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25 Oct 2020, Edition - 1930, Sunday

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India News

Why the ‘spray walk’ may not work in the fight against Covid-19 pandemic.

Dr Soundararajan

Coimbatore has set up ‘disinfectant’ tunnels at especially vegetable markets following its introduction in Tiruppur, recently, to fight the coronavirus epidemic.

I understand from a news report the disinfectant that is sprayed on people as they pass through the tunnel, is diluted bleach.

We may possibly overlook some scientific facts here – something the service providers must understand.

1.One, bleach as a disinfectant is active only as a wet contact media requiring minimal average contact time of 10 minutes to be fully effective fully.

2.Two, the concentration of the diluted bleach is very critical for its efficacy as antimicrobial. Voluminous scientific data is available on this topic. For example, Hepatitis A virus needs 0.5 ppm for 3.5 minutes at low temperature. But Hepatitis B virus requires 500 ppm for 10 minutes at room temperature (RT) and HIV virus requires 5000 ppm at RT. No one has studied so far, how effectively bleach works on the Covid-19 virus.

In my limited report searches, I find that the providers and promoters of this bleach spray solution use 0.5 ppm (need to verify) which may not be effective at all at this very low concentration.

Moreover, the ‘spray walk’ in the tunnel is for 10 to 15 seconds, which is theoretically and practically not enough for the disinfectant to be effective. Remember, the bleach requires a wet contact for a specific amount of time to be powerful enough to killing the virus. If this requirement has to be met, the person has to be bathed, fully clothed, to disinfect him. (PLEASE DON’T TRY THIS).

The material safety data sheet (MSDS) on bleach clearly warns of damage to retina and other parts of the eyes, and lungs by an active ingredient in the bleach called hypochlorus acid. Many other health hazards are are mentioned in the data.

In my opinion, the disinfectant tunnel measure, though well-intentioned, completely lacks a scientific approach.

At the best, it is a feel good treatment of little value in killing microbes. With a lot of money spent, the tunnel may not serve any purpose.

There are other safer and effective alternatives to this method.

If anyone wishes to know more about this topic, please contact me at 9446438876.

(The author is former research Scientist at Purdue University, USA and Washington State University, USA.)

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