Pressure Treated Lumber
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growsherown
Location: Olympic Peninsula
Posted: Sep-10-2004 at 8:57am
*From the WSU co-op website:
Pressure treated Wood:
Toxic terror in the backyard or just another scary story?
Gardeners are constantly faced w/ the decision of which yard and garden technologies are environmentally friendly and which will wreak havoc.This years pot of controversy has been seasoned by the national magazine Organic Gardening w/ a series of articles and responses to letters concerning the hazzards of using pressure-treated wood as framing material for raised beds and compost bins. The articles recommend that gardeners absolutely not use treated wood. Furthermore, the authors feel the hazard is so great, that people should rip out or seal treated wood already in place.
While Organic Gardening's risk management response to a percieved hazard has some merit, I believe thier lack of risk assesment has led to the incorrect conclusion that existing treated wood barriers need to be removed.
Treated wood has been saturated under pressure with chromated copper arsenate (CCA), a fungicide that prevents rot. The elemental components of CCA are chrome, copper and arsenic. Every movie fan who has watched Cary Grant in "Arsenic and old lace" can tell you that arsenic is a poison w/ murderous consequences. Fortunately for gardeners, this chemistry is much more complicated than that, and all toxicity is a matter of dose and exposure.
The elements present in CCA are known as metal oxides. Arsenic Pentoxide and cupric oxide are considered to have VERY LOW toxicity to mammals. The dangers of these elements are tempered, however, by consideration of its behavior in the environment. The main concern is how much will leach from treated wood.
Some leaching of CCA occurs from treated wood, but the next question is its fate once in the soil or compost. The metal oxides tend to bind the soil particles, except in highly acid soils,(ph of 4.0 or lower),and, therefore, are NOT easily absorbed by the plants! Even if maximum amounts of CCA leach, little chemical actually enters the root and edible parts of the plants. Furthermore, the plant itself is likely to show you symptoms of the toxicity at levels far below those considered to be toxic to humans.
Soils naturally contain copper, chromium, and arsenic because these elements and thier oxides are natural constituents of rock from which soil originates. These elements are actually essential micronutrients, meaning plant and animal cells require small amounts of these for normal functioning. Even food naturally contains measurable levels of copper, chromium and arsenic. Because toxicity is related to dose, there is little argument that high enough doses can harm plants and people, BUT "small amounts" of these essential elements are normal and present everywhere.
Gardeners, (if they still feel they need to after reading this), can avoid treated wood by using rot resistant materials such as plastic lumber. If they do decide to use treated wood...(and I myself do without losing any sleep over it), they can further reduce any hazard by simply lining the bed w/ plastic before filling w/ soil.
I guess my point here of posting this article, is that gardening, (whether your the average backyarder or a hard core capital O'ist), was meant to be relaxing and fun, as well as economical. The simple beauty of it can get lost in a jumble of fears and paranoia about issues such as these, and trendy recommendations about materials. I think the best garden philosophy is "catch can", meaning use whats available to you w/o going thru all the unnecessary financial and emotional expense of the "proper" materials. Treated wood, old bricks, even peeler core logs or alder poles anchored w/ rebar can make for a quaint and beautiful raised bed.
If you find yourself in a situation like myself, where someone gives you materials, or you come by them cheaply...use them! Treated wood can be lined, as the article says. Even bricks contain certain levels of toxins as they use some pretty hard core chemicals to mine the stone to make the concrete. Even still, it's up to you to decide how "hung-up" you are about these scare stories.
I guess what Im trying to say is.....enjoy your garden. Dont let all these myths and warnings and hearsays get in the way of you creating your own beautiful raised bed or gardens. As you can see from the article above, certain materials deemed as "bad" in popular circles, arent really all that..they're just missunderstood!
Get those raised beds in...any way you can......and enjoy!!!
trav
Location: Washington, Western
Posted: Sep-10-2004 at 2:48pm
I have some problems with that article, and the way it was used in this context as well. For one thing, the thrust of the article is simply that the author felt that Organic Gardening's mid-1990's call to rip out existing installations of CCA-treated wood was excessive.
1) The author, Allan Felsot, is certainly well educated; but after looking at some of the stuff he's said/authored it's obvious he has his own set of biases that I don't necessarilly share. On several different topics it seemed to me he tends to focus on some small piece of an issue (treated wood, bioengineered plants) without addressing the main concerns people actually have on the particular topic. In other words, he tries to convince you by redefining the argument in his narrow terms - much like a politician actually.
