12 min read time

Is Mould Dangerous: Dead or Alive?

Updated on
February 20, 2024

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The Background

The mould remediation industry vertical is relatively unregulated and much less is known by the public, therefore, about best practice or safety and quality criteria. This is typical of an industry vertical which is not at the same level of maturity as its counterparts, in this case within the cleaning and restoration industry. This is most likely due to three things. First, the knowledge that mould was toxic only started to become widespread amongst the public at large during the 20th century. Second, the incidence rate of household mould significantly increased in the 70s, when changes to building materials and techniques meant buildings became more airtight, making it harder for moist air to escape, and cheaper materials like drywall or plasterboard reduced the drying potential of the structures, making moisture problems more prevalent (Landrigan PJ, Etzel RA (2013)). Consequently, there was little to no demand for professional mould remediation services given the historically lower instance rate of household mould and the limited prevalence of individuals who understood the health risks posed by household mould. Third, even as the mould incidence rate increased, and the knowledge that mould was toxic became more widespread, it was still widely believed that bleach killed mould until as late as the 90s. It wasn’t until the 21st century that public advisory bodies began to change their remedial recommendations to reflect this knowledge. You can still find many OTC bleach-based cleaners purporting to be an all-in-one mould eradication solution. Consequently, there has not been a perceived need for mould remediation until relatively recently.

Unfortunately, a relatively young and unregulated industry allows for a proliferation of companies that employ questionable practices under the false pretence that their services are comprehensive in their efficacy and safety. It is perfectly reasonable, indeed commendable, that a consumer undertakes research into a company, their technology and the veracity of its claims. This article will hopefully help in that regard.

Our objective

We're going to get to grips with an idea often used to either discredit or validate a given mould remediator's methodology. The idea - dead mould is more dangerous than live mould (viable Vs. non-viable mould). This is a worrying claim when you consider the potential ramifications. What if a remediation company turns up, kills all the mould in your house, but you end up in an even more dangerous environment than before? If dead mould is just as, or more dangerous than live mould, is there any point in paying professionals to come and kill the mould in your home?

This concept is perpetuated on mould forums, social media groups and the websites of various independent mould-related bodies. We've found that the concept can be regurgitated without context, elaboration and when used to discredit, it's done so in a manner which has certainly not been weighed against the nuanced approaches that new technologies can bring to the market.

This article will ask the questions; where did the idea come from? is it true? what can be done about it? and what does it mean for the variety of mould remediation technologies currently on the market?

The claims about dead mould

First, let's take a look at some of the claims regarding the dangers of dead mould:

"Mold does not have to be alive to cause an allergic reaction. Dead or alive, mold can cause allergic reactions in some people."

US Environmental Protection Agency

The first issue, then, is that dead mould is still allergenic and can cause adverse health effects. If a remediation company kills the mould but does not remove it, it has not done much, if anything, to reduce the potential for toxic exposure in the home. This argument could conceivably have started when remediators began to actually kill mould, as opposed to turning it invisible through the application of bleach. Mould remediators would have killed the mould in a home, removed any visible residue, and would have congratulated themselves on a job well done. However, the mould sensitive would have continued to experience poor health, and in some cases, their health would have sharply declined shortly thereafter due to the invisible, residual dead mould spores.

However, the dangers of not properly dealing with dead mould go beyond the above. Consider the following two statements:

“The use of fungicides and antimicrobials is controversial, due to concerns about the toxicity of the compounds, the questionable effectiveness in killing and preventing mould growth, and the concern that dead mould and fragments are still toxic/antigenic.”

Prezant B, Weekes DM, Miller JD, American Industrial Hygiene Association (2008)

Some remediation techniques, including the use of fungicides and antimicrobials, kill mould cells by breaking them apart into tiny fragments. Job done, right? Unfortunately, in isolation, fracturing mould cells into tiny fragments can actually make the problem worse, particularly as it relates to the health risks posed. Consider the following:

“Both live and dead mould and mould fragments contribute mycotoxins and other mould products which have been shown to retain their antigenic and/or toxic properties over extended periods of time.”

