Friday, 7 October 2011

CCA - Copper Chrome Arsenic, a mouthful you could never digest.

Treated timber in playspaces, CCA, ACQ, LOSP & Tanalith E.

This summary is an excerpt from  my book "Garden maintenance for playspaces" and is referenced through the Information derived from the CSIRO, APVMA, ERMA, EnHealth, US EPA, Better Health Victoria 
                                                                                                              
Summary
Be aware of the regulations/ legislation in place in your country in respect to the use of timber treated with CCA preservatives. In Canada, the US and Europe their use is prohibited, in others the use of existing structures is allowed (using recommended procedures- see below), in some no guidelines exist.

1) There are no conclusive studies that link playground structures made with timber treated with CCA and cancer. In fact there are a number of studies focused on children’s play environments that indicate that any transfer of arsenic in any form did not pose a health risk.[i] [ii] The UK Health and Safety Executive released the following directive,”Play providers and users should be assured that there is no need to remove CCA-treated items that are otherwise in good order simply because of the presence of CCA. The risk from CCA in this case is extremely low[iii]

2) A link between handling CCA-treated timber (using recommended procedures) and cancer has not been demonstrated, as the potential ingestion rates of arsenic that can be calculated from valid available research are well within tolerable limits[iv].

3) For the wary the following precautions are advised:
· Always wash your hands before eating,
· Do not use wood chip (fines) mulch that have originated from CCA treated timber,
· Paint any existing structures made from CCA timber with exterior coloured UV (opaque) paint. Structures that are constantly used will obviously show greater wear, repaint them yearly or as required.
· If you have or intend to use CCA treated timber in the construction of a raised garden bed line the inside of the bed with plastic and/or plant any root crops at least 100mm from the wood.
· Do not clean CCA treated timber with bleaches, deck cleaners or brighteners that contain sodium hypochlorite, sodium hydroxide, sodium percarbonate, oxalic acid, or citric acid may release toxic chemicals from CCA-treated wood.
· If any construction is being carried out on existing CCA structures ensure that cuts are sealed as above and that any off cuts are disposed off as per your localities regulations. Any individual carrying out work on the structures should be familiar with the PPE that is required as well as safe work procedures relating to any dust generated, sealing of cuts and disposal of off cuts. Under no circumstances can the off cuts be disposed of by burning

4) If, despite the information provided here you are still unhappy or wary of the use of CCA treated timber or have or know of a child who has a particular sensitivity to CCA treated timber DO NOT USE IT, use ACQ, LOSP or Tanalith E- where available).

The main concern with CCA is that it contains arsenic. While not a mutagen, arsenic acts as a carcinogen when ingested at rates above certain tolerable limits. It may initiate skin and liver cancers. The safe or tolerable amounts of arsenic that can be ingested by humans have been accurately determined because, unlike most other pesticides, arsenic occurs naturally and can be found in relatively high levels in the drinking water of some towns in Bangladesh, Japan, Argentina and Taiwan.

Extensive research has shown that arsenic is safe or tolerable to ingest at rates below two µg/kg of body weight per day (World Health Organisation limit), or three µg/kg of body weight per day (Food Standards Australia limit).

Arsenic is the 20th most common element on earth, so the ability for animal life to cope with some level of arsenic is to be expected. Arsenic occurs naturally in Australian soil at concentrations between 0.2 and 50 parts per million (ppm, equal to mg/kg), with an average of five to six ppm.

Copper chromium arsenic (CCA) is Australia's most widely used wood preservative. It has been used safely in Australia for 50 years and some 120 treatment plants are currently operating around the country. During CCA treatment, timber is impregnated with the preservative solution using controlled vacuum/pressure processes

The arsenic used in CCA is in a form (arsenate or pentavalent arsenic) that is five to ten times less toxic than the most toxic form, arsenite (trivalent arsenic). Fixation modifies the arsenate into metal-metal complexes and organo-complexes with wood. Ingestion studies with animals have shown that this greatly reduces its mammalian toxicity.

The fixation process ensures that virtually all the CCA becomes chemically bonded within the wood structure. Since March 2006 producers have been obliged to ensure that the product is adequately fixed before dispatching it from their sites.