2) In my opinion, he relies on hand-waving way too much. He provided no support for any of his statements - you're expected to accept his statements as self-evident facts. I mean, I can factually point out that some PNW soils naturally contain low levels of Uranium. The real question is exactly what empirical amounts constitute "low levels", and whether the "low level" that leaches out of the wood corresponds to the "low level" that's considered safe exposure.
3) I've never heard any knowledgeable person express concern about arsenic uptake in plants - and that seems to be the whole thrust of his argument regarding its relative safety. The concern, rather, is with direct ingestion (dust or larger wood pieces) and with indirect ingestion (soil). That's why ...
4) CCA-treated wood is expressly prohibited for use in situations where it may come in direct or indirect contact with food - check out its MSDS. I would argue that this means its use in a vegetable garden is unwise.
5) CCA-treated wood is currently being removed from the market completely as the result of negotiations between the EPA (under the current administration, no less) and the wood products industry. Their main concern is the level of arsenic exposure to children. Evidently he EPA does not seem to share Dr. Felsot's opinion regarding how well the soil binds to the arsenic...
BTW note that the article was amended to mention the "voluntary" CCA ban. The article itself is about 10 years old, and most of the science that's lead to the CCA ban has been done since then.
Travis
growsherown
Location: Olympic Peninsula
Posted: Sep-14-2004 at 7:26am
Oh I agree completely, trav..science has come along way on this topic. My reason for posting this article wasnt to mislead anyone on this topic, only to express how important it is to use whats available, and to be leary of falling into "trends" that can be expensive and not work as well as some of the old standbys. I would hate to see anyone turning down a nice pile of PT timbers for thier garden, when they can be either sealed or the beds can be lined before planting, as some folks do anyways to prevent weeds.
Additionally, I think that someone would litterally have to ingest a wheelbarrow full for PT wood in order to sustain any ill effects at all, and as the article mentions, the plants themselves would show toxicity way before they produced edibles.
Who knows....maybe in another 10 years, science will be led again down the popular belief road, (as scientific discovery is often fueled by some groups concerns and innacurate statistical evidence)...and change this again. A good example of this would be....The Oat Bran trend. Remember when science determined that Oat Bran was this amazing heart disease and cholesterol fighter??.....sent people flocking to the stores....Cheerios flying off the shelves in record numbers..only to later be determined that unless used in smaller quantities, was causing bowel and digestive disorders such as Irritable Bowel Syndrome and Colitis?
Just goes to show you.....in certain circumstances, science can be way off base too......as fickle as it is. Sure..its all we've got to go on, but Im sure not going to rip out my raised beds....nor will I turn down any offered to me.
Just taking all avenues in for consideration....
Happy Gardening!
DebbieTT
Location: Washington, Kitsap Peninsula
Posted: Sep-15-2004 at 4:16pm
I moved this over to a new topic since Nui is an organic gardener and her topic isn't about the pros and cons of PTL.
Personally I would not use pressure treated lumber near any food source, I have read all the facts about it and I think you missed Trav's point that "CCA-treated wood is expressly prohibited for use in situations where it may come in direct or indirect contact with food - check out its MSDS. I would argue that this means its use in a vegetable garden is unwise. "
Before anyone decides to use PTL in their vegetable garden I think it very wise to read all the updated facts about it. That it has been pulled off the market makes it some what a mute point. I do not know much about the replacement product yet and I am not willing to be an industries' guinea pig as to whether it is safe or not. Too many safe alternatives out there to build a raised veg garden with.
gary
Location: Washington, Puget Sound Corridor
Posted: Sep-15-2004 at 6:51pm
Sorry Trav, but here we disagree.
Comparing a cutting board, honey in a bee hive, etc. to even carrots or beets in a raised veggie bed has nothing to do with exposing "under circumstances where the preservative may become a component of food or animal feed"!
Governments like my nuc-free Olympia are now starting to replace cca playgrounds, on a 10-year cycle, to avoid exposing young children to licking the dust off there hands. That is the same reason that stoping using it for deck wood is happening.
Some years ago, Kitchen Gardener Magazine editor, Ruth LIvely, did an article on this and found that beyond TWO INCHES from the frame cca wood, the arsenic level was lower than the native soil below the raised bed. If you did a complete soil test, I think that you'd find that your location slightly east of downwind of the old ASARCO stack has MUCH higher (>8 ppm) arsenic levels than could ever come from cca treated raised beds. In fact, the improved drainage above your clay soil would likely reduce your exposure to arsenic.
And wait until I tell you how high grocery store carrots are in arsenic. My point is if you wash your root veggies, you will not be exposing any food as in on a "cutting board".
Gary
trav
Location: Washington, Western
Posted: Sep-15-2004 at 9:18pm
Originally posted by gary If you did a complete soil test, I think that you'd find that your location slightly east of downwind of the old ASARCO stack has MUCH higher (>8 ppm) arsenic levels than could ever come from cca treated raised beds.
