When the U.S. Environmental Protection Agency (EPA) issued a report last year on the safety of pressure-treated lumber, they acknowledged the danger of arsenic, a poison and carcinogen, which is used widely in wood preservatives like chromated copper arsenate (CCA). They announced a phase-out of some uses of the preservative by the end of 2003.
Unfortunately, this phase-out will not affect existing outdoor wooden structures in the United States, an estimated 90 percent of which are treated with arsenic-based preservatives. The EPA may have misled the public when it asserted that it "does not believe there is any reason to remove or replace arsenic-treated structures."
Contradicting stated EPA beliefs is a recent study by the independent organization Environmental Working Group (EWG)*. The EWG report concludes that millions of people, especially children, remain at risk from older decks, picnic tables, and play structures, which continue to leach out high levels of arsenic for years after construction.
Findings reported in EWG's "All Hands on Deck" indicate that arsenic easily wipes off the surfaces of old wood structures. Their study was based on samples nationwide from 263 structures and the arsenic-contaminated soil beneath them. The samples were analyzed by the University of North Carolina - Asheville's Environmental Quality Institute.
The EWG study shows that pressure-treated wood up to 15 years old exposes people to as much arsenic as newly treated wood. The amount of arsenic that testers wiped off a small area of wood about the size of a four-year-old's handprint (15 square inches, or 100 square centimeters) typically far exceeds what the EPA allows in a glass of water under the Safe Drinking Water Act standard. Arsenic in the soil from 40 percent of test sites exceeds the EPA's Superfund cleanup level of 20 parts per million.
Other studies have shown that arsenic sticks to children's hands when they play on treated wood and is absorbed through the skin and ingested when they put their hands in their mouths. Exposure to arsenic is known to cause acute poisoning as well as lung, bladder, and skin cancer in humans, and it is suspected as a cause of other cancers.
Arsenic-treated wood may be difficult to identify visually. Some wood treated with arsenic compounds sports a characteristic faded green color, and/or rows of tread-like puncture marks. However, more recent CCA treatment processes, including the "Wolmanzing" of the "Outdoor Wood" brand of lumber, can leave wood with a pleasant, natural brown color. After weathering, "Wolmanzed" wood is even less distinguishable from untreated wood.
More than a year after the EPA phase-out announcement, and with only about nine months remaining to the final date, large amounts of CCA-treated wood apparently still flow through the U.S. lumber supply chain, representing a continuing source of potential toxic exposure to builders and building occupants.
According to an EPA publication, "Your local hardware store or lumberyard can provide more information on available alternatives." Such vague advice may not be adequate for concerned design and building professionals, who may want to carefully conduct their own literature survey on alternative preservative treatments like Alkaline Copper Quaternary (ACQ).
A quick survey of home improvement superstores showed mixed progress. A large independent outlet had a mixture of CCA or "Wolmanized" arsenic-treated wood shelved together with hopefully safer lumber treated with non-arsenic ACQ. However, their free "How-To Booklet #82: Preserved Wood" still includes discredited if not dangerous statements like "no chemicals can leave the wood or enter the ground water or your body."
Home Depot has received some credit in the green-building community for stating a corporate commitment to stopping distribution of CCA-treated wood. At a local Home Depot, we found relatively up-to-date consumer safety tear-sheets, in accord with current EPA recommendations for handling arsenic-treated wood, posted at most of the pressure-treated lumber racks. The racked wood, however, was all CCA-treated, presenting no direct alternative for customers at that store.
According to Ontario activist Deborah Elaine Barrie, CCA-treated lumber can contain a large amount of arsenic, on the order of one ounce (28 grams) per board. California State Senator Gloria Romero (Democrat, Los Angeles) introduced legislation in February, 2003 to ban the use and production of three dangerous wood preservatives, CCA, pentachlorophenol (penta), and creosote. This legislation would allow arsenic-treated wood in California to receive the more careful disposal appropriate for toxic materials.
Experts say that boards in high-contact areas such as handrails should be replaced with arsenic-free alternatives. In light of the documented risks, removal of arsenic-treated wood from all areas of contact with people, water, or weather may be prudent.
Short of replacing their decks, families may be able to lower their arsenic exposure somewhat by sealing the wood at least every six months and by washing hands thoroughly after contacting the wood.
Written by: Architecture Week
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