Fungi's Job is to Eat, Decompose Your House

    Knight Ridder Newspapers

    AKRON, Ohio


    What you don't see can hurt you. Mold in buildings can compromise structures and make people sick. Often, that mold lurks in hidden places - behind the walls, in the air conditioning system, on the underside of Grandma's old chest of drawers.

    Yet people often ignore those sources, simply because they're not visible, said Jeffrey May, a mold-investigation specialist and author of "The Mold Survival Guide."

    "People react most strongly to what they can see," said May, who owns May Indoor Air Investigations in Cambridge, Mass. So the slimy gunk in the shower or the black stuff in the attic may worry them, when those probably aren't nearly as threatening as what's under the basement carpet or behind the paneling.

    Before you panic and start tearing out drywall, however, you should know that serious mold infestations aren't rampant. In fact, most houses don't have a significant mold problem, said Andrew Sill, owner of Cierra Environmental, an Ohio company that specializes in mold inspection, testing and remediation.

    In those that do, there's some sort of underlying cause, such as improper ventilation, a leak in a water pipe or a bathtub overflow, Sill said. "The mold follows the water," he said, "and the water doesn't just appear in the house."

    Even if your house does have mold, the problem may not be significant if no one in the house is sensitive to it, said Thad Godish, a professor of natural resources and environmental management at Ball State University, who has researched mold contamination of buildings. But for people who are sensitive to it, mold can trigger asthma, chronic coughs and more serious respiratory ailments.

    Mold is in the air all the time, Sill and May said, so it's impossible to achieve a level of sterility that would make a house mold-free. Nevertheless, May believes mold shouldn't be growing unchecked in any home.

    So what is mold, anyway?

    Mold is fungus - actually, any of many types of fungi. Mold plays a useful role in nature, because it secretes enzymes that break down matter.

    Mold becomes a problem, however, when it starts feeding on things we don't want it to, such as the wood frames of our houses or the paper that covers drywall. Mold can weaken and ultimately destroy parts of a house. It can send spores and other particles into the air we breathe.

    "Mold is out there doing its job," Godish said. "It's trying to eat your house down. If you give it a chance, it will."

    The most common types of fungi in a home - what we typically refer to as mold or mildew - belong to the genera "Cladosporium, Penicillium, Aspergillus, Alternaria, Stachybotrys and Chaetomium." Different types of mold feed on different substances, such as wood, cellulose, dust and soap scum. All need food and water to grow.

    How big a problem these molds pose depends partly on how much is present. A trace of mold around the edges of windows isn't likely to release enough spores to cause health problems, Sill said, while a moldy section of basement wall could be a breeding ground of misery.


    The type of mold is significant, too. Many molds found in a house are superficial, May said - they grow on a surface but don't attack what's underneath. But Godish said those molds can set the stage for other fungi to come in and hasten the destruction.

    And while May said any type of mold can cause allergic reactions when it's breathed, some molds produce tinier spores that float in the air longer and lodge more deeply in the lungs. "Aspergillus," for example, is often linked to a condition called homes-in-stocktonsensitivity pneumonitis, a chronic lung disease that he said is relatively rare but often misdiagnosed as pneumonia.


    One of the most common hidden sources of mold in modern buildings is the air-conditioning system, May said. In summer, water pools in the unit and provides the perfect breeding ground for mold. In winter, when the mold is dry, particles are easily picked up and blown through the air.

    Basements and crawl spaces are other places where mold tends to grow. The relative humidity typically is higher there than in the rest of the house, and Sill said the darkness allows mold to grow faster.

    Mold is also common in attics and bathrooms - particularly bathrooms that don't have a fan or that stay steamy for a long time, Sill said. Houses that are left unheated can experience mold growth, too, because moisture from the air condenses on the cold walls.

    Paradoxically, the one type of mold that's probably gotten the most attention and caused the most fear - the so-called toxic black mold - isn't a common source of health problems, May and Godish said.


    When people talk about toxic black mold, they're usually referring to "Stachybotrys chartarum," May said. But "toxic black mold" is a term he and Godish avoid.

    For one thing, it's technically incorrect. It's not the mold that's toxic, Godish noted; it's the substance it produces. For another, the term is misleading, he and May said. It tends to make people think all black mold is highly threatening, when it's not. Black molds are common in bathrooms and attics, for example, but they're usually not "Stachybotrys."

