Timber Leachates Prompt Preservative Review

Sharon Beder


Citation: Sharon Beder, 'Timber Leachates Prompt Preservative Review', Engineers Australia 75(6), June 2003, pp. 32-4.

This is a final version submitted for publication.
Minor editorial changes may have subsequently been made.

Sharon Beder's Other Publications


A growing body of new scientific evidence that CCA-treated timber poses a danger to both humans and the environment is causing authorities around the world to impose tighter restrictions on its manufacture, use and disposal. In Australia a major review is being undertaken in the light of this mounting international evidence. The national registration authority for CCA is APVMA (the Australian Pesticides and Veterinary Medicines Authority). 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. (APVMA will also be reviewing arsenic trioxide which is used as a dust inside and outside the home for treating termites.)

CCA or copper chromium arsenic is a timber preservative. It has been widely used in Australia for residential, recreational and industrial purposes for several decades. These purposes include power poles, boat bulkheads, dock pilings, posts and trellises in vineyards, decking, playground equipment, picnic tables, fencing, retaining walls, and other outdoor uses of timber. CCA-treated timber can be identified when it is new by its green tinge but this fades with time.

Wood, such as radiata pine, is treated with CCA to prolong its life. According to the CSIRO, "preservation allows about $500 million dollars worth of timber to be used in Australia in areas and applications where it would otherwise be unsuitable". The copper (23-25%) and arsenic (30-37%) in CCA act as fungicides and insecticides, while the chromium (38-45%) fixes the chemicals into the wood. The chemical mixture is injected into the wood under pressure so that the wood is saturated with the chemicals. It prevents rotting, fungi, termites and marine organisms.

However there is evidence from several published scientific studies that the arsenic leaches out of the wood over time. This means that there can be residues of arsenic on the surfaces of the wood and it can be washed off by rain to accumulate in the soil or water below. According to the US Environmental Protection Agency (EPA) "The amount and rate at which arsenic leaches, however, varies considerably depending on numerous factors, such as local climate, acidity of rain and soil, age of the wood product, and how much CCA was applied."

According to the World Health Organisation (WHO) and the US EPA arsenic is "a known carcinogen and is acutely toxic". It can cause various cancers including lung, bladder and skin cancer, as well as non-cancer damage, including reproductive and neurological. People can be exposed through touching the timber as surface arsenic sticks to human skin. It can be absorbed by the skin (less likely), breathed in with wood dust particles, or transferred to the mouth, for example by subsequent handling of food. 

There are already alternatives to using CCA treated timber that include substituting alternative timber treatments, naturally resistant woods that don’t need treating, or alternative materials. According to the CSIRO, if the alternatives were used more their price would probably fall. Also more alternatives would be developed if CCA was not available. Chemistry and Industry, the magazine of the Society of Chemical Industry in the UK, reported that in Europe, the "increasing scrutiny" that CCA treatments was coming under in the 1990s was "one of the major driving forces in the development of new wood preservation systems." 

In February 2002 the US EPA announced that manufacturers had agreed to voluntarily phase out the production of CCA-treated timber for residential uses over the following 2 years and in January 2004 the EPA would officially ban the manufacture of CCA-treated timber for residential use. Although the EPA had not completed its risk assessment of CCA it claimed that because arsenic was a known carcinogen "any reduction in the levels of potential exposure to arsenic is desirable". A similar voluntary phase out for non-industrial uses has been instituted in Canada.

Environmental groups who had been lobbying the EPA to ban CCA-treated timber immediately pointed out that the decision not only allowed continuing manufacture for another two years, and continued sales of that product after the deadline, but did nothing to deal with treated-timber already in the community already. Older timber is just as likely to leach arsenic. A 2002 study by the Washington DC-based Environmental Working Group (EWG) involving "300 wipe tests from 263 decks, playsets, picnic tables, and sandboxes across 45 states" found that arsenic levels on CCA-treated wood remained high for 20 years and sealants are only effective at reducing arsenic levels on the surface of the wood for about six months. 

