There's no one solution that will eliminate every contaminant. However, a home can be made safer and more comfortable through a four-pronged approach: eliminating the source, improving ventilation, cleaning the house frequently, and having the heating, ventilation and air-conditioning (HVAC) system inspected regularly.
Types of Pollutants Indoor pollutants can be grouped into several categories. Biological contaminants include mold, mildew, dust mites, viruses, animal dander (skin flakes) and animal fur. Household pets; poorly maintained humidifiers and dehumidifiers; and wet or moist structures, furnishings and bedding are potential sources.
Unvented or malfunctioning gas appliances, wood stoves and tobacco smoke can produce carbon monoxide and nitrogen dioxide, while respirable particles (particulates) result from house dust, pollen, cleaning sprays, tobacco smoke, fireplaces, woodstoves, unvented gas or space heaters, and kerosene heaters. Radon is a colorless, odorless, radioactive gas that is released as uranium breaks down in the soil or rock underneath the house. The gas seeps through dirt floors, cracks in concrete walls and floors, and floor drains, and can sometimes enter a home through well water and building materials. Asbestos, normally found in older homes, is a mineral fiber that was once used in a variety of building materials for insulation and as a fire retardant.
The U.S. Environmental Protection Agency and Consumer Product Safety Commission have banned a number of asbestos-containing products, and manufacturers have voluntarily limited its use. Deteriorating, damaged, or disturbed insulation, fireproofing and floor tiles are among the possible sources. If asbestos fibers are released into the air and inhaled, there is a long-term risk of cancer. Statistics confirm that indoor air pollution poses a serious health threat.
According to the EPA, levels of air pollution inside the home can be two to five times higher - and occasionally 100 times higher - than outdoor levels. The EPA states that six out of 10 homes and buildings may be "sick" and hazardous to occupants. Furthermore, the American Journal of Respiratory and Critical Care Medicine reports that asthma and allergies are increasing at epidemic proportions, affecting one out of five Americans - which isn't surprising given the EPA's claim that we spend as much as 90 percent of our time indoors. Symptoms of poor indoor air quality include headaches, nausea, lethargy, impaired vision, sinus infections, and eye, nose and throat irritation. However, people may not experience the effects immediately.
Radon exposure, for example, carries a long-term risk of lung cancer. Also, some household members are more susceptible than others, such as infants and toddlers, pregnant women, the elderly, and those who already have chronic ailments, such as allergies and asthma. Why Houses Get Sick Like any living thing, mold, mildew and dust mites require food, air and water to survive, says John Bower, founder of the Healthy House Institute in Bloomington, Ind. "If you remove one of those things, they won't grow," Bower says. "It's hard to remove air, and they eat a variety of things, but moisture can be controlled. It doesn't have to be moisture you can see; it can just be a high relative humidity." Until 25 or 30 years ago, houses were more loosely constructed, he says. "If moisture collected inside a building cavity or in a corner, there was so much ventilation it tended to dry things out pretty quickly. But as houses have gotten tighter, they're less forgiving, so you can get moisture problems you may not have had in the old, leaky farmhouse."
Pollutants can work their way into carpet fibers and upholstery, making it difficult to keep them clean. In fact, it's virtually impossible to rid conventional carpeting of all pollutants, which is why Bower and other healthy-house experts recommend hard-surface flooring, such as ceramic tile and wood. Some indoor pollutants are easy to identify. For instance, there may be an odor such as sewer gas from a malfunctioning septic system, propane from a leaking gas fixture, or a mustiness that indicates the presence of mold. Moisture can be seen condensing on windows, or sometimes on drywall, during the heating season. If you find mold or fungus in a closet or other area that doesn't get much ventilation, there's too much moisture in the home.
Other pollutants, such as radon, don't produce an odor or other obvious sign. The only way to tell if the gas is present is to use a measuring device. Many inexpensive, do-it-yourself radon test kits can be obtained by mail or at hardware stores and other retail outlets. Make sure the kit has passed the EPA's testing program or is state certified. You can also hire a trained contractor to do the testing for you. Call your state radon office for a list of qualified contractors in your area (for a list of offices, call 800-SOS-RADON). Most radon problems are easily fixed, but high levels require technical knowledge and special skills. Your state radon office can help you find a radon-reduction contractor. The presence of pollutant sources can alert you to potential problems. Unvented kerosene heaters, unvented gas ranges and gas ranges that are used for heating and cigarette, cigar, or pipe smoking all produce unhealthy levels of fine particulates and gases.
Undamaged asbestos-containing material should be left alone but periodically inspected for deterioration. Always use a trained, qualified contractor for asbestos containment or removal, especially if you are planning to have your house remodeled and there's a possibility the material may be disturbed in the process. Steps to a Solution Mold thrives in basements when warm summer air hits the cool concrete or masonry walls, causing moisture to condense on the surface (just like a glass of ice water on a hot day).
