Use of antimicrobials in mold remediation
November 24, 2020 5:08 PM   Subscribe

We're planning to get mold remediated in our house. The assessor's plan calls for the use of antimicrobial products after the contamination is removed. Are there significant health risks to this, and is this likely to be helpful in preventing the mold from returning?

It seems that biocides aren't typically recommended for mold clean-up, according to the EPA.

But I'm not sure if that refers specifically to chlorine bleach-type biocides (which our contractor and assessor have made clear isn't the right solution!) or also to mold-specific anti-microbials. This post by a different mold company (not in our area) seems to suggest antimicrobials do more harm than good as well.

However, our contractor has an A+ rating from BBB and comes very highly recommended, and we received a positive recommendation for the assessor as well. And the antimicrobial products they use (this one, and also unspecified EPA-registered sealant) appear to be specifically formulated for mold.

I'm sure my own limited Internet research skills aren't nearly as useful as field-specific expertise, though - so I'd greatly appreciate a reality check here.
posted by beryllium to Home & Garden (4 answers total) 1 user marked this as a favorite
I'm an ecologist. I have no special mold training. On basic principles and lived experience, I posit that no amount of antimicrobial biocides will help in the medium term if you don't rectify the underlying cause.

And if you do rectify the underlying cause (usually too much moisture and too little ventilation), you don't need any additional treatment because the environment is no longer viable to the microbes.
posted by SaltySalticid at 5:56 PM on November 24, 2020

Response by poster: Clarification - there are two underlying causes
- a plumbing issue (which appears to have been a leaky toilet) that we think has now been fixed, though it's possible drywall removal will uncover other issues
- long-term moisture getting into the basement (apparently unrelated to the first issue), which we'll look at ways to get further sealed

The existing mold and water damage is significant enough that professional removal seems necessary, and we like the professionals we're working with. (The state requires the contractor to follow the assessor's plan calling for the use of antimicrobials, so I think we would have to either ask the assessor to re-write the plan or use a different assessor if we wanted to change it?).

It's okay with us if they aren't super-useful as long as they aren't actively harmful (to either us or the risk of having to do this again in the future).

Thank you so much, out of the thread now :-)
posted by beryllium at 6:12 PM on November 24, 2020

Yeah, speaking as someone with a passing familiarity with mold work (although not your person with a passing familiarity with mold work), SaltySalticid has it. The crucial thing in any mold abatement project is to fix whatever is causing the mold first. If you don't do that, you'll be back at square one soon - maybe a little less soon with the biocides (which is not something I've personally worked with before), but ultimately, mold loves moisture and if you keep giving it moisture, it's going to find a way.

I can't speak to the specific chemicals they're planning on using. For what it's worth, I'd imagine you won't be the first person to ask the assessor about the chemicals; they're working for you and they should be willing to walk you through this type of thing, and potentially update the abatement plan.
posted by pie ninja at 6:24 PM on November 24, 2020

Caveat: I am not a professional at all, just a person with a biochem research background.

The science in that anti-biocide article you linked is not great; for example its assertion that bleach is an ineffective disinfectant because it gets the area wet is just silly.

The American Industrial Hygiene Association says "Biocidal treatments are indicated only when the contaminant is one of the few fungi that are known to cause human infection." They also mention that commonly used biocides do not effectively kill molds because they still leave viable spores behind (they're not going to get the spores in the air, for example). It's referring to chlorine and anti-microbial-type biocides.

In this chapter from the Navy's Industrial Hygiene Operations Field Manual they also recommend against the general use of biocides (also referring to bleach and anti-microbials). They provide a list of common ingredients in biocides and their effectiveness. I compared the list against the ingredients in Mediclean and all of its ingredients are considered of lesser effectiveness against spores.

This paper (full text available via Sci-Hub) tests a few sealants as well as cleaning with bleach, and while the sealants do help restrict mold growth on applied surfaces it's only on applied surfaces. So for example the back of your wet drywall is going to continue to grow mold. It also tests using 6-7% bleach as a cleaner, and it does kill the mold on the surface of the drywall. However, again, it will not kill the spores in the air. It also cites another paper which studied the effectiveness of cleaners and sealants against one specific type of mold (and there are many types of mold!) and from what they cited it sounds like a sealant can help delay growth up to 8 weeks. Unfortunately I was not able to find that cited paper.

In conclusion: if you do go with a biocide, scrubbing with a simple bleach solution and wiping excess with a cloth will probably do and the biocidal chosen by this remediation company may not be the best choice (it will also be more expensive). The sealant may help restrict growth but not for long, you're just buying time. If you seal but the area stays moist you'll just have to repeat the process until you remove the source of moisture.
posted by Anonymous at 10:44 AM on November 25, 2020

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