Signs Your House Has Mold—And How to Get Rid of It

Time​ Magazine

2 days ago

In the early 1990s, the U.S. was shocked by the mysterious deaths of 12 babies in Cleveland's poorest neighborhoods. Evidence, while not conclusive, suggested the babies died from breathing in toxic black mold contaminating their homes due to water leaks.
The tragedy had a lasting impact on people's beliefs about the unique effects of black mold, says Karen Dannemiller, associate professor of engineering and public health at Ohio State University. Although mold can be hazardous, scientists now understand 'the color doesn't matter,' Dannemiller says.
It's just one of several points of confusion about mold, researchers say. Here are the keys to mold detection, removal, and prevention.
How mold affects your health
Mold is a type of microbe that thrives in damp places. The specific kind depends on factors like building materials and geographic region of the country.
Indoor microbes like bacteria and fungi aren't inherently bad. 'Even a healthy home has a rich and diverse indoor microbial community,' Dannemiller says. Things go wrong when there's excess moisture, such as after a leak. 'Then the fungi start to grow to create areas of mold and produce things that are linked to health impacts.'
Concerning types of mold 'come in many colors and species,' says Ginger Chew, an epidemiologist at the U.S. Centers for Disease Control and Prevention (CDC). The most researched problems from exposure are asthma attacks and chronic asthma, particularly in kids. Studies also show associations with other respiratory diseases like hypersensitivity pneumonitis and allergic rhinitis.
Remote work is a risk factor for increased mold exposure just by virtue of spending more time indoors, says David Miller, professor of fungal toxins and allergens at Carleton University.
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Besides misunderstandings about color, another mold misconception is the effect of inhaling mycotoxins, compounds produced by certain molds. Mycotoxins can be hazardous when found in food (though U.S. regulations allow limited levels.) But when it comes to inhaling mycotoxins, 'very low evidence' supports any association with illness, Chew says.
Jeff May, a mold inspector in Massachusetts who co-wrote a book on improving home health called My House Is Killing Me! A Complete Guide to a Healthier Indoor Environment, adds that expensive urine tests looking for mycotoxin usually don't reflect actual mold growth in one's home. But he thinks patients should take such tests if recommended by a doctor.
Symptoms of mold exposure
People sometimes blame mold for symptoms that could be caused by other issues. 'There's a constellation of non-specific symptoms,' and more research is needed to understand which ones do and don't relate to mold, Chew explains.
An individual's response to mold depends on the type, as different molds contain distinct allergens that cause a range of reactions. Mold could be the culprit if you're coughing a lot, May says. Frequent sneezing is possibly related, though it's more often due to outdoor allergies like pollen, he adds.
With increased mold exposure, you're more likely to develop an allergy to it, Miller says. 'We know it makes you more allergic to outdoor molds and even outdoor allergens,' he explains. 'It causes chaos in your immune system.'
More anecdotally, people have speculated about fatigue and brain fog being linked to mold. Research in animals shows that mold affects cognition, though data are limited in humans, Miller says. Dannemiller thinks mold could hinder cognition because of the lungs' interconnections with the brain, but 'we don't necessarily have conclusive evidence yet.'
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Allergy tests may help diagnose a mold allergy. Chew says these tests have improved in recent decades, but a remaining challenge is that, when checking skin reactions, different types of mold can cross-react with each other. 'So the particular type of mold can be hard to pinpoint,' she says.
'Allergy testing can be hit or miss,' Dannemiller says. 'The fungi tested may not be what you're exposed to.' She recommends each individual speak with their doctor to understand what's causing symptoms and whether they should try allergy testing.
The see/smell test
Instead of relying only on symptoms or allergy testing, the most important factor is if you see or smell mold. 'Your nose is a good indicator of a problem,' Dannemiller says. 'Odor strongly associates with health problems.'
Mold may look black, green or orange, with patches that are fuzzy or powdery, depending on the species and surface. The smell is damp and musty, like rotting leaves.
Any amount of mold is cause for concern; scientists haven't found a minimal level that won't bother anyone—partly because individual reactions differ so much. 'There have been attempts to find a threshold limit, but many people who have allergies, upon repeated exposure, mount a faster and more intense response,' Chew says. 'It's just so very individual,' May adds.
What to do about mold
If you see or smell any mold, call a professional to inspect it. They can confirm or identify problem spots and count the mold spores coming from them.
However, keep in mind that mold tests aren't definitive. 'Tests are only weakly associated with health outcomes,' Dannemiller explains. 'Good inspectors put the tests into context as one small piece of the bigger picture.'
More critical are the expert's subjective assessments, like whether they observe mold and related dampness or water damage. If these boxes are checked, you need to look into getting it professionally cleaned up, Dannemiller says.
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An expert should also examine your air conditioning equipment. 'If you don't have good filtration, dust builds up on the AC coil and gets wet,' says May 'When you have wet dust, that's a formula for mold growth.' May has looked at thousands of AC units, and most are full of mold. 'That's what people are exposed to, and they don't always smell it,' he says. 'The inspector should take a sample of the air coming from the system.'
The basement is another place notorious for mold. 'Aside from air conditioning, that's the most common source,' May says.
If you need professional mold removal, the Find-a-Pro directory, provided by the nonprofit Indoor Air Quality Association, is searchable by city for inspectors who specialize in mold remediation. You can also find qualified professionals through the Institute of Inspection Cleaning and Restoration Certification and the American Industrial Hygiene Association.
Isolated problems, such as refrigerator mold, can be tackled by homeowners with household cleaners, May says. Fridge door seals and drip pans can release spores into the air, potentially triggering allergic reactions in sensitive people. The trim behind storm windows can develop mold, too. 'Anybody can clean it,' May says. Safe and effective options for cleaning include either hydrogen peroxide or white vinegar. The EPA discourages the use of bleach for this purpose.
To address symptoms of a mold allergy, some research suggests that immunotherapy can help. One method, in which patients are increasingly exposed to mold allergens, is approved for treatment.
How to prevent mold from taking over your house
The U.S. Department of Housing and Urban Development (HUD) supports eight principles on healthy housing. Each principle helps prevent mold—especially maintaining a relatively dry home.
'Keep humidity below 50%, because that's the threshold where mold can start growing,' Chew says. Nearly 50% of residences have dampness that leads to mold.
HUD and CDC recommend monitors for indoor humidity. Dannemiller suggests getting multiple monitors and positioning them around the home, 'because one room might be really dry, but you've got another place near the bathroom that may have higher humidity at times.'
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Homes with weak seals often become humid in the summer even with windows shut. If your home's humidity is consistently over 60%, consider buying a dehumidifier to thwart mold, Chew says.
Avoid certain materials like wall-to-wall carpeting in the bathroom. Other bathroom-related priorities are shower curtains. To speed up the drying process, keep your curtain partly extended after showering and turn on a fan, May suggests. Regularly wash the curtain or replace it often.
While AC does reduce humidity, overusing it can make the air too cold and ironically increase mold risk by chilling surfaces and causing condensation, Chew says.
HEPA air purifiers with carbon filters can trap mold particles. But they won't bring down moisture in your home, which is your best mold-prevention strategy, May says. 'Any kind of filtration is going to be helpful, but I always tell people, remove the source.'