Similarly, a 1999 study by David Stilwell of the Department of Analytical Chemistry, Connecticut Agricultural Experiment Station involved a study of treated decks that were between 4 months and 15 years old He took 45 wipe samples from horizontal deck plank surfaces and 12 from vertical poles holding up decks and found arsenic in all cases. There was no correlation between the amount of arsenic and the age of the deck although there was large variability between decks and also places on the deck. 

Stilwell also found that there were elevated levels of copper, chrome and arsenic in the soils below the decks and that the amounts increased with the age of the deck. The average amount of arsenic was 76 mg/kg (138 mg/kg after 8 years) compared with a state safety limit of 10 mg/kg in residential soils. The EWG study found that in "two of five backyards and parks, the soil tested had enough arsenic to qualify as a Superfund site." This means that if it were an industrial site it would be considered hazardous and have to be cleaned up.

EWG, a non-profit research organization, noted that "Over 90 percent of all outdoor wooden structures in the United States are made with arsenic-treated lumber. Under the terms of the phase out, all of these structures will remain in place. Indeed, thousands more will be added to the human environment up until the final phase out date for the pesticide of January 2004." However manufacturers wanted the time so that the 350 or so treatment plants could retool and convert their operations for alternative treatments.

At the end of 2002 a coalition of groups, including the Communications Workers of America (CWA) and the environmental group Beyond Pesticides, sued the EPA to ban the use of various wood preservatives including CCA because of their potential to harm children, utility workers – particularly those installing power and telegraph poles, and the environment. They claimed that alternatives existed including "sustainably-harvested and naturally pest resistant wood species, such as cedar and redwood; recycled steel, fibreglass, or concrete for utility poles or burial of utility lines; recycled plastic for marine pilings; composite lumber made with recycled plastic, borate-based wood preservatives…"

The contamination of sites where the treatment of timber is carried out has long been recognised. The Scientific Committee on Toxicity, Ecotoxicity and the Environment (CSTEE) of the European Commission noted: "There is extensive documentation of past substantial soil and groundwater contamination at wood treatment sites…There is also evidence in the published literature… that contamination of the soil and vegetation can extend to the area beyond the immediate boundaries of such sites, something that has been attributed to wind erosion, percolation, surface drainage as well as on-site incineration of wood waste. Moreover, a number of studies… have reported urinary arsenic concentrations to be substantially elevated (up to ca. tenfold as compared to controls) in wood impregnation workers."

Of most concern is the exposure of children to treated timber. Children are especially vulnerable because they often put their hands in their mouths whilst they are playing, put soil from beneath the play equipment in their mouths, or put food and toys in their mouths that they have handled without washing their hands. They are also more vulnerable than adults as their bodies are less able to metabolise arsenic and are still developing.

EWG and the Healthy Building Network (HBN) published a report in 2001 entitled Poisoned Playgrounds. They had tested treated wood samples and surveyed the scientific literature to find that an "average five-year-old, playing less than two weeks on a CCA-treated playset would exceed the cancer risk considered acceptable under federal pesticide law. Their report, also cited other studies that confirmed their findings.

A 1987 study by the Californian Department of Health Services took samples of arsenic from hands that had touched treated playground equipment and estimated an increased risk of 1 to 60 in 10,000 to children playing on such equipment. A much more recent University of Florida study found that children who regularly touched CCA-treated timber would have an increased risk of cancer over their lifetimes of between 4 in 100,000 and more than 1 in 1000. Dozens of playgrounds in Florida were closed after unsafe levels of arsenic were discovered. The CSTEE recognised in 1998 that there was an additional risk to "children through the ingestion or inhalation of sand particles in playground sandpits" made from treated timber.

