Mold
Mold and IAQ

Mold and IAQ  

What mold is
Sources of mold
Testing for mold
Health problems associated with mold
Decreasing exposure to mold
Dealing with mold after a flood
Other mold-related resources

What Mold Is

Mold and fungi are organisms with rigid cell walls but no chlorophyll, which grow wherever there is both water and a source of organic nutrition. The most common indoor molds are Cladosporium, Penicillium, Aspergillus, and Alternaria. All molds may cause allergy in humans. Some molds can produce certain chemicals, such as mycotoxins and volatile organic compounds (VOCs). Some of the VOCs produced, such as 3-methyl-1-butanol, 2-hexanone, 2-heptanone, 3-methylfuran, and 1-octen-3-ol might be toxic to people and animals.

Molds may release other volatile organic chemicals, referred to as microbial VOCs or MVOCs, with noticeable odors. These chemicals are known to have characteristic odors described as musty, moldy, and earthy. Often times the odor of molds can be detected even though visible mold is not. They may be the first indication of mold contamination. These MVOCs can be in wall cavities or other hidden areas of a home or building, and they can easily permeate construction materials and adsorb in porous materials and furnishings. Microbial VOCs themselves have been found to be associated with poor indoor air quality, and animal studies have shown them to be human irritants.

In nature, molds can be found on plants, foods, dry leaves, and other organic material. They are needed for breaking down dead material. However, because they are such small, microscopic organisms, they can travel through the air and get inside homes and buildings. As a result, molds will grow anywhere indoors where there is moisture and a food source. Many building materials provide this needed food source?many consist of cellulose materials that are particularly suitable for mold growth when they are wet. Examples include paper and paper products, cardboard, ceiling tiles, wood, and wood products. Other materials that also support mold growth include dust, paints, wallpaper, insulation materials, drywall, grease, soap scum, carpet (especially those backed with jute which is a plant fiber), carpet pads, draperies, fabric, and upholstery. Mold and fungi generally need a relative humidity of at least 60 percent to give them enough moisture to survive or significant moisture intrusion, regardless of humidity. When molds and fungi grow on building materials, they inevitably digest the materials, destroying the surfaces and ultimately weakening underlying structures.

Mold and fungi are a major indoor air concern. Companies specializing in indoor air complaints have seen an eight-fold increase in mold related complaints over the past five years. Mold may cause building occupants to experience building-related symptoms.1 As research strengthens the link between common molds and illnesses, insurance companies are afraid of the possible escalation of costs of cleaning up mold contaminations.

Sources of Mold

According to the Consumer Product Safety Commission (CSPC), surveys of large office buildings and homes in northern US and Canada show that 30 percent to 50 percent of them may have damp conditions which may encourage the growth and buildup of biological pollutants such as mold. Typically, fungi make up two-thirds of all of airborne, living organisms.2 Mold and fungi may be found wherever there is moisture and a food source. Some common places where mold has been found include:

  • Antique shops

  • Greenhouses

  • Saunas

  • Farms

  • Mills

  • Construction areas

  • Flower shops

  • Summer cottages

In addition to these places, mold spores drop on places where there is excessive moisture, such as where leakage may have occurred in roofs, pipes, walls, potted plants, or where there has been flooding. The following are sources of indoor moisture that may cause mold or fungus problems:

  • Regularly used furniture is a major source of fungal spores since Penicillium and Aspergillus have been found there.2

  • Flooding

  • Backed-up sewers

  • Leaky roofs

  • Damp basement or crawl spaces

  • Constant plumbing leaks

  • The can used to water house plants may generate large amounts of moisture

  • Unseasoned firewood

  • Steam from cooking

  • Yard work such as disturbing compost piles or mowing the lawn can increase outdoor mold counts greater than 1,000-fold3

  • Marked shade around the house, which can increase indoor mold counts fivefold3

  • Shower/bath steam and leaks, especially on shower curtains

  • Wet clothes on indoor drying lines

  • Clothes dryers vented indoors

  • Combustion appliances (e.g. stoves) not exhausted to the outdoors

  • Carpet directly on cement floors may absorb moisture and as a result encourage mold growth

  • Stagnant water that has accumulated in:

    • Ducts

    • Humidifiers

    • Dehumidifiers

    • Air-conditioners

    • Drain pans/drip pans under cooling coils (as in refrigerators)

  • Where water has collected on ceiling tiles, carpeting, or insulation

Testing for Mold

Testing can identify the presence, concentration, and type of mold you may have. This may be helpful if you have large, contaminated areas (more than 10 sq ft to 20 sq ft) and want to know how extensive cleanup efforts might be and if special safeguards may be needed. For example, Stachybotrys is a black mold and when found covering more than a few square feet and growing on a (cellulose) surface, such as wood, cardboard, wallboard, ceiling tile and paper, could be a serious health risk. You should have this mold analyzed before proceeding with cleanup. If not, testing can become quite extensive and expensive.

