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
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
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
CCA-treated wood has been banned in several countries, including Switzerland,
Vietnam and Indonesia and severely restricted in others such as Japan, Sweden
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
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
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
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:
- Use alternatives to CCA-treated wood around the home
- Never burn treated wood
- Always wash hands thoroughly after contact with treated wood, particularly
before eating, smoking or drinking
- Never put food into contact with treated wood (eg. picnic tables, verandas
- Do not allow drinking water to come in direct or indirect contact with the
- Do not let children eat when visiting playgrounds with treated timber playsets
- Do not let children eat at treated picnic tables
- Do not let children play under treated decks
- Do not compost or mulch treated wood or sawdust
- Do not place animal feed near treated wood
- Do not store food, toys, tools or animal feed in structures made of treated
timber or under treated decks
- Do not allow animals (or small children) to chew on the treated wood
- Do not grow food in garden beds constructed of treated timber
- Seal treated wood structures with polyurethane or other hard lacquer every
- Carefully avoid splinters; do not sand rough wood
- Do not use commercial "deck washing" solutions because they can
convert chemicals on the wood to a more toxic form