Paul Nicol (pmgnicolxtra.co.nz) asks:     [Oct 11, 2007]
Tanalised timber in gardens

Is it proven that there is risk to people from eating vegetables grown in tanalised timber bordered gardens or is it speculation. I wouls suspect that there are many organic gardens in NZ with tanalised timber. I am interested to hear feedback on this.

I also would like to know as I have tanilised posts in my garden with the occasional tanalised 6x4s. Most of the beds are recycled totara posts and old car tyres.

Nadene (nadenehactrix.co.nz) says:

According to this link...

http://www.waitakere.govt.nz/AbtCit/ec/bldsus/pdf/materials/timber.pdf

... which is an ecology factsheet written by Reinhard Kanuka-Fuchs, ANZIA, architect and director of the Building Biology and Ecology Institute of New Zealand for the Waitakere City Council...

The most common timber preservation in NZ is CCA - Copper Chrome Arsenic.
Commonly known as tanalised timber, it has a distinctive greenish colouration. CCA is a mixture of metallic salts composed of arsenic, copper and chromium, which protects wood from decay by microbes, fungi and wood-feeding insects. The
treatment chemical is highly toxic but once chemically fixed to the timber it is inert. Be suspicious of timber that shows surface wetness from excess chemicals or
which has crystalline chemical deposits on it. If you buy timber with the Timber Preservation Authority’s "Woodmark" brand you can be confident that it has been processed in a modern treatment plant to the standards of MP.3604.

Chew (permaculture.b70gishpuppy.com) says:

Hello Paul

Toxins (heavy metals) leached by treated timbers are accumulated in plant tissue so their use in food production systems to be discouraged (as is using tyres but that's another issue!)

From a permaculture perspective materials that have high production energy requirements and large environmental footprint should be avoided if possible in any sustainable design

From an organic prospective treated timbers separated from the growth medium with plastic sheeting prevents any leached chemicals coming into contact with the roots of plants

Source: Raised beds
http://www.50connect.co.uk/50c/organicgardening.asp?article=2756

"The American magazine 'Organic Gardening' has been leading the fight against using pressure treated timber in the garden for the last few years. They often refer to scientific research showing that CCA treated timber leaches arsenic and chromium into the soil. And from the soil it goes into your homegrown vegetables and then according to OG into you"

Source: Wood Preservatives & The Organic Standards Covering their Use
http://files.recycleworks.co.uk/files/Wood%20preservatives.pdf

"Tanalised, pressure treated or CCA timber are all terms for a wood
preservative system based on copper, chrome and arsenic. For years we at HDRA
have advised our members not to use tanalised timber to edge vegetable beds
and make compost boxes, simply because we felt that the chrome, a toxic heavy
metal, and arsenic, a poison used in the preservative had no place in an organic
garden

These worries were confirmed in spring 1997 by alarming reports from the
USA. Researchers found that decks made from tanalised timber can leach high
amounts of arsenic into nearby soil. Samples taken from beneath treated
decking contained up to 80 times more arsenic than surrounding soil and as much
as 35 times the legal limit for arsenic in the soil. The study found that arsenic leaches quickly from treated wood..."

Chew

Joerg Haase (jkhaaseclaer.net.nz) says:

Hi Paul,
funny to find another question from you.
Any chemical protection for timber has to be toxic. Otherwise it would not work. If it would affect no other plants or animals it would not protect the timber against them. So it will also affect the plants you want to eat. There is no chemical protection that lasts for ever, they only slow the process of rottening down. This processes will set the chemicals free and it will not start in some years but now, only a bit slower.
Many of these remedies are soluble in water (metal salts)and are only considert for internal applycation like framing for walls and roofs and the oil based ones have quite bad effects on the humans ( neurologic poisen ).
I would suggest to make stone borders to avoid the timber-soil touchment.
You have to appologize sat mi inglish is stil not gud enaf to explain more.
Regards Joerg

Sarah (Sarahbogle-callaghan.net) says:

NZs vineyards have been ripping out their tanelised posts over the last few years. For more info see Marlborough District Council Report on Arsenic Leaching from treated Vineyard Posts

In summary the findings are that:

* Overseas studies have found that over time arsenic from treated posts leaches into the soil.
* Arsenic leachate has been found leaching from posts in Marlborough. In some cases it was found up to 500mm from the posts and further beneath the post.
* Some 25% of the tests exceeded health guideline levels.
* So far, evidence has yet to determine the amount of leachate as a casual agent in death. The Environmental Protection Agency of the United States Government has been moved to ban all treated timber in house construction, playgrounds etc.
* Arsenic apart from being a deadly poison is also a carcinogen in lesser quantities and has been found to cause skin cancers, oesophageal cancer and lung cancer.
* With the rise and fall of the water table in the Marlborough region and the fact that posts are dipping in and out of the groundwater it is reasonable to assume leaching of arsenic into that water.

