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Walnut Creek District


Molds are fungi that are found everywhere - both indoors and outdoors all year round. The terms fungi and mold are often used interchangeably, but mold is actually a type of fungi. Concern about indoor exposure to mold has increased along with public awareness that exposure to mold can cause a variety of adverse health effects. There are many thousands of species of mold and most if not all of the mold found indoors comes from outdoor sources. It seems likely to grow and become a problem only when there is water damage, high humidity, or dampness.

Molds produce and release millions of spores small enough to be air-, water-, or insect-borne. They can also produce toxic agents known as mycotoxins. According to the United States Department of Labor, Occupational Safety and Health Administration, spores and mycotoxins can have a negative effect on human health. Mold does not affect everyone, and different people are affected differently when mold is breathed or inhaled. People with allergies or asthma are more sensitive to mold.

Mold can range in color from white to green and orange to brown and black.

Health effects of mold

Mold exposure may cause:

  • cold-like symptoms
  • watery eyes
  • sore throat
  • wheezing
  • dizziness
  • and may trigger asthma attacks

Because mold spores are very small and can be easily inhaled, it is not safe to live in houses with high mold levels. Exposure to prolonged high spore levels may cause the development of an allergy to mold.

Types of people who are most severely affected by indoor mold growth include:

  • Infants and children
  • Elderly people
  • Individuals with respiratory conditions or sensitivities such as allergies and asthma
  • Persons having weakened immune systems (people with HIV infection, chemotherapy patients, organ transplant recipients)

Detections of Mold

Molds can usually be detected by a musty odor and discoloration of surfaces is common with mold growth.

If you see or smell mold, you have a problem. Reliable sampling for mold can be expensive since it requires special equipment and training. Testing is not generally recommended as a first step. Usually it is not necessary to determine what type of mold you have. All molds should be treated the same and regarded as potential health risks.

Causes of Mold Growth

Mold can grow in a home for various reasons including:

  • Flooding
  • Condensation - on windows or walls caused by indoor humidity that is high or surfaces that are cold (such as North-facing walls and moist summer air contacting air conditioned surfaces)
  • Poor ventilation in attics and closets
  • Overflow from tubs, sinks, or toilets
  • Excessive moisture from firewood stored indoors
  • Excessive humidifier use - increases relative humidity
  • Inadequate venting of kitchen and bath humidity
  • Improper venting of combustion appliances (such as kerosene and gas heaters)
  • Failure to vent clothes dryer exhaust outdoors (including electric dryers), or using indoor clothes lines
  • House plants -water from a large number of plants can generate large amounts of moisture.
  • Excessive moisture from inadequate de-humidification during air conditioning (oversized system)
  • Standing water found in condensate drains pans (refrigerator, air conditioner) and in crawl spaces
  • Leaky basement
  • Dripping pipes
  • Roofs in need of repair or faulty gutters
  • In areas of high relative humidity, additional precautions may be necessary to ensure that your home stays mold free, for example the use of vinyl wallpaper on exterior walls can cause vapor to be trapped inside your walls, thus creating excellent conditions for mold growth.
  • Avoid using carpeting in areas of the home that may become wet, such as kitchens, bathrooms and basements.

Clean Up and Removal of Mold

People can experience health effects when exposed to mold even if it is dead, so it must be removed. Killing it by applying a biocide such as chlorine bleach does not minimize health risks.

Anyone spending more than a brief time cleaning in a moldy environment should use a HEPA filter or N95 rated mask, and use gloves.

(Above information is from the Extension Disaster Education Network)