Uh, no. You're not getting the prevailing wind direction correct. We don't get winds from the west where I live. They're from the south most of the time, but occasionally from the north. Every once in a while we'll get an east wind downslope from the Cascade foothills.
Here's a map showing the prevailing winds at the smelter site. Note they run roughly north-south there as well.
As an interesting aside, here are WSU's recommendations for vegetable handling when grown in arsenic contaminated soil (Taken from the state dept of ecology pages having to do with remediation of the Ruston Smelter contamination). You might find bullet point #5 somewhat interesting:
But back to CCA treated wood. Bottom line: It has been withdrawn from the market for non-industrial residential uses. Period. I'm sure you can still buy it, but you're not supposed to be using it for any of the things you're probably considering it for!
Travis
cjmiller
Location: Oregon, Willamette Valley
Posted: Sep-16-2004 at 5:16pm
Consider using cement block for raised beds instead of wood. Simple construction, doesnt rot, easy to move, can be done by a little old lady like me, although, Husband's raised beds are perfect, mine still keep the soil somewhat in line! Lol--I thought it meant "Little Old Lady, not laughing out loud! Ha.
Carol
sparklemama
Location: Western Washington
Posted: Sep-21-2004 at 2:50pm
You garden your way, I'll garden mine.
My husband builds buildings for a living and on an average month he brings home over 5 stacks of all kinda of wood, lots of it PT. Infact I have the most beautiful, sturdy as heck veggie beds made out of..guess what pressure treats. They are well lined and I am not in any way worried that my kids are going to lick their hands after they have been out there. Neither am I worried about ingesting anything from my veggies as they are well washed.
All I know is that without all that free wood I would never have been able to have one heck of a veggie garden thats for sure. And i guess if its not for residential use, then I am breaking the law.
Lisa A
Location: Oregon, Greater Portland Metro
Posted: Sep-22-2004 at 10:06am
Posted in big letters at my local yard debris recycler is a sign that says they do not accept pressure treated lumber. They have a few other exceptions - particle board, too, I think. However, when we've dumped yard debris, we've been side by side with people dumping PTL, ignoring the prohibition. It doesn't happen often, thankfully, but it does happen. Since the wood will, at some point, need to be replaced, it has to go somewhere - to a yard debris recycler or to the dump/landfill.
What happens when this stuff is composted and used in mulch? Are there any studies that talk about this issue? I could google but I'm hoping someone has already looked into this. I've already posted that I'm relying on my local supplier as my source for garden mulch/compost, knowing the chances I take, and I'd like to be more informed about this matter. TIA!
Screaming Eagle
Location: Puget Sound corridor
Posted: Sep-22-2004 at 12:04pm
Just my two cents but whenever there is even a bit of concern about a chemical, I prefer to avoid it if at all possible. Especially when it comes to my children. It has been proven that they are more suseptible to toxins in general because of their growth rate and the fact that they are still developing.
We built a tree house and used treated wood for the supports, but used non-treated wood on all the other surfaces since they'd be touching those. Maybe I'm overly cautious, maybe a little paranoid. But I don't like to wait until someone proves it's harmful. I also don't believe you can count on the government to protect consumers it's up to us as consumers to use commen sense and educate ourselves as much as possible.
Lisa A
Location: Oregon, Greater Portland Metro
Posted: Sep-23-2004 at 9:24am
I haven't had time to call Metro Recycling or my local mulch supplier to ask them about any concerns regarding PTL in compost so I did a little googling and found some informative and, IMO unbiased, articles about PTL. It is, as is the case with many things, a complex issue.
Personally, I choose not to use PTL. I can look at several examples of materials we used to use in abundance, believing them to be safe, that now are shown to have serious health risks. One example is asbestos. Once upon a time, it was everywhere - it ceiling tiles, in floor tiles, in insulation, in school labs. After years of working around asbestos in his job as a welder at Carnation, my uncle is now terminally ill with Pulmonary Fibrosis, a result of his long-term exposure to asbestos. This may or may not be a valid comparison since my uncle's illness was due to chronic exposure and these are 2 different elements so effects will likely be dissimilar. But I also recognize that we will not know long term effects for years and I prefer, as Theresa does, to not take the chance when I have other options (I like grammagt's suggestion of cement blocks). That's my choice.
If you'd like to learn more to decide this issue for yourself, read the following articles.
