Posted on: Monday, June 6, 2005

By Jan TenBruggencate
Advertiser Science Writer

Most of the construction lumber sold in Hawai'i today is termite-treated with borate-based compounds that are considered much less toxic to humans than the arsenic-based wood treatment products of the past, but there's still a lot of the old lumber still in use in the Islands.

And if you have it, you ought to seal it.

There are disagreements over how likely it is that the toxic arsenic compounds can leach out of the wood, but the U.S. Environmental Protection Agency suggests caution. The agency has issued a number of guidelines on the safe use and handling of these products, including washing your hands after working with them and wearing masks when sawing them.

The terms for a couple of the most popular of the old pressure-treatment methods were CCA (chromated copper-arsenate) and ACZA (ammoniacal copper zinc arsenate).

If Hawai'i residents have older treated wood products in exposed locations where children or others might be in contact with them — such as playground equipment, decks, and railings and fences — the agency recommends sealing the wood's surface at least annually. And it says something that soaks into the wood, such as an oil- or water-based sealer, is probably better than a coating compound such as paint that could flake off and expose the treated lumber.

"The data show that oil- or water-based sealants or stains that can penetrate wood surfaces are preferable to products such as paint, because paints and other film-formers can chip or flake, requiring scraping or sanding for removal, which can increase exposure to arsenic," the EPA says on its Web site. For detailed recommendations, see www.epa.gov/oppad001/reregistration/cca/#sealants.

A Hawai'i expert on wood treatment agrees.

"Seal it. That eliminates any possible contact with the chemical," said Hap Person, head of Honolulu Wood Treating and president of the nonprofit Hawai'i Lumber Products Association.

Hawai'i building codes require that lumber used in structural work be treated to prevent termite damage, and most of that treatment is now done with the borate compounds. Arsenic compounds are no longer permitted in most applications, although Person said they can show up in some plywood and a few other special products.

The public-interest Environmental Working Group has recommendations on reducing possible exposure to arsenic in wood at its Web site, www.ewg.org/issues/arsenic/10tips.php.

Reach Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766, or jant@honoluluadvertiser.com; or call (808) 245-3074.