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Overseas research has come to some worrying conclusions about the effects of chemically treated outdoor timber. Sharon Beder writes that Australian manufacturers are still selling until they see more conclusive research.
WOOD treated with arsenic is commonly used for decking, fencing, poles and most outdoor uses of timber. It can be recognised by its green tinge. Families eat their lunches off arsenic-treated picnic tables, children clamber over arsenic-treated playsets, home handymen and women saw and sand the treated wood, and the sawdust is even composted and put onto vegetable gardens.
The green tinge comes from the chemicals that are used to saturate the wood. A potent mixture of copper, chromium and arsenic (referred to as CCA) is injected into the wood under pressure. The chemicals prevent rotting, fungi and wood-boring insects and allows wood such as pine to last outdoors for decades.
Australian authorities are reviewing the use of preserved timber in the light of evidence that wood treated with arsenic poses a health threat. Arsenic-based timber preservatives are being banned and phased out overseas.
However, Australian manufacturers insist they are safe.
New studies have found that the arsenic leaches out of the wood over time, leaving a residue on the surface and in the soil.
Last year a study by the Washington DC-based Environmental Working Group (EWG), with the University of North Carolina-Asheville's Environmental Quality Institute, found the "amount of arsenic that testers wiped off a small area of wood about the size of a four-year-old's handprint (100 square centimetres) typically far exceeds" what US environmental authorities consider safe in a glass of water.
According to the World Health Organisation, arsenic causes various cancers, including lung, bladder and skin.
Sean Gray and Jane Houlihan, the authors of the EWG report, point out that "children put their fingers and hands in their mouths frequently and can ingest significant amounts of arsenic". Arsenic can be transferred to the mouth by adults if they don't wash their hands before eating or if food is placed directly on treated decks or picnic tables.
Because of concerns raised by its study, EWG petitioned the US Consumer Product Safety Commission (CPSC) for a ban on the use of CCA-treated timber for playground equipment. CPSC then did its own studies.
Last February, CPSC scientists published their findings that "exposure to arsenic from CCA-treated playgrounds could be a significant source of arsenic" for children. They estimated that children between two and six years old who play regularly on CCA-treated playground equipment have a significantly increased risk of lung or bladder cancer over their lifetimes. Australian manufacturers dispute these findings.
Elias Akle, general manager of Osmose Australia, a major manufacturer of the CCA timber preservative, says: "We believe properly CCA-treated timber poses no health hazards when handled correctly. We believe that CCA-treated timber is fine for children to play on. People should follow commonsense practice. People should not eat food which is placed on treated timber in the same way they should not eat food placed on a concrete path, etc."
Peter Carruthers, the marketing manager for Koppers Arch, a major manufacturer of treated wood in Australia, says: "We support the continuing use of CCA until there is conclusive scientific evidence that shows that CCA poses unacceptable risks to the community or the environment."
Koppers Arch contends that the CPSC study should be dismissed because the American watchdog is not "an expert authority in this type of epidemiological risk analysis". However, CPSC's studies have been peer-reviewed by scientists in the field.
And Koppers Arch has been citing an older CPSC study for many years to support its claims that CCA-treated timber is safe. On its web page Koppers Arch states: "Our industry has often referred to that original study when defending CCA so it is particularly concerning that the CPSC has now apparently changed its position."
Koppers Arch plays down the CPSC report by describing the study as finding only "a slightly increased risk of certain cancers (lung and bladder cancers)".
However, paradoxically, Koppers Arch also says, "if the estimates of the risks from this level of arsenic exposure are anywhere near correct, then there should be epidemic levels of those cancers in the community as a result of this exposure".
CCA-treated wood has been banned in several countries, including Switzerland, Vietnam and Indonesia and severely restricted in others such as Japan, Sweden and Germany.
In January this year the European Commission issued a directive that arsenic compounds could not be used for the preservation of wood and CCA-treated wood could not be marketed. The only exception was for necessary industrial purposes where there was no viable alternative.
Manufacturers in the US have agreed to voluntarily phase out the production of CCA-treated timber for residential uses and the US Environmental Protection Agency will ban production for residential uses from next January.
Although the EPA had not completed its risk assessment of CCA it said that because arsenic was a known carcinogen "any reduction in the levels of potential exposure to arsenic isdesirable".
A similar voluntary phase-out for non-industrial uses has been instituted in Canada.
The Australian Pesticides and Veterinary Medicines Authority (APVMA) is the national registration authority for CCA in Australia. It decides whether CCA is safe to use, whether its use and disposal are safe for the environment, and what warnings and instructions should be put on the label of CCA products.
Dr David Loschke , the principal scientist with APVMA, says "the decision to review the registration of these products follows international reports of new scientific information that suggests possible risks associated with their use".
Carruthers says that Koppers Arch will be making a submission to the review and putting the best case it can that CCA should not be restricted in the way it has been overseas.
"We have been assured that APVMA will be rigorous and balanced and take into account not only recent overseas trends but also local market and industry conditions that may set the Australian situation apart from that in North America and Europe, for example."
APVMA will prepare a draft report for comment by about the middle of next year.
In the meantime, CCA-treated timber is being sold to the public from hardware stores without warning labels. Two years ago manufacturers in the US agreed to put warning labels on CCA-treated timber and provide consumer safety information sheets.
No such labelling is necessary in Australia.
According to Osmose Australia's Akle, "All treated timber as well as untreated timber requires special handling guidelines. We produce a variety of literature which outlines these requirements and this is available to anyone, including our customers, wholesalers, retailers and the general public."
The US EPA advises, "Saw, sand and machine CCA-treated wood outdoors. Wear a dust mask, goggles, and gloves. Clean up all sawdust, scraps, and other construction debris thoroughly. Do not compost or mulch sawdust or remnants. Do not burn CCA-treated wood, as toxic chemicals may be released as part of the smoke and ashes. After working with the wood, wash all exposed areas of your body, especially the hands, thoroughly with soap and water before eating, drinking, toileting, or using tobacco products. Wash your work clothes separately from other household clothing before wearing them again."
However, hardware sales staff are unaware of the need for such precautions. In one of Bunning's timber yards a salesman said the treated wood was fresh from the factory and "it would be best to leave it to dry out for a month or so before painting it because otherwise the chemicals in it would ooze out through the paint". He knew nothing of other precautions to be taken when working with it.
It is not just freshly treated timber that is a problem.
The EWG study found that arsenic levels on CCA-treated wood remained high for 20 years and sealants such as paint and varnish are effective at reducing arsenic levels on the surface of the wood for only about six months. The green tinge fades with time but the arsenic keeps on leaching.
There are alternatives to using CCA-treated timber that include substituting alternative timber treatments, naturally resistant woods that don't need treating, or alternative materials.
Koppers Arch sells an alternative called Ecowood, which it says performs just as well, and Osmose manufactures NatureWood ACQ which, according to the Prime Pine website, comes with a 40-year-guarantee, "is competitively priced with CCA-treated timber" and "requires no special precautions" to work with.
Carruthers admits there is considerable support for changing to alternative treatments but argues that these alternatives are expensive and "there could be a risk that enforcing this change in certain product areas may just cause loss of market to substitute materials".
In other words, if the price of treated timber increased then consumers might choose other materials such as plastic, steel or concrete rather than wood.
According to the CSIRO's division of Forestry and Forest Products, "preservation allows about $500 million worth of timber to be used in Australia in areas and applications where it would otherwise be unsuitable".
To be treated with care
Steps an individual can to take to reduce exposure: