How Effective is Fogging/Fumigation to Prevent Spread of COVID-19?
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In the wake of detection of the Omicron variant of COVID-19 in India, health authorities in different states have started taking preemptive steps to control the spread of the virus.
Apart from increasing the health and safety measures at airports, railways stations and public places, authorities in Bengaluru have started fogging and spraying disinfectants in pubic and commercial spaces.
While there is some research that shows that fogging in closed indoor spaces does help in rendering the virus inactive, fumigating large and open public places is not recommended by the World Health Organisation or other health authorities around the world. Not only is the practice ineffective, it can also be harmful for the health of people who come in contact with vapourised disinfections.
Let's see where and how can fogging help and what are the precautions one must take:
What is fogging/fumigation?
Fogging or fumigation is the process of spraying or dispersing disinfectants through fog, vapour or mist.
Fogging is mainly used to disinfect surfaces that may be hard to reach for cleaning manually. The disinfectants are converted into aerosols, which allows them to be suspended in the air for longer, and clean places and surfaces that may have been infected.
A diluted bleach solution is typically used as a disinfectant.
Does fogging help in reducing the spread of COVID-19 indoors?
Fogging or spraying of disinfectants can be an effective method to reduce the spread of COVID-19 in non-healthcare settings such as homes, offices, schools, gyms etc.
However, such spaces should be sealed off during the application of disinfectants as it may cause irritation to eyes and other respiratory issues in people. It is also not recommended to spray disinfectants directly on people.
Additionally, some surfaces that may get corroded by the use of bleach should only be cleaned with a cloth and 70 percent alcohol solution.
The Ministry of Health and Family Welfare advices to clean high-touch surfaces with a disinfectant with 1 per cent sodium hypochlorite or phenolic disinfectants.
After using disinfectant in closed spaces, proper ventilation should be ensured to clear the disinfectants.
What about fogging outdoor spaces?
The WHO and other health authorities do not recommend spraying disinfectants in large and open public spaces.
The reason for this, according to the health department of UK, is "the dispersion of the chemical hazards and possible unintended exposure to people cannot be controlled".
The WHO says that "spraying disinfectants, even outdoors, can be noxious for people’s health and cause eye, respiratory or skin irritation or damage". Moreover, dirt, dust and UV rays would render the bleach useless in a matter of minutes.
"The toxic effect of spraying with chemicals such as chlorine on individuals can lead to eye and skin irritation, bronchospasm due to inhalation, and potentially gastrointestinal effects such as nausea and vomiting", the WHO advisory adds.
What precautions must one take while using disinfectants?
The concentration of the disinfectants should be carefully selected to avoid damaging surfaces and reduce the toxic effects on humans.
Children and pets should be kept away during the application of disinfectants and food items should also be kept shut.
People spraying disinfectants should use masks and PPE kits to avoid direct contact with bleach and ammonia. And those protective items should be disposed off after the application of disinfectants and not reused.
Is surface transmission a risk?
A study published in the Lancet gave strong evidence that COVID-19 is primarily an airborne pathogen. The small aerosols remain suspended for hours and disperse over time.
The other way, which is less likely, is surface transmission. One study published in the New England Journal of Medicine found that the virus can survive on surfaces for as long as 72 hours, depending on environmental conditions and the type of surfaces. High-contact surfaces can, hence, be cleaned regularly with a mop.
The US Centres for Disease Control and Prevention too, in May, said that the possibility for people to be infected through contact with contaminated surfaces is considered very low.
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