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Why UV is better and crucial in the fight against infectious diseases

According to Harvard University, the Coronavirus can stay alive in the air for up to 3 hours and on surfaces up to 3 days [1]. Other research pegs the number at upto 9 or even 28 days [2]. Therefore, to successfully contain the spread of SARS-CoV 2, there is an urgent need to sanitize and disinfect surfaces effectively, particularly items such as wallets, cash, masks, gloves, phones, e-commerce packages, dairy packaging, CPG, office supplies and other items that are part of our high touch supply chains. As the lockdown is lifted and the economy tries to return to normalcy, such sanitization efforts will be crucial to prevent an even more dire relapse. Moreover, to ensure we don't see a repeat of a pandemic, we must incorporate such sanitization efforts into standard cleanliness procedures permanently, like we incorporated handwashing in the late 90s [2]. The US Centre for Disease Control recommends disinfecting regularly used surfaces daily [3].

Currently deployed methods such as electrostatic spraying of disinfectants like Sodium Hypochlorite (bleach) [4, 5, 6] are suboptimal. As per the Environment Protection Agency[7, 8], chemical disinfectants (including Sodium Hypochlorite) are not effective on soft, porous surfaces (eg: paper, cash, clothes, textiles, upholstery, covers, leather). Moreover, the spraying method is not thorough (the spray can easily miss parts of surfaces during application), does not work on airborne droplets, is prone to human errors while spraying, and can damage electronics. Chemical disinfectants like bleach have also been linked to chronic pulmonary disease [9, 10]. The process is also is labor-intensive and time-consuming, as well as expensive. 

UVC promises a more efficient, inexpensive, and effective way and to sanitize not just soft surfaces but all surfaces. 

Around the world, hospitals [13, 14], governments [15], and airlines [16] are adopting UV-C technology to battle COVID-19. However, the UV-C radiation is harmful to humans and long exposure[17] can cause temporary and chronic complications such as cataract and skin cancer. 

Large area UV sanitization has safely been used for years by professionals in hospitals [17, 18]. It has also been used in closed consumer applications such as water purifiers [19], HVAC systems [20], and cellphone disinfectants [21]. Given the scale of the COVID-19 pandemic, however, there is a need to produce a cheap and safe alternative that can be used for large spaces by non-professionals in real-world settings.

How it works: Exposure to UV-C spectrum (200-280nm wavelength light) is known to degrade [11, 12] the DNA and RNA structures present in bacteria, molds, and viruses including SARS-COV-2. The American Food and Drug Administration has added UV-C disinfection to it's list of solutions to kill the Coronavirus [13]. In India, renowned institutions like the DRDO have designed a host of UV-C based devices to fight COVID-19 [14].  

Exhibit 1: UV doses required to kill various pathogens, including Coronavirus

Source: [15] 

As per studies by Jingwen (2020), a 7J/m2 dose is determined to be adequate. For our calculations, we have used a 5X buffer. The effectiveness of a UV-C lamp at a certain distance and exposure time can be calculated using the formula presented by Marcel Bentancor and Sabina Vidal[16] given the required dosage as ascertained earlier:

Where t is the time of exposure, L the length of the lamp, r the distance of the surface from the lamp, D the dosage required, and P the power of the lamp.

UVC rays work on the principle of "Line of Sight". That means it does not permeate most opaque solid barries. This means that opaque objects shield one from UVC rays. It also means that UVC only disinfects surfaces it lands on. To read about how UVC works please refer this great blog [17] by GermFalcon.

UVC has also long been used in the disinfection of edible substances like juices, vegetables, fruits. This use is backed by research [18, 19].