Safe handling and disposal
As we’ve discussed in previous lessons, different chemical formulations have different levels of toxicity. This applies both to the organisms that the timber is being protected from and the humans who are handling it.
At the lower end of the scale, boron-treated timber is very low in toxicity to humans and can be handled safety using the normal precautions that apply to untreated timber. This includes avoiding the inhalation of dust from cutting and machining, and protecting your skin from splinters.
At the higher end of the scale is CCA treated timber. Although the chemicals are fixed into the wood and highly resistant to leaching, it’s still possible for small amounts of arsenic to be absorbed through the skin. In 2006 the Australian Pesticides and Veterinary Medicines Authority (APVMA) introduced restrictions on the use of CCA treated timber in structures where regular close human contact was likely to occur – such as in children’s playground equipment, picnic tables, handrails, decking and garden furniture.
For industrially-exposed people, including timber workers, the safety requirements for handling CCA treated timber are more rigorous than for timber treated with arsenic-free preservatives. They include stricter controls on the collection and disposal of sawdust and wood, and more diligent usage of PPE while handling or working with the material.
General precautions
Below are some general precautions that apply to handling CCA treated timber in a wholesale or retail timber yard, frame and truss plant or other re-manufacturing business.
Other types of treated timber may have less strict requirements, depending on the preservatives used. You’ll find the specific precautions that apply to particular treatment formulations on the producers’ websites and in their safety data sheets (SDSs).
Wear gloves to avoid skin contact and splinters.
Wear a dust mask and safety glasses whenever airborne dust is being created, including when changing bags on a dust extractor or cleaning down work areas with compressed air.
Collect dust at its source by using a good dust extraction system.
Wash hands and face thoroughly before eating, drinking, smoking or going to the toilet.
Do not burn the timber or allow it to be collected for firewood. Arsenic and other chemicals are given off in the smoke and also remain in a concentrated form in the ashes.
Do not use CCA sawdust or shavings in mulch, compost or animal bedding.
Dispose of CCA timber, offcuts and residues at an approved waste facility, in accordance with their disposal policies.
Recycling
Research is currently taking place into processes for recycling treated timber, including the heavy metals contained in CCA preservatives. One technique is to burn the timber in a high-temperature incinerator and recover the metals from the ash residues. Another is to use fungi or bacteria to break down the wood fibres and allow the metals to be liberated.
Treated timber is also able to be used in various composite board products made from wood particles or flakes. This research is continuing, and given the high volumes of available waste material that currently goes directly to landfill, these projects are likely to become increasingly viable as the technology improves.