A greenish tint is usually the giveaway of CCA-treated wood, though it's not as obvious in older wood, as it fades to gray. The underside of the shingles is where to look. There are arsenic test kits for water available for fairly low cost. Not sure how well they work for this application, though. An inquiry to the EPA about testing options may be in order.

EPA would tell you to find a local lab that can test materials for metals. If you're in DFW area there will surely be one. Search for 'analytical laboratories' or 'environmental laboratories'. The cost may be more than their value as mulch, though.

But I have a simpler test: burn one. Or a small piece of one. If it burns with regular old yellow flames it's untreated. If it makes pretty colors, it's treated. Copper would give a blue-green flame. Now I wouldn't normally recommend burning treated wood but a small piece won't destroy the planet - just don't inhale the smoke until you know for sure.

If they are treated, the landfill is the only safe option to dispose of them.

Assurance from the internet? Come on man!

That's a good point about flame tests. Arsenic and copper both burn blue. Arsenic, when burned, also emits a garlicky smell. Not enough to smell it? Forensic science says that arsenic tastes like garlic as well. Yep, keep it our of your food, but put it on your tongue! Lick a shingle?

That all being said, a real chemical test would be smart.

If there is one thing I learned as a roofer the older a building product is the higher chance it is poison to you and the environment. You want to take special care with any any sealing products prior to 1970. Some used asbestos strands to strengthen them similar to how steel rebar is used in concrete. I believe Canada used it until the 1990s. So be careful on the edge work like around windows and chimneys.

I have found many very well preserved shingles that were dropped among the framing or used as shims as we've had work done all around the house. They look like slightly oxidized fresh cut cedar with none of the discoloration common with CCA treatment. Combine that with the industry info that very few treated shingles were used here in that time-frame, am over 90% certain they are untreated. Appreciate the suggestions on how to narrow that last bit of doubt.

toxcrusadr, Have seen that color change before when someone unwittingly put treated wood onto a campfire, but wouldn't have thought to use it as a test here. That may be good enough for me if I can't find another cost effective test.

daninthedirt, After your comments, I did some checking on testing options and found this arsenic wood field testing kit which I'm considering.

John, Fortunately this is about a 30ft long section of roofing material enclosed when a flat patio roof was replaced with a hip roof. All the old stack and edge sealing material was removed during the remodel; there's not even any tar felt - just cedar and nails.

Thanks!

Old cedar shingles are so rare around here one dude assembles them into an Objet d'art and hangs them up for sale. Bird feeders and bird houses were once popular uses. My mother had an uncle who amused kids by carving them into whirligigs.

Arsenic is a chemical element. Sun and rain won't degrade it. Nor would fire and or acid. Would take a nuclear accelerator to degrade it. In alkaline media, it will dissolve and form arsenites, which are just as poisonous. Rain may eventually wash the stuff off, but then of course, it's in your soil.

Albert, Hah... have seen such art - would be tougher here, too, if shingles/shakes were your medium. Almost all the homes in our neighborhood were built with cedar shingles in the late '60s/early '70s, but am not aware of one that still has them. Insuring them in north Texas for fire and hail became one, if not the compelling, reason.

Bossyvossy, Believe you're right for any treatments that could have been applied after installation. Seems that is most likely what would have been used here back then if ours had been treated at all. The exposed areas of the old shingles where the preservative would have been applied show a lot of wood loss, so you're right that much of any surface application would have been gone with it. Am not so concerned about those chemicals, but making some effort to rule out the slim chance that arsenic, chromium, or other toxic elements could be embedded throughout the wood from pressure treatment for the reasons Dan gave.

True that the metals won't degrade, but a good portion does leach out over time. If a piece of wood is CCA though, it's always CCA.

Preservatives after installation reminded me of Penta, or pentachlorophenol, which was a very common wood preservative up through the 80s. I used it on the family picnic table etc. as a high-schooler. It's somewhat soluble so it would leach away in the rain and had to be reapplied. If it WAS ever used, there is probably not much left to speak of on those shingles after this long. So I don't think this is a problem. Just don't burn them, the combustion byproducts are worse than the original stuff. ;-)

It's worth noting that CCA-treated lumber has been shown to be pretty innocuous when used as soil retaining walls. The arsenic doesn't migrate far from the wood once it leaches out of the wood and is in the soil. But CCA-treated wood ground up as mulch is a very different situation, and certainly a health risk. I'd be far more concerned about CCA-treated wood mulch than CCA-treated wood.

Just registered to post this:

If you are not 100% sure, just don't use it. Peace of mind is worth more than the value of mulch + recycling/environment benefit.

Thanks to everyone for the insights and suggestions. Am now confident that our shingles are not CCA treated and very doubtful that anything else was applied for a variety of reasons. One other relevant observation is that subterranean termites had tunneled through a defect in the slab ledge, up the back of the brick veneer, and into the cedar shingles. There were thousands (tens of thousands?) of the little beasts found eating a large section of cedar when the contractor pulled off the composition roof the previous owner had installed over the original. Just recalled this wouldn't have happened in the presence of CCA, though unsure how much they would have been bothered by other possible preservative/retardant chemical treatments.

I probably gave too much emphasis to CCA in the initial post because it was my greatest concern in using as mulch for reasons discussed earlier. The broader question is whether there were any chemical treatments for cedar shingles in common use at the build time and location that would still pose a danger in mulch/compost. I couldn't find any that would not have leached, eroded, or otherwise broken down sufficiently by now. If you have an interest or are bothered with insomnia one night, Performance of Preservative-treated Wood Shingles and Shakes (pdf) gives a good summary of treatment options at around 1995.

Also read somewhere that a tablespoon of ash from CCA treated wood is considered a lethal dose for humans. That's a lot to ingest unintentionally, but a reminder of how dangerous this stuff can become if mishandled.

I didn't believe you about the tablespoon of ash (sorry, nothing personal!) so I had to do some calculations. Apparently there could be enough arsenic in that much ash to exceed the LD50 (the one for rats and mice, anyway) based on my back of the envelope figures. However, I did not take into account how well that form (oxide) is absorbed into the body if ingested. But in any case that's a good reason why CCA was pretty much banned and why we always say not to burn it.

toxcrusadr, I'm impressed you have a good enough grasp on the details to crank out such a check. "Tablespoon" is mentioned in several places as a potentially lethal dose of CCA ash, but without authoritative references. Though did find where Charlie McGolda of the Virginia Department of Agriculture and Consumer Services is quoted as saying ingesting that amount could be lethal to an adult in this 2013 fluff piece: Treated wood could pose a danger to animals, humans.

We're certainly not removing CCA treated wood installed around our house until it ultimately degrades. But anyone in doubt about the variety of troubles this stuff can cause when mishandled, should glance through the case reports under the Chromated Copper Arsenate Toxnet page on the NIH site.