from corona virus. UV light has been shown to destroy other corona viruses, so it will probably work on the novel corona virus. It is claimed that UV light can destroy the novel corona virus that causes COVID-19. Scientists are studying the use of ultraviolet germicidal radiation (UVGI) to detect the virus in schools, restaurants and other public places. Through this method, ultraviolet (UV) lights would be able to disinfect contaminated public spaces to stop the transmission of the virus. But UV light damages human skin, so it should only be used on objects or surfaces. UV-C light has the most energy of the three types and this energy destroys the genetic material inside viruses and other microbes. Therefore, UV-C light is used for disinfection. It works because UV-C light is strong enough to destroy the genetic material –either DNA or RNA- of viruses and bacteria. There's no evidence right now that typical sun exposure can kill the coronavirus, so no, going outside on a sunny day won't reduce your risk of catching it. Therefore, the health experts and the UV technology industry are working to define standards for UV disinfection technologies in healthcare settings.
Widespread adoption of efficient UV approach is much in demand during the current pandemic, but it requires UV radiation sources that emit sufficiently high doses of UV light. While devices with these high doses currently exist, the UV radiation source is typically an expensive mercury-containing gas discharge lamp, which requires high power, has a relatively short lifetime, and is bulky. The solution is to develop high-performance, UV light emitting diodes, which would be far more portable, long-lasting, energy efficient and environmentally benign. While these LEDs exist, applying a current to them for light emission is complicated by the fact that the electrode material also has to be transparent to UV light. To ensure a sufficient UV light dose to kill all the viruses we need a high-performance UV LED emitting a high intensity of UV light, which is currently limited by the transparent electrode material being used. While finding transparent electrode materials operating in the visible spectrum for displays, smartphones and LED lighting is a long-standing problem, the challenge is even more difficult for ultraviolet light.
Consumer devices aren't the only place to find UV light sanitization. Some brick-and-mortar businesses are installing UV light fixtures in their facilities in an attempt to completely disinfect the building and mitigate the risk of contracting COVID-19 through air or surfaces. Again, because UV light is the primary germ-killer in the natural environment, it makes sense to take this approach. This practice, called "ultraviolet germicidal irradiation," has long been used in hospitals where pathogens abound. While the effectiveness of environmental UV sterilization on surfaces such as floors has been confirmed, however, further research is needed about the safety of indoor UV light fixtures, as well as its efficacy at sterilizing clothes and human skin. A personal, handheld device emitting high-intensity ultraviolet light to disinfect areas by killing the novel coronavirus is now feasible. UV-C lamps and robots are commonly used to sanitize water, objects such as laboratory equipment, and spaces such as buses and airplanes.
Everyone would want to disinfect their new purchases as they bring home groceries and to solve this concern a company has developed a new product called CoronaOven that uses ultra violet light to kill coronavirus is a box shaped disinfection chamber that uses UV-C rays to kill coronavirus in ten minutes. Once an object is placed inside the box, the device will kill all types of viruses/pathogens from all sides, ensuring each side and surface gets the UVC radiation. It can be used for personal use and also by firms to disinfect surfaces of various objects, household and grocery items, food items, delivery parcels, masks, hospital PPE & tools etc. The Bangalore-based firm has developed this technology in partnership with Indian Institute of Science (IISC), Bangalore. The product has been scientifically reviewed and verified in terms of UV intensity at the laboratories of IISC.
Precautions and safety
According to the latest guideline on the diagnosis and treatment of the novel corona virus released by the National Health Commission (China), the virus is sensitive to ultraviolet light and heat, so ultraviolet radiation can effectively eliminate the virus. Though scientists are working on ways to make these powerful disinfecting products safe for people to use, current devices are not safe to use on our body. Scientists are exploring ways to use a specific type of UV-C light for devices that could be safe for humans. Till now, it is not safe to use UV sanitizers on the body because exposure to UV-C light is dangerous for human. UV-C sanitizers can damage our eyes and skin and can also cause cancer. UV-C wands, pouches, and lamps are also sold for home use—for example, disinfecting cell phones. However, the safety and effectiveness of these products is not known. Beware of false claims that say these products are effective or are for use on humans. However, till date the existing UV based products in the market are not proved to be safe to use on our body. According to the guideline, indoor spaces should be disinfected with ultraviolet light with an intensity of over 1.5 watts per cubic meter. A UV lamp can disinfect objects within one meter for at least half an hour. Longer exposure to radiation is needed when the temperature indoors is below 20 C or above 40 C and relative humidity is over 60 percent. A room should be ventilated after UV disinfection, and people are suggested to enter the room half an hour later.
The amount of ultraviolet required varied widely, depending on factors such as the shape and type of material the virus was on. Nevertheless, a concentrated form of UVC is now on the front line in the fight against Covid-19. Whole buses are being lit up by the ghostly blue light each night, while squat, UVC-emitting robots have been cleaning floors in hospitals and banks have even been using the light to disinfect their money.