After receiving several hundred complaints about possible carpet-related health effects, the U.S. Consumer Product Safety Commission (CPSC) commissioned a study by Hodgson and others at LBL of chemical emissions from carpets. Dozens of chemicals released from carpets were observed and 31 were positively identified. Emission levels of these chemicals were then compared to existing data about their health effects. As the measured emissions were considered peak values to which people would be exposed for only a few hours or days, they were compared only to known short-term health effects. No attempt was made to assess the possible effect of chronic or long-term exposure. As measured, none of the chemicals approached levels known to be hazardous upon short-term exposure.
Of the chemicals released, most notable are styrene and 4-PC, both of which come from the SB latex backing that is used on 95% of carpets. Styrene is a known toxin and suspected carcinogen. 4-PC has not been shown to be toxic, but it has a detectable odor even at levels below one part per billion and is the chemical most responsible for the distinctive smell associated with new carpets. It is also less volatile than many of the other chemicals measured, so it continues to be emitted at measurable levels for a longer time.
After the EPA headquarters incident, all the chemical companies supplying SB latex to the carpet industry joined forces to create the Styrene Butadiene Latex Manufacturers Council. The council coordinated response to public concerns about the material and sponsored several tests on the toxicity of 4-PC, none of which indicated toxic effects.
Vinyl-backed carpet tiles used in some commercial installations were also tested. They emitted a distinctly different set of chemicals, notably vinyl acetate and formaldehyde. These, too, were determined by the CPSC study to be at levels far below those likely to contribute to adverse health effects.
The CPSC study's authors offer several explanations for the carpet-related complaints, given that they didn't discover any notable health hazards in their tests. First, there may be interactive effects between two or more of the many chemicals involved that greatly exceed the impact of any one substance. Second, they only tested four random samples. It may be that periodic fluctuations in the manufacturing process may generate occasional batches of particularly volatile carpet with far higher emissions. IAQ expert Levin echoes this possibility as a likely scenario. Whatever the reason, health complaints associated with carpets, including severe neurological and respiratory problems, continue to surface.
One component of the problem appears to be that some people are simply much more sensitized to the effects of chemicals that have no noticeable effect on most. These individuals with Multiple Chemical Sensitivity (MCS) or Environmental Illness (EI) appear to be severely affected by conditions that most people consider normal. Advocates for this community point out that most of them can identify a specific event, when they were exposed to unusual levels of toxins, that "tipped them over the edge." They warn that the syndrome may result from the cumulative effects of low-level chemical exposure and that everyone is potentially at risk.
In an agreement negotiated with the EPA, The Carpet and Rug Institute (CRI) began a testing and labeling program in 1992. The program was widely criticized by consumer advocates and the attorney generals of several states for failing to warn consumers about potential hazards and for inadequate testing. The program was strengthened in January 1994.
At present, each carpet line is tested four times a year for four categories of emissions: total volatile organic chemicals (VOCs), styrene, 4-PC, and formaldehyde. As no industry standards exist, somewhat arbitrary maximum emission levels, measured at 24 hours after manufacture, have been established. Products that pass the test can carry the new label (see illustration). The Canadian Carpet Institute (CCI) recently joined with CRI in offering this labeling program. All testing for the program and most of the industry- sponsored research on carpets has been done by Air Quality Sciences, Inc., of Atlanta, Georgia.
Consumer advocates are pleased that the labeling program has been improved and that the label now includes a warning for chemically sensitive individuals. They point out, however, that the testing is still not nearly frequent enough to catch occasional bad batches of carpet and that the tests are checking for far too few substances. Improvement is occurring though. While about 20% of carpets tested failed when the testing began in 1992, "there has been a marked decrease in the emissions of the carpet now being tested," according to CRI spokesperson Kathryn Wise, "and the percentages of those not meeting the criteria are way down." Meanwhile, the State of Washington has proposed a program establishing maximum emissions for new carpet used in State projects that are stricter than the industry's voluntary standards.
It is not at all clear that the carpet itself is the biggest IAQ problem in new carpet installations. The carpet industry is quick to point out that carpet adhesives and seam sealants emit far more pollutants, especially in the first few weeks after installation. Carpet cushions, or pads, may be at fault as well. In a typical commercial installation, carpet adhesive is spread over the entire surface, covering between 7 and 16 square yards per gallon, depending on the carpet type. There are many different types of adhesives, but the majority are based on SB latex, the same resin used in carpet backing. With such a large volume used, adhesives have generally been by far the largest short-term source of VOC emissions, but change is underway.
Although true solvent-based adhesives have not been used since 1970, most adhesives have continued, until recently, to use volatile solvents to emulsify, or liquefy, the bonding resin. Until 1990 VOC levels in these adhesives typically ranged from 200 to 600 grams per liter (g/l). Air quality regulations promulgated in 1990 in southern California limited VOCs in adhesives to 150 g/l. This became an accepted standard nationwide in 1991, according to Ken Knudtzon of DAP, chairman of the Floor Covering Adhesives Manufacturers Committee of the National Association of Floor Covering Distributors. The California regulations are based on VOC levels as calculated from the ingredients; actual levels measured in the adhesives tend to be slightly higher.
Since 1991 IAQ concerns have led adhesive manufacturers to find ways to reduce solvent levels even further, and some now claim a calculated VOC level of zero. They have accomplished this reduction by using heat or other processes, instead of solvents, to emulsify the resin. Several manufacturers, including the W. F. Taylor Company and the Henry Company, now sell only low-VOC products, and products with calculated levels below 50 g/l are now available from all manufacturers.
