Log Home Building Course

Timber preservative treatment: CCA timber treatment

thumbs down icon CCA (Copper, Chrome, Arsenic)
cca treated timber

A very effective timber treatment - Toxic - not compatible with life.
This chemical can only be applied in a controlled industrial process and is forced into the timber under pressure. The intention is that they get forced right into the timber cells and remains bound or 'fixed', therefore this is not a timber treatment which an individual can apply.
The treatment solution is acutely and chronically toxic.

Methods of ingestion:

  • Oral - eat it.
  • Dermal - anything that you touch (floor, deck, handrail, children's playground climbing frame, etc).
  • Inhaled - Burn it and inhale the fumes.

What effects can it have?

  • Mutagen.
  • Carcinogen.
  • Reproductive / Developmental.
  • Systemic, possible nervous system damage - Getting nervous yet?

Ok, lets take a brief look at the ingredients of the solution:

  1. Copper: prevents decay
  2. Chromium trioxide: acts as a binder
  3. Arsenic pentoxide: prevents insect damage

1: Arsenic pentoxide:

  • Very toxic - Category 1
  • Group-A Carcinogen
  • Ranks No.1 on the ATSDR Toxic substances list, this list considers toxicity and availability
  • Arsenic - LD50 = 8mg/kg body mass, a 100kg person may only consume 0.8g for death to occur. This works out that 1 cubic meter of timber, CCA treated to H4 specifications contains sufficient Arsenic to kill around 3000 people
  • Arsenic accounts for about 20% of the treatment solution
  • A 100kg person's arsenic lethal dose (LD-50) requirement would amount to a small block of H4 treated timber - 76 X 38 X 140cm to cause death (as pictured above). Do not eat the timber!
  • If I where to use just 10 cubic meters of this treated timber to build a timber home, I would be exposing my family to a home which has been impregnated with enough Arsenic to kill 30 000 X 100kg people, and at no time in the foreseeable future, while we live in that house, do I expect them to come into ANY contact with the treated timber at all.
  • I guess it must be OK, clearly stamped on each piece of timber 'SABS approved' - approved by our government after receiving 'input' (see pg3) from the treatment chemical manufacturers - seems legit. If we cannot trust the government, who can we trust?

2: Chromium trioxide:

  • Firstly: South African websites do not seem to have much available information on this chemical, even though it is present in every single piece of CCA treated timber, therefore I will quote New Zealand hazardous substances classification codes , after all, these are the same chemicals and we are the same species of human animal (well, nearly, they are Kiwis, that is a bit different).
  • 9.1A ecotoxic - Aquatic environment. Very toxic to aquatic organism at low concentration.
  • 9.2B ecotoxic - Soil environment. Very toxic to organisms in the soil and higher plants.
  • 9.3B ecotoxic - terrestrial vertebrates (The human animal being just one of them)
  • 9.4C harmful to terrestrial invertebrates.
  • Sooo, to sum it up, if it is toxic to Aquatics, soil organisms, plants, vertebrates and invertebrates, that doesn't leave much does it? I tell you - the human being animal sure has learned how to kill things efficiently!

cca treated timber A bit of advice:

  • After working with the treated wood, wash all exposed areas of your body, especially the hands, thoroughly with soap and water before eating, drinking, toileting, or using tobacco products.
  • Wear gloves when handling treated timber(SANS 10005: 9.6b)
  • Wear breathing apparatus when there is any chance of inhaling sawdust, use a dust extractor (SANS 10005: 9.6b).
  • Wash your work clothes separately from your other laundry.
  • Do not compost or mulch sawdust or remnants from CCA-treated wood - dispose in a municipal waste dump.
  • Do not ever burn CCA treated wood - ever! no matter how cold you are, this is the most effective and available method to extract the Highly toxic Arsine gas which will be released in the smoke (SANS 10005: 9.6a).
  • CCA treated timber contains copper, when you use galvanized metal fasteners (screws, nails, brackets), a galvanic reaction occurs where the zinc galvanizing is in contact with the copper, you have made an effective zinc - copper battery (0.8 volt electrical difference, free power!), this strips the galvanizing off the fasteners very quickly, significantly reducing their lifespan. all that is required is the smallest amount of moisture to act as an electrolyte (SANS 10005, 4.2.2.2.c). What this means is that a timber home, built from CCA treated timber has a very short lifespan, due to the fasteners corroding and failing, all that is needed is the smallest amount of moisture.
  • CCA treated timber is more susceptible to damage by fire, due to afterglow (SANS 10005, 4.2.2.2.g).
  • CCA treatment causes your tools to go blunt quicker than untreated timber (SANS 10005, 4.2.2.2.h).

Finally, the question is, since there are safer alternatives, why do we keep using this stuff?
I can only imagine it must be about money. Is money really so much more important than a healthy life? Really?
I could keep banging on about it, there's plenty more and I got other things to do, but by now I'm sure that you get the point.

The good folks at SAWPA have some advice on the safe handling and disposal of preservative treated wood.