If testing needs to be done, choose a laboratory that specializes in environmental mold and fungi and make sure that the laboratory is accredited by the American Industrial Hygiene Association's EMLAP program. It is important to know what species of mold is growing. Certain species may be more common than others. Just knowing that a mold is Cladosporium, for example is not enough. You need to know the particular species, such as Cladosporium sphaerospermum. In general, moldy materials will contain many different molds. The laboratory can assist in understanding what is normal and what is not. They can also help in establishing a sampling strategy to address the particular situation. It is important to remember that dead mold spores are just as allergenic as those that are actively growing. Culture sampling alone may not be adequate.

Culturable mold or mold spores are measured in colony forming units per cubic meter of air (CFU/m3) or particles per cubic meter (p/m3)?the number of spores or particles in a one-meter cube of air. There are no specific standards for levels of mold spores. Airborne levels indoor must be compared to the outdoor air. Even very low levels of certain molds can be hazardous. Higher levels of common outdoor molds may be normal. Mold problems can happen throughout the year, but may be escalated during rainy seasons or periods of high temperature and high humidity. Though you would need to have special testing conducted to know the exact concentration and type of mold, remember that, if you can see or smell it, the concentration is great enough that you should take steps to eliminate the excess moisture, and clean up and remove the mold. Appropriate safety precautions should be used in mold removal.

Health Problems Associated with Mold

Health problems caused by mold can be acute, which occur immediately or within a few days of exposure. Health problems may also be chronic, which are long-term health effects that might not occur immediately.

Acute health problems associated with unusual indoor mold exposure include:

  • Irritated eyes, nose and throat

  • Headache

  • Difficulty with concentrating or short-term memory

These symptoms together are often called sick building syndrome, but are more correctly referred to as building-related symptoms. Generally, this collection of symptoms completely resolves when the sufferer is removed from exposure.

The chronic conditions known to be associated with unusual indoor mold exposures are the allergic respiratory diseases:

These diseases may permanently worsen the health of persons affected even after they have been removed from exposure. Mycotoxin-induced diseases have been postulated, but scientific consensus about the nature of these diseases has not been reached.

Decreasing Exposure to Mold

First, do not rely on natural ventilation to reduce exposure to mold spores. Natural ventilation improves indoor air quality, but it has several limitations. It is an inefficient means to dilute contaminants in a home because the air is not uniformly distributed and the flow cannot be controlled. Increased ventilation could also increase pollen and mold spore levels, if outdoor counts are elevated. 4

  • Maintain relative humidity between 40 percent and 60 percent.

  • Keep the home clean.

  • Don't over water plants and keep them healthy.

  • Repair insulation defects.

  • Cover pots when cooking.

  • Properly maintain and run exhaust fans when cooking and bathing to help control humidity; run the fan 15 minutes after bathing.

  • Do not hang wet laundry indoors.

  • Vent the dryer to the outside.

  • Buy a hygrometer to monitor interior humidity levels, especially along exterior walls and in basements.

  • Use dehumidifiers in basements and other areas where humidity is difficult to control by ventilation alone.

  • Use an air-conditioner or a dehumidifier during humid months.

  • Heat all rooms during the winter.

  • Clean refrigerator drip pans regularly according to manufacturer's instructions. If refrigerator and freezer doors do not seal properly, moisture may build up and mold can grow. Remove any mold on door gaskets and replace faulty gaskets.

  • Use mold inhibitors which can be added to paints.

  • Provide extra ventilation if green lumber or wet wood is used for construction.4

  • Use double or triple-paned windows to help with condensation problems. A storm window installed on the inside works better than one installed on the outside.

  • Clean bathroom with mold killing product.

  • Buy mold-resistant shower curtains.

  • Do not carpet bathrooms.

  • Install high-efficiency air filters in air-handling systems.

  • Put high-efficiency particulate air (HEPA) bags on your vacuum cleaner or install HEPA filters on a central vacuum system. A central vacuum system is the preferable way to vacuum since it exhausts air outside which helps reduce the spread of indoor pollutants.

  • Empty and clean sources of standing water (humidifiers, dehumidifiers, and air-conditioners) regularly with disinfectants according to manufacturers' instructions. Do not forget the drip pan under the refrigerator since this can be a big source of mold. Avoid cool-mist humidifiers. Preferred are steam-generating humidifiers or air-to-furnace humidifiers, cleaned regularly.

  • Cover exposed earth in basement or crawl space with a heavy plastic vapor barrier .

