'Treated' Pine - poisoning our environment?

It’s my understanding that treated pine is 'treated with arsenic, and that this leaches by contact or water.
Trying to get quotes for - fence / pergola / decking frame - all have recommended treated pine as the cheapest and best long lasting option.
I am concerned about our environment and wondering if for example fences are built with treated pine, when it rains does the run off contain arsenic / other preservatives and run into our oceans? our gardens?


To address your concern, yes, but. This page addresses the status and use of CCA treated pine.




This may also be useful,

As it discusses some alternatives and product lifespan. Generally timber in contact with the ground or in the weather needs some sort of protection to ensure it long term durability.

Also from experience, CCA pine won’t have the same durability/lifespan as CCA treated old hardwood (not sapwood). Pine is cheaper, but potentially won’t last as long.

These are all factors which need to be considered when making decisions.

It is also worth noting that arsenic, copper and chromium occurs naturally in soils, at significantly lower concentrations where naturally present. The timber is immersed in a solution which leaves the concentrations in the timber when dried at concentrations/levels which protect it from timber eating insects such as borers and termites.


Should have also said that many tradies will recommend pine over hardwood as it is easier for them to work and handle.

An non-rimber alternative which is a lot safer but more expensive is galvanised steel for posts and rails which are in the weather/ground.

Also the use of CCA in accordance with that recommended by the manufacturer/supplier is unlikely to cause soil contamination or significantly impact on downstream water were used.


If you do use treated pine or other CCA treated timber, make sure you do not burn any of it, or allow dogs or birds to chew on it.

Some years ago, a timber business in PNG gave a lot of CCA treated timber offcuts to a group of Nationals who then used if for the fire in the men’s longhouse, resulting in a significant number of deaths from the toxic gases released.

Our local Council includes old CCA treated timber in the green waste that the contractor mulches and sells. I would not touch it with a barge pole, even when the Council provides it to residents for free once or twice a year.


Looks like you have plenty of feedback on the CCA chemical risks.

Cheapest probably. There are the right materials and cost for a job and there is too cheap!

Long lasting - we all have budgets to live by. I have lots of termites so our options are more limited.

Note that there is bare finished CCA treated pine typically used for fences and out door garden features, and there is CAA treated pine building timbers, plain for framing or pre-primed painted.

CCA treatment may not treat fully the timber, so once it is cut or drilled unless you have a very fussy fencing contractor or builder it will be left as is. It is recommended you hand treat the exposed timber. CCA also comes in a wide range of grades based on the application. The lower the CCA grade the cheaper the timber.

For above ground decking pergola etc, CCA pine is not set and forget. No timber is, although some timbers will last longer with less care. Timber will weather and where ever water can be trapped can start to rot out. To get the best outcome you need a trustworthy experienced builder to minimise these risks and ensure the timber is the required grade. All commonly used timbers require regular “painting” with a suitable preservative treatment or finish.

Outdoor timber needs to be genuinely treated, carry a brand with CCA marking, and be at least the minimum grade for the application. For many of these smaller jobs the contractor is self checking, IE only basic approval and no certifier required, which makes getting a reliable builder essential. It can help to get as many references as you can including checking the business name out online for unhappy customers.

This may explain some of the key points: http://www.tpaa.com.au/faq/
They apply to all treated timber, soft or hardwood

P.S. If you are considering other options:
For fencing look to what others have used in the neighbourhood that appears to have stood the test of decades, for guidance, and pick what you fits your needs after shopping around for the best deal.

For the other project areas look at how other quality homes have been built in your area. Builders can purchase preprimed outdoor graded and treated softwood timber at a reasonable price if you are prepared to paint. There are non timber decking materials and hardwoods that look great oiled. The non timber based products are mould resistant, don’t warp or bend and may also be fire resistant.

Considering four different properties we have owned in four very different regions, the CCA bare finished pine products we have had outdoors in structures or fencing have all required major repairs or replacement within 10 to 20 years. All had issues due to cheap materials or poor construction details. All could have had a longer life, however one was a rail and balustrade on a second floor that totally failed through weather effect and poor construction details despite maintenance by the professional painter as required.