See http://www.marlborough.govt.nz/content/docs/documents/CCAReport-HortResearch-Public.pdf for full report

Cameron Wilkes (cameronenviroguard.co.nz) says:

This is an old topic but I have a alternative to tanalising timber.

It's water based, non-flammable, ecologically safe, biologically safe & non-hazardous.


Here's what the label reads:

ECOSHIELD is a revolutionary, water-based silicone rubber liquid emulsion designed to penetrate and seal porous surfaces, thereby making them resistant to penetration by water, other liquids, oils and mild acids.
ECOSHIELD’s water-based formula allows the silicone rubber to be carried into the substrate, forming a bond within, sealing pores and cavities, thereby giving a depth of protection rather than just a surface coating as with most other sealants.
ECOSHIELD is permeable, which allows it to breath, releasing trapped moisture beneath the surface in
the form of vapour.
ECOSHIELD is an almost odourless, non-toxic,
non-flammable, environmentally safe formula and just one liberal coat is guaranteed to protect the life and beauty of any porous surface for at least 10 years.
ECOSHIELD can be applied by the do-it-yourselfer
or tradesman alike. Best of all, ECOSHIELD washes up
in soap and water and there is no need for seasonal
re-applications.

ECOSHIELD’s Beneficial Properties Include:
• Elastic - up to 400% stretch
• Penetrating and bonding formula designed to seal and protect hidden substrate voids and channels in porous surfaces.
• ECOSHIELD is unaffected UV light, salts, mild acids, other liquids including oils and is guaranteed to never crack, yellow or degrade.
• ECOSHIELD is permeable meaning it breathes which allows any trapped moisture to escape in the form of vapour from within the substrate.
• ECOSHIELD is a fire retardant
• ECOSHIELD is timber’s best protection from the elements such as water penetration and mould growth.

It mentions a 10 year guarantee - it would last at least twice to three times as long with no foot traffic etc.

www.enviroguard.co.nz is underconstruction but should be online by December 08

Adam Guyton (aguy10actrix.co.nz) says:

I'd be very cautious as a permaculturist using ANY product, whether it be Tanalised, sealed, ECOSHIELD'ed or anything which is designed to stop things decomposing, burning or degrading, which seems to be the aim of many naive innovators.

Even if something doesn't "chemically" poison the soil (or person), it is still a physical pollutant and will become the bane of future gardeners who have to pick up the splinters of indestructable wood covered in *#**! silicone :(

It is VERY unwise to create any product which is intended to last forever. And it is extremely arrogant to believe that any such thing (be it garden bed or fence) is worthy of outlasting it's conciever!

Paul... Mayor of Edivale!!! you know better!

And besides... garden edgings limit the movement and natural development of the garden ecosystem.

If you must, use clay or wood or some other natural thing which will be returned to the soil

Adam (aguy10actrix.co.nz) says:

my apologies Paul, you aren't the paul i thought you were! :)

david n (davidnixtra.co.nz) says:

I've put all my food plants near my treated-timber in pots because I'm worried about this poisoning risk. However, most of my pots are plastic, someone I know who reads the paper tells me plastic leaches out toxins too! I think I'll worry about that another day.

As is common with science it seems hard to get a straight answer from anyone on this treated timber issue. Many sites appear potentially biased, either industry insiders or (possibly) green zealots(I'm not referring to anyone here), most of the sources I've found agree some leaches out close to the wood but whether it it worth worrying about may actually be uncertain. Still best to take precautions if poss I reckon.

Vicki (raevparadise.net.nz) says:

I have a new large wooden planter box I just bought to grow salad vegetables in. It occurred to me it might contain arsenic etc. I rang the supplier who said arsenic/chrome etc no longer used but "tannins" instead. I assume they meant tanalised which gets back to Arsenic/chrome/copper etc.
I am reluctant to line the box with plastic for the same reason. Any suggestions?
Thanks
Vicki

David (davidnixtra.co.nz) says:

The Institute for Local Self Reliance Website has quite a bit on plastic safety, if there's a problem they'll know about it;

http://sustainableplastics.org/problems

They might answer questions, I haven't tried.
some plastics are apparently ok at least

Glen K (glenkclear.net.nz) says:

I have another question of a relative nature. How about the mortar used for creating brick or stone gardens ? Also.. does anyone know about using bleached paper in a garden ?
Thanks.