    While it's true that "Stachybotrys chartarum" produces a mycotoxin that's very poisonous - you can die from eating it - May and Godish said there's no strong scientific evidence that the mold causes significant health problems if it's not disturbed. It also grows only in areas that stay very wet, so it's not all that common.

    Nevertheless, the mold can cause such fear that people overreact, Godish said. "I've seen people basically abandon their houses with a little bit of "Stachybotrys" around their bathtub," he said.

    Overreactions to mold in general aren't uncommon. Sill said many people have the misconception that any kind of mold permanently harms a home's value. "It can be fixed," he said.

    How mold is remediated depends on the material it has affected, Sill said. Treatment might involve removing the mold using a HEPA vacuum, sanding surfaces, treating with a biocide or applying a material that encapsulates the surface. Porous materials such as drywall, insulation and mattresses may need to be removed.

    Depending on the extent of the problem, the cost of testing remediation can be significant, although some insurance policies will cover it.

    Better to prevent the problem in the first place, the experts agree.

    Because other than the Camembert in your refrigerator, mold in the house just isn't a good thing.



    Here are some answers to questions about mold, gathered from mold authorities Thad Godish, Jeffrey May and Andrew Sill:

    Q: How can I prevent mold?

    A: The best prevention is careful home maintenance. Never ignore a leak, because it takes only days for mold to grow. Fix openings in the house's outer shell where water can seep in, and make sure your attic is properly ventilated.

    In the bathroom, open a window or use a ventilating fan when you take showers. Make sure the fan is vented to the outside of the house, not into the attic. If you don't have a window or ventilating fan, set a small oscillating fan on the vanity to help dry the room. You might even dry your towels outside the bathroom if the moisture is significant.

    In the basement, use a dehumidifier if the relative humidity there is higher than 50 percent, and keep the temperature at 60 degrees or above. That's critical in a finished basement that's frequently occupied, May said. "It should be illegal to have a finished basement without a dehumidifier," he said.

    Carpet in basements frequently harbors mold, since moisture condenses on the cold floor. Consider a hard floor with an area rug instead.

    Even something as simple as regular cleaning helps prevent mold growth, since mold grows on dust, dirt and soap residue.

    Q: How do I know I have a mold problem?

    A: Mold can be hard to detect, because it often hides where we can't see it.

    A moldy smell is a tipoff, although you can have mold without the odor. Unexplained respiratory symptoms are another clue, particularly if they go away when the affected person leaves for an extended period.

    Suspect mold in any house that's had a leak or flood, particularly if the problem wasn't remedied and the area dried out promptly.

    An older home is more likely than a newer one to have mold, simply because the probability of leaks and other problems increases with age, Godish said.

    Q: What should I do if I suspect I have a mold problem?

    A: Have an inspection done and the air in your house tested to find out whether a problem exists. Expect to pay $100 to $250 for an inspection, Sill said.

    An inspection may not be necessary if the source of the mold is obvious, he said.

    If the inspection shows you do have a problem, multiple samples will often be required to determine the source. Those samples need to be analyzed by a laboratory, so they aren't cheap - about $75 each, Sill said.

    Mold inspectors and remediation specialists are not all equally qualified, so May suggested finding someone certified by one of the following institutions: ACGIH Professional Learning Center in Cincinnati; the Indoor Air Quality Association in Rockville, Md.; MidAtlantic Environmental Hygiene Resource Center in Cherry Hill, N.J.; or Restoration Consultants in Sacramento, Calif.

    Sill suggested getting two or three estimates from mold remediation specialists. Avoid anyone who offers ozone-type products or promises to get rid of all the mold in the house, he said.

    Q: Can I remove the mold myself?

    A: Maybe, if you have only a small amount of visible mold - less than 10 square feet - and you know what you're doing, May said.

    Nonporous surfaces can be cleaned with a solution of chlorine bleach and water. But don't just spray the bleach solution on, Sill said; apply it with a towel, so you don't leave excess moisture on the surface to start the whole mold-growth process again. Wear proper gear to protect your skin and eyes.

    After you've removed the mold, you can prevent a recurrence by applying special bathroom paint formulated to prevent mildew growth.

    Porous surfaces, such as insulation and drywall, need to be replaced.

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