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· Registered
78 Posts
Discussion Starter · #1 ·
I need advice about using pressure-treated wood in the garden.
We are tearing down our old deck and I am eying some of the boards for cold frames.
I have heard of the evils of pressure-treated wood. Does anyone know how long the wood leaches out the chemicals? The wood is at least 12 years old. Does it wear off over time or is it a danger forever?
Is there anything I could use to seal off the wood to prevent the leaching that wouldn't cause a problem also?
I garden organically and wouldn't want to contaminate my soil.

· Registered
17 Posts
The pressure treated wood with which I am familiar (but then I am not young) came in three flavors: creosote, firex, and a greenish copper-based something. In all three cases there were chemicals that outlasted the wood and were harmful in soil or in the human body; the firex (which was manufactured to federal standards as fire-resistant) contained quite a lot of arsenic.

We have never bothered with structural beds; we throw mulch everywhere in the garden, call it "sheet-composting;" and where we want pathways we fork the top layer of mulch from that over onto the "beds" and there you are -- a raised bed.

This year we are making new beds on a quarter acre of sod by laying out the beds with string, covering the sod in the beds with cardboard and newspapers and hiding that under eight inches of hay, straw, leaves, and compost. After a year or so the beds are ready to plant as worms eat up the grass rhizomes and cardboard and aerate the soil.

The paths remain in grass and are mowed and the clippings scattered over the beds. Clippings should not be too deep or they will slime anaerobically.

A handful of potting soil nestled into the mulch makes a perfectly good "hill" and this method seems to us to yield as much or more than the tilled gardens we used to do, with about 1/4 the effort. And not a board in sight! :)

· ke4sky
190 Posts
Copper arsenate pressure treated lumber - CDC FAQ

These links from the Centers for Disease Control provide authoritative information on copper arsenate poisoning. Most arsenic poisonings are due to unintentional ingestion by children. In 1989, EPA instituted a phase-out of certain arsenic-containing ant poisons in an effort to reduce the incidence of children's arsenic ingestion. Children who play on wood structures treated with copper arsenate are at risk of dermal contact or ingestion of the arsenical through normal mouthing and play activities.

Wood treated with arsenate wood preservatives is an important source of arsenic exposure. Burning plywood treated with an arsenate wood preservative in a poorly ventilated cabin has been blamed for poisoning a family in rural Wisconsin. Green wood or pressed wood treated with copper arsenate to prevent mildew is commonly used in marine applications, patio decks, and recreational structures for children's playgrounds. Cutting this wood or erosion of the veneer may lead to arsenic exposure. If you use arsenic-treated wood in home projects, you should wear dust masks, gloves, and protective clothing to decrease exposure to sawdust.

This fact sheet answers the most frequently asked health questions (FAQs) about arsenic. For more information, call the ATSDR Information Center at 1-800-232-4636. This fact sheet is one in a series of summaries about hazardous substances and their health effects. It is important you understand this information because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present. ATSDR - ToxFAQs™: Arsenic

See also:
Arsenic (As) Toxicity: Who is at Risk | ATSDR - CSEM
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