Updated: Nov 30, 2022
SINGAPORE — They are lightweight, portable and are touted as a more “natural” way of killing germs without the use of chemicals.
As more people explore ways to decontaminate surfaces and their personal items in a fast and convenient way, newer consumer-friendly versions of ultraviolet (UV) light sterilisers have been flooding the market, with some even claiming to rid the coronavirus causing Covid-19.
The key thing to note is that there can be real danger when they are used improperly, and there is not enough published data to show that they are entirely effective in eliminating viruses in home and casual settings.
However, these nifty disinfection gadgets have been selling fast in retail stores and are available in various shapes and sizes — from boxes, lamps, handheld wands to mini cabinets.
A spokesperson for online retailer Lazada said that sales of UV sterilisers had gone up and peaked in March where it saw a month-on-month increase of 300 per cent.
Demand remains high with average monthly sales from March to July that were two to four times of those in January and February, the spokesperson added.
Mr Wes Ng, chief executive officer and co-founder of global tech accessories brand Casetify, told TODAY: “The need for safe and effective ways to disinfect our surroundings has definitely boosted the popularity of our UV sanitiser. Since its release in March, we’ve seen a 70 per cent increase in searches for these types of devices within the Singapore market.”
“In the first month of the (product) release, we were able to raise and donate US$100,000 (around S$136,500) to GlobalGiving’s Coronavirus Relief Fund,” he added. The sum was from all proceeds for every UV sanitiser sold.
Casetify’s product, which retails at US$120 (about S$160) on its webstore and multitasks as a wireless charger for phones, features six mercury-free UV-C LED lamps that are said to be able to eliminate germs such as bacteria and viruses found on phones and other small devices.
Casetify’s website states that consumers should be aware that the product is not proven to kill coronavirus. While it disinfects, it does not have a way now to test its effectiveness against Covid-19 yet, the disclaimer stated.
Experts, too, are advising consumers to be aware of the risks when using such devices, because they could cause damage to the skin and eyes and a high-level of care is needed for its safe and effective use.
HOW UV LIGHT KILLS GERMS
The idea of using UV light as a disinfection tool is not new, particularly in healthcare and research settings where it has been used to decontaminate surfaces.
For example, Singapore General Hospital (SGH) has been using UV-C light-emitting cleaning machines to disinfect rooms since 2017.
Dr Ling Moi Lin, director of SGH’s department of infection prevention and epidemiology, said that there are now six of such machines and SGH has ordered two more during the Covid-19 period.
The machines are used as an added cleaning tool for certain rooms, on top of the regular disinfection processes in place at the hospital, Dr Ling said.
There are three types of UV light, namely UV-A, UV-B and UV-C. However, only UVC — with a wavelength of between 200 and 280 nanometres — is used for disinfecting purposes, she said.
“What (UV-C) does is it breaks up the DNA (of the germ) and therefore the organism dies. Studies have shown that UV-C has pretty good results for most micro-organisms, like bacteria, viruses and fungi, although not everything has been tested,” Dr Ling said.
Studies have shown that UV-C light, when used properly, are effective against a range of pathogens, including the superbug methicillin-resistant Staphylococcus aureus (MRSA) bacteria, H1N1 virus and other coronaviruses such as the one that causes the deadly severe acute respiratory syndrome (Sars).
It has also been tested on the Sars-CoV-2, the coronavirus behind the Covid-19 pandemic, and results from some studies have been promising.
For example, a study published last month in the pre-print database medRxiv has found that UV-C, at a specific wavelength of 254 nanometres, could effectively eliminate Sars-CoV-2 on certain models of N95 respirators. The study is now awaiting peer review.
HOW SAFE IS IT FOR HOME USE
When TODAY did a check with experts on how safe is it for consumers to use portable UV sterilisers, they said that people should leave this method of disinfection to trained professionals and proceed with high caution when using UV-C light sterilisers at home.
When contacted, the National Environment Agency (NEA) pointed TODAY to information on its website, which states that the effectiveness of such devices in inactivating micro-organisms depends on the duration of exposure, intensity, distance of surface from source and wavelength of the UV radiation. In short, there is a need for careful calibration and monitoring.
Dr Ling said that it is hard to say if the UV-C sterilisers sold for personal and home use are effective because they may not be tested, unlike medical-grade ones used in hospitals.
“There are also many types of UV machines so we cannot give a blanket statement to say (which one) works as well as the other,” she added.
For the Sars-CoV-2 coronavirus, NEA does not recommend UV-C sterilisers for home use because the efficacy and safety of these devices have not been proven.
WHAT ARE THE LIMITATIONS
Users should be aware of the limitations of such portable devices as well.
For one, there must be a clear line of sight from the UV-C source to the surface for the disinfection to be effective.
“That’s because light travels in a straight line, so if there are shadows or if (the pathogen) is not in the pathway of the light, it doesn’t get killed,” Dr Ling explained.
UV lamps, for instance, work well only under certain conditions and maintenance can be tricky.
“The lamp must be used in a dry environment and the humidity cannot be more than 60 per cent. Also, once you have a layer of dust on the UV lamp, it doesn’t work anymore. After all, it is light and nothing should be in its path when it is in use,” Dr Ling said.
“The duration of exposure also matters, but that would have to be worked out by the manufacturer.”
Those who intend to use such devices should strictly follow instructions, and ensure that they are not directly exposed to the UV lamps when they are operating.
WHAT ARE THE HEALTH RISKS
Professor Christian Kurtsiefer, from National University of Singapore’s department of physics in the Faculty of Science, cautioned people against using UV light to disinfect their hands or areas of their skin.
“If a UV light source kills germs, it is also harmful to the human skin and may cause anything from a sunburn to more serious damage to the skin cells,” he warned.
Dr Ling said that UV-C light exposure may also damage the cornea of the eye and cause blindness.
“One should not be able to look at the UV-C light when it is being shone.
When it is turned on, nobody should be in the room,” she said.
At SGH, a list of safety measures are in place whenever the UV-C cleaning machines are running. For example, they are used only in an enclosed room, and activated from a remote control outside the room.
Further illustrating the high level of care needed to operate the devices, Dr Ling said: “We also put up clear signs to warn people not to enter the room. If a person accidentally walks into the room, the machine will shut down on its own. Everything’s done carefully.”
Dr Ling’s view is that there is no need for a UV-C steriliser at home, and the public should not go overboard thinking they must own one to disinfect their carry-along items.
“Maybe it is a nice-to-have item but it’s not a must-have. Just use the usual disinfectants to clean whatever you need to clean. You could easily wipe down your phone if you want to disinfect it,” she said.
The World Health Organization had already warned that UV radiation can cause skin irritation and damage the eyes, stressing that washing hands with soap and water or cleaning hands with alcohol-based hand rub are the most effective ways to remove the coronavirus.
The United States Food and Drug Administration (FDA) also warned in a statement this week that direct exposure of skin and eyes to radiation from some UV-C lamps may cause painful eye injury and burn-like skin reactions. It also said that some UV-C lamps generate ozone, which can irritate airways.
And for LED lamps that produce UV radiation, they cover small areas and are thus "less effective for germicidal applications", the FDA said.
For general surface cleaning and disinfection for viruses, NEA recommends a wipe-down of surfaces with an effective disinfectant. The list of suitable active ingredients, household disinfectants and cleaning products can be found on its website.
[Source: Today Online - Experts warn consumers to beware of risks when buying UV sterilisers for personal and home use]