Mold is a living organism, neither plant nor animal, but rather a fungus
Mold is found virtually everywhere, indoors and out. Mold’s primary function is to break down dead organic material and recycle nutrients back to the earth. There are at least 1,000 varieties of molds common to the United States, and there are tens of thousands of different species worldwide.
Molds multiply by producing microscopic spores, similar to the seeds produced by plants. To understand how molds use spores to reproduce, picture a field of dandelions. The dandelion forms seeds attached to white fluff. This fluff is easily detached from the flower when stirred by a wind, an animal, or even you walking near it. Once airborne, the seed lands in a new location where—with the right soil, sunlight, and water—it may grow into a new dandelion.
This is similar to how molds reproduce, on a much smaller scale. Instead of seeds, molds produce and eject spores. Like dandelion seeds, these spores can easily float through the air and can be carried great distances by even a gentle breeze.
When the spores become airborne and land in a new location—with the right food source and moisture—they may form a new mold growth. The problem for us mammals is that, between the ejection of the spore and its growth into a new mold, plenty of spores are floating around in the air, both inside and outside our houses.
Unless you live in a bubble, inhaling spores is as inevitable as inhaling pollen during certain times of the year. Many people suffer from seasonal allergies or “hay fever.” This sensitivity to pollen or mold spores triggers a reaction from your immune system, causing an allergic reaction.
The number of mold spores suspended in the air fluctuates a great deal, season to season. In temperate climates, outdoor spore counts often number in the thousands during the summer but may go down to zero in mid-winter, when everything is snow-covered. Inside your house, mold spores are always present. Doubt it? Leave a piece of bread on the kitchen counter for a week and see what grows.
Mold becomes more of a problem when it starts growing inside homes and occupied spaces. Modern construction techniques, meant to improve comfort and energy conservation, can actually increase your exposure. As homes become increasingly airtight, fresh air exchanges are reduced, leading to a potential buildup of excess moisture and mold growth. In addition, modern construction materials (drywall instead of plaster, for example) are often more conducive to mold growth.
Moisture (water or even elevated humidity) is the crucial ingredient for mold growth. Mold can grow on just about any surface, but it prefers to feed on porous, organic materials—things that were once alive themselves, like plants or trees for example. Certain molds are particularly fond of cellulose materials such as wood, drywall, or ceiling tiles, and can potentially cause structural problems.
Not all types of molds are toxic
However, many common molds can create health problems; and, just like sensitivity to pollen, some people are more sensitive than others. Infants, children, the elderly, pregnant women, immune-compromised people, and people with respiratory conditions all may have a greater risk for adverse health effects to mold. Beyond that, it’s just luck of the draw: Some people are more sensitive to molds than others. Mold plays an essential role in the ecosystem, and mold spores are around us all the time; however, visible mold growth in a building may increase your exposure, is a potential health hazard, and should therefore be removed.
In future articles, I will discuss the origins of the phrase “black mold” and how it helped raise awareness of indoor air quality, as well as how to diagnose and eliminate indoor mold problems.