As a building biologist I test people’s homes for numerous things that may be contributing to health: air quality, water quality, electric fields, magnetic fields, radio frequency, dirty electricity, light and sound quality, radon, combustible gasses, carbon monoxide, carbon dioxide, chemicals, and VOC’s, etc.  But nothing, and I mean nothing, instills fear in my clients as the two dreaded words (cue scary music): Black Mold!

It’s understandable.  If you or someone you know has suffered with mold illness, you know how devastating it can be.  Not only is remediation of your home very expensive and time consuming, but the toll it takes on your health can completely upend your life.  Toxic mold exposure is a serious concern.  But there is also a lot of confusion about the various aspects of mold: Which molds are ‘toxic’? What is the best way to test? Do I have to get rid of all my stuff? Can’t I just fog my home? What do I do about the mold in my body? How do I test myself? 

I can go on all day.  There is a lot of information out there on the innerwebs, and a lot of it is very misleading or downright inaccurate.  In this post I want to help clarify the basic points you need to know.  In future posts, I will go into much more detail regarding mitigation, testing, and occupant health.

First let’s define what mold actually is.  Mold (or mould for you Canadians and Europeans) is a type of fungi, as is yeast, mushrooms, lichens, and truffles. These forms of fungi are actually quite different. Yeast for example, is a single-celled organism, whereas mold is a multicellular organism that grows hyphae, or long, branching filaments. 

There are over 100,000 species of mold at least, some claim it’s more like 300,000. Mold is known the ‘great decomposer’, responsible for breaking down organic matter in both living, and dead organisms. 

Cathy Cook, BBEC, EMRS

Mold plays an important role in nature, helping to decompose materials back into the earth.  In fact, if it weren’t for mold, our forests would be thick with centuries of old trees as almost nothing decomposes wood except for mold.  As with all microbes, mold has its place. Mold spores are found everywhere, indoors and out.  Nature has checks and balances like sunlight and microbes to keep mold from dominating any given area.

Mold rarely causes serious health issues when found in nature. More often, toxic mold becomes an issue when it’s found in an unnatural environment.  When we separate ourselves and our living spaces from the natural world, then we begin to see problems. Unfortunately, this is how we create our homes and workplaces today. We put up four walls and roof, then wrap that entire structure in plastic in the name of energy efficiency.  We keep our homes closed 24 hours a day in order to enjoy a pleasant 72 degrees year-round.  In many places we build above a damp, dark crawl space, and then run water pipes through the walls.  See any problems here?

It’s very difficult to create a truly water-tight building.  And frankly, many contractors and builders don’t invest the proper time and care to ensure the building will not be vulnerable to water intrusion.  Ultra-fast construction paired with unskilled, underpaid labor and petroleum-based building materials create lots of opportunity for leaks and condensation.  It’s no wonder that many mold inspectors claim up to 80% of homes have mold.

That’s an alarming number for sure.  But not ALL mold is toxic. Invariably mold spores make their way into our home. Every time we open a window or door, every time we walk inside, we carry in packages, our pets come inside, etc.  They’re everywhere, and that’s ok, they’re supposed to be. Imagine you just built a brand-new house, and you know for sure there is absolutely no water damage or sources of mold in this house.  If you were to take a dust collection and send that to a lab, you’d probably be amazed at how many mold spores are found. Without a doubt the lab will find Cladosporium herbarum, Acremonium strictum, Cladosporium cladosporioides, and/or a handful of other ‘common indoor molds’.  This is normal and expected, and not generally a problem.  These are mold spores that don’t have a propensity to create mycotoxins, and if they’re not creating mycotoxins, they’re generally not much of a health concern.

Mycotoxins are the gas-like chemical byproduct of mold spores. When mold becomes threatened, (it loses a food source, loses a water source, or competes with other species), it releases its toxin in the name of survival and dominance. It’s these toxins that cause the health symptoms that many people experience.  Different species can produce the same mycotoxins, and one mold species can produce different mycotoxins.  

It’s the ‘water-damaged molds’ we find inside our homes that are the real problem.  When a modern-day home experiences some type of water intrusion, be it from a plumbing leak, ill-fitted window, sloping towards the house, foundation penetrations, condensation, or other failure, then ‘water-damaged molds’ have an opportunity to grow inside.  They only need two things to grow: water, and a food source.  Like we established earlier, we run plumbing through our walls, we cook, bathe, breathe, and run air conditioning inside our homes.  So yes, we have water sources.  Cellulose is a great food source for mold; found in wood, drywall, paper, and natural fibers.  Dust is also a choice cuisine for mold. So yes, we have a food source!