[EXPERT REACTION] Disinfection tunnels cause more harm than good?

A disinfectant tunnel set up near a supermarket in Kelantan recently - BERNAMA / Twitter

Despite the lack of evidence, disinfection tunnels are being set up at crowded places like malls, markets and offices as it was initially believed that the tunnel would work as a mass disinfectant. Health director-general Datuk Dr Noor Hisham Abdullah has reiterated that there is no evidence that the use of disinfection tunnel can effectively prevent the spread of COVID-19.

We asked experts to explain the risk of disinfection tunnel and does it cause more harm than good?


Dr Bimo Ario Tejo, Chemist & Associate Professor at the Department of Chemistry, Universiti Putra Malaysia, said:

“The safety and effectiveness aspects of disinfection tunnels must be assessed carefully. Safety aspect must be emphasized because our eyes, mouth, and skin are exposed to chemicals for 10-20 seconds in the disinfection tunnel. The aspect of effectiveness must also be given attention because we must ensure that the virus has completely died. 

Many disinfection tunnels use alcohol and hypochlorite (bleach) as disinfectants. The World Health Organization (WHO) issued an official statement on February 12, 2020 that alcohol and chlorine-based disinfecting liquids should not be sprayed on the human body because they can damage the mucous membrane in the eyes and mouth. Therefore, the use of alcohol and bleach in disinfection tunnels violates WHO regulations and poses a health hazard.

In addition to the safety aspect, the effectiveness of disinfection tunnels must also be assessed carefully. The effectiveness of a disinfection solution to kill the virus depends on two factors, i.e. the concentration of the liquid and the exposure time. Exposure time means the minimum time required for disinfectants to kill the virus.

In the list of 351 disinfectant products for SARS-CoV-2 issued by the United States Environmental Protection Agency (US EPA), the majority requires 10 minutes as a minimum exposure time. This 10-minute exposure time has become the gold standard for the SARS-CoV-2 disinfection process. 

Therefore, the effectiveness of disinfection tunnels to kill the SARS-CoV-2 virus is doubtful. The notion that 10-20 seconds of exposure time is enough to kill the virus gives a false sense of security.”

Dr Chai Lay Ching, Microbiologist at the Institute of Biological Sciences, University of Malaya, said:

“Not only spraying disinfectant on human does not help in preventing COVID-19, it could potentially bring more harm. My justifications are as follow:

Justification #1

With the information and evidences collected thus far, WHO has reported that SARS-CoV-2 is primarily spread from human to human through two scenarios: 

  1. In close contact (within 1 meter) with an infected person when they cough or sneeze that sent the respiratory droplets which contain the SARS-CoV-2 virus in the air. And as the result, the infective respiratory droplets could be inhaled into nose or mouth or reach the soft tissue of eyes of others in close contact.
  2. The infective respiratory droplets could contaminate the surfaces around the infective person when they cough or sneeze. Transmission could occur by touching these contaminated surfaces (usually with hands) and the virus then can get into our body when we touch our nose, mouth or eyes with the contaminated hands.

Therefore, effective ways to prevent the spread of COVID-19 are via social distancing, wearing face masks (particularly those who are infected, with symptoms or without symptoms), washing hands and disinfect surfaces in public area. Spraying disinfectant on an infected person does not stop him/her from sneezing and coughing and sending viruses in the air. Spraying disinfectant on healthy person does not provide an invisible layer to protect them from the virus too!

Justification #2

Sodium/calcium hypochlorite and hydrogen peroxide are found to be used to create the disinfectant mist in the disinfecting tunnel. Both sodium/calcium hypochlorite and hydrogen peroxide are commonly used to disinfect inanimate surfaces (e.g. floor, table, doorknob, kitchen top, cloths, utensils, etc.) in households, hospitals and food manufacturing environments. Generally, both chemicals are effective in killing bacteria, fungi and virus. However, no research data or evidence is available at the moment that these chemicals used at a low concentration, that is safe on human skin, is effective in killing SARS-CoV-2 in a short contact time (presumably 30-60 seconds). 

Justification #3

At certain concentration, these chemicals might be safe on human skin but not on soft tissues in your eyes, nose and lung. 

Centers for Disease Control and Prevention (CDC) stated that:

“Hydrogen peroxide can be toxic if ingested, inhaled, or by contact with the skin or eyes. Inhalation of household strength hydrogen peroxide (3%) can cause respiratory irritation…. Eye exposure to 3% hydrogen peroxide may result in pain and irritation, but severe injury is rare. More concentrated solution may result in ulceration or perforation of the cornea. Skin contact can cause irritation and temporary bleaching of the skin and hair. Contact with concentrated solutions may cause severe skin burns with blisters.”

“Sodium and calcium hypochlorite can cause irritation of the eyes, skin, respiratory and gastrointestinal tract. …. The toxic effects of sodium and calcium hypochlorite are due primarily to the corrosive properties of hypochlorite. … In general, children may be more vulnerable to corrosive agents than adults because of the smaller diameter of their airways.”

Disclaimer: These comments were complied to provide journalists with a range of expert perspectives on the subject. The views expressed here are the personal opinions of the experts. They do not necessarily reflect the views of the Science Media Centre or any other organisation unless specifically stated. 

Bionotes of experts

Dr Bimo Ario Tejo obtained his BSc in Chemistry from the University of Indonesia in 1999 and his PhD in Biotechnology from Universiti Putra Malaysia in 2004. He did his postdoctorate in Pharmaceutical Chemistry at the University of Kansas. He held deanship posts at private universities in Indonesia and Malaysia. He is currently an associate professor at the Department of Chemistry, Universiti Putra Malaysia. He has almost 20 years of research experience in protein and peptide chemistry, pharmaceutical chemistry, and computational biology. He has published over 50 peer-reviewed papers, presented his work at 60 seminars and conferences, and filed 5 patents out of his work.

Dr Chai Lay Ching is a microbiologist from Institute of Biological Sciences, University of Malaya. Her research focuses on microbial risk assessment in food and water. Dr Chai serves as the Vice-Chair of the Technical Working Group of Microbiology under the Food Analysis Committee (JKAM) chaired by the Department of Chemistry Malaysia, MOSTI; nominated as a risk assessor in the ASEAN Risk Assessor Directory; scientific advisor of International Life Science Institute South-East Asia Region; vice-Chair of the Southeast Asia International Association of Food Protection; and member of the Research Ethics Committee and Institutional Biosafety and Biosecurity Committee University of Malaya. Dr Chai is the chairperson of the Young Scientists Network-Academy of Sciences Malaysia, that functions as the national young academies Malaysia that consists of more than 150 top and passionate scientists under the age of 40 years old. Dr Chai is an awardee of the L’Oreal-UNESCO Women in Science Award 2018. She was also listed as Marie Claire’s Amazing Woman in Malaysia 2019, and included in Prestige’s 40 under 40 Malaysia.

**All previous posts about COVID-19 here: https://sciencemediacentremalaysia.com/tag/covid-19/  

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