PROS AND CONS OF
PRESSURE TREATED WOOD
Pressure Treated Wood: Should I or Shouldn't I Use It? Of course, no one can answer this question but you, but it might help to look at the facts.
Pressure treated wood is 30 to 40% cheaper and last twice as long as redwood. However, the rest of the picture is not so pretty.
By far the most common type is designated PT CCA (Pressure Treated Chromated Copper Arsenate).The publication Environmental Building News (March 1997) has called for a phase-out of PT CCA. This is largely due to concerns related to its disposal.
Pressure Treated Wood is poisonous to insects, fungus, and bacteria. It is also poison to humans and other life forms. It is listed by the State of California (and most other states) as a carcinogen.
The basic elements involved are copper, chromium, and arsenic. All are hazardous to human health and the environment and do not break down into harmless substances.
The companies that produce this product claim that the compounds are chemically locked to the wood itself and therefore not a hazard to human health and the environment. However, they don't tell us that these compounds and particularly the arsenic are released in highly toxic levels when the wood is burned. It should never, ever be burned!
There is also evidence of arsenic leaching from CCA-treated wood into the surrounding environment. Leaching of arsenic from PT CCA wood in raised garden beds has been found to be limited to about 6", but that 6" is permanently contaminated. It means that you should not grow vegetables in that strip nor can you turn that soil into the rest of your garden. It also means that that soil is still contaminated long after you and your garden are gone. Not a good legacy!
This leaching also means that arsenic salts are continually coming to the surface of the wood where they can easily be transferred to you or your children by contact. Try teaching your 6-year old to keep his or her hands out of their mouth or for that matter not to eat dirt!
Only small amounts of these compounds are taken up in vegetables grown in contaminated soil. These amounts are generally considered too small to be immediately toxic. However, the effects of repeated exposure to these low levels are not well understood.
The disposal of this product is by far the more serious environmental problem. It should be placed in lined landfills (itself not a great solution) but construction waste is often too bulky and not allowed in these special landfills. The fact is that it often ends up in unlined landfills where it is subject to eventual leakage into the environment at large.
There are alternatives. They fall into 4 general categories
1. Other types of wood preservatives
2. Naturally resistant woods
3. Synthetic and composite wood products.
4. Reused lumber.
Alternative Treatments - By far the best alternative pressure treatment seems to be Alkaline Copper Quaternary, or "Quat" for short. It is manufactured by Chemical Specialties, Inc. (CSI). While not entirely benign, it does replace the more seriously toxic chromium and arsenic in the CCA treated products. It is the treatment of choice in several European countries and in Japan, where CCA treated wood is banned. You may also run into a treatment called ACZA. It stands for Ammoniacal Copper Zinc Arsenate. Notice that it still has arsenic, the worst of the offenders in CCA-treated woods so it is not a good choice.
Naturally Resistant Woods - Naturally resistant woods such as redwood and cedar require careful consideration. Their availability and environmental impact differ widely. On the West Coast, for example, redwood is readily available. However, much of it comes from clear-cut old-growth forests. Not only are these old-growth forests a much-depleted natural resource, but the loss of habitat and watershed cause serious environmental damage. Some of the supply comes from managed plantations, but one must be careful to ensure proper verification of the source. (Note: Also when considering the environmental impacts of tree plantations, consider the effects of their use of pesticides and other non-organic inputs on the environment.)
Synthetic and Composite Wood Products - Note: The Ecology Center does not endorse plastic lumber, for waste and health reasons. Reused Lumber - Another option (and probably the best) is to use reclaimed redwood or cedar, sometimes found at some building material reuse centers.
One might also consider using cheaper non-resistant woods and sealing them with linseed oil to add some resistance and just replacing them more often.
Written by: Gregory W. Lemley
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