white top border box

The Truth About 'Black Mold'

By Jason Earle Google+

If you have gotten a glimpse of the internet conversation going on about indoor mold, you have seen the term “black mold,” or “toxic mold,” or “toxic black mold.” Perhaps you have even seen mold assessment companies or home mold test kits claim they can find and eliminate black mold from your home.

Beware the black mold hype. It's a sales pitch based on fear, often accompanied by inferior abilities and practices on the part of the seller. Treat these hucksters the same as you would the character who knocks on your door and offers to seal your driveway or patch your roof.

So what is the truth about black mold? Is it as dangerous as it's made out to be? Well, that's a gray area. The type of mold most people refer to when they say “black mold” is Stachybotrys (Stak-ē-bot′ris) chartarum. It is blamed for many serious illnesses, but the science is still out on exactly what stachybotrys does or does not do.

There are other so-called black molds, so named because they appear black, as opposed to green, yellow, orange or white. The blackness is due to the fact that these molds produce melanin, the same pigment that protects human skin from sunburn and makes dark-skinned people dark. Because of this, black mold is more tolerant of light and more resistant to dehydration than other molds.

Along with this added toughness come some tough weapons, called mycotoxins, which give black molds their toxic reputation. More on mycotoxins below.

All mold is a problem

But should you check your house for black mold? In a word, no. You should check your house for  moisture problems and for mold, period. It doesn't matter what kind. If mold is growing in your house, you have a problem, which will not correct itself.

The most important truth is: Indoor mold is bad for people. Mold growth left unchecked will get worse over time, and can make virtually anyone sick. How sick depends on the individual, and sometimes the types and extent of mold growth. Indoors, there is no good mold, except in beer, wine, bread and some cheeses.

Perhaps the most profane use of the “black mold” term to generate sales is in the realm of cheap home mold test kits. One such kit in particular, which uses “settling plates”, which look like Petri dishes, to collect airborne mold, claims it can detect “black mold.” The statement is utterly false, for several reasons.

1.     Stachybotrys spores are large, heavy and often wet, compared to other molds. This means it's difficult for them to become airborne, so they're unlikely to fall into a settling plate and set up house there.

2.     Stachybotrys is very slow to grow (we'll explain why below), so any spores that may find their way into the dish may not form a colony large enough to analyze before you throw the whole thing out.

3.     The culture medium used in these kits will not grow Stachybotrys. You read that right. Even if you threw a fistful of Stachybotrys into the dish, the nutrient is the wrong stuff, and it won't breed.

4.     Adding insult to injury, this company and others like it leave it up to you to analyze what sprouted in your dish, unless you pay extra.

5.     The final insult is that the growth in the dish tells you exactly nothing about whether you have a mold problem. Mold is everywhere. Set out a moist meal for mold, and it will partake. A slice of bread, a piece of fruit, whatever, will grow mold in virtually any environment.

Three stages of mold growth

Molds such as Penicillium and Aspergillus are common first-stage molds that can begin to grow within 24 hours of the introduction of moisture to a nutrient base. Fungal nutrients are primarily cellulose, meaning plant material, such as paper, wood, fabric; pretty much everything humans use for clothing and shelter.  Even things as simple as household dust can support a pretty wicked fungal infestation.

If moisture is sufficient, secondary molds are likely to appear, including Cladosporium, Alternaria and some varieties of Aspergillus.

Over time and with continued ample moisture, the tertiary molds develop: Stachybotrys, Chaetomium and others.

One simple fact to draw from all this is: If you have stachybotrys indoors, you have a serious, long-standing moisture problem that may soon threaten the structure of the building if left unchecked and in areas where the wooden parts of the structure might be at risk. Moisture intrusion of this magnitude also leads to wood rot.

Finding real evidence of indoor mold growth

One of the few industry standard, consensus-accepted and scientifically valid approaches to testing indoor air for evidence of mold problems is to use  air-sampling cassettes, each of which contains a small slide coated with a sticky adhesive, and which requires that a measured quantity of air be drawn past the slide. A minimum of three samples should be taken: One outdoors to establish a baseline, a second indoors in an area suspected of having a problem, and the third indoors in an area considered non-suspect.

