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What is that mould smell, and is it worth $5m?

Uncategorized Oct 09, 2020

Hi, there. My name is Cameron Jones, and I'm an environmental microbiologist. And on this week's live stream, we're going to be talking about mould odour. I'm going to be talking to you about smells, particularly decaying smells, especially after water damage. And I want to focus on the question, can we trust our sense of smell, and how important is it when we discover that there might be a funky mould smell in our home, or office, or car. And that is the topic of this week's live stream.

And to kick it off, I want to focus on the well-known model and actress, Megan Fox, who is currently in a legal dispute with a range of different people regarding the mould contamination that she alleges pervades her home. And I want to use this as the springboard for talking about this central question, can we trust our sense of smell to protect us from danger? And I want you to just think about smell for a little bit. Over summer, for example, you might think of coconuts and think of sun or sand. If you smell cut grass, do you automatically think of springtime? But what is it when you think about mould? Is it always decay? If you're a horticulturalist, it might be a nice smell with a compost heap. And so I want to get into what are the foundations of mould odour.

And it's something that you need to consider. Smells from fungi are called aroma compounds, and they are specifically called volatile organic compounds, or VOCs. Now, many VOCs are pleasant. Think of fermentation from grapes, for example. But some of them are definitely unpleasant. Think of a waste pit with garbage. Now that's not a nice smell, but what is that mould smell? Well, it's something called Mushroom liquor, and it has a chemical formula which I have up on this slide here. 1-Octen-3-ol. And there're approximately 300 VOCs. The dominant one which causes that mould smell is this 1-Octen-3-ol. And scientists are beginning to study these aroma compounds, and similar to the microbiome, they call it the volatilome. And this is something which I predict will be an increasingly important area of research and applied research to understand how water affects buildings, and what smells are given off during the decay process, if there is in fact one.

And that leads me on to something that we need to discuss about odour. And Shakespeare summed this up in his quote, "A rose by any other name," what would it smell like. And so if we look at what the research says about this question, we need to recognize that the words we use to explain or associate a particular smell has a very strong impact on whether we register that smell as being pleasant, or how intense that smell odour will be. And in essence, how aroused we will be by that smell.

Now, certainly, when people ring me on the phone, week in, week out, to talk about their specific situation surrounding water damage and their fears for their health and that of their family, oftentimes they say, "After the water damage, the smell was really bad. We couldn't go into the room. But now it's not as bad, but we've got mould on the wall." And so in this week's live stream, I'm explaining why that phenomena actually occurs.

But I want to take you back to the connection with the words we use to describe odours. And some really important research discovered that even a positive experience to a plate of food which people find agreeable, after a few minutes of smelling that agreeable smell, it's going to lose its power of arousal. And so the words that are used, such as countryside farm, or banana bread, or even spearmint chewing gum, when odours are presented to subjects with those names, people overwhelmingly find them more pleasant than when the same odours are presented to the subjects with negative words, such as cheap cologne, or dirty clothes, or hospital disinfectant. Meaning that the words we use to describe the odour has a significant impact on how we register those smells.

So therefore, can we trust our sense of smell, because universally, people usually consider mould to have negative associations. So we need to go into the research literature yet again, and focus on something called microbial VOCs. Now, these are the specific odour compounds given off by bacteria, yeast, and fungi, and they are strongly associated with the experience of sick building syndrome. So those individuals who are exposed to mVOC odours, that is, the odours themselves, often complain of headaches, dizziness, fatigue, and asthma-like symptoms. Now, I want to review a publication which just came out in the research literature, which examined when odours were emitted from wet building materials. And these scientists looked at a particular fungus called Aspergillus niger, and they discovered that the mVOCs were given off in what's called the primary growth phase, or the exponential growth phase. That's when all of the odour-producing mVOCs are liberated.

And guess when that exponential phase starts and finishes? It's approximately one to 14 days. After that two week period, the mould, the Aspergillus niger, goes into its resting phase, or its lag phase. And the liberational production of mVOCs is greatly reduced. So we don't need to put a name to that odour. We all know what mould smells like. So in a sense, forget about the association of the word with the odour. If you can smell mould, it means there is active mould or active cell growth occurring.

And that is really important to be aware of, which leads me into the conclusion to this presentation. And that is, mVOCs are early warning signs of microbial activity in the exponential growth phase. And these odour clues are particularly useful for tenants and homeowners, or anyone concerned about being exposed to water damage, especially if you can't see it. If you can smell it, it means that there is a strong probability that there is active mould growth going on somewhere. And this cannot be underestimated by insurance assessors and anyone involved in inspecting buildings for suspect mould hazards to occupants.

I should conclude by saying that the study of the volatilome is a beautiful area of research, and there is a lot of fantastic studies being done. And that mould odour, that 1-Octen-3-ol smell, when this is presented to embryonic cells, it's found to be 80 times more toxic than toluene, which is found in petrol, acrylics, glues, and that sort of thing. Similarly, this 1-Octen-3-ol is also associated with Parkinson's disease. So it's important to be aware that the field of research is called the volatilome, but the very identification of that pungent mould odour means that there is definitely cell activity, and that cannot be underestimated.

In any case, thanks for joining me this week. Please follow and subscribe to any of my social channels, @drcameronjones. See you next week. Stay safe. Bye for now.

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Inamdar AA, Morath S, Bennett JW. Fungal Volatile Organic Compounds: More Than Just a Funky Smell? Annu Rev Microbiol. 2020 Sep 8;74:101-116. doi: 10.1146/annurev-micro-012420-080428. PMID: 32905756.

Djordjevic J, Lundstrom JN, Clément F, Boyle JA, Pouliot S, Jones-Gotman M. A rose by any other name: would it smell as sweet? J Neurophysiol. 2008 Jan;99(1):386-93. doi: 10.1152/jn.00896.2007. Epub 2007 Oct 24. PMID: 17959740.

Kalalian C, Abis L, Depoorter A, Lunardelli B, Perrier S, George C. Influence of indoor chemistry on the emission of mVOCs from Aspergillus niger molds. Sci Total Environ. 2020 Nov 1;741:140148. doi: 10.1016/j.scitotenv.2020.140148. Epub 2020 Jun 13. PMID: 32610229.

Elmassry MM, Piechulla B. Volatilomes of Bacterial Infections in Humans. Front Neurosci. 2020 Mar 25;14:257. doi: 10.3389/fnins.2020.00257. PMID: 32269511; PMCID: PMC7111428.

Greenberg MI, Curtis JA, Vearrier D. The perception of odor is not a surrogate marker for chemical exposure: a review of factors influencing human odor perception. Clin Toxicol (Phila). 2013 Feb;51(2):70-6. doi: 10.3109/15563650.2013.767908. PMID: 23387344.

Parry, E., 2020. Megan Fox 'Sick And Stressed After Buying Moldy House From Brad Pitt's Manager'. [online] The US Sun. Available at: <> [Accessed 6 October 2020].



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