  • Ventilate crawl spaces and basements during warm weather.

  • Prevent seepage into the home by correcting roof, gutter and drainage problems.

  • Use exhaust fans above the stove and in the bathroom that vent to the outside. Make sure the exhaust fans are working correctly since some are accidentally wired backwards. To test it, light a match, turn on the fan, and blow out the match. If the smoke gets sucked up, it is working properly. If the smoke falls downward, call the electrician and have it rewired.

  • Inspect your home for signs of elevated humidity including:

    • A musty smell

    • Moisture condensation on windows and walls

    • Cracking or staining of plasterboard

    • Drywall tape loosening

    • Wood warping

    • Visible mold growth on books, shoes, or other items

    • Peeling paint

  • Areas that have been soaked by water leaks should be inspected for water damage.

  • Repair any leaks in pipes or roofs.

  • If you find any wet areas in your home, take care of it within 24 hours. If you cannot clean the materials, you may need to throw them away.

  • Clean and disinfect the basement floor drain regularly.

  • Do not finish a basement below ground level unless all water leaks are patched and outdoor ventilation and adequate heat to prevent condensation are provided.

Dealing with Mold After a Flood

If you have areas of your home or workplace that suffered major flood or water damage, you must take all proper precautions to clean up the affected materials. That is because during the cleaning of mold damaged materials, mold counts are typically 10 to 1000 times higher than background levels. A manager at a hotel learned this the hard way. One day he got a call that there was a major leak in one of the rooms. When the walls were ripped open, there was foul-smelling mold (Aspergillus) everywhere. For a year, he worked to rid his hotel of the mold. The mold landed in his lungs, caused chronic inflammation of his airways, and eventually led to a medical diagnosis of hypersensitivity pneumonitis. This condition further scarred his lungs and eventually progressed into pulmonary fibrosis, a disease that is painful, debilitating, and sometimes even fatal.5

For minor wet and/or moldy areas:

  • Identify and correct the moisture source (e.g. leaky roof or window).

  • Clean up wet areas within 24 hours since mold will grow within 24 to 48 hours.

  • Wear personal protection like eye protection, dust mask, and rubber gloves before beginning any minor cleanup.

  • Remove any moldy materials by bagging and discarding them.

  • Wash the area with soap and water before disinfecting.

  • Disinfect the area using a solution of 10 percent household bleach (e.g., 1 to 1½ cup bleach per gallon of water). Using bleach straight from the bottle will not be more effective.

  • Apply disinfectant with a sponge or spray bottle and let it sit for 15 to 20 minutes before cleaning.

  • Let cleaned areas dry overnight and use ample ventilation.

Remember that dead mold spores can also be allergenic. If mold contamination is extensive, materials need to be replaced.

References

  1. USA Today. Finding causes of sick building syndrome. Aug 1999;128(2651):13.

  2. Trudeau WL, Fernández-Caldas E. Identifying and measuring indoor biologic agents. J Allergy Clin Immunol. 1994 Aug;94(2 Pt 2):393-400.

  3. Seltzer JM. Biologic contaminants. Occupational Medicine: State of the Art Reviews. 1995;10(1):1-25.

  4. Fernández-Caldas E and Trudeau WL. Environmental control of indoor biologic agents. J Allergy Clin Immunol. 1994 Aug;94(2 Pt 2):404-412.

  5. Conlin M, Carey J. "Is Your Office Killing You." Business Week. June 5, 2000;issue #3684:114-128.

Other Mold-Related Resources

  • Flannigan B, Morey PR. Control of moisture problems affecting biological indoor air quality: International Society of Indoor Air Quality and Climate, Ottawa, Canada, ISIAQ Guideline TF1-1996. 1996. www.isiaq.org

  • Health Canada: Fungal Contamination in Public Buildings: A guide to recognition and management. 1995.

  • Horner WE, Lehrer SB, Salvaggio, JE. Aerobiology. In: Lockey RF, Burkhartz SC. Allergens and Allergy Immunotherapy, 2nd ed. New York, NY: Marcel Dekker, 1999:53-72. (212) 696-9000

  • Macher J, et al., eds. Bioaerosols: Assessment and Control. Cincinnati, OH: ACGIH, 1999. (513) 742-6163

  • Miller JD, et al. Fungi and Fungal Products in Some Canadian Homes. International Biodeterioration 1988;24:103-120.

  • Morey PR, Horner WE, Epstien BL, Worthan AG, Black MS. Indoor Air Quality in Nonindustrial Occupational Environments. In: Harris RL, ed. Patty's Industrial Hygiene, 5th ed. New York, NY: John Wiley & Sons, 2000:3149-3241.

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Updated May 17, 2002