Molds in the Environment FAQ

Q: What are molds?
A: Molds are fungi that can be found both indoors and outdoors. No one knows how many species of fungi exist but estimates range from tens of thousands to perhaps three hundred thousand or more. Molds grow best in warm, damp, and humid conditions, and spread and reproduce by making spores. Mold spores can survive harsh environmental conditions, such as dry conditions, that do not support normal mold growth.

Q: What are some of the common indoor molds?
A:

  • Cladosporium
  • Penicillium
  • Alternaria
  • Aspergillus

Q: How do molds affect people?
A: Some people are sensitive to molds. For these people, exposure to molds can cause symptoms such as nasal stuffiness, eye irritation, wheezing, or skin irritation. Some people, such as those with serious allergies to molds, may have more severe reactions. Severe reactions may occur among workers exposed to large amounts of molds in occupational settings, such as farmers working around moldy hay. Severe reactions may include fever and shortness of breath. Some people with chronic lung illnesses, such as obstructive lung disease, may develop mold infections in their lungs.

Q: Where are molds found?
A:Molds are found in virtually every environment and can be detected, both indoors and outdoors, year round. Mold growth is encouraged by warm and humid conditions. Outdoors they can be found in shady, damp areas or places where leaves or other vegetation is decomposing. Indoors they can be found where humidity levels are high, such as basements or showers.

Q: How can people decrease mold exposure?
A:Sensitive individuals should avoid areas that are likely to have mold, such as compost piles, cut grass, and wooded areas. Inside homes, mold growth can be slowed by keeping humidity levels between 40% and 60%, and ventilating showers and cooking areas. If there is mold growth in your home, you should clean up the mold and fix the water problem. Mold growth can be removed from hard surfaces with commercial products, soap and water, or a weak bleach solution (1 cup of bleach in 1 gallon of water).

Following are some specific recommendations for decreasing mold exposure:

  • Keep the humidity level in the house between 40% and 60%.
  • Use an air conditioner or a dehumidifier during humid months.
  • Be sure the home has adequate ventilation, including exhaust fans.
  • Add mold inhibitors to paints before application.
  • Clean bathrooms with mold killing products.
  • Do not carpet bathrooms and basements.
  • Remove or replace previously soaked carpets and upholstery.

Q: What areas have high mold exposures?
A:

  • Antique shops
  • Greenhouses
  • Saunas
  • Farms
  • Mills
  • Construction areas
  • Flower shops
  • Summer cottages

Q: I found mold growing in my home. How do I test the mold?
A:Generally, it is not necessary to identify the species of mold growing in a residence, and CDC does not recommend routine sampling for molds. Current evidence indicates that allergies are the type of diseases most often associated with molds. Since the susceptibility of individuals can vary greatly either because of the amount or type of mold, sampling and culturing are not reliable in determining your health risk. If you are susceptible to mold and mold is seen or smelled, there is a potential health risk; therefore, no matter what type of mold is present, you should arrange for its removal. Furthermore, reliable sampling for mold can be expensive, and standards for judging what is and what is not an acceptable or tolerable quantity of mold have not been established.

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