The majority of the CCA fixed within timber remains there over its lifetime of service. If it did not, the wood would rot and fail in much less than the 30 - 50 year period for which it is often guaranteed. However, a small amount of leaching inevitably occurs. This can show up in small rises in arsenic levels in the soil close to posts and poles. Studies have found levels return to normal within about 100 mm of posts and 150 - 200 mm of poles or decking.

A number of studies have shown that CCA is not absorbed into above-ground food crops such as grapes[v], tomatoes and cucumbers. There are, however, some reports of a slight increase in arsenic content in root crops such as carrots and beets grown against treated timber, although the arsenic is in a safe organic form and most of it is removed with peeling. Any concern can be eliminated by growing these vegetables more than 100 mm from treated timber garden edgings or by lining the edgings with plastic.

Painting sawn CCA-treated timber has long been recommended as a way of reducing warping and checking and will also reduce dislodgeable arsenic from the timber surface. Oils, stains and clear finishes are often not particularly durable coatings, so that arsenic may still dislodge from the coated timbers. The more durable exterior coloured (opaque) paints reduce levels of dislodgeable arsenic more significantly [vi] [vii].

In Australia, CCA preservatives are regulated by the Australian Pesticides and Veterinary Medicines Authority (APVMA). The APVMA implemented a number of restrictions on CCA that became effective in March 2006. The main implementation affecting the public is that CCA is no longer used to treat timber for structures where there is frequent and intimate contact, such as playground equipment, picnic tables, handrails, decking boards, garden furniture and exterior seating.

A review by ERMA in New Zealand[viii] did not find increased health risks from using CCA-treated timber. Nevertheless, the APVMA felt that more studies were needed to support the continued use of a potential carcinogen in high human contact applications and that without those studies it should be restricted.

An important question, following the APVMA decision to restrict CCA for certain uses, is whether to retain existing CCA-treated timber structures, especially playgrounds. Ultimately, this will be an individual's or organisation's decision. Credible research to date suggests that arsenic ingestion from handling CCA-treated timber occurs at well below tolerable levels if the precautions mentioned above are followed.

You therefore need to make your own informed decisions, and not necessarily believe alarmist claims. Note that the USA EPA in its announcement to restrict CCA stated: 'EPA has not concluded that CCA-treated wood poses unreasonable risks to the public for existing CCA-treated wood being used around or near their homes or from wood that remains available in stores. EPA does not believe there is any reason to remove or replace CCA-treated structures, including decks or playground equipment. EPA is not recommending that existing structures or surrounding soils be removed or replaced.'

Similar statements in Australia can be found from EnHealth Council[ix] and Better Health Victoria[x].

One study by the CSIRO in some local kindergartens found that playground equipment would not pose a health risk due to arsenic[xi]. This suggestion was further supported by a comprehensive study in Canada of dislodgeable arsenic levels on the hands of children, which were lower than anticipated in the APVMA review[xii].

ACQ - Alkaline Copper Quartenary is a relatively new treatment which is a water based solution (copper, Didecyldimethylammonium chloride and water) which uses copper to protect against rot and fungal attack and Ammonium Quartenary as a pesticide. ACQ treated timber possesses most of the same qualities as CCA timber in that it can be used in inground applications. It is considered a very safe and very effective product with no risk to humans. At the moment it is approximately 25% more expensive than the CCA and can be sometimes difficult to source. The Osmose company produces both ACQ and LOSP sealants[xiii] .

LOSP - Light Organic Solvent Preservative is a treatment that is usually a white spirit based solvent which contains copper naphthenates and synthetic pyrethroids as well as other chemicals to provide protection from insects and decay. As an alternative to CCA and ACQ treated timber it is generally more expensive and far less effective.

