News Coverage
Danger on Deck?
Kids may need protection from wood structures in the play yard
Published January 31, 2004
For 3 decades, builders of outdoor decks, arbors, swing sets, and other unpainted structures have relied almost exclusively on the greenish wood known as pressure-treated lumber. Annual sales of some 7 billion board feet of this wood created a U.S. industry worth $4 billion per year. What makes the lumber so useful is what the pressure treatment forced into it: a toxic cocktail of arsenic and other pesticides that deters termites, other insects, fungi, and microbes.
Until this year, 90 percent or more of pressure-treated wood had been infused with chromated-copper arsenate, or CCA. In 2001 alone, CCA production devoured some 40 million pounds of arsenic and 64 million pounds of hexavalent chromium. Both arsenic and that form of chromium at relatively low concentrations are carcinogens, but arsenic is of greater concern because it leaches from the wood more readily.
The Environmental Protection Agency had approved pressure-treated wood decades ago, but the agency announced 2 years ago that it would begin reevaluating whether CCA\\\'s ingredients posed a cancer risk to children. Wood-preservative makers responded by volunteering to phase out CCA for residential and almost all other uses where substantial human contact could be expected.
Indeed, as of Dec. 30, 2003, U.S. chemical companies no longer have EPA approval to sell CCA to treat wood for use around homes, though retailers have until May 16 to sell CCA-infused lumber still in supply pipelines. Because CCA production had accounted for 90 percent of domestic arsenic use, EPA notes that the treated lumber\\\'s phaseout should \\\"virtually eliminate\\\" this poison\\\'s U.S. market.
Several relatively nontoxic wood preservatives are already available, and they repel rot and bugs about as well as CCA does, notes Jim Jones, director of EPA\\\'s Office of Pesticide Programs in Arlington, Va. The primary difference, he says, will be their 10-to-15-percent higher cost.
But what about risks from continuing exposures to the CCA in existing outdoor structures that will remain in place for years? Two months ago, EPA completed a draft risk assessment for CCA-treated decks and playground equipment. It concluded that some U.S. children, depending on where they live and how they behave, could indeed face an unacceptably high cancer risk from exposure to the treated wood.
The American Wood Preservers Institute of Reston, Va., an industry group, challenges that assessment. The group cites a California study on CCA-treated playground equipment as showing there is \\\"negligible risk to children.\\\"
At the other end of the spectrum is a Washington, D.C.-based advocacy organization, the Environmental Working Group. In May 2001, it petitioned the Consumer Product Safety Commission (CPSC) to require removal and safe disposal of treated wood from equipment in public playgrounds and to force CCA makers to refund to consumers the cost of old treated backyard play sets.
On Nov. 4, 2003, the commission unanimously rejected the petition. Chairman Hal Stratton explained that children already confront comparable exposures to arsenic from the diet and other sources, although he conceded that CCA-treated equipment \\\"could be a significant source of [a day\\\'s] arsenic for children\\\" who play on it.
Stratton also argued that the chemical industry\\\'s new voluntary phase-out of playground and backyard lumber would essentially \\\"render the petition moot.\\\"
Moreover, for structures already in place, some treatments may lock CCA within pressure-treated wood and thereby render it harmless. In fact, EPA and the U.S. Forest Service have recently launched independent investigations into the efficacy of water repellents and coatings on pressure-treated lumber. Although their preliminary data indicate that such finishes keep arsenic and chromium in place, neither agency has data yet that indicates how often treated wood would have to be resealed.
Kid stuff
Although CCA-treated lumber has been available for 60 years, it didn\\\'t become the outdoor product of choice until the 1970s, when the United States\\\' love affair with home decks heated up. Realizing the toxic nature of CCA\\\'s ingredients, EPA has long warned against breathing sawdust from pressure-treated wood or burning the material.
Two years ago, as part of an ongoing safety reevaluation of long-used pesticides, EPA announced it was investigating cancer risks that CCA-treated wood might pose to consumers. The agency focused on children because they tend to spend much more time on decks and play equipment than adults do and because young kids frequently put hands, toys, and other items into their mouths.
EPA\\\'s new hazard assessment proved tricky. The presumed route of most CCA exposure is from the wood to hands or other items that enter a child\\\'s mouth. Because kids vary widely in how often they put nonfood items into their mouths, EPA needed to have researchers monitor and quantify this behavior in a large sample.
The agency also considered how much time children play outside. For instance, Minnesota youngsters have a shorter outdoor-play season than do children in Gulf Coast states.
Further complicating the risk evaluation, EPA\\\'s study of some 1,000 samples of pressure-treated lumber revealed that CCA leaches from weathered wood at widely varying rates. Because ultraviolet light and rain can accelerate CCA\\\'s release, the EPA scientists have surmised that wood structures in the southern United States release more arsenic than do decks and swing sets further north.
These variables prompted agency scientists to make what\\\'s called a probabilistic risk assessment for kids from CCA, Jones says. For CCA from lumber, the end result was cancer-risk estimates for children in the top 10 percent of projected exposures, the bottom 10 percent, and the groups in between.
Ordinarily, EPA considers a cancer risk as excessive when it\\\'s higher than 1 in a million. On average, kids exhibiting extensive hand-to-mouth behaviors who live in warm environments face a 2.5 in 100,000 cancer risk-or more than 10 times the risk that triggers EPA concern. The agency now projects that for the top 5 percent of exposed children, the cancer risk could be 1.4 in 10,000, or more than 100 times the value that might be deemed acceptable. An EPA report dated Nov. 10, 2003, outlines the details of these calculations (http://www.epa.gov/oscpmont/sap/2003/december3/ shedsprobabalisticriskassessmentnov03.pdf).
Within a few months, Jones says, the agency plans to release a companion cancer assessment for adults who make or use CCA-treated lumber.
Parents\\\' dilemma
If CCA is a cancer risk to at least 5 percent of the nation\\\'s youngsters, why doesn\\\'t EPA advocate the removal of treated wood from yards and decks? The situation parallels the case of asbestos, a potent carcinogen present in many building materials. Currently, EPA recommends strongly against removing asbestos from buildings if it\\\'s in undamaged ceiling or floor tiles, for instance. The agency argues that removal risks releasing dangerous concentrations of the currently sequestered, toxic fibers.
Similarly, EPA notes that removing all CCA-treated structures could release large amounts of now-interred pesticides.
The Environmental Working Group doesn\\\'t accept that argument because its staff concludes that leaving the structures in place has a high cost. Last year in testimony before CPSC, the group\\\'s vice president for research, Jane Houlihan, said that her organization\\\'s tests indicate that homeowners with old CCA-treated decks, play sets, and picnic tables \\\"remain at risk from high levels of arsenic . . . for 20 years, the entire useful life of the wood.\\\"
For its study, Houlihan\\\'s group measured arsenic residues on the surfaces of 598 treated-wood structures, including play sets, picnic tables, decks, and tree houses. Moist swabbing of 100 square centimeters of the surface-an area comparable to the size of a preschooler\\\'s hand-picked up 0 to 2,813 micrograms of arsenic. The median value was 9