Macher J, American Conference of Governmental Industrial Hygienists (2008)

Dead mould fragments are still toxic. But the splintering of a mould cell has many wider-reaching problems in that it also releases the various toxic agents of mould into the airspace. Mould spores, hyphal fragments, β-glucans, mycotoxins, VOCs, mVOCs are all toxic to varying degrees and depending on the strains of mould presence. The aforementioned agents become airborne anyway when a house has a mould problem, which is what makes mould dangerous. However, when mould is agitated, disturbed or broken into fragments, these agents become airborne in a much greater density and over a much shorter time horizon than would otherwise have been the case.

It's worth remembering; spores are typically 2–10 μm (microns) in length. They can stay airborne for long periods of time, meaning they can be inhaled. Luckily, the body has lots of filtration systems that have evolved to stop potential threats from reaching vital internal systems. However, mould spores toward the smaller end of the scale can actually bypass any filters and can even reach the alveoli, the microscopic sacs in your lungs which exchange the carbon dioxide in your bloodstream with the new oxygen held in your lungs. However, when mould spores are “killed”, i.e. the cell is ripped apart, they often fragment. This means they are often torn into pieces that are <1μm in size. It also means that the constituent agents of mould can become dislodged or disconnected, and either fall to the floor, become airborne or attached to dust particulate. Most toxic agents of mould are <1μm in size. These much smaller fragments and detached toxic agents much more easily bypass the body’s filtration systems. They can reach the alveoli with relative ease and can even be absorbed through the skin.

How do remediators typically overcome this problem?

"Dead mold is allergenic and may cause allergic reactions and other health effects in some individuals, so it is not enough to simply kill the mold. It must also be removed."

US Environmental Protection Agency

There are a number of means through which, as the EPA recommend, mould can be removed. Below are some of the most commonly used methods of removing dead mould fragments and the toxic agents they may have secreted during the sterilisation process:

  • HEPA vacuums. HEPA (high-efficiency particulate air) vacuums are fitted with a filtration system that can trap particles not visible to the naked eye. They're used by mould remediators to suck up and trap particles as small as 0.3 microns in size. Clearly, they are an effective means of removing most of the mould spores, hyphal fragments, β-glucans, mycotoxins, VOCs, mVOCs that have been released by the mould and have fallen to the floor following the initial sterilisation of the mould.
  • Air scrubbers. The air scrubber draws in the air from within the compromised environment and filters out the mould fragments and various associated toxic agents, again using HEPA filtration, which traps particles as small as 0.3 microns in size.
  • Air purifiers. They employ a two-stage purification process. First, they work through the use of ultraviolet germicidal radiation (UV-C lights) or UV light air purifiers to take care of the mould spores and larger fragments. Second, they too depend on HEPA filtration to trap the smaller fragments and toxic agents.

This is a fairly robust process. It does a good job of mitigating against the risk of the dangers posed by dead mould and, in particular, mould fragments and toxic agents both airborne and left behind on surfaces. However, we know that some hyphal fragments, β-glucans, mycotoxins, VOCs, mVOCs can be smaller than 0.3 microns, meaning the above products, used by most mould remediation companies, are not going to comprehensively remove the various toxic agents caused by disturbing, splintering and agitating mould spores.

Our technology is new to the UK market and, while we have HEPA vacuums and air scrubbers, our core process is innovative and patented:

The Pure Maintenance UK approach

Our core remediation process accomplishes the following outcomes:

