Ohio State University Extension

Community Development

700 Ackerman Rd., Suite 235, Columbus, OH 43202-1578

Indoor Air Quality: Molds and Dust

CDFS-191-96

Jacqueline LaMuth

Research indicates that people spend approximately 90% of their time indoors. So, the risks to human health may be greater due to exposure to air pollution indoors than outdoors. Further, those people who may be most susceptible to the adverse effects of indoor air pollution are those who tend to spend the greatest amount of time indoors. Such groups include young children, the elderly and the chronically ill. This fact sheet will examine molds, house dust, and other biologicals that can reduce the quality of indoor air. It will offer suggestions for minimizing, eliminating and preventing contact with molds and dust.

Dust and Indoor Air Quality Problems

The amounts and kinds of contaminants that are suspended in the air determine air "quality." Potential sources of indoor air pollution fall into several categories including: nitrogen dioxide, respirable particles (particles that can be drawn into the lungs), formaldehyde, asbestos, organic gasses, pesticides, lead, and biologicals. Biological contaminants are naturally occurring air pollutants that come from living (biological) sources; they are commonly called "house dust."

House dust is not dust that blows in from the outside. House dust is produced indoors from several sources:

1. The breakdown and release of plant and animal materials used in the home. These contaminants include such items as feathers, cotton, wool, jute, hemp, and animal hairs. They come from clothing, carpets, rugs and furniture.
2. The disintegrated stuffing material from mattresses, pillows, quilts, and upholstered furniture. Prolonged use seems to cause these resilient fibers to weaken and eventually break down into particles small enough to be inhaled.
3. Human skin scales, animal dander, insect parts from cockroaches and dust mites, saliva, molds and mildew, bacteria, viruses, and pollen. As people go through their daily activities, particles that have settled onto the floor and other surfaces are stirred into the air.
4. Other contaminants deliberately introduced into the indoor environment. These can include tobacco smoke from pipes, cigars and cigarettes, cosmetic powders, baby powder and some powdered laundry detergents, aerosols such as air fresheners, and cleaning products with strong odors.

Problems with Buildings and Building Systems

Ventilation systems are designed and installed in buildings to replace stale, contaminated air with fresh air from the outside. Air enters and leaves a house in several other ways too. It can enter by infiltration, through construction joints and cracks around windows and doors, through the foundation, and crawl spaces. Air also enters through natural ventilation openings, such as open doors and windows. The rate at which outdoor air replaces indoor air is the "exchange rate." It measures how many times the complete volume of air inside the house is replaced with fresh outside air. In typical U.S. homes, the average exchange rate is 0.7 to 1 complete air exchanges per hour. In tight homes, the exchange rate can be as low as 0.02 complete air exchanges per hour. In leaky homes it may be as high as 2 complete air changes per hour.

During the past twenty-five years, interest in building energy-efficient buildings has increased. Some current construction practices can trap pollutants that normally form inside the house along with those brought inside with everyday traffic. Heating, cooling and ventilation systems that recycle existing indoor air and windows that do not open, can result in greater concentrations of indoor pollutants because they do not allow enough fresh outside air to dilute the trapped pollutants.

Dust Mites

Dust mites (Dermatophagoides Farinae) are microscopic spiderlike insects found everywhere. They are thought to be the principle irritant found in house dust when inhaled by sensitive people. During warm weather when the humidity is above 50%, they thrive and produce waste pellets. They live about 30 days and the female lays approximately one egg each day. In less than ideal conditions, they can go into dormancy. When they die their bodies disintegrate into small fragments which can be stirred into the air and inhaled by people in that environment.

Molds in the Air

Molds play an important part in life cycles. They assist with the rotting of organic materials. Some molds cause illness and some, such as penicillin, cure illness. Certain molds help to develop the flavor of wines and cheeses, while others can cause them to spoil.

Molds are persistent. They can live for years in a dormant state. To grow, the spores need moisture, warmth, still air, and a food source. When homes are dry, the spores are dormant. As soon as ordinary home humidity increases due to normal changing conditions like outdoor humidity or seasonally occurring basement seepage, the life cycle of the spores begins and the spores bloom and grow. As they mature, they produce more spores that are so tiny they can drift on air currents throughout the building. They eventually land on surfaces and settle into the tiniest cracks and crevices of carpets, furniture, draperies, insulation, rough textures and smooth surfaces.

Dirty heating and cooling ducts, wet carpets, damp upholstery and dirty air filters on air conditioners and furnaces become hiding places for molds making it difficult to completely rid a home of mold spores.