To prevent this from happening, either insulate the basement walls or treat the area the same way as upstairs living space. "It should have the air changed regularly; it should be kept warm, and it should be kept dry," Bower says. "You need good drainage on the outside and good dampproofing." Ideally, basements should be insulated, heated and air-conditioned - or at least dehumidified, he says. Manufacturers such as G-P Gypsum are introducing building materials that don't provide a food source for mold. One of G-P's newest products is a wallboard with a glass surface that resists mold growth. "Ultimately, mold can grow on anything, even glass," says Chris Beyer, marketing manager for G-P Gypsum. "But our product has been tested under extremely wet conditions and didn't develop mold." Two versions are available: DensArmor, which has glass on the wall cavity side and paper on the finish side, and DensArmor Plus, which has fiberglass on both sides.
For a 2,300-square-foot house, DensArmor costs approximately $800 more than conventional wallboard, while DensArmor Plus costs $1,500 to $1,800 more. While pet dander can aggravate allergies, getting rid of the pet is not an option for most people. The next best thing is to keep the house clean, vacuum often and launder bed linens, blankets, and furniture slipcovers frequently in hot water. Bathe and groom pets regularly to remove dead hair and skin. Dust mites are found wherever humans spend a great deal of time, such as beds and sofas. They live on human skin flakes, and their excretions can provoke an allergic reaction. Due to their microscopic size, dust mites can easily work their way into a pillow or mattress, but a number of companies, such as Cuddledown of Portland, Maine, sell mite-proof, machine-washable covers for bedding.
Cuddledown President Chris Bradley recommends protectors for pillows made of latex foam, fiberfill or any other material with an open weave that would allow dust mites to penetrate. Down pillows and comforters are an exception; they're naturally mite-proof because the fabric that holds the down inside is very tightly woven, says Bradley. "A dust mite is too big to go through that fabric."
Upgrading the furnace filter is another way to lower the particle count in your home. "The average furnace filter is maybe 3 or 4 percent efficient, at most, at capturing the particulates that tend to bother people," says Bower, who recommends a medium-efficiency filter, preferably the pleated kind. It won't capture microscopically small particles, but it will trap allergens such as pet dander and mold spores. "Electrostatic precipitators are actually better at filtering, but only when they're clean, and within a few days they may get dirty enough that the efficiency drops off a lot," Bower says. "You can (also) get HEPA (high-efficiency particulate air) super filters, but that's overkill for most people."
Medium-efficiency filters are optimal in forced-air heating and cooling systems where the fan runs 24 hours a day. That can be an expensive proposition considering the cost of electricity. However, there are new furnaces on the market with fan motors (called ECMs, or electrically commutated motors) that run more efficiently at a lower speed.
The furnaces cost more up front but are much cheaper to operate over the long haul. "If you're replacing your forced-air system or building a new house, you'll probably want to incorporate that kind of fan motor," he says. While frequent vacuuming helps, the filter in some conventional vacuum cleaners will only pick up large particles. Small particles are drawn through the filter and blown out the exhaust back into the room. "Now you can get vacuum cleaners with better-than-average filters, but I think the best (solution) is a central vacuum system," Bower says. "It's actually more convenient to use because you don't have to drag anything but a hose around with you." Be sure to buy a system that vents to the outdoors, he says.
Bower believes that portable air-cleaning machines work best in one room with the door closed and the unit running continuously. However, if the home has a forced-air heating and cooling system, air from other parts of the house will enter the room through the register, defeating the purpose of the machine. "That's where a whole-house (air-cleaning) system would be better," he says. The Association of Home Appliance Manufacturers has developed an American National Standards Institute-approved standard for portable air cleaners that may be useful in estimating the effectiveness of such units. Under the standard, room air-cleaner effectiveness is rated by a clean-air delivery rate (CADR) for each of three particle types in indoor air: tobacco smoke, dust and pollen. For more information about the rating program, contact AHAM at 202-872-5955 or visit www.aham.org. A complete listing of current AHAM-certified room air cleaners can be obtained from the CADR website, www.cadr.org.
Household cleaning products are designed to remove dust, dirt, bacteria, germs and odors, but may leave behind harmful chemicals that can pollute the air. These include aerosol sprays, chlorine bleach and insect repellent. Such products should only be used for short periods of time and in small quantities. You can also buy less-toxic versions, Bower says. "They have less solvent, perfume and other things that bother chemically sensitive people," he says. In addition, the American Lung Association Health House website (www.healthhouse.org) offers a list of effective, chemical-free cleaning alternatives, such as a lemon juice and water solution to cut grease. Indoor air quality is a complex subject, but fortunately there is a great deal of information available. In addition to the Health House site, visit the EPA at www.epa.gov for a detailed overview and recommendations for dealing with each type of pollutant. Susan Bady is a freelance writer based in Chicago.