Having had sections of a new salvaged Jarrah post and rail fence fall over within a year thanks to termites, and seen a friends lovey painted but otherwise untreated pine pergola also disintegrate within a year , I would like to use treated pine for structures but hear conflicting stories as to its saftey. I was told by a chemist once that the toxic treatment mixture is rendered inert and doesn’t leach once applied to wood. He had used it throughout his garden. I just found some good info on this subject that may be useful to anyone making the big effort to create permaculture structures. Certainly we want these projects to endure so something must be done to protect against termites. Pine is a renewable resource and I think better environmentally than using native timber or steel. Apparently "a small amount" of chemicals do leach out. I would avoid using treated pine in wet or irrigated areas, but be comfortable using it (for fencing say) in high and dry areas of the property only. Treated pine should also be fine in above ground applications where people and animals don't usually have physical contact. You can also paint over it for extra security.
CCA treated timber (also commonly called tanalised timber) contains copper, chromium and arsenic, which is a toxic chemical mixture but is relatively inert once fixed in the timber. However, it is not recommended in skin contact use such as children’s playground equipment and hand rails. Treatments such as ACQ and copper azole do not have the chrome and the arsenic but the higher levels of copper increase the corrosion potential with steel and galvanised steel fixings.
Use and handling
- Carry out all cutting, sanding and so on outside.
- Wear a filter mask, safety glasses and gloves when cutting and sawing.
- Take particular care when the timber surface is wet or has crystalline chemical deposits on it.
- Clean up (timber scraps, sawdust) thoroughly afterwards.
- Dispose of waste to an approved (municipal) waste disposal area.
- Do not compost or mulch waste.
- Do not burn waste.
- Wash your hands before eating, drinking or smoking.
- Wash exposed areas of your body after working with treated timber.
- Wash work clothes separately from other clothes.
Small quantities of chemicals can leach out over time so it should not be used where it may come into contact with public drinking water. Thanks to working with treated timber website