Cameron Wilkes (cameronecoshield.co.nz) says:

Adam,

I respect your stand but unfortunately most people don't have the time for the permaculturist lifestyle and are still going to use treatments and sealants regardless.

This product is the least toxic of any similar products on the market.

Step O'Rafferty (hutuangagmail.com) says:

I feel that any toxic chemical, whether directly applied to the soil or impregnated into materials in contact with the soil has no place in an organic garden or in any food producing garden for that matter. Any person who does apply toxic chemicals is indicating that he/she has no regard for the rights of any person in the future who may need to have access to clean and healthy soil in order to produce food.

Chris (chriscovichlycos.com) says:

I like the pragmatic suggestion of lining with plastic, but in the case of a compost bin will paint or a sealer of some kind prevent leaching?

Jessica (vega12comcast.net) says:

I have been told that Cedar is the best wood to use for organic raised garden beds, due to it's natural oils which act as repellants. As far as I know, Cedar does not need any chemical treatment because of it's natural composition. Does anyone know either pros or cons about using Cedar wood for a vegetable garden? Any help would be appreciated!! Running out of options here.... can't use plastics and I have yet to find any other untreated type of wood. Thanks!

Lynn (freshair94066yahoo.com) says:

This is so frustrating. Am currently planning to buid a veggie patch and compost bins in Queensland, and while my seedlings are growing bigger every day in pots without a permanent home, am wondering what to do. Of course, the guys at the lumber yard say the tanalised wood is no problem, but they're not the ones who are going to all the trouble of growing from seed, and eating the food the garden produces. May end up using rocks as garden edge, even though my partner hates the idea (doesn't look as nice, etc.).

For aesthetic edges, plant box hedge, and run the grass up to that. on the other side make your garden beds.

Entirely natural edge definition. To make this easier, and more noticeable at the start, trench around your garden beds and use branches and logs sawn from trees. Seriously. It works great.

Ben Elms (benelmsparadise.net.nz) says:

there are many pros to raised beds and I'm sure cons too. Macrocarpa is commonly used, in the south Island a lot of it coming out of old windbreaks, the trees coming to the end of their useful lives.
You can expect to get up to 10 years out of Macrocarpa used for a raised bed. Though this does depend on the environment. I doubt you'd get that in Queensland. But for NZ it does offer an option.Larch is another option. I don't know much about Cedar, but I imagine it will come down to availability and cost. Other options would include clean old hardwood railway sleepers/bridges/telephone poles but again cost and availability will be major determinants. With a little work corrugated iron from old roofs will make great raised beds, put a wooden top on any exposed edges and corners and you have a long lasting / asthetically pleasing raised bed (and cheap compared to the price of all that wood, the iron often dumped or very reasonably priced at recycling centres. Another option is Straw bales. They create an edge for all the insect goodies in the garden and in a couple of years replace with new bales and the old ones become a lovely decomposing mulch for your garden. Happy growing!

Wanakabob (sunnatavodafone.co.nz) says:

It has been a pleasure to read all of these postings {excuse the pun} treat them all with respect but not with CCA I say. I have recently arrived back here in Wanaka, Sth Island from West Oz and have been appalled at the enormous usage of treated timber for garden landscaping,decking,playgrounds and fencing etc etc etc.The Green Image of N.Z.should not be Copper Chromium Arsenate. It has prompted me to write in to the local rag with concerned information as to the health risks attributed to both CCA and Creosote treated timber.There are sooo many alternatives.I have 20 years experience as a Permy Facilitator and have researched this one a lot. Bear in mind N.Z. is the 2nd largest producer of CCA treated timber on earth and remember that Govt. economic decisions almost always impact decisions regarding project materials and sooo much reporting on this topic has been carefully dumbed down to keep the Industry pumping. Wade through all the guff on line and stay focussed, I think you will all see the truth, the bullshit,and go natural, clean and green.

bec may (freelancefaeriegmail.com) says:

bugger. secretly, at the back of my mind, i knew all this. but then i let the man at the timber place sell me treated timber as the best option for long term use in the garden... tragically, too many of my decisions are budget driven, as with this one. however, i do have the option to line my bed (not too difficult!). and of course, in the future, trust my own instincts (how often to i say that?!)
many thanks for the information
b