LOSP treated pine is usually machined to the required lengths and shapes before the treatment is applied. As a result of this less pressure is used in the treatment process and a little less penetration of solution is achieved. This does not affect the longevity of the timber, however it means that LOSP timber must not go in ground and if the timber is cut the cut ends must be resealed with a suitable sealant. Most LOSP treated pine must be painted to maintain its warranty, without painting LOSP treated timbers may only last a few years. NB: The exact type of LOSP treatment will determine its lifespan, and if it has to be over painted. Always request from your supplier written details of painting requirements for any LOSP products. Additionally, due to the solvents in LOSP products they are generally more flammable.

LOSP timber is frequently coated with a protective oil based primer which is usually pink. This primer is applied to stabilise and protect timber during storage and installation, not as a paint primer. As a result it is recommended that LOSP primed timber be sanded down to remove the primer before painting. Unprimed LOSP timber is natural in its appearance as the solution used is clear and hence causes no discolouration of the timber. Like CCA the timber will weather and discolour if not stained or painted.

Tanalith E or Copper Azole - is a new water borne solution which again uses copper as a fungicide and azole as a pesticide, it can be used in inground applications and has most of the same properties as CCA treated timber. Water-based preservatives like copper azole leave wood with a clean, paintable surface after they dry. There are two types of Copper Azole: A (CBA-A), and B (CA-B). Copper azole wood preservative is used for treating a variety of softwood species including southern pine, red pine, ponderosa pine, hem-fir and Douglas fir.

· CBA-A: Copper Boron Azole type A was standardized by the American Wood-Preservers' Association (AWPA)1 in 1995 and contains the following ingredients: copper (49%), boron as boric acid (49%), and azole as tebuconazole (2%). Wood treated with CBA-A has a greenish-brown colour and little or no odour.

The use of CBA-A has been generally supplanted by the newer CA-B product.
· CA-B: Copper Azole type B was standardized by the AWPA in 2002 and is composed of copper (96.1%) and azole as tebuconazole (3.9%). Wood treated with CA-B has a greenish-brown colour and little or no odour. CA-B is in widespread use throughout the United States and Canada.

Koppers[xiv] produce a product called Tanalised Ecowood which meets US EPA and European Union standards for use in playgrounds.


[i] Cookson LJ. 2005. Arsenic content of soil and wood chip fines in three kindergartens Ensis Technical Report No. 151, 16 pp.
[ii] Kwon E, Zhang H, Wang Z, Jhangri G, La X, Fok N, Gabos S, Li XF, Le X. 2004. Arsenic on the hands of children after playing in playgrounds. Environmental Health Perspectives 112: 1375-1380.
[iii] UK H&SE Guidance: Copper, Chrome and Arsenic Treated Timber in Children's Playgrounds. Local Authority Circular 47/18, 2004.
[iv] http://www.csiro.au/resources/CCATreatedTimber.html
[v] Levi MP, Huisingh D, Nesbit WB. 1974. Uptake by grape plants of preservatives from pressure-treated posts not detected. Forest Products J. 24: 97-98.
[vi] Lebow S, Foster D, Lebow P. 2004. Rate of CCA leaching from commercially treated decking. Forest Products J. 54: 81-88.
[vii] Stilwell DE and Musante CL. 2004. Effect of Coatings on CCA Leaching From Wood in a Soil Environment. In: pre-conference proceedings, Environmental impacts of preservative-treated wood. Florida Center for Solid and Hazardous Waste Management, Gainesville, Florida, pp 113-123.
[viii] Read D. 2003. Report on Copper Chromium and Arsenic(CCA) Treated Timber Environmental Risk Management Authority (ERMA).
[ix] EnHealth. 2005. enHealth Council position on copper chrome arsenate (CCA) treated timber products
[x] Better Health. 2005. Copper chrome arsenic (CCA) treated timber
[xi] Cookson LJ. 2005. Arsenic content of soil and wood chip fines in three kindergartens
[xii] Kwon E, Zhang H, Wang Z, Jhangri G, La X, Fok N, Gabos S, Li XF, Le X. 2004. Arsenic on the hands of children after playing in playgrounds. Environmental Health Perspectives 112: 1375-1380
[xiii] http://www.osmose.com.au/
[xiv] http://www.koppers.com.au/ArticleDocuments/38/Tan%20E%20FAQ_2.pdf.aspx?Embed=Y


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