Kevin McCloud's 43 Principles of Home by Kevin McCloud

Author:Kevin McCloud [McCloud, Kevin]
Language: eng
Format: epub
ISBN: 978-0-00-741235-8
Publisher: HarperCollins Publishers
Published: 2010-04-02T04:00:00+00:00

Copper-chrome-arsenic-treated timber

Chromated copper arsenate (CCA) is a wood preservative that has been used for timber treatment since the mid-1930s. It’s a mix of copper, chromium and arsenic formulated as oxides or salts, and it preserves wood from decay, fungi, wood-attacking insects, including termites, and marine borers. It also improves the weather resistance of treated timber and may assist paint adherence in the long term. CCA treatments have been phased out in many countries; since 2003 in the United States and 2007 in Europe, non-arsenic compounds have replaced CCA for use in the domestic environment.

However, since its main job has been to preserve timber, there are millions of tonnes of timber extant that have been treated with CCA. Your home may have decking, play equipment, a gazebo, cladding, roofing timbers and garden fencing, all of which could have been treated with this highly effective and highly toxic wood preserver.

CCA is recognized by the greenish tint it gives timber. The chromium acts as a chemical fixing agent and has few or no preserving properties, helping the other chemicals stay in the timber, binding them through chemical complexes to the wood’s cellulose and lignin. The copper acts primarily to protect the wood against decay, fungi and bacteria, while the arsenic is the main insecticidal component of CCA. Arsenic is a known human carcinogen and is acutely toxic.

Over time small amounts of the CCA chemicals, mainly the arsenic, can leach out of the treated timber into surrounding soil. This is particularly the case in acidic environments and of concern when treated timber is used outdoors near food-growing areas and in children’s play equipment. A more serious risk is presented if CCA-treated timber is burnt in confined spaces such as a domestic fire or barbecue. Scrap CCA construction timber continues to be widely burnt through ignorance, in both commercial and domestic fires. Treated wood remains in building structures, especially timber-framed buildings and on roofs. Here are the US Environmental Protection Agency’s recommendations for dealing with treated timbers:

—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 and dispose of as solid waste.

—Do not compost or mulch sawdust or remnants from CCA-treated wood.

—Do not burn CCA-treated wood, as toxic chemicals may be released as part of the smoke.

—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.

—Homeowners should never burn CCA-treated wood or use it as compost or mulch. 22

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