Outdoor Dilemma: To Keep or Replace Pressure-Treated Lumber 2/5/04

MANHATTAN, Kan. – A big question in home landscaping this year is likely to be what to do about pressure-treated lumber. Should homeowners be getting rid of what they already have, because the lumber is a cancer risk? Or, should they be quickly buying more, because it’s long-lasting and cheap?

On Jan. 1, new federal regulations stopped production of what’s been the nation’s far-and-away top building material for home landscapes. The lumber (usually pine) has been pressure-treated to saturate it with chromated copper arsenate or CCA. Stores may sell what they have on hand until supplies run out.

Millions of Americans have billions of board feet of the green-tinted wood. CCA lumber is in use as fences, retaining walls, picnic tables, playground equipment, decks, docks, tree houses and gazebos.

Pressure-Treated Lumber Advice From USDA

MANHATTAN, Kan. – The U.S. Department of Agriculture’s Forest Service Lab recently evaluated three common coatings for lumber that’s been pressure-treated with chromated copper arsenate (CCA). The researchers found promising results for those wanting to limit contact with the wood’s preservative, which contains cancer-causing arsenic.

They exposed the coated and uncoated CCA lumber samples to water – the universal solvent. Then they tested each sample’s water for traces of arsenic pentoxide, chromium trioxide and copper oxide – the compounds that could derive from CCA-treated wood. All three test coatings brought more than a 99 percent improvement over the uncoated lumber’s ability to “hold its chemicals.”

The tested coatings were:

* Latex primer, followed by one coat of outdoor latex paint.

* Oil-based primer, followed by one coat of oil-based paint.

* Two coats of a semi-transparent, penetrating oil stain.

The painted samples yielded no detectable CCA. The stain treatment kept the level of water-dissolved arsenic well below the EPA drinking-water standard.

– Source: Kansas State University Research and Extension

The problem is, the treated wood contains arsenic. In recent years, the lumber has come with a label that warned wood workers to wear protective gear while handling, sawing or sanding it.

“Many people hear the word ‘arsenic’ and assume poisoning is the lumber’s biggest risk,” said Chuck Marr, horticulturist with Kansas State University Research and Extension. “They think about the CCA-treated wood they’ve used around vegetable and fruit plants. They worry that arsenic could be leaching into the soil and getting into their homegrown food. But research indicates that’s not the problem.”

The U.S. Environmental Protection Agency mostly is basing its new regulations on another fact: Repeated exposure to arsenic can increase the odds for lung, liver, skin and other cancers, Marr said. The EPA is being proactive, trying to head off future health impacts. The agency is particularly concerned about those who have frequent physical contact with the lumber or its potential byproducts.

“Apparently, those most at risk are people who regularly breathe in CCA-treated sawdust and those who accidentally breathe in the burning wood’s smoke. That could include anyone in lumber or construction,” Marr said. “But an equal concern is children who often play on pressure-treated lumber.

“This is particularly true for new products. After the lumber has been in place for several years, much of the treated material will have washed or leached from the wood so that handling it or walking on it with bare feet is likely to be a minimal concern.”

The EPA is not recommending that U.S. homeowners immediately get rid of all pressure-treated wood products. Rather, it’s promoting sealing such items with an oil-based, semi-transparent stain or a similar penetrating-type coating every year or two, depending on weather and wear. (See box.)

“So far, the data on how completely effective that will be are limited,” Marr said. “However, we do know what will NOT be effective – the film-forming or non-penetrating stains that sometimes peel and flake. This includes a number of the stains classified as latex semitransparent, latex opaque, and oil-based opaque. Homeowners should talk to their paint or hardware dealer about what’s best to use.”

Up to now, the lumber’s main competition has been redwood and cedar, which are naturally rot- and insect-resistant. Compared to them, CCA wood has cost half as much and often lasted longer outdoors. Plus, it soon weathered to a cedar-like gray.

The lumber industry voluntarily agreed to take CCA-treated lumber off the home market and is trying to gear up to replace it with lumber pressure-treated with compounds that do not contain arsenic. Many of the replacement formulas depend on copper and other ingredients to repel rot-causing fungi and bacteria. The common compounds are ACQ (ammoniacal copper quat) and CBA (copper boron azole).

“Copper is the major preservative in CCA wood, too. It protects against rot, decay and insects – which can be vital in the Termite Belt,” Marr said. “The arsenic has been a second line of defense.”

Other choices in landscape building materials include pest-resistant exotic hardwoods, plastic-wood composites, and a variety of non-wood products (such as engineered vinyl either to cover or to replace CAA wood).

“Unfortunately, the availability of some of these products is limited now. And their prices range from somewhat to quite a bit more expensive than CCA lumber’s,” Marr said.

Gardeners who are more worried about CCA’s exposure to soil than its contact with humans have cheaper options. They can seal the wood. Or, they can place plastic sheeting between it and the soil.

“That kind of barrier isn’t necessary, but it can serve as an extra precaution if you are concerned,” Marr said. “EPA and other plant-growing experts have conducted many studies regarding plants’ arsenic uptake from pressure-treated lumber. That’s why their current recommendations are to not consider replacing any treated gardening structures until you’re ready to build new ones.”

For families making a list of what to replace first, the horticulturist recommends starting with structures that have high odds for direct contact with human skin – play equipment, outdoor furniture, swimming pool and patio decks, and the like.

“The old wood will have to go to the landfill – where, unfortunately, it probably will last for decades. You must not burn it. You must not chip it to use as mulch or as a compost ingredient,” Marr warned. “While handling it, you also need to remember that both old and new CCA wood is completely safe only if you’re protected from skin contact and from any particles that might get in your eyes, mouth or lungs – just as the labels said.”

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.