Affects on People's Health

Allergic reactions are the most common health problems that people experience regarding indoor air pollution. An individual can be affected by inhaling particles or vapors, by ingesting or eating it, and by having it come in contact with the skin. The effects may be immediate or not show up for years. Immediate responses that may be noted after a single exposure or repeated exposure include irritation of the eyes, nose and throat, headaches, dizziness and fatigue. These are usually short-term and treatable.

Molds can cause continuing health problems for individuals who may not realize they are mold sensitive. Health hazards range from infections to irritant and toxic type allergic reactions. Reactions to molds can result in a sneeze, itching, coughing, wheezing, shortness of breath and sometimes, chest pain.

Mold is measured in particles per cubic meter (pcm) - the number of spores in a one-meter cube of air. A mold count of 0-500 particles pcm is considered low, 500-1500 particles cpm is moderate, and a count of 1501 and greater qualifies as high. Mold problems are more common in summer and gradually decline from September through November.

Summary: Prevention

• Unless the room can be well ventilated, avoid the use of aerosols, including air fresheners, adhesives and cleaning solvents that release small particulates into the air.
• Clean the source producing an odor or ventilate the area. Deodorants "mask" the odor, they do not eliminate them.
• Use unscented cosmetic, toiletry, cleaning and laundry products.
• Wear rubber gloves, long pants, a long-sleeved shirt and a dust mask when conducting an activity that will stir up dust.
• Properly maintain flues and chimney of furnaces, hot water heaters and fireplaces to keep smoke from entering the living areas of homes.
• Check and clean refrigeration equipment annually to be sure the air intake and exhaust system are working correctly. In addition to changing filters and cleaning coils, remember the drop pan that is often hidden at the base.
• Avoid stove fans and other filter systems that recirculate the air rather than exhaust it to the outside of the home. Replace them with models that exhaust to the outside. If that is not possible, keep filters of recirculating models very clean.

Mold Growth When there is Water Damage

Molds are common; their spores are everywhere. Maintaining the relative humidity level in a building at 30-50% minimizes the growth of molds and other biologicals. Do not allow furnace and air conditioner air filters to become clogged; change them regularly. Clean and dry areas that become damp or wet within 24 hours to prevent molds from establishing themselves. Soaked carpeting presents special challenges. It must be professionally cleaned within 24 hours or it will be destroyed by the mold and bacteria that will grow in the fibers, backing and under the carpeting. If that happens, remove and throw away the carpeting and pad. Clean and disinfect the floor.

Tear out soaked wall materials, ceiling tiles, and wet insulation. Disinfect the area. Use protective eye wear, gloves and wear a mask. In the case of flooding, look above the flood line. Water may have run through materials and/or been absorbed to a higher level. Dry the area as quickly as possible. Use fans to bring in cold dry winter air and warm it by turning up the furnace. This air will absorb moisture quickly.

Vacuum the entire house and immediately discard the disposable bags. Steam clean all carpets and dry quickly. Discard potential sources of molds such as accumulations of old newspapers, boxes, and clothing.

The disinfectant recommended for mold removal is a solution of one part bleach to two parts water.

Commercial disinfectants are also available through janitorial supply stores. Use a household or garden sprayer and spray all surfaces that have been touched by flood water or have been soaked by water from some other source. Use a brush or broom to force the solution into crevices.

Removing contaminants from the air:

1. One of the most effective ways to reduce indoor contaminants is to control or remove them by filtering the air. Mechanical filters that use standard disposal fiberglass filters should be changed monthly. Permanent filters with baffles should be cleaned periodically. The most effective mechanical filter is a high-efficiency particulate (HEPA) filter. An electrostatic precipitator is an electric filter. These must be cleaned frequently to prevent the production of irritating ozone.
2. Encase mattresses in airtight covers. After vacuuming pillows, mattresses and box springs, encase them in zippered, airtight plastic or special allergen-proof fabric covers.
3. Replace comforters and pillows made with down feathers, kapok, and cotton with ones made with synthetic fibers such as Dacron and Orlon.
4. Wash bedding weekly in hot water (130 deg F to kill dust mites. Wash comforters and pillows regularly. Replace synthetic pillows every two to three years.
5. When possible, remove carpeting where dust mites, mold spores, animal dander and other particulates can accumulate. Carpeting laid over concrete floors tends to have more dust mites because of increased humidity. Replace carpeted floors with hardwood or linoleum. Wash scatter rugs and furniture covers regularly.
6. Vacuuming can stir dust into the air. Use high-quality vacuum bags and change them frequently. Wet mop or wet-wipe hard surfaces such as floors, walls and ceilings.

Summary

Although dust and molds are natural and commonly found both indoors and outdoors, they can cause illness and allergic reactions for those who are sensitive. While total elimination of these invisible contaminants is unrealistic, there are many ways to control the amounts that are present. Simple housekeeping habits and home maintenance practices can make a difference.