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Carpet
Carpet: A Haven For Unwanted Guests

Carpet: A Haven For Unwanted Guests Overview Issues with carpet Chemicals Dust mites Mold Preventing health problems associated with carpeting Reducing the problems associated with carpeting Overview Carpet is one type of floor covering that is commonly used in homes, commercial buildings, schools, cars, and public facilities. IAQ issues often associated with carpet range from odor and off-gassing of organic vapors from the carpet backing or adhesive, to retention of allergens from dust mites and pet dander. Carpet that is poorly maintained or water damaged may result in fungal contamination. Like many other household products and furnishings, new carpet can be a source of chemical emissions. Most carpet used in residential, public, and commercial settings consists of synthetic pile, usually nylon or olefin, cut pile or nylon tufted through a primary backing with a back coating of solvent-based adhesive. The loop of the tufted pile is set into a styrene-butadiene rubber (SBR) latex base, which is sandwiched between backings made of woven polypropylene or jute. Other common carpet types in schools and office buildings include carpet tiles usually made with a hard backing of polyvinyl chloride (PVC) or hydrocarbon resin. The new carpet odor that people may smell after carpet is installed is usually 4-phenylcyclohexene (4-PCH), which is a by-product of the styrene butadiene latex binder, used to hold the fibers to the backing. This chemical has a very low odor threshold, which means it can be in the air at very trace levels and still be detected by the human nose. Toxicology studies have shown that 4-PC is not a health hazard at the levels experienced from carpet, but that it does contribute an odor. Generally, the emissions from new carpet are at very low levels one week after installation and odors should go away within a 2-4 week period. There are carpets, formulated with different chemicals and backings that do not have this odor. Issues with Carpet New carpet may emit organic vapors from the solvents used in the manufacturing of the carpet itself as well as its latex backing and glues used to hold it down. In addition, carpet and other textiles in the home such as upholstery, bedding, and drapes are fleecy materials that can act as a "sink" for airborne pollutants and aerosols. Fleecy materials can absorb and potentially re-release pollutants into the air such as allergens, chemicals, and mold spores. These materials can be hosts to mold and dust mite growth if they are chronically exposed to dirt and moisture. Proper maintenance and environmental control in buildings can prevent this from occurring. Carpet tiles with PVC backing are sensitive to humidity and may have some plasticizers that react with moisture to produce sweet or "play dough" odors. This has been an issue in some buildings where the excessive moisture is present in the concrete sub floor.¹ Excessive moisture in the sub floor can also encourage mold growth on the back of carpet or in its fibers. Chemicals Carpet emits volatile organic compounds (VOCs), as do products that accompany carpet installation such as adhesives and padding. Some of the chemicals that might be emitted by glued carpet include:² Styrene 1,2-Dichloroethane Ethyl benzene Toluene 1,1,1-Trichloroethane Xylenes One VOC that is not a concern is formaldehyde, since formaldehyde is not added as an ingredient in the manufacturing process in the United States. In a study where 19 new SBR latex-backed carpets were tested, no formaldehyde emissions were detected.³ Sometimes formaldehyde emissions can be found from carpet removed form buildings. In these cases, the carpet most likely adsorbed formaldehyde from other building materials or sources in the building. Styrene usually has few immediate health effects, but it can be stored in body fat for up to 13 days after exposure. Butadiene, the other major chemical used in carpet latex, is found in greater amounts in other sources such as tobacco smoke, car exhaust, and combustion of other fossil fuels. The chemical latex used to make carpet should not be confused with natural latex that is used in surgical gloves and other products, which may trigger allergic reactions. Dust mites Dust mites can be found in some carpets in high humidity environments. Some studies show that loop carpet usually has eight percent to nine percent more dust mites than pile carpets. Additionally, it is easier to clean dust mites out of carpets that are coated with Teflon^® than carpets without Teflon^®.