Very recently, one of my friends pinged me on messenger asking the following :
“Can I use bleaching powder mixed in water for cleaning & disinfection of the floors of my house? Will it be effective to kill the COVID-19 virus?”
That is actually a very nice question.
Before we come to the answer, what we need to know is:
Bleaching agent is made of chlorine compounds (calcium & sodium compounds of chlorine in the form of calcium hypochlorite & sodium hypochlorite respectively).
Chlorine is often used as a chemical method for controlling microbial growth.
In the presence of water, hypochlorites undergo hydrolysis resulting in the formation of hypochlorous acid which then decomposes into HCl & atomic oxygen [O]. This atomic oxygen, also known as nascent oxygen, is a strong oxidising agent which acts on cellular constituents of microorganisms & results in their death.
Now, the question comes, “What type of germs?”
It majorly affects vegetative bacteria & fungi, although not spores (resistant & dormant forms of bacteria and fungi can withstand highly adverse environmental conditions, e.g, excessive heat & drought).
Now, I should come to the most important question:
What kind of disinfectants must we use to get the protection from the novel Corona virus while wiping the households and whether we use bleach-water?
Actually, the novel Corona virus (SARS-CoV-2) is an RNA virus covered by an outer membrane like structure called the envelope, which is made up of lipids.
Soap interferes with the fats in the virus shell and lifts the virus from surfaces which is then rinsed off by water.
Surgical spirit or hand sanitisers is mostly made up of the alcohol, ethanol which can kill the virus within half a minute by destroying its proteins, a vital component of the cellular structure of the virus.
It’s so efficient!
Alcohols are also solvents of lipids, and hence may damage the lipid complexes in the viral envelope.
Therefore, soap-water or alcohol are your first line of defence.
One must remember that alcohol concentrations only above 70% are effective but one must definitely not use 100% alcohol.
Hence, after returning home, we should immediately wash our hands with soap-water or 70% alcohol.
Besides, moisten a cloth with some soap-water or surgical spirit & rub it to clean tables, chairs and furniture.
As said, these two are the primary defences against the SARS-CoV-2.
Now, regarding the bleach-water, bleach is very effective at killing certain viruses including the influenza virus whose RNA & proteins are reported to be damaged by it.
Generally, an enveloped virus (having an outermost lipid envelope, like SARS-CoV-2) is less tolerant than a naked virus (which does not possess a lipid cover) to the stress. This is due to the fact that, once the envelop is lysed, the virus loses its functionality & is no longer able to infect susceptible cells. In contrast, naked viruses can survive on surfaces for months even under harsh conditions, as if, “A destitute has no fear of losing anything.”!
Therefore, one can undoubtedly use liquid bleach to wipe surfaces. Moreover, it is the cheapest disinfectant that can be used for cleaning of large surfaces like residential floors.
There are certain points to keep in mind.
1. Bleach decomposes under heat and sun-light.Therefore, it needs to be protected from these & also kept out of the reach of children.
2. Bleach irritates the skin & eyes. It is injurious to the airways if it is inhaled for long.Therefore, do use it cautiously and never use bleaching water for washing hands.
3. It requires longer contact time (10-60 min) to act, as compared to alcohol or soap. Therefore, you shouldn’t immediately wipe the cleaning solution off as soon as you’ve applied it to a surface. Let it sit there for long enough to kill the viruses.
4. Being a strong reactant, it reacts easily with other chemicals & hence, loose its effectiveness. Use cold water to mix the bleach. Hot water decomposes the hypochlorite & renders it ineffective.
5. Dont deviate from the recommended dilution (either stronger or weeker). High concentrations of chlorine may contribute to many serious health complications including cancer.
In contrast, lesser amount may reduce its activities.
Most household bleach solutions generally contain 5% sodium hypochlorite. 1:100 dilution of this 5%
sodium hypochlorite is the usual recommendation. Use 1 part bleach to 99 parts cold water (0.05% final concentration) for disinfection of surfaces. Adjust the ratio of bleach to water as needed to achieve the appropriate concentration. For example, if you have a 2.5% sodium hypochlorite stock, use 2 parts (instead of 1 part) of the bleach to 98 parts of cold water. Prepare the diluted bleach afresh daily.
6. It would be better to use a detergent first to rinse the surface thoroughly with water before using the bleach for disinfection.
There are actually two benefits out of this practice.
a) If any dirt or organic matetial (e.g.,
saliva, mucus, vomit, blood or other body fluids) are present there, it would get cleaned of. Otherwise, those organic matter can inactivate the bleach.
b) two weapons, instead of one, are being employed.
Do not use bleach together with other household detergents.
It is to be noted that routine human activities like coughing, sneezing and even talking generates millions of droplets. In droplet spread, the pathogen is carried on particles larger than 5-10 micrometer in diameter in air but only for a very short
distance—usually less than a meter. As these particles are relatively
large, they quickly settle out of the air according to the law of gravitation. As a result droplet transmission of a pathogen depends on the proximity of the source and the host. As the novel Corona virus is known to be transmitted through the contact (& not yet proven to be air-borne), this is the reason why we all are currently maintaining social distancing.
Though, a recent work has come up which demonstrates that exhalations, sneezes, and coughs consist of not only relatively larger mucosalivary droplets following the short-range emission, but also a multiphase turbulent gas cloud that carries clusters of droplets in a gradual sequence of sizes. Depending on the environmental conditions, like humidity and temperature, the gas cloud carrying the pathogen-bearing microdroplets can travel upto 23 -27 feet (7-8 m), thus extending the lifetime & distance travelled by the contained microbes inside.
Today, we all know that the novel Corona virus can survive in air for atleast 3 hours.
Therefore, practicing good cleaning & sanitisation of household objects to get rid of settled droplets, is of utmost importance. Two recent studies have found that Corona viruses survive for anything between one to nine days depending on the type of surfaces.
So, what are you waiting for? Carry on.
Oh yes! If all gentlemen extend their helping hands, then, we women, can do these tasks quickly and more efficiently.
PS: In the picture above, I have tried to explain the major differences between enveloped & naked viruses.