Is Black Mold Dangerous? What the CDC Says About Stachybotrys

"Black mold" is one of the most searched phrases in home repair, and much of what's online makes it sound uniquely toxic. The public health guidance is calmer, and more practical: mold of any color can affect your health, and the answer is the same every time. Remove it, fix the water, and protect the people most at risk. If you've found mold that's large, hidden in walls or keeps returning, ReestorianPros can connect you with a local provider for mold removal and remediation in Littleton.

This is general information, not medical advice. A doctor is the right person to ask about symptoms or exposure.

What is black mold?

"Black mold" usually refers to Stachybotrys chartarum, a greenish-black mold that tends to grow on paper-based and wood materials, such as drywall facing, ceiling tiles and cardboard, when they stay wet. It needs sustained moisture, so it tends to show up after leaks, floods or long-term dampness.

But many common indoor molds are dark or black. You can't identify Stachybotrys by looking at it, and you don't need to. The CDC says you don't need to know the type of mold to clean it up.

Is black mold dangerous?

Mold can make some people sick, and that includes black mold. Here's what the CDC says:

• Symptoms: For some people, mold can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes or a skin rash.
• Higher risk: People with asthma or mold allergies may have severe reactions. People with weakened immune systems or chronic lung disease may get lung infections from mold.
• Black mold specifically: The CDC says Stachybotrys chartarum and other molds may cause nonspecific health symptoms, and that all molds should be treated the same with respect to health risks and removal.

Cleveland Clinic describes black mold as no more dangerous than other molds, and says it rarely causes serious illness. It notes that typical reactions are allergy-like, such as congestion, sneezing, coughing and itchy eyes.

Can black mold kill you?

For healthy people, that's very unlikely. The phrase "toxic black mold" comes partly from reports in the 1990s that linked Stachybotrys to a rare lung bleeding condition in infants. The CDC says a possible association between that condition and Stachybotrys chartarum has not been proven. Cleveland Clinic also says there's no clear scientific evidence for "toxic mold syndrome."

That doesn't make mold harmless. For people with weakened immune systems or chronic lung disease, mold can cause serious lung infections, according to the CDC. If someone in your home is in that group, keep them away from the mold and the cleanup.

What does black mold look like?

• Dark green, gray or black spots or patches
• Slimy or wet-looking when moisture is active; powdery or sooty when it dries out
• Often on drywall paper, ceiling tiles, wood, wallpaper backing and cardboard
• Often near a water source: under sinks, around windows, behind toilets, in basements

Some things look like mold but aren't. Soot from candles appears as gray streaks near ceilings and vents. White, powdery deposits on concrete are often efflorescence, minerals left by water moving through the wall.

What does black mold smell like?

Mold usually smells musty or earthy, like damp soil, wet wood or old books. You'll often smell it before you see it. A musty smell that's strongest in one closet, corner or cabinet usually means moisture, and possibly mold, is hiding there.

Should you test for black mold?

Usually not. The CDC does not recommend mold testing, because sampling can't tell you whether someone will get sick, it's often expensive and there are no standards for an acceptable amount of mold. NIOSH adds that there are no health-based limits for mold in indoor air, and that looking for visible mold and noticing musty smells is more reliable than air sampling.

Testing can help in narrow cases, such as tracing hidden growth or checking a cleanup for a legal or insurance reason. For most homes, if you see or smell mold, the next step is removal.

How to get rid of black mold

The removal steps are the same for black mold as for any mold:

• Find and fix the moisture. Mold comes back if the leak, seepage or humidity isn't fixed.
• Decide on DIY or a professional. The EPA says areas larger than about 10 square feet usually call for a professional.
• Protect yourself. Wear an N95 respirator, goggles that seal around the eyes, and long gloves.
• Keep others out, especially people with asthma, allergies, weak immune systems or lung disease.
• Remove porous materials that are moldy, such as drywall, ceiling tiles, insulation and carpet.
• Clean hard surfaces with detergent and water, then dry them completely.
• Dry the area and keep humidity below 50 percent, as the CDC advises.

Does bleach kill black mold?

On hard surfaces, the CDC says you can use a bleach solution of no more than 1 cup of household bleach in 1 gallon of water. Open windows, wear gloves and goggles, and never mix bleach with ammonia or other cleaners. Bleach doesn't fix moldy drywall, carpet or insulation; those need to come out. Painting over mold doesn't work either: NIOSH warns that it can cause further problems.

What causes black mold?

Black mold grows where materials stay wet. The EPA says mold usually won't grow if wet materials are dried within 24 to 48 hours. Common causes:

• Slow plumbing leaks under sinks, behind toilets and inside walls
• Roof leaks and ice dams that wet ceilings and attics
• Basements with seepage, high humidity or a past flood
• Water damage that was cleaned up but not dried with measured readings

Black mold in Colorado homes

Colorado's dry climate helps, but it doesn't prevent mold. In Littleton-area homes, mold often traces back to liquid water: a frozen pipe that leaked in a wall, an ice dam over a bedroom ceiling, a sump pump overflow or a slow drip under a sink. Finished basements are a common spot, because carpet and drywall sit right where water ends up. If a room smells musty, look for the water first. Read how long it takes for mold to grow for the timeline after a leak.

How to prevent black mold

Black mold needs a material that stays wet. Take away the moisture and it has nowhere to grow:

• Dry leaks and spills fast. The EPA says wet materials dried within 24 to 48 hours usually won't grow mold.
• Fix the source, whether it's a dripping supply line, a roof leak or seepage through a foundation wall.
• Watch indoor humidity. The CDC advises keeping it no higher than 50%, and a simple hygrometer shows where you stand.
• Run bathroom and kitchen exhaust fans during and after showers and cooking.
• Don't store cardboard or paper directly on basement floors or against cold concrete walls.
• Replace materials that stayed soaked, like carpet pad or the bottom of drywall, instead of drying them in place for weeks.

Related reading: See how long it takes for mold to grow after water damage, and how to deal with mold in the basement.

When should you call a mold remediation professional?

Call a professional when:

• Mold covers more than about 10 square feet
• It's inside walls, under flooring or in ductwork
• It followed a flood, sewer backup or long-running leak
• It keeps coming back after cleaning
• Someone in the home has asthma, allergies, a weakened immune system or lung disease

Found black mold in Littleton? Call (303) 879-0950 to reach a local mold remediation provider.