The slides are then sent to a lab accredited by the American Industrial Hygiene Association and examined microscopically by a qualified lab technician. The fungal particles are identified and counted, to reach an estimated number of mold particles per cubic meter of air. These samples are then compared with each other and with ambient mold levels outside. If there is a higher concentration indoors than outdoors, or if the types of molds found indoors are not seen in the outdoor sample, it is a strong indication of an indoor mold problem.

If Stachybotrys is found on the indoor sample in quantities greater than outdoors, it is a near certainty that there is a serious indoor mold problem due to the reasons described earlier. Stachybotrys spores settle out of the air much faster than most other spores commonly found indoors where a mold problem exists.

Medical research moves slowly

While Stachybotrys is associated with some extreme cases of illness, the medical community has not done enough research to  prove this type of mold is more toxic than others. It's only within the past decade or so that medical studies have dealt with mold at all. The landmark case was a 1999 study by the Mayo Clinic, which concluded that 96 percent of the 37 million cases of chronic sinusitis (persistent sinus infections) is caused by fungus in the nasal mucous.

But the Stachybotrys research has not been as clear. The Illinois Department of Public Health reports:

 In 1994, the U.S. Centers for Disease Control and Prevention (CDC) investigated whether exposure to stachybotrys might be related to pulmonary hemorrhage, also known as bleeding lungs, in infants in Cleveland, Ohio. While the CDC initially concluded that there was a possible link between exposure to the mold and the condition, stachybotrys was not found in the homes of seven children with bleeding lungs identified in the Chicago area between April 1992 and January 1995. A subsequent review of the Cleveland study by a group of CDC experts concluded that a link between exposure to stachybotrys and bleeding lungs in infants was not proven.”

Millions of people in moldy environments suffer a broad spectrum of symptoms, ranging from allergy-like sneezing, coughing and runny eyes all the way to brain fog, memory loss, chronic fatigue and bleeding lungs. In many cases, these symptoms disappear when mold is removed from their environment, or when they leave a mold-infested place.

What is unknown is precisely what causes these various ailments.

Mold, or fungi, produce three basic substances that can irritate people: Spores (microscopic “seeds”) and fragments of the organism (hyphae); microbial Volatile Organic Compounds (mVOCs); and mycotoxins, meaning poisons produced by fungi.

Spores and hyphae

Spores and hyphae can cause irritation, sneezing, itchy eyes and similar symptoms. It is these microscopic particles that are most commonly associated with mold, and most commonly assumed to be the only active ingredient with any impact on human health. Thus thousands of doctors and so-called health experts naively dismiss indoor mold as a serious health problem.

Fortunately for all of us, this cavalier attitude toward indoor mold is slowly fading, being supplanted by a growing awareness of the real dangers of living in a moldy environment.


It is the mycotoxins of stachybotrys that are believed to be the key to this mold's toxicity to humans, and the theory makes sense, though as we said it's unproven. Stachybotrys produces trichothecenes, which are suspected of being able to cause bleeding in the lungs. It also emits an enzyme which digests protein (a protease), which some research suggests may combine with trichothecenes to wreak even more lung havoc.

Mycotoxins are believed to be part of the coating on mold spores, meaning that in the case of stachybotrys the spores need to become airborne in the living space for people to inhale them, before they can be affected by the toxins.

Earlier we mentioned that stachybotrys is slow to grow. That's because it is what's known as a “tertiary” mold, meaning that it arrives as the third stage of mold growth in an ongoing infestation. It requires a stable, very moist environment with the right food in order to thrive.

Many molds produce mycotoxins, whose purpose is primarily self defense. Penicillin, for example, is a mycotoxin from the Penicillium chrysogenum fungus. It's a powerful antibiotic, because bacteria are molds' chief competitors for food. Take a Petri dish with a thriving bacteria culture in it, drop in the right species of Penicillium, and the bacterial culture will die off in a circle around the fungus.

Aflatoxin B1, a known carcinogen, is a product of Aspergillus flavus, which grows commonly on stored nuts, grains and peanut butter.

