It's not only nasty, it's dangerous—to you and your property. Learn how to prevent and combat mold.
With more than 100,000 species worldwide, roughly a thousand of which are native to the United States, molds are literally everywhere on the planet, including Antarctica. In nature, these fungi serve as a catalyst—speeding decomposition and ridding the planet of megatons of dead plant matter. And some varieties even have a time-honored place within our homes. After all, you owe the penicillin in your medicine cabinet to a mold called Penicillium chrysogenum, part of the same genus as Penicillium roqueforti, the mold you can thank for that delightful Roquefort cheese stinking up your fridge.
But no good can come from uninvited mold (aka mildew) indoors, since these microscopic organisms make their living by consuming the surface they're growing upon. It's bad enough when their food source is a little soap scum in your shower, but when it's the cellulose in wallboards or ceiling tiles, or worse yet, in the wooden studs that support them, the resulting property damage can be significant. Even more serious are the potential health effects for your home's occupants.
Little more than a year ago, it was an all-too-familiar sight in the media: homes deluged by the flood waters of Hurricane Katrina. Less ubiquitous, however, were images of the secondary setback suffered by New Orleans homeowners: an onslaught of aggressive mold left behind by the receding waters, an example of which can be seen in this photo taken less than a month after the storm hit, showing the scarred walls of Danielle Boyce Batten's home in Lakeview, where the 17th Street Canal levee was breached.
"The first time I went back, I wore a mask and only stayed ten or fifteen minutes," Danielle recalls. "There was a moldy smell, and it just affected your whole sinuses. You really could feel it. It burned your throat, it burned your eyes—I mean, it was that strong." Danielle's family members have suffered with health problems that she attributes to their mold exposure. "My sister Dionne was the first person to get into the house," Danielle says, "and she developed some sort of upper-respiratory condition that the doctors in Baton Rouge thought was caused by the mold." Last September, Danielle and her husband had the home demolished. "The mold," she says, "was one of many factors in our decision."
"We have studies that show we have volumes of mold in New Orleans that have never been seen in any other city in this country before," says Dr. Kevin Stephens, Director of the City of New Orleans Health Department. "The long-term health effects are only theoretical, because we don't have any comparable case in history, but in the short-term we do know that mold is one of the known triggers of bronchial constriction."
Molds reproduce by releasing spores that can provoke allergic reactions ranging from the mild (itchy eyes, runny nose, head congestion, coughing) to the more severe (skin rashes and worsened asthma). "We have a prevalence of asthma, specifically in children, of about 15%. That's a very high rate," Dr. Stephens says. "Anything that can trigger airway obstruction and an asthma attack is problematic."
"Mold should not be the determining factor in the demolition of a house," says Dr. Stephens, "but it can be a criterion in deciding to gut a house—because if you have mold behind your walls, it's very difficult to get rid of." Simply waiting for flood waters to evaporate is not a viable option, as that could take months or even years, during which mold constantly works its mischief. "If you have a significant amount of mold, as in 60% of your walls being covered with it, we recommend that you actually remove the sheetrock and dry your house out," he says. "It's like a fruit bowl: if you have mold on just one orange, you can throw that one away and keep the rest. But if most of the fruit is covered with mold, it's best to throw it all out."
Though many mold species can grow indoors, the list of usual suspects is much shorter—and one variety gets the lion's share of attention. Columbia University's Dr. Ginger Chew studies asthmas and allergies related to mold. "When people think of mold, they usually mention toxic black mold, or Stachybotrys chartarum," she notes. This home invader defends itself from rival microorganisms by releasing poisons called mycotoxins, which can cause serious illness in humans. "Mycotoxins tend to inhibit protein synthesis, which your body needs to survive," says Dr. Chew. "They can cause hemorrhaging in various body tissues."
Regardless of the variety, "mold growth should always be taken care of, whether you have the chartarum or not," says Dr. Chew, "as all molds have the potential to pose health risks." Don't waste your time trying to determine what kind of mold you have. For one thing, it's probably a futile effort. "There's a lot of cross-reactivity between species," she says, "so it's hard to figure out which mold is which." And even if you're not allergic now, don't count on staying that way; as Dr. Chew points out, "People can develop allergies throughout their lives."
Besides, even people who aren't allergic can be adversely affected. "That musty, moldy odor comes from volatile organic compounds, which are mainly alcohols and ketones," says Dr. Chew. "Inhaling alcohol for a long time, in sufficient quantity, can result in headaches, watery eyes, mucous membrane irritation—and that can affect anyone."
"Prevention is the key," says Kristy Miller, spokesperson for the Indoor Environments Division of the Environmental Protection Agency. "Moisture and water are what allow mold to grow, and it'll grow on just about anything, almost anywhere. But if you keep your surfaces and materials dry, it will help prevent most mold growth. It's commonsense."
