Is Black Mold Dangerous? What the CDC and EPA Actually Say

You pull out the bathroom vanity or look behind the washer and find dark spots on the wall. Then you search online and see the words "toxic black mold." It's easy to panic.

Take a breath. Mold indoors is worth dealing with, but the facts from the CDC and EPA are calmer than most of what you'll read online. This guide covers what "black mold" really means, what health agencies say about it, who should be more careful, and how to clean it up the right way.

What "black mold" actually means

When people say black mold, they usually mean Stachybotrys chartarum, which the CDC describes as a greenish-black mold. It grows on materials high in cellulose, like drywall, fiberboard, and paper. It also needs constant moisture, which can come from leaks, condensation, water getting in from outside, or flooding.

But plenty of other molds look dark too. The CDC lists Cladosporium, Penicillium, and Aspergillus as the most common indoor molds, and Cladosporium often grows in olive-brown to nearly black patches. You can't tell which mold you have by its color. Only a lab can do that, and the CDC says it isn't necessary.

What matters more is where it's growing. Mold on drywall or wood usually means that spot has stayed wet for a while, and that water problem needs fixing.

What the CDC says about health effects

The CDC says mold affects people differently. For some people, it can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or a skin rash. Others have no effects at all.

You may also read that black mold causes serious illness. The CDC says a possible link between Stachybotrys and bleeding in the lungs of infants has not been proven, and that no test can prove a link between Stachybotrys and specific symptoms. The CDC's advice is to treat all molds the same and remove them, and to see a doctor if you have symptoms that don't go away.

Who is more at risk

According to the CDC, some people are more likely to have serious reactions:

• 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.
• People with asthma, COPD, or a weakened immune system should stay away from moldy spaces during cleanup, the CDC advises.

If someone in your home is in one of these groups, have a professional handle the cleanup, keep kids and pets out of the work area, and talk to a doctor about any symptoms.

Do you need a mold test?

Usually not. The CDC does not recommend mold testing, because mold affects people differently and a test can't tell you whether you'll get sick. The EPA says that if mold is visible, sampling is usually unnecessary. When sampling is done, the EPA says it should be done by professionals with specific experience, and it can be useful to check whether an area was properly cleaned.

In most homes, the more useful step is finding where the water is coming from and measuring how wet the materials are.

Can you clean it yourself?

The EPA says that if the moldy area is less than about 10 square feet (roughly a 3-foot by 3-foot patch), most homeowners can handle it. Call a professional when:

• The moldy area is larger than about 10 square feet
• There was a lot of water damage, or materials stayed wet more than a day or two
• The water came from a sewer backup or other dirty source
• You smell mold but can't find it, or it may be behind wallpaper or paneling (the EPA warns that removing it can release a lot of spores)
• You think mold is in your heating or AC system - the EPA advises not running it if you suspect contamination
• Someone in the home has asthma, allergies, or a weakened immune system

Cleanup basics for a small area

1. Fix the water first. If the leak or dampness continues, the mold will come back.
2. Protect yourself. The EPA recommends an N-95 respirator, gloves, and goggles. The respirator has to fit properly to work.
3. Scrub hard surfaces with detergent and water, then dry them completely.
4. Throw away moldy porous materials. The EPA notes that absorbent materials like ceiling tiles and carpet may have to be thrown away if they get moldy.
5. Be careful with bleach. If you use it, the CDC says to use no more than 1 cup of household bleach per gallon of water. Never mix bleach with ammonia or other cleaners, and open windows for fresh air.
6. Don't paint or caulk over mold. The EPA says paint over moldy surfaces is likely to peel.

Fix the moisture so it doesn't come back

Mold needs moisture, and moisture is the part you can control. The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent, and drying water-damaged areas within 24 to 48 hours. Learn more in how fast does mold grow after water damage.

• Fix drips under sinks, around toilets, and at the water heater.
• Run bathroom and kitchen exhaust fans, and keep them clean.
• Check AC condensate lines and drain pans in attics and closets.
• If floors feel damp or warm with no clear source, the leak may be under the slab. See signs of a slab leak.

How we help

First Call Plumbing & Restoration serves homes across the Inland Empire and handles both the plumbing that causes mold and the mold remediation that follows. Our IICRC-certified techs find and fix the moisture source, set up containment, remove damaged materials, clean with HEPA filtration, and confirm the area is dry before rebuilding. If you're comparing companies, read mold remediation vs. mold removal. We document the damage and can work with your adjuster, but coverage decisions are up to your insurer.

Found mold, or smell it but can't find it? We're open 24/7. Call (909) 751-2323 or contact us, and we'll help you find the source and get it fixed.