Excess Mois ture in the H o m e

A Breeding Ground for

Potent Asthma Triggers

By Teresa Them

bronchial hyperreactivity and respira- tory symptoms in asthmatic children and adolescents. Adolescents were more than five times as likely to have asthma attacks if their disease was trig- gered by allergens and more than 16 times as likely if they lived in a damp home. Nighttime wheezing and short- ness of breath also were linked to dampness in the home (Thorax

1998:53:1035-1040). Children, the elderly, and those with allergies and lung diseases are particularly suscepti- ble to such biological agents in indoor air. In a house where a person has asthma or allergies, reducing levels of indoor moisture just makes sense.

The primary sources of moisture- related problems in the home include walls, the roof and the foundation, according to David L. Johnson, vice chairman of the Department of Occupational and Environmental Health in the College of Public Health at the University of Oklahoma Health Sciences Center. Outdoor moisture readily enters the home from areas that are not well-sealed. These include leaks in or around roofs, vents, sky- lights, doors, windows, and cracks or leaky seams in basement walls. Moisture can also originate from indoor sources, such as leaky pipes, and heating, ventilation and air condition- ing systems. The lack of adequate ven-

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titation in rooms where daily activi- ties raise moisture levels--such as bathrooms, kitchens and spas--keeps water vapor in the house instead of venting it outside. Basements, too, are notorious for being damp. Also, if you have standing water in the house, you can be sure molds are colonizing very close-by.

A good rule of thumb for those with allergies and asthma is to pre- vent additional moisture from enter- ing the home. For example, house humidifier systems or room humidi- fiers should not be used. Do not have carpets steam cleaned. Also, an increasingly recognized source of dampness--particularly in new homes--is carpeting installed directly on concrete floors. This carpeting may remain damp much of the time due to moisture from the concrete.

M o l d s

Excess moisture levels and wet surfaces provide molds with the perfect environment in which to thrive. Although dormant at times, molds start growing and reproducing once conditions are right. They reproduce by releas- ing microscopic spores, which ride air currents through the house until attaching to new growth mediums. It is while these spores are airborne that they cause us problems, for they are easily inhaled.

Unfortunately, molds are fond of many build-

ing materials and interior home fin- ishes, which often makes getting rid of the mold a challenge. For example, ceiling tiles, insulation, wood and wood products, drywall, carpet, wall- paper (especially vinyl), fabric and upholstery, are all known for harbor- ing mold in houses.

Dr. Johnson cautions that there are items in the home that, once

molded, are molded forever. "This includes carpet, upholstered furni- ture, fabrics, gypsum board walls, wallpaper, wood--any porous materi- al," he explains. "If these items stay wet for more than 24 hours, they wilt mold. Then no amount of washing will get rid of the mold spores perma- nently." Sometimes gypsum board walls can be scraped, cleaned, sealed with a barrier primer and then paint- ed, which kills surface mold and seals in the rest. However, if water damage is extensive and molds are growing inside the walls, surface cleaning will not stop that growth. Dr. Johnson says that in such cases, it is best to take down the walls, clean and seal the inside stud walls and replace the drywall. "This is expensive, but it is the only way to eliminate the source and stop the mold from spreading," he explains.

By controlling the relative humidity level in a home (the amount of moisture in the air as a percentage of what the air can hold) and immediately repairing sources of moisture, the growth of biological contaminants can be minimized. A relative humidity of 30 to 50 percent is generally recommended. Operate a dehumidifier in the basement or other damp areas, if necessary, to stay within the desired range. Be aware, however, that dehumidifier drip pans as well as air conditioner A-frames, coils and pans are perfect environ- ments for mold growth, io keep them clean and in good working order.

D u s t M i t e s

Keeping humidity low not only reduces mold growth, but also makes the home less hospitable to dust mites--the source of one of the most powerful allergens found in homes. Dust mites are microscopic spider- like organisms that live in our homes and feed on human skin dander (dead skin flakes). Upholstered furni- ture, mattresses, box springs,

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draperies, pillows and stuffed toys are all common quarters for dust mites and their waste material, which is highly allergenic. When these remains are in the home, they become air- borne and are easily inhaled.

Dust mite allergy is believed to plague 60 to 70 percent of people with asthma in the United States. Not only is dust mite allergen a major asthma and allergy trigger, but according to a recent report from the Institute of Medicine of the National Academies in Washington, DC, it may actually cause susceptible indi- viduals to develop asthma.

Keeping relative humidity in the home below 50 percent helps reduce dust mite populations, since they cannot live in such an environment. There is a catch, however. Dean A. Atkinson, MD, a board-certified allergist at the Oklahoma Allergy & Asthma Clinic, says that moisture from human perspiration accumu- lates in mattresses and box springs even when air humidity is low, allow- ing mites to live. Given that most people spend a good eight hours in their beds each night, this is where much of the exposure occurs, and where the focus on avoidance mea- sures needs to occur as well. (See sidebar for steps to reduce dust mite exposure.)

W h e n E n v i r o n m e n t a l C o n t r o l M e a s u r e s A r e n ' t E n o u g h

Since humidity is necessary for the growth of both molds and dust mites, controlling the humidity levels in the home is a measure that helps to reduce both contaminants. While making changes to your indoor envi- ronment may take some time, even small improvements will add up and result in a home environment that is cleaner and healthier for the entire family. If, despite stringent environ- mental control measures, you or a household member still has signifi-

cant asthma or allergy symptoms, talk to your health care provider. There are a number of ways to reduce aller-- gic symptoms, including adjusting medications and receiving allergy vac- cinations, when appropriate. This dual approach of improving the indoor environment to reduce aller-

gens and treating allergic symptoms is the most effective approach to more comfortable and healthier living.

Teresa Thorn is a freelance writer liv- ing in Oklahoma City, Oklahoma. She specializes in medical and health-relat- ed topics.

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