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Bleach is an effective way to kill mold and mycotoxins (even on non-porous surfaces)

There is a myth on the internet that ammonia is better than bleach at removing mold. I bust this myth with information provided below from credible sources. The same myth for using vinegar to treat mold is also busted, at the very bottom.

Millions of people are sick with mold illness and need a way to kill mold in their homes. There is a myth propagated by non-scientists that bleach should not be used. While other products may also kill mold and mold spores, bleach is extremely effective and I think the best overall solution. See the bottom of this page for a comparison with ammonia, which is promoted by a lot of people as the best mold cleaner.

For those people who say that bleach is toxic: it has been safely used in households and laboratories on a daily basis for decades.

 

My credentials:

  • BS in Microbiology
  • PhD in Biochemistry
  • Taught Microbiology at the University level
  • A scientist with active microbiology and clinical labs for 15+ years at multiple institutions

We use bleach every single day in our microbiology and clinical laboratories, as it is the most effective chemical to kill microbes, their spores, and inactivate small molecules. It also has no health effects when properly used (in a ventilated area) or cleaned up quickly.

 

Bleach safety and best way to use it

  • As many sources point out, do not mix bleach with ammonia or acids (such as vinegar). Simply use it on its own. 
  • Ventilate the area where you will be using bleach. This is not just good for you to avoid the fumes, but also to dry the treated area and prevent future mold growth.
  • Dilute the bleach 1:1 with water if the bleach is 6% sodium hypochlorite. If it's 3% sodium hypochlorite, do not dilute it with water at all.
  • For best efficacy, leave the bleach to soak a surface for 10 min. If it will dry up or run off, simply soak a paper towel with bleach and leave it on the surface for 10 min to soak it.
  • You can remove the bleach by:
    • wiping it with dry paper towels, and
    • removing the last bits with 70% ethanol. You can either spray the ethanol on the surface and wipe it dry, or you can spray a paper towel with ethanol and use it to clean the bleach. The remaining 70% ethanol evaporates very quickly. 
    • You can buy 70% ethanol, also known as the rubbing alcohol:
      https://www.cvs.com/shop/cvs-health-70-ethyl-rubbing-alcohol-prodid-304659
    • Or Isopropanol
  • Remember that mold is a living microbe. If favorable growth conditions remain, the mold will likely come back. Click here for more info on long-term removal of mold.

 

Here is the myth:

  • Someone, somewhere, stated that bleach pisses mold off (that's a very non-scientific term and was made up by a non-scientist).
  • A bunch of people with no scientific background have propagated this myth on their websites, to draw attention and get clicks.
  • Even some "professionals" propagate this myth. To be a professional in the field of mold, all you have to do is charge people money for it. You don't need to have a science degree of any kind, or understand what mold is.
  • There is a scientific reference that claims bleach was not effective at killing mold. However, their experimental design was flawed. They measured the effectiveness of bleach after 28 days, by which time the small amounts of mold left after the bleaching had grown back. If you have conditions that grow mold, no amount of bleach can fully get rid of it. See this article on how to get rid of mold permanently.

 

The best evidence for effectiveness of bleach in killing mold

Here are two peer-reviewed scientific articles that show the effectiveness of bleach in killing mold, including on porous surfaces:

1. https://www.tandfonline.com/doi/abs/10.1080/15459624.2012.724650

"The use of low concentrations (2.4%) of NaOCl for the reduction of culturable indoor mold and related allergens is effective and recommended." 

"Five-minute exposures to 2.4% NaOCl resulted in a >3 to >6-log10 reduction of culturable mold counts in controlled laboratory studies. Organisms were nonculturable after 5- and 10-min contact times on non-porous and porous ceramic carriers, respectively, and A. fumigatus spore-eluted allergen levels were reduced by an average 95.8% in 30 sec, as indicated by immunoassay."

 2. https://link.springer.com/article/10.1007/BF02350963

"Sodium hypochlorite (bleach) solution was used to spray all surfaces during remediation. Although spore counts and toxicity were high during remediation, air samples taken postremediation showed no detectable levels of S. chartarum or related toxicity".


Typical bleach at the store has 6% sodium hypochlorite, so to match the bleach solution used in this study, you need to dilute the store-bought bleach roughly 1:1 with water (to be on the safe side).

 

Additional credible evidence (but not peer-reviewed scientific research):

 

Bleach can even inactivate mycotoxins

Here is one important and relevant reference, from the official website of the US Military Health System:

  • https://gulflink.health.mil/bw/bw_tabe.htm

This statement from the US Military says that bleach can destroy trichothecene mycotoxins. The only other method they list that can inactivate the mycotoxins is heating to 500F for 30 min.

"The trichothecene mycotoxins are nonvolatile compounds produced by molds. These substances are relatively insoluble in water but highly soluble in ethanol, methanol, and propylene glycol. The trichothecenes are very stable and resist heat- and ultraviolet light-induced inactivation. Heating to 500 F for 30 minutes will inactivate the toxins, while exposure to sodium hypochlorite destroys toxic activity."

 

What about ammonia? Many people say it's better than bleach.

Myth 1: Bleach is worse because it's mostly water

  • Myth busted: Ammonia is mostly water as well. In fact, they are both 90-95% water.

Myth 2: Bleach is worse for your health.

  • Myth busted: While bleach is mildly bad, ammonia is likely worse. Here is the description from the New York Department of Health:
  • https://www.health.ny.gov/environmental/emergency/chemical_terrorism/ammonia_tech.htm
  • Inhalation: Ammonia is irritating and corrosive. Exposure to high concentrations of ammonia in air causes immediate burning of the nose, throat and respiratory tract. This can cause bronchiolar and alveolar edema, and airway destruction resulting in respiratory distress or failure. Inhalation of lower concentrations can cause coughing, and nose and throat irritation. Ammonia's odor provides adequate early warning of its presence, but ammonia also causes olfactory fatigue or adaptation, reducing awareness of one's prolonged exposure at low concentrations. Children exposed to the same concentrations of ammonia vapor as adults may receive a larger dose because they have greater lung surface area-to-body weight ratios and increased minute volumes-to-weight ratios. In addition, they may be exposed to higher concentrations than adults in the same location because of their shorter height and the higher concentrations of ammonia vapor initially found near the ground.
  • Skin or eye contact: Exposure to low concentrations of ammonia in air or solution may produce rapid skin or eye irritation. Higher concentrations of ammonia may cause severe injury and burns. Contact with concentrated ammonia solutions such as industrial cleaners may cause corrosive injury including skin burns, permanent eye damage or blindness. The full extent of eye injury may not be apparent for up to a week after the exposure. Contact with liquefied ammonia can also cause frostbite injury.

 

What about hydrogen peroxide?

  • This is the only peer-reviewed article I could find.
  • https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3252664/
  • They aerosolized hydrogen peroxide for 2 hours in a room where they had sprayed mold.
  • They show that if the mold was present at a certain amount, the treatment removed 99.99% of the mold, but at higher mold amounts, the peroxide did not work well at all.

 

What about vinegar?

Vinegar is not only bad at killing mold, it:

  • feeds mold and helps it grow
  • can make mold more pathogenic and resistant to anti-fungals
(https://journals.asm.org/doi/10.1128/mBio.01682-21)

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