Minimum concentration/time of application of bleach to kill all viruses?

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Discussion Overview

The discussion centers on the effectiveness of bleach, specifically sodium hypochlorite, in killing the plantar wart virus (Verruca plantaris) and other viruses. Participants explore the minimum concentration and time of application necessary for effective disinfection while considering safety and regulatory requirements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks to determine the minimum concentration of bleach needed to effectively kill the plantar wart virus while minimizing costs and exposure to fumes.
  • Another participant suggests that a 5% bleach solution may be the weakest effective concentration, but notes that regulatory requirements might necessitate higher concentrations, such as 10% or 15%.
  • Concerns are raised about the efficacy of high concentrations of bleach, with one participant mentioning that even 100% bleach does not kill all viruses and questioning the meaning of "offgas."
  • A participant shares their practice of using 10% bleach for decontamination and mentions using 15% bleach for sensitive operations, suggesting a titration measurement for further exploration.
  • Clarification is provided regarding OSHA requirements, indicating that a dilution of 1% to 10% of 5.25% sodium hypochlorite is sufficient for bloodborne pathogens, although one participant expresses caution about going that low.
  • Discussion includes the idea that creating chlorine gas from sodium hypochlorite breakdown may be necessary for killing certain viruses, rather than relying solely on direct contact with the bleach.

Areas of Agreement / Disagreement

Participants express varying opinions on the minimum effective concentration of bleach, with no consensus reached on the optimal dilution or application time. There are also differing interpretations of regulatory requirements and the role of offgassing in the disinfection process.

Contextual Notes

Participants reference specific concentrations and regulatory standards, but there are unresolved questions about the effectiveness of different bleach concentrations and the implications of offgassing in relation to virus disinfection.

Spirochete
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I am specifically interested in using bleach to kill the plantars wart virus (Verruca plantaris), part of the HPV family. It is a DNA virus. I know bleach will destroy DNA but I'm looking to minimize the concentration used to save money and prevent exposure to concentrated bleach fumes. "Full strength" is 6% sodium hypochlorite. Anyone know how much water I can mix it with to assure full destruction of virus particles on a surface?
 
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A 5% bleach solution (0.25-0.3% sodium hypochlorite) is the weakest that you can generally get away with. But usually destroying the viruses is easier than meeting statutory requirements, so you may need 15% or more depending on the regulations.

I think OSHA requires 10% for many applications. Note, also, that full 5-6% sodium hypochlorite is not good enough for some applications -- high concentrations sometimes don't offgass sufficiently to kill certain viruses! I can't remember, I think Hep-C might be one.
 
Strange that OSHA requires around 15%, when even 100% doesn't kill all viruses. What does "offgas" mean out of curiosity?
 
We decontaminate our flow hood with 10% bleach for 20 minutes. We also put 10% bleach in the waste trap from suctioning off media, etc. I have 15% bleach for DNA/RNA sensitive operations on the bench.

Try a titration-type measurement, see what you get. I'd be curious.

The term "offgas", in my experience, means trapped gases that slowly diffuse out of a solid (infrequently a liquid). As in, formaldehyde offgases from new carpet.
 
Spirochete said:
Strange that OSHA requires around 15%, when even 100% doesn't kill all viruses. What does "offgas" mean out of curiosity?

OK, I looked it up, and it actually doesn't need to be anywhere near that strong. OSHA requires 1% to 10% dillution of 5.25% sodium hypochlorite for bloodborne pathogens, so the minimum OSHA concentration of 6% bleach would be something like 1:114. But I wouldn't go that low.

Of course depending on what you need to do you may need a disinfectant from EPA List A, List E, or List D instead.

Offgas may not be the right term, I'm not sure. But you're looking to create chlorine gas from the breakdown of the sodium hypochlorite if you want to kill certain viruses, rather than direct contact with the sodium hypochlorite itself.