Bleach is a water-soluble chemical compound. Household bleach, or sodium hypochlorite, is manufactured as a powder or a liquid. Because it is a cheap and effective antimicrobial agent, it is used to disinfect water tanks, sumps and wells. It also helps brighten white cotton fabrics in the wash and to clean contaminated surfaces. Diluted bleach is only mildly irritating to the skin, but bleach can be corrosive and repeated exposure can damage the lungs.
Wiping down surfaces with bleach is laborious. So these days, disinfectant jets, mists and sprays seem to have become weapons of choice against the coronavirus in public areas. Bleach is sprayed on trees and vegetation, on streets and buses.
To onlookers, the spray of a disinfectant liquid flying through the air may seem especially satisfying. Civic-minded groups and bodies in Karnataka, Odisha, Tamil Nadu and other states have moved enthusiastically and quickly to spraying public areas, including roads. According to news reports, a group of young men in Andhra Pradesh pooled their own money, purchased a small hand-held sprayer and went around streets doing the needful. In some villages, officials have been repurposing fertiliser sprayers as well.
But to what extent does bleach really protect against the new coronavirus, particularly in outdoor areas?
The coronavirus is borne in droplets from coughs and sneezes. It falls onto nearby surfaces or to the ground. Depending on the surface, it can last for a few hours or days. People could be infected if they touch a contaminated surface, don’t wash their hands with soap + water and then touch their own face.
Soap and water is the quickest way to break down the lipid envelope that surrounds the virus. Alcohol-based sanitizers and other disinfectants like bleach are second-best. Bleach, in particular, loses its effectiveness within 24 hours because it is neutralised by sunlight in much the same way the virus is as well.
The Union ministry of health has issued a document entitled ‘COVID-19: Guidelines on disinfection of common public places including offices’. In six concise pages, it covers 1) indoor areas including office spaces; 2) outdoor areas; 3) public toilets; and 4) personal protective equipment (including disposable rubber boots, heavy-duty gloves and properly-fitted three-layered masks). Three annexures provide instructions on how to prepare a fresh 1% sodium hypochlorite solution; wash hands with soap and water, and use masks properly.
As it happens, it deals with outdoor areas in just one paragraph:
“Outdoor areas have less risk then indoor areas due to air currents and exposure to sunlight. These include bus stops, railway platforms, parks, roads, etc. Cleaning and disinfection efforts should be targeted to frequently touched/contaminated surfaces as already detailed above.”
Spraying tree-tops and roads may not be as useful. But it does make sense to use bleach to wipe down, say, office spaces, desks, doorknobs, handrails and elevator buttons, if it isn’t possible to do so with soap and water.
