Mold in the Indoor Environment

There has been a great deal of publicity, fear and concern about the presence of mold in our homes, schools and businesses.  The news media have featured many stories about a species of mold that they have labeled “toxic black mold.”  Unfortunately, most of the articles and features are sensational, incomplete, or inaccurate.  For example, the particular mold species that has come to be known as “killer mold” or “toxic black mold” (Stachybotrus Chartarum) is rarely found in significant quantities in the indoor environment, and it requires a very special circumstances to grow. Further, the link between this particular mold species and illness is uncertain.  A study conducted in Cleveland in the mid-1990s appeared to link the presence of Stachybotrus Chartarum to pulmonary hemorrage in infants.  That findings of that study have since been disputed.

• Mold spores exist in the air all of the time. They are part of the natural world, and there    are present in the air inside and outside.

• Molds are very simple, single-celled organisms that grow by dividing themselves.  They grow rapidly under the right conditions, and they become dormant (form spores) when the conditions for their continued growth aren’t right.   Mold spores can live for a very long time in the dormant state.

• Some mold species produce by - products when they are growing that have been implicated as potential allergy and asthma triggers. Children, the elderly and people with diseases such as HIV, chronic respiratory conditions such as asthma and emphysema and immuno-suppressed individuals may be at a greater risk from higher than normal amounts of mold spores in the air  Mold spores themselves may trigger allergic reactions and asthmatic episodes. Some diseases, such as histoplasmosis, (a mold that grows in bird and bat droppings) can cause serious illness in workers who inhale VERY large numbers of the spores when they are removing contaminated materials in an enclosed space.

• Testing for mold is NOT generally recommended!  The typical mold test is conducted by collecting a given quantity of air from a room or building, and then taking it to a laboratory, where the mold spores are encouraged to grow.  The results are generally compared against a sample of the outside air that was collected at the same time.  However, there are no standards for an acceptable number of mold spores per unit of air in the United States, and using the outside air as a standard is often misleading, since the numbers can fluctuate widely, depending upon weather conditions.

Mold is everywhere. We cannot keep it from entering the indoor environment. Mold will grow on nearly any material, so we cannot deprive it of a food source.  The one way that we can control mold is to prevent it from getting enough water to grow.

Many scientists and physicians are conducting research on mold and its potential effects upon our health.  So far, we know that mold can cause health problems for some very sensitive people.  But we are all exposed to mold every moment of the day, and most people do not react to the mold spores that they inhale.  So is all of the concern about mold justified?  The answer to that question is, “”yes,” and “no.” 

We should be concerned about mold if:

• There is very high humidity in a building for an extended period of time.  Relative humidity above 50%  encourages the growth of mold. For this reason, poorly ventilated bathrooms and kitchens, and unvented dryers, can contribute enough moisture to the indoor air to allow mold to grow.  Poor air movement through a building may encourage mold to grow in buildings without air conditioning in the summer.

• There is evidence of a water leak from broken plumbing, a roof leak, a damaged gutter, or some other source. If the source of the water leak or intrusion isn’t corrected, the mold will return time and again. Water-saturated materials such as wallboard, carpeting, clothing and furniture  provide an ideal growth medium for mold.  Contaminated materials  should be removed and discarded.

• There is moisture condensing on windows or walls.  Condensation indicates that the warm, moist air in the building is contacting a much colder surface.  The moisture condenses from the air onto the walls and windows, much like it does on the outside of a cold glass on a hot summer day.  The condensation may indicate that there is very poor air movement in the space, that the walls and / or windows aren’t properly insulated, or that there is too much humidity in the air.  Many poorly insulated buildings develop heavy mold growth on the inner surface of the exterior walls during prolonged cold weather for this reason.

• There is poor air circulation in the room or building.  Blocked registers and returns reduce the airflow through a room.  Keep them open and free flowing.  Placing large furniture against an exterior wall can create a “cold spot,” especially in a poorly insulated building.  Keep the furniture about a foot from the wall, if possible.

• There is visible mold is growing on surfaces, or the air has a strong, musty odor.  Note: Not all mold colonies are black.  Some are red, pink, gray and green. But many mold species produce black colonies. Mold colonies have different textures, too. Some are smooth, others are shiny. And some are fuzzy-looking. Just because a mold colony is black does not mean it is Stachybotrus Chartarum!

• The amount of visible mold is extensive.  A few small patches of mold growing on a surface are not a serious concern. But just as if the area of visible mold is very large, all mold must be removed immediately. However, the methods for cleaning the mold vary with the size of the contaminated area.

• If there is extensive mold growth (more than 10 feet2) and someone in the building suffers from asthma, properly diagnosed and documented mold allergies, emphysema, or an immune disorder, it may be appropriate to remove them from the immediate area.

When NOT to be concerned about mold:

• There is no visible mold or musty odor.

• The amount of mold is small (<10ft2.) Small amounts of mold can be easily cleaned, using a good detergent, or a solution of 1 cup of household bleach to a gallon of water.  

What to do if there is a large amount of mold growing in a room or building:

• If there is more than 10 ft2 of mold in a space, the area should be isolated (everyone should leave it, except the people doing the clean up) until the source of the water is found and corrected.  Damaged or heavily contaminated absorbent materials should be removed and discarded.  Hard surfaces, such as concrete block, plaster and tile must be thoroughly cleaned.                           

For additional information please check these links:

US Environmental Protection Agency

http://www.epa.gov/iaq/molds/index.html
http://www.epa.gov/iaq/molds/moldguide.html
http://www.epa.gov/iaq/largebldgs/i-beam_html/ibeam.htm
http://www.epa.gov/iaq/