Early generations of low-VOC adhesives were harder to work with than traditional products, giving them a bad name with installers. "When the new adhesives first came out, their adhesion properties were not as good," said Fred Williamson, president of the flooring firm CSI/CDC Corp. in New York City. Product performance is continually improving, however, as manufacturers get more experience with the new formulations. "We test some of our competitors' products, and the ones they have now are better than the ones they had a year ago, which were better than the year before that," Knudtzon reported. Although the low-VOC adhesives are at present more expensive to make, Knudtzon insists that the cost is no more than 5% higher to the installer.
Seam sealants have been another serious offender, releasing known toxins including 1,1,1-trichloroethane and toluene. The trichloroethane must be eliminated by 1996 to meet new government regulations, and some manufacturers have introduced new formulations with zero calculated VOCs.
Many IAQ experts suggest that the biggest problem with carpets may not be new carpet emissions at all. Once installed, a carpet acts like a filter for anything in the air, trapping particulates and pollutants. Anything carried onto a carpet on shoes or wheels can also become lodged in it. Hydrocarbons from a street or pesticides from a yard can enter the carpet matrix. Outdoors, ultraviolet sunlight eventually breaks down these chemicals, but in the carpet there is nothing to remove them. Frequent and effective vacuuming can reduce the accumulation of such contaminants, but not even hot-water extraction can eliminate them all.
VOCs can be adsorbed onto carpet fibers, stored there for an indefinite time, and eventually released back into the air. Thus, carpet that is exposed when an area is painted, for example, can become loaded with VOCs from the curing paint. These VOCs can then add to the overall pollutant level in the space for an extended period of time, long after the paint has cured and stabilized. Wool fibers appear to have an even greater capacity than synthetics for trapping VOCs, especially formaldehyde and nitrogen oxides. Some wool-industry-sponsored research suggests that such substances are chemically bonded to the wool and will not be released, but such claims haven't been verified.
Carpets are also an ideal environment for dust mites, which consume flakes of dead human skin and leave highly allergenic excrement. Wet carpet is an ideal breeding ground for another allergen: mold and mildew. In fact, most experts recommend that any carpet that has been wet for over 24 hours be removed, because there is no effective way to eliminate the mildew growth. Some aggressive cleaning products can themselves leave toxic residues in carpet, especially if they are improperly used.
The most common carpets today have nylon face fibers that are stitched into a polypropylene primary backing. The fibers are locked in place with a coating of styrene butadiene latex (SB latex, sometimes called SBR for styrene butadiene rubber) adhesive on the underside. A thick application of SB latex--as much as two pounds per square yard of carpet--is the secondary backing for most inexpensive carpets.
There are many variations: nylon face fiber may be either nylon 6, made from a single molecule type, or nylon 6,6, made from two alternating molecules. Or, the face fiber can be polypropylene, polyester (possibly including recycled PET from soda bottles) or wool. Except in the case of all-natural woven wool carpets, which are sometimes woven into a jute primary backing, polypropylene is almost always the primary backing material. Higher-end products sometimes have a fabric or polymer secondary backing, often attached to the carpet with a thin coat of SB latex. Occasionally a synthetic foam cushion is laminated directly to the back of a carpet, which can then be attached directly to a hard surface.
A rash of alleged health problems with carpet have yet to be properly explained, suggesting that all carpets, and especially the less expensive synthetics, should be used with great caution. In addition, the relatively short life expectancy of most carpet and the heavy dependence on fossil fuels as a raw material make it incumbent on those specifying carpet to see that it will be maintained and protected for a long, safe service life. The recommendations that follow are far from exhaustive, but they are a step towards safer, better floorcoverings. - Nadav Malin
Checklist for Minimizing IAQ Problems With Carpets
TacFast(TM) is a hook-and-loop ("Velcro") carpet fastening technology that is licensed on a royalty basis to carpet manufacturers. The principle is very simple: a fabric with protruding fiber loops is attached to the back of the carpet, and a four-inch-wide tape with hooks on the back goes down on the floor. The hook tape is installed around the perimeter of rooms, at all carpet seams, and any other place where extra bonding of the carpet is advised. Tape for the TacFast system is manufactured by both Velcro Industries and 3M. This system holds the carpet firmly in place, yet permits easy removal for repositioning or replacement. Wes Conneley, a technical manager for Wools of New Zealand, was sold on TacFast when he saw it working at the North York Performing Arts Center in Ontario, Canada. Painters working on a section of wall had simply peeled the carpet back out of harm's way and were saved from the usual hassle of protecting a carpet from spills and splatters.
TacFast Systems Canada Limited
15 Wertheim Court, Suite 710
Richmond Hill, ON L4B 3H7
Marilyn Black, Chief Scientist
Air Quality Sciences, Inc.
1331 Capital Circle
Atlanta, GA 30067
Anderson Laboratories Inc.
30 River Street
Dedham, MA 02026-2948
The Carpet and Rug Institute
P.O. Box 2048
Dalton, GA 30722
706/278-3176, 706/278-8835 (fax)
Hal Levin, Editor and Publisher
Indoor Air Bulletin
2548 Empire Grade
Santa Cruz, CA 95060
408/425-3946, 408/426-6522 (fax)
P.O. Box 935
Williston, ND 58802-0935
William H. Oler
Carpet Cushion Council
P. O. Box 546
Riverside, CT 06878
c/o DAP, Inc.
P. O. Box 277
Dayton, OH 45401
513/667-4461, x 2257
Styrene Butadiene Latex Manufacturers Council, Inc.
655 15th Street, NW, Suite 1200
Washington, DC 20005
Todd Stevenson, Freedom of Information Officer
Office of the Secretary
US Consumer Product Safety Commission
Washington, DC 20207
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