Treated lumber now being scrutinized

By Jan TenBruggencate
Advertiser Columnist

Termites are a big problem in the Islands, leading most builders to use pressure-treated lumber that is impregnated with a green-colored pesticide called chromated copper arsenate.

There are other options for builders, such as placing specially sized gravel under homes, or stainless steel screens, both of which prevent termites from crossing the barrier. There are alternative treatment compounds, such as borates and naturally resistant woods, such as some types of redwood.

But the green lumber is still commonly used.

How safe is it?

The Environmental Protection Agency says that in normal use, it's safe. There is little doubt that the compounds in the green pressure-treated lumber are toxic in certain forms. That's why they are so effective.

The compounds are considered hazardous chemicals in their liquid form before they enter the wood.

Treatment plants require special permits and workers need protective clothing when they work with it.

And the compounds are potentially toxic if burned. Studies on the smoke from treated lumber burned after 1992's Hurricane Iniki on Kaua'i found arsenic, chromium and copper were present. For that reason, health officials recommend treated lumber not be used in mulch or compost and not be burned. It can be reused or buried in a landfill.

Various agencies differ on the compounds' toxicity while in the wood. The industry argues that the compounds are firmly bonded to the wood molecules and do not leach out, or do so in very small amounts.

The University of Wisconsin Extension Service says that it seems safe to use treated lumber, for instance, for the sides of raised gardens, because studies show plants don't take up much of the chemical treatment. Other studies suggest there is mild uptake. So if you must use treated lumber, line the garden beds with plastic.

The EPA recommends against putting treated wood in places where it will come in contact with food. Carpenters are urged to wear masks and goggles to keep the dust from treated lumber out of eyes and lungs, and some agencies recommend that if they are used in areas where children are likely to play, the wood should be painted to limit contact.

A range of studies suggests that treated lumber is very resistant to leaching out of its treatment chemicals, but small amounts do leach out. Higher levels of arsenic, for example, are found in soils under treated wood decks. The suggestion: If using treated lumber, particularly in places where kids play, seal it.

Some environmental organizations say such precautions aren't enough, and are arguing for a ban on the use of arsenic in wood treatment.

You can reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.