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I just learned that the green stuff overlapping the wood board is a pretty positive sign that the pressure treated wood contains arsenic. We just bought a house and didn't realize until now. The CCA woods are in lots of areas. Instead of replacing all of them, is there any effective way to reduce or eliminate the toxic? Perhaps paint them? Any suggestions of what kind of paint?

Thank you!

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    This might be a better question for the DIY stackexchange site... – SaSSafraS1232 Jun 8 '18 at 17:03
  • If you can paint, or varnish, then this is an effective way of locking in toxic penetrants or surface contamination since either produce a continuous film over the wood. Do be aware however that this sets you on the road to regular maintenance of the paint/varnish, where every couple/few years you need to reapply. And if the finish is left a bit too long at some point, so it degrades badly, all of it has to be removed to get back to bare wood, with the attendant toxicity concerns because of what you know is underneath. So extra safety precautions would have to be taken. – Graphus supports Monica Jun 8 '18 at 22:11
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    Can you post a picture? CCA does indeed give the wood a green tinge but since CCA has been banned, most treated wood is now dyed green because that is what people expect "treated" wood to look like. – Martin Bonner supports Monica Jun 11 '18 at 15:16
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In the immortal words of Douglas Adams:

Don't Panic

Arsenic impregnated wood is not that toxic. Obviously, you don't want to make a baby teething ring from it, and if I had to sand it, I would work outside and wear a mask. There is also general consensus that you should not use the wood as firewood (because the ash is pretty toxic).

However, apart from that, I wouldn't worry about it. See this from the government of Victoria in Australia.

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I found this:

To protect against arsenic exposure, Warren recommends using oil-based semi-transparent sealant every two years. He explains they make a clear seal, but it is not recommended because it only lasts 6 months. Warren says a seal with a little color that repels ultra-violet rays is recommended. Don't use latex-based because it will blister and peal-off.

Warren recommends staining the whole deck, if it is needed. But if money is an issue, he says, you should do areas that are most commonly touched such as ballisters and handrails.

As I understand it, so long as you don't cut or burn it, and you avoid skin contact then it shouldn't pose any great threat.

When it comes time to get rid of it you should use care and appropriate PPE - i.e. respirator mask, gloves, protective clothing such as one of those Tyvek boiler suits and contact your local government for advice on where you can dispose of it safely.

  • You don't need a respirator or protective clothing to remove a deck with a crowbar! – Martin Bonner supports Monica Jun 11 '18 at 15:32
  • Better safe than sorry. You might be disturbing dust that was deposited when the deck was installed. – WhatEvil Jun 11 '18 at 15:36
  • any saw dust particles small enough to be a respiratory concern would have broken down on an outside structure years ago, treated or not. I would be more worried about skin contact than breathing dust when dismantling a deck - and for years old CCA timber, I wouldn't be worried about skin contact at all beyond washing my hands afterwards. – Dave Smylie Jun 11 '18 at 23:49
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If that isn't a ringing endorsement, I don't know what is!

I would go to a good paint store (not Lowes or Home Depot) and find out the best way to seal the wood based on your climate, how much sun/water the surface gets, what the deck is use for, etc. Some typical wood sealers may not be durable when in contact with wood treated with arsenic.

Treated wood can be bad stuff, esepically CCA-treated wood (aka chromated copper arsenate). No matter the treatment, until you get it sealed, I wouldn't let my kids crawl around on it or lay on it for a sun bath, for example. I'll admit I'm paranoid, but I worked as a consultant for the EPA too long.

Here's what the EPA has to say about wood treatments: Overview of Wood Preservative Chemicals. Then here's a special brochure about CCA pressure treated wood: Guidance for Outdoor Wooden Structures Decks • Playgrounds • Picnic Tables

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    "I wouldn't let my kids crawl around on it or lay on it for a sun bath" - You may have worked as a consultant for the EPA, but that is definitely over-hyping the risk. – Martin Bonner supports Monica Jun 11 '18 at 15:26
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    "Cooper, PA. Leaching of Preservatives from Treated Wood in Service. (1991) notes that the US Environmental Protec- tion Agency and the US Consumer Products Safety Commission Health Serv- ices Directorate consider health risks associated with dermal absorbance of arsenic through contact with CCA-treated wood to be negligible" – Dave Smylie Jun 11 '18 at 23:55

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