⁴ However, in most residential environments, bedding provides the primary source of exposure to dust mite allergens. Mold Mold can grow in carpet if it remains chronically damp or has been water damaged. If you have your carpets cleaned, you should make sure that they are dry within 24 hours to prevent mold growth. You should also provide plenty of ventilation so that the moisture evaporates into the air. Soaked carpeting, like with flooding, creates special problems. Soaked carpet should be professionally cleaned and dried within 24 hours. Carpet that is damaged by sewage or other biologically contaminated water or soaked carpet that cannot be dried quickly should be replaced. Concrete floors should be cured and dry before installing carpet over them. Otherwise, the carpet can absorb moisture and serve as a place for mold to grow. If you do decide to install carpet on a concrete floor, you may want to use a vapor barrier (like plastic sheeting) over the concrete and cover that with sub-flooring (insulation covered with plywood) to prevent a moisture problem. Preventing Health Problems Associated with Carpeting Some people say they have begun feeling suddenly ill 1 to 3 days after installing new carpet in their home or office with flu-like symptoms including headache, dizziness, irritation to eyes, nose, and throat, or difficulty breathing. Even though the US Environmental Protection Agency says that there is no proven cause-and-effect relationship between carpet emissions and health effects, EPA officials dialogued with the carpet industry on how to reduce VOCs.⁵ In January 1993, the Carpet and Rug Institute (the national trade association for the carpet and rug industry) began a voluntary indoor air quality testing and labeling program that tests the chemical emissions of new carpet. In order to qualify for this "Green Label" approval, the carpet must give off very little VOC vapors and meet certain emission levels for styrene, 4-PCH, and formaldehyde. Carpet that has past these tests carries a label with "CRI" inside a house icon. It is a voluntary industry program in which carpet manufacturers sign up to have the product independently tested and verified on a quarterly basis. Reducing the Problems Associated with Carpeting If you carpet your floors, purchase only products (e.g. carpet, adhesive, and cushion) that meet the low emitting criteria for indoor air quality acceptance, as the Carpet and Rug Institute's Green Label Program. Ask for verification of the style that you are using. Verification would be its listing on the appropriate program, and certification number. Before new carpet is installed, consider airing it out in a clean, well-ventilated area before installing. Ask to have the carpet tacked down with carpet tacks rather than being glued down. Make sure the installer follows industry installation guidelines following the Carpet and Rug Institute's Commercial and Residential Installation Standards. Leave the home or building during and immediately after carpet installation or schedule the installation when the space is unoccupied. Open doors and windows and use fans and room air-conditioners to increase the amount of fresh air indoors and decrease the concentration of chemicals released from the newly installed carpet for at least 48 hours following installation. If possible, air out the carpet for a week before the space is occupied. This will minimize exposure to emissions. Follow the manufacturer's instructions for proper carpet maintenance. This should include cleaning the carpet regularly with systems that leave the carpet dry and that are very effective in the removal of dirt, mold, and allergens. A recent study showed that cleaning systems should assure that carpet is dry within 24 hours of cleaning and that it is greater than 98 percent effective in the removal of settled dust, allergens, and mold.⁶ Protect carpet and textile surfaces when potentially hazardous products such as VOCs or pesticides are being used inside. Do not apply solvents or pesticides to carpet. Provide walk-off mats so outside dirt and debris is eliminated from shoes before walking on carpet. Some homeowners may want people to remove their shoes before entry. In new construction or remodeling, the carpet should not be installed until high VOC processes are completed such as painting, installation of vinyl wallcoverings, and application of adhesives. Keep indoor humidity levels between 40 percent and 60 percent to decrease dust mites and mold growth. Vacuum carpet frequently with a high efficiency filtration system (HEPA) or use a central vacuum system that exhausts to the outside of the building. Use approved carpet cleaning systems that are verified to leave the carpet dry no later than 12 to 24 hours after cleaning and will remove over 98 percent of dust, surface mold, and allergens such as dust mite and cat allergens. References Mclaughlin P, Aigner R. Higher alcohols as indoor air pollutants: source, cause, mitigation. Toronto, Canada: Indoor Air 1990;3:587-591. Hoddinott KB, Lee AP. The use of environmental risk assessment methodologies for an indoor air quality investigation. Chemosphere 2000;41:77-84. Dietert, R.R. and Hedge A. (1996). Toxicological considerations in evaluating indoor air quality and human health: Impact of new carpet emissions. Critical Reviews in Toxicology, 26 (6); 633-707. Lewis RD, Breysse PN, Lees PSJ, Diener-West M, Hamilton RG, Eggleston P Factors affecting the retention of dust mite allergen on carpet. AIHA Journal. 1998;59:606-613. USEPA. Carpet and indoor air quality. October 1992. Black M. Carpet cleaning and acceptable IAQ. AWMA June 1999.