  1. Our sterilant, InstaPURE, erodes the outer membrane of the mould cells with which it comes into contact. It does so through oxidising the membrane, which is a process known as lysis.
  2. Once the outer membrane has been oxidised, the sterilant then entirely destroys the cell, a process called denaturing. This is the process by which the characteristic properties of a protein or biological macromolecule are destroyed by heat, acidity, or other effects that disrupt the molecular conformation. This, unlike many sterilants, doesn't leave behind dead mould. Rather, the two processes render the mould into an 'inert nothingness'.
  3. Our patented fogging process creates positive air pressure in a room or building. This forces our sterilant, InstaPURE, which is deployed as dry fog, to fill the entire volume of a room. This means it comes into contact with every mould cell, facilitating lysis and the denaturing of all the mould cells in a designated space.
  4. Because it's a dry fog, the particle size is much smaller than other 'wetter' fogging methods, such as ULV fogging. This means it can reach every conceivable space in a designated building. Its 'dryness' also means it doesn't condense on surfaces. This allows it to kill the abundance of spores, fragments and toxic agents in the air.
  5. The second dry fog we distribute, EverPURE, is a non-toxic antimicrobial, which creates a film when it covalently bonds with a surface. Using the same patented fogger, we create positive air pressure meaning the EverPURE bonds with every square inch of a given room or property. EverPURE is constituted of positively charged nitrogen molecules, with a carbon atom stacked on top, which forms a microscopic spike. Any remaining mould spores, fragments or toxic agents, or even pathogens reintroduced to a treated building, are electrostatically attracted to the positive charge and are eradicated.

The benefit of using electrostatic attraction is that there we aren't subject to the 0.3-micron limitations that come with reliance on HEPA filtration systems in the removal of mould fragments and toxic agents, as it attracts all pathogens, fragments and toxic agents of all sizes. Of course, we wouldn't expect you to take our word for it. Pure Maintenance in the US carried out a study with the US Army Corps of Engineers to demonstrate the efficacy of the process outlined above. The purpose of the study was as follows:

"The objective of this ITTP demonstration was to conduct independent performance testing of the novel dry-fog mould remediation and prevention process to determine the effectiveness of the treatment process at eliminating mould and preventing regrowth at military installations and contingency basing locations."

Pure Maintenance

Below is a snapshot of some of the results from the study.

The dry-fog treatment was successful in reducing and maintaining mould at below background levels over the 6-month demonstration period. Figures 21 to 23 show the results of air sampling and surface sampling at Bldg. 2261.

Figure 22 shows that the total spore count weighted across all air sampling locations associated with Bldg. 2261 decreased from 64,126 spores/m3 before treatment, to 3,067 spores/m3 at 6 months after treatment. Over this same time period, the outdoor/background total spore count increased from 590 spores/m3 before treatment, to 19,000 spores/m3 at 6 months after treatment. Simply put, while the outdoor/background total spore count increased by 3,120%, the indoor (i.e., treated space) total spore count decreased by 95.21%.

Here's the full case study if you'd like to look into it further:

However, while the above constitutes our core process, we don't believe it is, nor is there a 'silver bullet' solution for all mould problems. An individual's mould treatment plan must reflect the fact that every mould problem is unique and needs a blend of remedial actions to truly resolve the mould problem for good. It's for that reason that we undertake an extensive survey of a mould-affected property prior to carrying out any work. If, for example, a building has an active water leak or ingress, it's vital that it be corrected before any further work is carried out.

We also believe in a holistic approach to remediation. There are a range of behavioural and structural factors that, if not addressed, could undermine our remedial work or jeopardise the integrity of our antimicrobial film. Our service also includes a tailored report outlining a list of both behavioural and structural recommendations that constitute part of our remediation. Ultimately, some of the responsibility must sit with the resident, as their behaviours can either increase or reduce moisture in the building.

We test the air before and after our treatment, using outdoor air as a control, to demonstrate the efficacy of our remediation. If we don't see a sufficient reduction in both spore count and mould strains per m3, we come back and investigate what may have gone wrong and work out the best course of action to correct the issue.

We have a range of additional tools at our disposal, such as the aforementioned HEPA vacuums and air scrubbers, should the situation call for it. We can also recommend and arrange for the permanent purchase of air purifiers for the most mould-sensitive or immuno-compromised of our customers so that they have an added layer of protection. We leave hygrometers behind, following remediation, to allow clients to quantify the impact their behaviours are having on household moisture and humidity levels.

Ultimately, we weigh the nuances of every job before we create a bespoke treatment plan. There are so many variables to consider with every job that it would be irresponsible to employ a 'one size fits all' approach.