Mold, Is It a Problem

What is mold and how common is it?
Although molds are a very common growth in buildings and homes, mold growth should be avoided because mold is a health risk and it often gradually destroys the things it grows on. Molds are a type of fungi that reproduce by means of tiny invisible spores that float in outdoor and indoor air. Mold may begin growing when mold spores land on surfaces that are wet. Mold will only grow in places with moisture or water, such as around leaks in roofs, windows, or pipes, or where there has been flooding. Mold grows well on paper products, cardboard, ceiling tiles, wood products, in dust, paints, wallpaper, insulation, drywall, carpet, fabric, and upholstery. Mold also can grow on food. The most common indoor molds are CladosporiumPenicillium, and Aspergillus. 

How risky are molds for people?
Mold in homes and buildings
Some people do not have any health problems when exposed to damp and moldy environments. But others, who are sensitive to molds, may experience upper respiratory tract symptoms, cough, stuffy nose, wheezing, and red or itchy eyes, or skin.

Some other people, especially those with allergies to molds or with asthma, may have more intense reactions. Allergic reactions to mold are common. They can be immediate or delayed. Molds can cause asthma attacks in people with asthma who are allergic to mold. Individuals with chronic respiratory disease (e.g., chronic obstructive pulmonary disorder, asthma) may experience difficulty breathing. Severe reactions may occur among workers exposed to large amounts of molds in occupational settings, such as farmers working around moldy hay. They may experience reactions including fever and shortness of breath. Studies have suggested a potential link of early mold exposure to development of asthma in some children, particularly among children who may be genetically susceptible to asthma development. Individuals with immune suppression are at increased risk for infection from molds. If you or your family members have these conditions, a qualified medical clinician should be consulted for diagnosis and treatment.

Certain molds are toxigenic, meaning they can produce toxins (specifically “mycotoxins”). The hazards presented by molds that may produce mycotoxins should be considered the same as other common molds which can grow in your house. Not all fungi produce mycotoxins and even those that do will not do so under all surface or environmental conditions.

There are a very few reports that toxigenic molds found inside homes can cause unique or rare sever adverse health effects, such as acute idiopathic pulmonary hemorrhage among infants, memory loss, or lethargy, including from the mold Stachybotrys chartarum. These case reports are rare, and a causal link between the presence of the toxigenic mold and these conditions has not been proven.

Mold In Food
Cleanliness is vital in controlling mold. Mold spores from affected food can build up in your refrigerator, dishcloths, and other cleaning utensils so keep them clean.

Ways to protect food from mold include:

  • When serving food, keep it covered to prevent exposure to mold spores in the air. Use plastic wrap to cover foods you want to stay moist — fresh or cut fruits and vegetables, and green and mixed salads.
  • Empty opened cans of perishable foods into clean storage containers and refrigerate them promptly.
  • Don't leave any perishables out of the refrigerator more than 2 hours.
  • Use leftovers within 3 to 4 days so mold doesn't have a chance to grow.

Don’t buy moldy food. Fresh meat and poultry are usually mold free, but cured and cooked meats may not be. Examine them carefully. According to the USAD, in general, moldy foods should be discarded, Foods with high moisture content can be contaminated below the surface. Moldy foods may also have bacteria growing along with the mold.


  • Hard salami and dry-cured country hams Some salamis — San Francisco, Italian, and Eastern European types — have a characteristic thin, white mold coating which is safe to consume; however, they shouldn't show any other mold. Dry-cured country hams normally have surface mold that must be scrubbed off before cooking.
  • Hard cheese (not cheese where mold is part of the processing) can be used. Cut off at least 1 inch around and below the mold spot (keep the knife out of the mold itself so it will not cross-contaminate other parts of the cheese). After trimming off the mold, re-cover the cheese in fresh wrap.
    Molds are used to make certain kinds of cheeses and can be on the surface of cheese or be developed internally. Blue veined cheese such as Roquefort, blue, Gorgonzola, and Stilton are created by the introduction of P. roqueforti or Penicillium roqueforti spores. Cheeses such as Brie and Camembert have white surface molds. Other cheeses have both an internal and a surface mold. The molds used to manufacture these cheeses are safe to eat.
  • Cheese made with mold (such as Roquefort, blue, Gorgonzola, Stilton, Brie, Camembert) should be discarded if they are soft cheeses such as Brie and Camembert and they contain molds that are not a part of the manufacturing process. If surface mold is on hard cheeses such as Gorgonzola and Stilton, cut off mold at least 1 inch around and below the mold spot and handle like hard cheese.
  • Soft cheese (such as cottage, cream cheese, Neufchatel, chevre, Bel Paese, etc.) 
  • Crumbled, shredded, and sliced cheeses (all types) with mold should be discarded. Foods with high moisture content can be contaminated below the surface. Shredded, sliced, or crumbled cheese can be contaminated by the cutting instrument. Moldy soft cheese can also have bacteria growing along with the mold.
  • Firm fruits and vegetables, with low moisture content (such as cabbage, bell peppers, carrots, etc.), can be used but cut off at least 1 inch around and below the mold spot (keep the knife out of the mold itself so it will not cross-contaminate other parts of the produce).
  • Soft fruits and vegetables, (such as cucumbers, peaches, tomatoes, etc.) with mold should be discarded because fruits and vegetables with high moisture content can be contaminated below the surface.