Accomplishing this involves thinking outside the house. "Keep gutters clean," she says. "If you have a roof leak, immediately find the source and fix it. If you have landscaping in your yard, make sure the yard slopes away from the foundation, downhill. Make sure all of your drains can drain freely. And make sure there's no standing water near your home."
Controlling moisture inside your home involves more than just sinks and showers. Pay attention to:
1) Houseplants: "You should not have standing water anywhere in your home," Miller says. "Be aware that something as simple as standing water in a pot under a plant could lead to mold."
2) Appliances: "Certain models of refrigerators have drain trays underneath," says Miller. "Make sure those are regularly cleaned and checked."
3) Carpets: Says Miller, "In just 24 to 48 hours, soaked carpeting can lead to mold if you don't get it dried."
4) Ventilation: Particularly in high-moisture areas like bathroom and kitchens, says Miller, "exhaust fans can help eliminate moisture, which can lead to mold. If you have an exhaust fan, use it. If you don't have one, you may want to think about installing one."
Of course, in the cold months many people think about how to get more humidity into their homes to combat the parching effects of winter's dry air. And the good news is that you don't have to forgo your humidifiers; with a little routine maintenance, you can ensure that they're not spewing mold into your air along with that soothing mist. "Change water regularly," says Miller. "And make sure you follow the manufacturer's directions." Some of those manufacturers, such as Holmes even incorporate antimicrobial products such as Microban® into their appliances, in part to inhibit mold growth.
When mold does take hold in your home, fight the temptation for a quick fix. "Address the source of the problem first and then deal with the mold growth," says Dr. Chew. "If you just paint over it, the front part of the wallboard may look fine, but if you look at the reverse side, inside the wall cavity, you could see the mold growing back," as in the image at left.
"I've done a lot of work with Katrina victims" she says, "and my fear is that even though they've done a lot of remediation, when you put up new sheet rock on wet wooden studs, the mold will just come back"—which means the troublesome stuff could be spreading through your home, releasing a high concentration of spores into the air you breathe, without your ever seeing it.
There are scads of mold remedies for sale, but the best advice may be to keep it simple. If the moldy area is less than 10 square feet, the EPA recommends good old-fashioned scrubbing with soap, water and plenty of elbow grease, followed by a thorough drying. Chlorine bleach kills the mold, but it only does part of the job. As Dr. Chew points out, "Even dead spores can cause allergic reactions", so it's essential that mold be scrubbed away after it's killed. To minimize exposure to mold spores during that process, the EPA suggests an N-95 respirator (available at many hardware stores), as well as long gloves and goggles.
Still, mold can hide within your home's crevices. So watch for telltale signs in addition symptoms such as unexplained runny noses, teary eyes and wheezing. "That mildewy odor is an indication," says Jeff Bishop, technical advisor to the non-profit Institute of Inspection, Cleaning and Restoration Certification. "Mold digests its food outside its body and then absorbs the nutrients through its cell wall. We digest inside our bodies, and in polite company we don't smell those gases. But molds are not that polite."
If you believe you have a serious problem, hire a pro. "Remediators use specialized instruments designed to detect moisture within walls, including infrared thermal-imaging cameras," says Bishop. "And we're experienced in following the route of water penetration." A good place to start your search for an experienced professional is IICRC's consumer website. "We have a certification program with pretty intense training and examinations," says Bishop. "People can visit our website and get the names of up to five firms in their area that employ our applied microbial remediation technicians, or AMRTs, who specialize in mold remediation. And there's no charge for that."
To prepare for a pro's visit, compile a building history. "You know," says Bishop, "the age of the building, likelihood of water damage, where leaks have been experienced lately, bathtub overflows. Consumers may think they mopped it all up, but that water may be pooled up below the floor." Leave the actual prep work for the pros. "When consumers start taking things apart, they often get into trouble," Bishop says. "Their well-meaning efforts to fix things up may result in increased cost." Pro fees range widely, says Bishop, "but any quality firm will give you a ballpark estimate. Then if they get into the project and discover that it's worse than expected, they should stop and discuss the increased price in advance."
Only after the source of the problem has been corrected and the cleanup is complete should you turn your attention to cosmetic damage. If repainting is called for, you might want to select a mold-inhibiting product such as Kilz Premium Primer. "It has a mildew-resistant coating," says brand manager Jason Long, "so it's perfect for kitchens, bathrooms and basements." It's important to note, however, that products of this sort are not a substitute for thorough remediation of the problem. They don't kill mold, and they are not going to stop mold from occurring under the coating, but they help prevent mold and mildew from forming on the dry film surface. Finishing off with a mold-resistant top coat is recommended.