The culprit, allegedly, is unacceptable levels of arsenic that have leaching from pressure-treated wood into the soil beneath.

But some scientists, the government and the industry itself all maintain that there is minimal or no risk with proper precautions. To ensure this, the US recently deemed that the industry must put handling advisories on each piece of wood; Environment Canada is following suit this fall. Meanwhile, in the US the industry itself is advising consumers to apply a sealer to the green-tinted wood, but the Canadian industry says there's no need.

Chromated copper arsenate (CCA) wood, which has excellent fungicidal (due to the copper) and insecticidal (arsenic) properties, is the most widely used pressure treated wood.

But studies show that over time and with rain exposure, the arsenic leaches out of the wood and accumulates in the soil below. High levels of ingested inorganic arsenic can be fatal, it may also damage nerves, stomach, intestine and skin, and is a known carcinogen, increasing the risk of skin cancer and tumors of the bladder, kidney, liver and lungs.

A recent Connecticut study (Bulletin of Environmental Contamination and Toxicology 1997;58:22-9) found that soil samples taken from beneath CCA wood decks contained, on average 20 times more arsenic than control soil, 76 mg/kg. This is 7 times Connecticut's legal limit of 10 mg/kg, and nearly twice as much as the US Environmental Protection Agency's regulatory guidelines of 41 mg/kg.

"Clearly, the arsenic levels pose a potential environmental problem," the study concluded.

Based on this, the Connecticut Department of Public Health warns that since "young children are most at risk… they should be prevented from playing underneath CCA treated structures." It also cautions against growing edible products near CCA-treated decks.

Of even larger concern, was the arsenic on the wood surface. "It's pretty clear there is a dislodgeable residue which with casual contact can be removed," says Connecticut Department of Health toxicologist Dr. Gary Ginsberg. Although virtually no arsenic is absorbed through the skin, it is readily absorbed orally, thus children, who frequently put their hands in their mouths, are considered most vulnerable.

Thus, the "prudent public health message" is to seal CCA-treated structures every 2 years with an oil-based stain, advises the state department.

Ginsberg says "I don't disagree with Environment Canada [saying it's safe]," but with existing data "the less [exposure], the better." A similar study of playground structures conducted at the University of Florida, found the average arsenic levels was 20.2 ppm. In Florida, the residential target level is 0.8 ppm; its industrial target level is 3.7 ppm. Its response was to close dozens of playgrounds.

Seven states are about to publicize information about the risks and the US Consumer Product Safety Commission has launched petition to ban CCA wood. Several European countries, including Holland, have already banned it.

Environment Canada's Barry Munson, calls such bans a "knee-jerk response." "I don't think the science justifies it." The head of Environment Canada's industrial contaminants says the actual danger to a child is "small to nil." "It's a good product. It's a safe product," he maintains, "as long as safety precautions are followed." These include protection during construction and never burning the wood. Still, he says arsenic does leach "a little," while dermal contact "is a problem with a deck." He too advises putting a sealant on the wood to "eliminate all concerns."

But the Canadian Institute of Treated Wood, which is paying for the new labels, says there's "no danger at all," and doesn't recommend sealing.

Meanwhile, the Canadian Institute of Child Health advocates the precautionary principal in saying that CCA wood "probably shouldn't be used in places where kids can come into regular contact with it."