As a result of its study EWG and HBN petitioned the US Consumer Product Safety Commission (CPSC) for a ban on the use of CCA-treated timber for playground equipment. The CPSC subsequently conducted peer-reviewed scientific studies of exposure to arsenic via playground equipment. Their scientists found that 2 to 6 year olds ingested 3.5µg arsenic on any day that included a playground visit and therefore "exposure to arsenic from CCA-treated playgrounds could be a significant source of arsenic" for children. They estimated that children at this age who play regularly on CCA-treated playground equipment, whatever the age of that equipment, have an increased lung or bladder cancer risk of between 2 and 100 in a million over their lifetimes. (The EPA considers a 1 in a million chance of cancer as the borderline of acceptability. Above this level regulatory action needs to be taken. )

Another concern with CCA-treated timber is disposal. If CCA-treated timber is burned the smoke and the ash contains high levels of copper, chrome and arsenic, so it is usually disposed of in municipal landfills where it continues to leach arsenic. In the US, material that leaches arsenic is classified as a hazardous waste and cannot be disposed of in municipal landfills. However, CCA-treated timber has again been granted an exemption. 

In Europe discarded CCA-treated timber has been classified as a hazardous waste since 2000. This was after the CSTEE raised concerns about the disposal of treated-timber in landfills: "The CSTEE wishes to underline that a major source of concern regarding the use of arsenic-containing wood preservatives relates to the high degree of uncertainty regarding the speciation of arsenic during its long-term storage in landfills (the major points of arsenic accumulation), making reliable quantitative predictions about its migration and bioavailability extremely difficult. This is a serious knowledge gap which the CSTEE recommends should be addressed by further research. In the meantime, it would be advisable to exercise caution by limiting the use of arsenic-based wood preservation to those situations where it is absolutely necessary."

CCA-treated wood has been banned altogether in several countries including Switzerland, Vietnam and Indonesia and severely restricted in others such as Japan, Sweden and Germany. Australia, New Zealand and the US are the three largest per capita users of treated timber in the world. 

In January this year the European Commission issued a directive on the basis of the CSTEE’s risk assessments which recognised that arsenic is both carcinogenic and genotoxic in minute quantities. The directive stated that arsenic compounds could not be used for the preservation of wood and CCA-treated wood could not be marketed. However an exception was made for industrial purposes "provided that the structural integrity of the wood is required for human or livestock safety and skin contact by the general public during its service life is unlikely." Such allowable uses included structural timber in non-residential buildings and industrial premises, bridges and jetties (but not in marine waters), noise barriers, avalanche control, highway fencing, earth retaining structures, power poles and underground railway sleepers. Member states must adopt and publish the directive by 30 June 2003 and implement it by 30 June 2004.

As could be expected, there has been a number of lawsuits in the US against manufacturers of CCA-treated timber over the last 20 years because of health impacts on consumers and workers but the threat of class actions is now looming. Timber giant Georgia Pacific already has one class-action pending against it. Class actions have also been taken against retailers of CCA-treated timber including Home Depot and Loews on the grounds that the stores did not adequately inform consumers of the health risks.

Elias Akle, General Manager of Osmose Australia, which claims to be a leading manufacture of the CCA timber preservative, says Osmose will not be voluntarily phasing out CCA-treated timber because "we believe that properly CCA-treated timber poses no health hazards when handled correctly". When asked if CCA-treated timber required special handling he replied, "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." However, retailers, whom I spoke to, that sell Prime Pine with Osmose's CCA preservative, had no knowledge of such literature.

Similarly, Koppers-Arch, which refers to itself as “the leading name for wood protection in Australia, NZ, Fiji, Asia and South Africa”,  states on its web-site that there is "overwhelming scientific evidence that CCA-treated timber is safe to use providing people use, simple, common sense precautions while working with it... It also presents little - if any - risk to the environment, if used as recommended."

Both companies also sell alternatives that do not contain arsenic. 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.

The APVMA review is open for submissions till the end of May (extensions are available) and APVMA is hoping to prepare a draft report for comment by mid 2004. Until then no action is being take to reduce use of or exposure to CCA-treated timber in Australia.


Professor Sharon Beder is a visiting professorial fellow at the University of Wollongong.
Sharon Beder's Publications can be found at http://www.uow.edu.au/~sharonb