Coronavirus News Asia

Far-UV radiation can help combat Covid-19


Ultraviolet radiation has been used as a microbicide for more than a century. From water purifiers to laboratory equipment, UV radiation has wide utility in rendering fluids and surfaces microbe-free.

However, its usage became limited to applications that did not involve direct human exposure because of its adverse effects on the skin and eyes. Although conventional near-UV radiation is indeed harmful to humans, it has been shown in recent years that far-UV radiation, contrary to intuition, is both an effective germicide and largely non-harmful to humans.

However, that research, although well received in scientific circles, has been largely ignored by non-scientists, leading to grossly misleading statements such as this one quoted in  The Washington Post: “Of the three types of ultraviolet light, UVC is the deadly one, long-established for water and air sanitizing, but also one that people should never fool with. The invisible light is highly carcinogenic, with disinfecting results that vary widely in professional settings depending on the setup.”

Such apprehensions are at odds with this rigorous research study published in the prestigious journal Nature Scientific Reports in February 2018. Although UV radiation is already being utilized to battle Covid-19, people are critical of its employment for human disinfection purposes such as hand sanitization. 

Far-UVC light (wavelength 207-222 nanometers) is effective in inactivating microbe cells, without harming the skin, over a variety of dose sizes and distributions, both acute and chronic. Far-UVC radiation cannot penetrate even the outer, non-living strata of human skin or eyes; however, because microbial pathogens have dimensions of microns (micrometers) or less, far-UVC can permeate and render them inactive. 

The aforementioned paper showed that far-UVC light also efficiently inactivates airborne aerosolized viruses, with a mere dose of 1.8mJ/cm2 (millijoules per square centimeter) of 222nm light inactivating 95% of aerosolized H1N1 influenza virus. Note that even by the old guidelines of the American Conference of Governmental Industrial Hygienists (ACGIH), which are inconsiderate of different effects of different frequencies of UV radiation, a dosage of 3mJ/cm2 in an eight-hour period is fixed as the safety limit.

It has also long been established that UV light under 285nm can also efficaciously attenuate both drug-sensitive and multi-drug-resistant bacteria, as well as render various strains of viruses ineffectual

UV radiation is mutagenic and breaks a variety of molecular bonds. It also interferes with certain cellular processes, hinders cell division, and damages genetic material in unicellular pathogens including viruses. However, being a carcinogenic and cataractogenic, conventional UV radiation was deemed unsuitable for everyday sanitation purposes to the point that the safety and efficacy of UVC radiation weren’t even distinctly explored.



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