Does Pressure Treated Wood Belong in Your Garden?. This is from the pages of Kitchen Garden, one of Gary's favorite, but sadly defunct, magazines and the article Gary quotes above. According to this article, leaching is only part of the concern about the product. While arsenic is in our soils, as Gary pointed out, it is organic arsenic; what is used in PTL is inorganic. The 2 types should not be compared, IMO, but I'd love to hear from someone with a chemist's degree (I took a few chem classes and loved - yes, I know, I'm weird - organic chemistry, but that was a long time ago and my knowledge is fuzzy.)
Raised beds--Is pressure-treated wood safe in raised beds? This article made a good point: If you are an organic gardener purist, then PTL has no place in your garden. It also mentions precautions that should be taken when working around PTL as well as proper disposal.
Both of the above point out that PTL has no place in compost. I'll post when I find out more about this issue.
JeanneK
Location: Oregon, Greater Portland Metro
Posted: Sep-23-2004 at 10:31am
Lisa, I am not a chemist but my husband is and he would say always follow the MSDS and all product directions. I have not told him about this thread but we have talked about PTL and would never use it for veggies. I'll send this post to him and we can get his 2 cents worth.
I do have PTL on my property. The previous owners built a fence out of PTL to house non-existant chickens. Evidently the lady who owned our house like to keep up the property just as her parents had it. They had chickens a long time ago and she had the fence replaced with PTL. Still looks as good as the day it was put in, I guess. I will probably dispose of them (properly, of course) when we take the fence down.
Jeanne
JeanneK
Location: Oregon, Greater Portland Metro
Posted: Sep-24-2004 at 8:36am
Well, my chemist hubby made a liar out of me. He says he would use it for raised beds but not for compost bins as Lisa's link from Fine Gardening above recommends. He felt the article was well-researched and explained the issue very well. Here is a link to MSDS and CSIS for CCA pressure treated wood for further backup information.
However, I agree with Theresa. It's better to be careful. I personally wouldn't use it for raised beds and definitely not for compost bins.
Jeanne
Lisa A
Location: Oregon, Greater Portland Metro
Posted: Sep-24-2004 at 9:10am
Oh, dear, Jeanne, shame on him for making you a liar! LOL
Thanks for posting his response and the additional information for our members.
Did he say whether effects of organic vs. inorganic arsenic can be compared? This may not have any bearing on this debate but I would like to know. TIA!
HarleyLady
Location: Willamette Valley
Posted: Sep-24-2004 at 12:44pm
I'm watching this with interest, particularly the discussion on organic vs. inorganic arsenic. Our water (from our well) has a higher than legal level of arsenic and we spent considerable money putting in a system to remove it.
I talked to a specialist at OSU, recommended by the agricultural agent, and she told me that the arsenic is in the rocks of our area and the level of arsenic could change from day to day depending on the depth of the water table and where the well was drawing.
She said it isn't safe to drink long-term but I needn't have any concerns about eating vegetables that had been irrigated with the well water.
HarleyLady
JeanneK
Location: Oregon, Greater Portland Metro
Posted: Sep-24-2004 at 1:05pm
Sounds like inorganic arsenic is more dangerous. This is an interesting quote from the Fine Gardening article in Lisa's link that talks about inorganic vs organic arsenic: "According to the Agency for Toxic Substances and Diseases Registry (ATSDR) in Atlanta, we can ingest up to 0.3 micrograms of inorganic arsenic per kilogram of body weight per day and not be harmed. The average American woman, who weighs 132 lb. or 60 kg., would have to eat more than 18 micrograms daily all her life to see any ill effects. Before you get alarmed, remember this is inorganic arsenic we're talking about, not the organic types predominant in our diet. And, an ATSDR spokesperson points out, 0.3 microgram is a low estimate for the maximum tolerable dose."
BTW, HarleyLady, you might be interested in a link we found on organic arsenic in the City of Fallon water source.
Jeanne
bakingbarb
Location: Washington, Western
Posted: Oct-30-2004 at 12:01pm
Ya know OG had included in the articles people that sued and were paid handsomely for the removal of the treated wood and the soil. This was years ago when I read the articles but how can this stuff be safe.
I love the acceptable levels. Who decides what is acceptable? I am not an alarmist or anti govt but the govt decides for us what is an acceptable level of poison in our soil. Why do I feel uncomfortable with that? ~BakingBarb
Red Hare
Location: Oregon coast
Posted: Nov-01-2004 at 2:48pm
I use regular lumber for my vegetable beds, but when I decided to rebuild the steps to my deck, I used pressure treated lumber. Then I gave the steps about 3 coats of deck paint. They look much nicer, and now I don't have to worry about tracking residue into the house.
Am I just fooling myself? Does coating the lumber with paint keep the chemicals from leaching out?
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