Oct. 5, 2000 Like unwanted guests who don't know when to leave, potentially toxic chemicals can stick around too long. The release of such substances from indoor sources such as mothballs in closets and cigarette smoke in carpeting is the subject of research presented in the current (October 1) issue of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.
Common household chemicals like those released from mothballs, deodorizers, pesticides and cigarette smoke typically settle in carpeting, said Richard Corsi, Ph.D., a professor at the University of Texas at Austin. Although they also adhere to wallpaper, ceilings and other indoor surfaces, the majority of chemicals trapped indoors make it to the floor, he said. Once there, they usually stick to the carpeting until they are released over time.
Carpet is a known repository for chemicals in indoor environments, including homes, offices and schools. The researchers, led by Corsi, sought to estimate and better understand the amount of time it takes for different substances to adhere to - and be completely emitted by - carpet after exposure.
The researchers tested potentially hazardous volatile organic compounds, or VOCs, in different types of carpets and under different conditions. They found that a chemical's makeup largely determines how long it lingers in carpet.
Chemicals that evaporate easily, like many components of gasoline, last for only a few days. Denser materials like the chemical components of pesticides and mothballs can take months or even years to come out. Denser materials stick to the carpeting more, and therefore take longer to remove, Corsi explained.
The amount of the chemicals stuck to the carpet and the rate at which they are emitted can have significant impact on people's exposure to toxic chemicals, Corsi said. It is potentially dangerous to breathe or be exposed to air contaminated by some chemicals, especially over long periods of time, he added.
"That's what we're dealing with here, the long-term re-emission of chemicals after the source event," he said. "An example is if you buy a house where there has been a lot of chemicals released - when you move in, those chemicals will continue to be emitted while you're living there."
Cleaning alone cannot prevent chemicals from sticking to carpet fibers because chemicals migrate through most fibers into the padding below, Corsi said. Because of this, the type of carpet - and whether it has been treated with a stain-resistant coating - likely has little impact on the chemical emissions, he continued.
The research cited above was funded by British Petroleum Oil and Exploration, Inc.
Richard Corsi, Ph.D., is an associate professor at the University of Texas at Austin and director of the Texas Institute for the Indoor Environment.
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