Microbial Volatile Organic Compounds

Another possible culprit is microbial Volatile Organic Compounds, or mVOCs. Molds produce a wide variety of gaseous chemicals, including acetones, alcohols, benzene, methyl chloride and so on. These are chemicals we typically associate with human industrial activity, and yet they are emitted by molds! It is this cocktail of chemicals that gives mold its musty smell, and which can cause burning, itchy eyes and skin, dizziness, headache and foggy thinking. Prolonged exposure, obviously, cannot be good for you.

As you might guess, mVOCs, because they are in gaseous form, are able to penetrate walls and ceilings, leak around switches and outlets, and are generally free to roam around your air supply and be inhaled. However, they cannot be detected by standard air sampling methods (there are tests for VOCs, but they are generally not used in pursuit of mold). Air sampling only captures airborne particles, certain types of bacteria, mold spores, skin cells, pet dander and pollen.

That is why air sampling often misses finding significant mold growth when it's hidden in closed cavities whose air doesn't circulate within the living space. Mold-detection dogs like those used by 1-800-GOT-MOLD?, however, can point quite accurately at hidden mold growths, because they can detect the tiny amounts (measured in parts per billion) of mVOCs in the air and trace them to their source.  This gives their human partners the opportunity to investigate further with various electronic tools, and by boring holes and taking air samples inside such cavities.

Electronic moisture detection and infrared thermal imaging are excellent tools for finding pockets of hidden moisture, where mold is likely to reside. These tools are often used to further investigate a dog's findings, prior to hole-boring and sample collection.

'Menace to humanity'

So is black mold toxic? Is it dangerous? There is little doubt. Nicholas P. Money, in his highly entertaining yet densely informative book, “Carpet Monsters and Killer Spores,” on which this article relies heavily, acknowledges the black molds, which include molds other than the notorious stachybotrys, as a “menace to humanity.”

Why is the black-mold menace coming to light so recently? According to author Money, stachybotrys may be a foreign import. The earliest known record of this deadly fungus is in the Ukraine in the 1930s, when many horses died due to exposure to moldy hay. This was no small matter, since horses then were like cars and tractors now. The cited cause of death was stachybotryotoxicosis (sorry for the double mouthful), meaning essentially stachybotrys poisoning. A number of people also were afflicted, either by handling the moldy hay, or sleeping on moldy hay mattresses.

Money indicates Stachybotrys may have come here from eastern Europe via trade products during the mid-20th Century, and may still be in the process of spreading.

The Centers for Disease Control and Prevention has this to say about toxic mold:

“Certain molds are toxigenic, meaning they can produce toxins (mycotoxins), but the molds themselves are not toxic, or poisonous. Hazards presented by molds that may produce mycotoxins should be considered the same as other common molds which can grow in your house or workplace. Contradicting research results exist regarding whether toxigenic mold found indoors causes unique or rare health conditions such as bleeding in the lungs. Research is ongoing in this area.

“Mold growing in buildings, whether it is Stachybotrys chartarum (Stachybotrys atra) or another mold, indicates that there is a problem with water or moisture. This is the first problem that needs to be addressed.”

Black mold is only part of the story

Black mold is most certainly to be avoided. But the lesson here is that it's not the first thing, or the only thing, to worry about. The thing to worry about is moisture problems indoors, because where you have these, you will inevitably have a whole assortment of uninvited guests making themselves at home in yours. All molds cans trigger asthma attacks and people die from asthma attacks every day. All molds can trigger allergic reactions and sinusitis. Mold is essential to the making of wine, beer, bread and some cheeses. It is decidedly undesirable in the making of a home.

If you think you may have a mold problem, or know that you have had any kind of water intrusion, a thorough investigation is in order. The best way to avoid black mold is to eliminate it before it germinates, which means preventing or eliminating moisture problems and removing mold-infested materials at the earliest possible time.

Prevention is the best defense against mold. This consists of thorough, regular maintenance of plumbing, siding, windows, roofing and drainage systems, semi-annual duct cleaning and HVAC maintenance, and constant vigilance for the slightest sign of excess moisture.

Maintaining relative humidity at or below 50% also is a key factor, especially in poorly ventilated areas such as attics, crawlspaces and basements. Ventilation, proper insulation and dehumidifiers are essential here.

Source: Habitat Quarterly  Issue 3


Leave a Comment

The Truth About 'Black Mold'
white down border box