Anyone who researches mold, especially on the internet has to bring a considerable amount of judgment to the information provided. With this article I will endeavor to bring a bit of my expertise and experience to bear on some of information that presents itself concerning this subject.
1) “Mold is everywhere so what is the problem if you have some in your house?”
You might have heard the statement that “the dose makes the poison.” I know there is a book by that title that I have read. A shot of whiskey might perk you up a bit. Several shots will likely make you drowsy. A whole liter of whiskey consumed in one setting could kill you. That datum was really tested recently when a radio station had a contest concerning who could drink the most water. The winner of the contest lost -- her life. Even too much water can be fatal. Certainly we are confronted with and breathe in mold spores every day. Mold is ubiquitous. It, indeed, is everywhere. When you have mold growth inside the home, however, you are likely to be exposed to much more on a continuing basis than normal. This increased exposure can result in developing allergies. Based on the type of mold, one might be exposed to high levels of toxins or pathogens. I have a sort of pet theory that I have never seen validated by clinical studies, but it does make some sense and appears to me that it is possible. Mold that is outdoors generally grows on natural materials. Indoors mold is often growing on any of a variety of man-altered substances. Alternation very often includes the addition of chemicals. Ingesting these materials, mold has to deal with the chemicals involved. This could be adding to potential toxins produced in the secondary metabolites (manifested as odors) by the molds involved. If there is any truth to this theory, it would make exposure to indoor molds more problematic than those outdoors.
2) “I sprayed with biocide that killed the mold, so that should take care of it, right?”
Mold exposure can have adverse effects due to three aspects. Virtually any mold can be allergenic for some individuals. Some molds are pathogenic in that they can grow at human body temperature and can infect the human body. Some mold types under certain conditions can produce toxins that might be harmful to humans. This is a controversial topic in that it has not been clinically established that mold toxins can be harmful by inhalation, but I still hold open that possibility. A dead spore is just as allergenic and just as toxic as a live one. A dead spore cannot germinate so is unable to infect so the only potential harmful effect of molds that is eliminated by killing them is the potential for infection. Allergies and toxic exposure are still possible.
3) “Heavy infestation of a house with “toxic” molds makes it necessary to discard everything in the house.”
It seems to me that if everything in the house has to be discarded including non-porous materials, then the entire house would need to be disposed of. The purpose of mold remediation is to remove the mold so that residents are no longer exposed. Certainly it might be necessary to discard much or all of any porous materials like clothing, fabric covered furniture and the like. Non-porous materials like wooden or metal furniture, picture frames, and in some cases even semi-porous materials like books can be salvaged simply by thorough cleaning. Actual mold growth on semi-porous materials could very well necessitate discarding. Mold growth on fabrics generally renders them unsalvageable. Fabrics exposed to airborne mold spores might also need to be discarded. It could be possible to salvage clothing by washing or dry cleaning, but more than one washing/cleaning might be needed. The only real measure is how wearing the clothing affects the wearer. If symptoms are displayed when wearing the clothing after repeated cleaning, it should be disposed of. There are companies that claim to remediate clothing and other fabric materials using a heat or chemical process. This is not effective because even though this process might kill the mold spores, even a dead spore is not harmless. As stated above, a dead spore is just as allergenic and just as toxic as a live one. It could even be more toxic due to any chemical used to kill the spore.
4) “If I remove mold growth from a surface, won’t it just come back?”
It might, but only if you fail to remove the source of moisture that fostered mold growth in the first place. Mold growth on building materials requires additional moisture in the form of actual liquid water, water vapor or very high humidity. You can get mold growth on an orange or other fruit without additional moisture because there is sufficient moisture in the fruit. Even bread has enough moisture to enable mold to grow. But drywall, ceiling tiles and wood, etc. require an external moisture source for mold infestation. So once you remove the mold you also have to remove the moisture source.
The behavior of molds is not mysterious, but there is mis-information out there. Any doubts can be resolved by referring to trusted professionals in the field. I say trusted because there are those out there who will promote falsehoods and fears for selfish purposes.