Comment to ERMA re the update review of CCA conducted by Dr Bruce Graham, June 2009

01 December 2009


1.1 The New Zealand Timber Preservation Council (NZTPC) is an organisation that:

1.1.1. Provides timber preservation quality assurance services to its licensed clients.
1.1.2. Promotes the WOODmark brand as a symbol of timber treatment quality.
1.1.3. Provides advice and services for compliance with relevant health and safety and environmental protection requirements.
1.1.4. Provides advice to members of the public about treated timber.
1.1.5. Advocates on behalf of the New Zealand timber preservation industry.

1.2 The NZTPC was established in 1987 and has operated continuously since then.

1.3 There are about 115 WOODmark licensed treatment plants, about 90% of all timber treatment plants in New Zealand.

2.0 CCA

2.1 CCA is a long established timber preservative having been used in New Zealand for about 50 years.

2.2 CCA has proven to be a very effective and economic timber preservative, especially for a wide range of outdoor uses of wood.

2.3 CCA treated timber is important to and widely used in the pastoral, horticultural and marine farming industries. In addition, CCA treated wood is an important component in the nation’s infrastructure being used in retaining walls, walkways, utility poles and marine structures. Domestic uses of CCA treated timber is common place in New Zealand in fencing, decking, garden edging, pergolas, hand rails and steps.

2.4 To the best of our knowledge there are no recorded cases of any person having succumbed to or contracted any serious illness as a result of exposure to CCA in timber or wood products or working with CCA in a timber treatment plant.

2.5 Treatment plant operators are monitored at frequent intervals for any signs of any elevated levels of preservatives in their bodies.

2.6 Alternative preservatives to CCA are available but are not suitable for marine applications. The alternatives are more expensive than CCA.

2.7 Recent industry initiatives have focussed on improving the handling and use of CCA to ensure greater protection for personnel and the environment. These initiatives have included:

2.7.1 Introduction of the Best Practice Guideline for Safe Use of Timber Preservatives & Antisapstain Chemicals as means of compliance with relevant health and safety and environmental protection legislation in New Zealand. This Guideline superceded the Approved Code of Practice of 1994.

2.7.2 Development of improved treatment processes that introduce improvements in terms of fixation, precise uptake of solution and eliminate over treatment and wastage.

2.8 HSNO requirements in relation to stationary storage container inspection and Approved Handler certification have introduced compliance standards that have resulted in greater controls in the use of CCA. Bunding requirements, drip pad roofing and similar requirements have also improved the operating environment for CCA treatment.

2.9 In terms of engineering safety/reliability for outdoor structural timber applications, CCA has by far the longest and best track record. The durability/lifespan requirements being introduced by regulators for structures such as earthworks retention can best be met by CCA treated wood products.


3.1 We have reviewed the following documents referred to in Dr Bruce Graham’s updated review of June 2009:

3.1.1 “A Probabilistic Risk Assessment for Children Who Contact CCA-treated Playsets and Decks” Chen J et al, OPP, US EPA, Washington, Final Report, 16 April 2008.

3.1.2 “Human Health Risk Assessment and Ecological Effects Assessment for the Reregistration Eligibility Decision (RED) Document of Inorganic Arsenicals and/or Chromium-based Wood Preservatives” Avaido D et al, OPP, US EPA, Washington, Final Report, 18 September 2008.

3.1.3 “A Set of Scientific Issues Being Considered by the EPA Regarding: Studies Evaluating the Impact of Surface Coatings on the Level of Dislodgeable Arsenic, Chromium and Copper from Chromated Copper Arsenate (CCA) – Treated Wood”, FIFRA Scientific Advisory Panel, US EPA, Washington, SAP Minutes No. 2007-02.

3.1.4 “Occupational Exposure Chapter for Inorganic Arsenicals and Chromium based Wood Preservatives in support of the Re-registration Eligibility Decision (RED Case 0132). Memorandum US EPA D Aviado et at 18 September 2008.

3.2 The “Probabilistic Risk Assessment for Children” reaches a number of conclusions of a comparative nature such as:

3.2.1 Risks are greater in warm climates than in cooler climates.

3.2.2 Exposure risks from playsets and decks are greater than from playsets alone.

3.2.3 Risk from residues is greater than risk from exposure to soil.

However it is concluded that there are uncertainties for both carcinogenic and non- carcinogenic effects in terms of:

3.2.4 Transfer efficiencies.

3.2.5 Residue concentrations.

3.2.6 Fraction of hand area that is mouthed.

3.2.7 Hand washing.

3.3 The “Impact of Surface Coatings” paper demonstrated convincingly that several coatings applied to CCA treated wood reduces the amount of dislodgeable arsenic (DA) by a factor of 10 or more for several months after which the DA returns to its original level.

However it is acknowledged that there are shortcomings in that:

3.3.1 The studies are confined to wood from just two sources in one climatic region and are therefore not broadly representative.

3.3.2 The range of coatings tested was limited.

3.3.3 The coatings used were not designed specifically to reduce DA.

3.3.4 The range of wood used was limited in terms of dimension and sapwood/heartwood content.

In addition there were uncertainties in respect of the:

3.3.5 Role of the surface preparations used.

3.3.6 The “wipe” protocol.

The report concluded that it could not say with any certainty whether further studies are worthwhile.

3.4 The memorandum regarding occupational exposure focuses on potential occupational exposures and risks to industrial workers in pressure treatment plants and subsequent exposure from contact with treated wood.

The memorandum noted the outcomes of studies into the non cancer and cancer dermal and inhalation exposure risks to those workers and noted that there were cases where the risks (short, intermediate and long term) were at or below the Agency’s target MOE and other cases where levels of concern could be exceeded. Mitigation measures were noted and in this regard we wish to point out that workers wear PPE, supplied by employers, as standard practice in New Zealand.

The memorandum noted several data limitations and uncertainties which support re-registration of chromatic arsenicals.


4.1 It is our opinion that the US EPA documents do not present any case at all that would support a review of the use of CCA treated timber in New Zealand.

4.2 The US EPA has re-registered CCA for use in the same categories in the United States.

4.3 The restrictive use decision reached in Australia was made on “precautionary” grounds and not on scientific evidence demonstrating any unacceptable risks.

4.4 The scientific evidence has not changed as far as New Zealand is concerned. The conclusions reached in the Read Report remain valid.

4.5 In light of the above we request that no change be made to the existing registration for CCA and that the uses of CCA treated timber and wood products be permitted to continue as at present.

New Zealand Timber Preservation Council
November 2009

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