  • In poor countries people sometimes consume corn and other grains contaminated with aflatoxin, a type of mycotoxin that can cause liver cancer.

How do you know if you have a mold problem?
Large mold infestations can usually be seen or smelled.

Preventing Mold
Routinely inspect buildings for water damage and visible mold. Correct conditions causing mold growth (e.g., water leaks, condensation, infiltration, or flooding) to prevent mold growth.

Prevent mold growth by:

  • Controlling humidity levels as low as you can—between 30% and 50%–all day long with an air conditioner or dehumidifier if needed.
  • Promptly fixing leaky roofs, windows, and pipes;
  • Thoroughly cleaning and drying after flooding;
  • Ventilating your home well; especially vent shower, laundry, and cooking areas with exhaust fans to outside of your home;
  • Consider not using carpet in rooms or areas like bathrooms or basements that may have a lot of moisture.

Should the mold growing in a home be tested?
According to the CDC, if you can see or smell mold, a health risk may be present. You do not need to know the type of mold growing in your home, and CDC does not recommend or perform routine sampling for molds. Standards for judging what is an acceptable, tolerable or normal quantity of mold have not been established. Sampling for mold can be expensive, and standards for judging what is and what is not an acceptable quantity of mold have not been set. The best practice is to remove the mold and work to prevent future growth.  No matter what type of mold is present, you should remove it. Since the effect of mold on people can vary greatly, either because of the amount or type of mold, you cannot rely on sampling and culturing to know your hea risk.

How do you get rid of molds?
Mold growth, which often looks like spots, can be many different colors, and can smell musty.  Color is not an indication of how dangerous a mold may be.  Any mold should be removed and the moisture source that helped it grow should be removed.

The CDC makes the following recommendations:

  • First eliminate water or moisture. This is the first problem to address.
  • Remove moldy items from living areas.  Once mold starts to grow in carpet, insulation, ceiling tiles, drywall, or wallboard, the only way to deal with the problem is by removal and replacement. It is important to properly clean and dry the area as you can still have an allergic reaction to parts of the dead mold and mold contamination may recur if there is still a source of moisture.
  • Remove or replace carpets and upholstery that have been soaked and cannot be dried promptly.
  • Clean up and dry out your home thoroughly and quickly (within 24-48 hours) after any flooding.  Dig out mud and dirt.  Use a wet vacuum to remove remaining dirt. Scrub cleanable surfaces (such as wood, tile, stone) with soapy water and a bristle brush.  Thoroughly clean all hard surfaces (such as flooring, molding, wood and metal furniture, countertops, and sinks) with water and dish detergent. Dry surfaces quickly and thoroughly after cleaning. If you have a fan, air conditioner or dehumidifier that wasn’t affected by flooding use it to help the surfaces dry after you finish cleaning.
  • Mold growth can be removed from hard surfaces with commercial products, soap and water, or a bleach solution of no more than 1 cup (8 ounces) of bleach in 1 gallon of water to kill mold on surfaces.

  • If you choose to use bleach to clean up mold:

  • Never mix bleach with ammonia or other household cleaners. Mixing bleach with ammonia or other cleaning products will produce dangerous, toxic fumes.
  • Open windows and doors to provide fresh air.
  • Wear non-porous gloves and protective eye wear.
  • Small areas (such as a shower, or an area the size of a door) can often be cleaned by residents, but larger areas might need more professional help.   Always follow the manufacturer’s instructions when using bleach or any other cleaning product.

If you have an extensive amount of mold and you do not think you can manage the cleanup on your own, you may want to contact a professional who has experience in cleaning mold in buildings and homes.

Are there any circumstances where people should vacate a home or other building because of mold?
These decisions have to be made individually. If you believe you are ill because of exposure to mold in a building, you should consult your physician to determine the appropriate action to take.


U.S. Centers for Disease Control and Prevention: Mold cdc.gov/mold
U.S. Environmental Protection Agency: Mold epa.gov/mold
National Institute of Environmental Health Sciences website and search on mold
Molds on foods–Are they dangerous? U. S. Department of Agriculture. https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/molds-food-are-they-dangerous#:~:text=If%20food%20is%20covered%20with,moldy%20food%20might%20have%20touched

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