Overview of the Review of Arsenic Timber Treatments

Products containing copper chrome arsenate (often referred to as CCA) and arsenic trioxide are used for the control and prevention of damage to timber and timber structures by insects, wood rot, wood fungus and general timber decay. CCA is generally used on wood intended for outdoor uses, such as telegraph poles, decking and fencing, in landscaping, and in building structures. Arsenic trioxide is commonly used for post-construction control of termites in the home. These treatments have been registered for use in Australia since the 1980's.

The APVMA decided to reconsider whether the registration of CCA and arsenic trioxide timber treatment products should continue because new information suggested that the potential for humans to be exposed to arsenic from treated timber may be greater than was previously thought. The information also raised concerns about environmental contamination at timber treatment sites and from use and disposal of treated timber.

As part of the reconsideration process the APVMA reviewed this new information as well as information submitted by chemical registrants, state environment and agriculture departments, timber industry representatives, environmental groups, and the wider community. Published literature and relevant international regulatory reports were also considered.

Review Findings

The focus of the review was to determine whether arsenic that may be present on the surface of treated timbers or in the topsoil surrounding CCA-treated timber structures is a public health risk. Young children, aged 3-5 were considered the most at-risk group. Arsenic is present in the natural environment (in air, food, water and soil) at low levels. Therefore the public is exposed to this chemical through sources other than treated timbers. The key issue is whether the additional exposure to arsenic that may arise from arsenic present on treated timber can significantly increase the total intake of arsenic.

The key questions investigated were:

How much arsenic leaches out from the surface of timber structures treated with CCA?
How much arsenic is likely to adhere to children's hands and other parts of the body when they come into contact with treated timber structures?
What fraction of such adhered arsenic will subsequently be transferred to the mouth or absorbed through the skin?

Recent research has brought into question the original belief that the process of treating timber with CCA 'tightly fixed' the chemical components within the wood structure.

Only limited information from properly conducted studies was available for consideration in the review. Data from a US study provided information on the amount of arsenic transferred to a child's hand when playing on wood treated with CCA, the likely hand-to-mouth transfer as well as skin absorption. The evaluation of the study suggests that public exposure, including of children, is below the threshold considered to be harmful. The study, while of good scientific quality and conducted under controlled conditions was however based only on a small sample in the USA. Other studies, including one from Australia, gave very variable results for the amount of arsenic released from CCA-treated timber, in some cases arsenic appeared to be released in very high quantities. Neither the overseas data nor the Australian data adequately covered different plant operation practices, the range of timber products, the age of treated timber structures or the environmental conditions to which treated timber structures might be exposed relevant to Australian conditions.

Since insufficient data are available to resolve key concerns, the APVMA has concluded that it cannot be satisfied that it is safe to continue the use of arsenic treatment for timber used in the manufacture of structures that the general community and children in particular, will have frequent close contact with.

The environmental assessment concluded that, to minimise the environmental risks, it is necessary that timber treatment is carried out only by those with special skills and knowledge and that the treatment process meets appropriate Australian Standards. The assessment also led the APVMA to conclude that product labels do not contain adequate instructions for timber treatment with respect to harmful effects on the environment. Leaching of arsenic from treated timber was found to be largely localised and is therefore not considered a significant risk to the environment.

While the review focussed on public health and environmental issues, some of the data submitted was also relevant to occupational health and safety (OH&S). In reviewing these data, it was recognised that further, more specific data relating to the risks to Australian timber treatment workers were required.

Products containing arsenic trioxide are used by licensed pest control operators (PCOs) and the treated timber parts are concealed. Holes are drilled into infested timber or trees and small amounts of the product are applied. The opening is then covered with a tape. The review found that products containing arsenic trioxide are not considered likely to present a public health risk. The review also concluded that the use of arsenic trioxide products would not be likely to have an unintended effect that is harmful to the environment.

Proposed Review Recommendations

The draft APVMA report of its review of arsenic based timber treatments sets out a number of recommendations for the proposed future regulation of these treatments. The key recommendations proposed are that:

CCA timber treatment products are declared Restricted Chemical Products. This would ensure that product can be supplied only to suitably trained persons;
CCA timber treatments NOT be permitted for timber intended for use in situations were people, particularly children will be able to come in close contact with it*. This includes children's play equipment, picnic tables, deckings and handrails.
Product labels are required to carry new instructions relating to the design and operation of timber treatment facilities, how the product should be used and its storage and disposal as well as the management of freshly treated timber.
Registrants are required to generate worker exposure data.

The draft recommendations relate to future use of arsenic timber treatments and do not extend to existing arsenic-treated timber structures. This is because the evidence that is available at this stage is not sufficient to indicate that the risks associated with existing structures are such that they should be dismantled.

*Implementation of this recommendation is contingent upon the successful development of effective ways to segregate CCA-treated timber products that should not be used in specified domestic applications.

Public Comment

Before the APVMA makes its final decision on arsenic timber treatment products it is seeking public comment on its findings and proposed recommendations. Comments need to be lodged with the APVMA by 29 February 2004 and should be addressed in writing to:

Manager Pesticides Review
APVMA
PO Box 6182
KINGSTON ACT 2604
or faxed to: (02) 6272 3218
or emailed to: chemrev@apvma.gov.au