Not only does the finished product leave a toxic legacy when disposed of, in addition to the dangers if handling it when in use, but the treatment factories can be toxic time bombs.
Martin St in Armidale comes to mind - a housing development on the site of an old treatment plant.

There’s a list of other toxic sites thanks to CCA treatment plants here:


For further reading on Treated Woods I do recommend visiting the Timber Preservers Association of Australia. (TPAA) at http://www.tpaa.com.au

They have a good selection of publications (http://www.tpaa.com.au/publications/) to download including how to best handle the products. A lot of timber now in Australia is not CCA treated but is using other Copper compounds (Copper Quaternary or ACQ, turns the wood green but a different shade compared to CCA &
Copper azole (CuAz) turns the wood a brown-green colour) that produce different greens to CCA treated wood but there are also others that are colourless or as in Creosote a brownish colour.


Not all treated pine contains arsenic. You have CCA (copper, chromium, arsenic) but others have an extra dose of other less harmful metals like copper. The latter are more expensive.

There is some leaching of all the metals and it will go into the environment, so potentially the soil and water. The question is does this really matter? As the references already provided show you the most common position is that it depends on the situation.

Not all treated pine has the same durability. Like non-treated timber products there are different durability ratings and you should check the rating before buying. As the lower ratings are cheaper there is an incentive for landscapers and fencers to economise. The higher ratings contain more metals. This is important because timber that is fine for general outdoor use (eg fence palings) may not be suitable for constant contact with the soil (eg buried fence posts).

For example a friend had a treated pine carport. After some years the main structure was still intact but most of the posts had rotted off at the ground. The builder should have used a higher rated timber for the posts or stood them in galvanised steel supports off the ground. But that costs money.

So like many situations that involve possible toxins and possible health consequences there is no “right” answer in all circumstances, you have to make a judgement.


As someone else pointed out a lot of it is that it’s easier to handle, it’s cheaper and the tradie won’t see you again so the lifespan doesn’t matter.

A hardwood deck on hardwood joists that is screwed down and maintained with a product like Flood spa n deck will last a lifetime. But it costs more and takes longer to build.

I don’t buy the whole treated pine lasts longer, I’ve put treated pine around the edges of gardens under a fence and they only last a few years before rotting away but now I use offcuts or older hardwood decking and they have lasted over five years so far without any sign of deterioration.

Pine is used extensively in Europe but it must be a combination of better quality pine and better workmanship as it seems to hold up better.

The quality of tradesman in Australia is truly appalling, some are great but many are not.

Research yourself before getting quotes, the renovate forums are a great place to start - https://www.renovateforum.com/f196/


Thanks Matthew. How much more is hardwood?

Thanks Syncretic
"does this really matter’ re poisons - I prefer to avoid any leaching to the environment.
How does a homeowner know what quality timber is required?

It’s hard to say as I don’t buy it a lot but the price differences in materials would be about 20-30%. This sounds like a lot but it’s not as the majority of the cost is labour. I would think that using hardwood would add 10-15% to the final cost. Screwing the boards down instead of using a nail gun would probably add 5% to a deck but you get a result that is stronger and won’t have nails popping.

I’m about to start pulling up the hardwood decking around my pool and will be screwing it back down. After 15 years 95% of the timber will be reused and the ones I’m replacing are only because they had imperfections when I installed them like low spots. I didn’t screw the deck but nailed it at the time and I didn’t put anything to protect the joists which I will this time.

The deck that was there when we purchased the house was pine decking on hardwood joists and they were rotting after under five years.

You may need to look for a timber merchant in your area and discuss to obtain indicative pricing for a reliable comparison.

Hardwood also takes more time and effort to work with compared to pine softwood options.

The cost difference to go to all hardwood may be more than twice that of treated pine. The difference in life is much more significant a factor, if you have the budget.

Bunnings lists 90mm ACQ treated pine decking at $9.44 per 3.6m length (approx $2.62 per metre) and 90mm select grade merbau hardwood decking at $5.44 per metre.

I paid over $12 per metre for our last lot of 140 mm spotted gum decking timber. Stainless decking screws are the way to go for an exposed timber deck but may need predrilled holes for hardwood joists (at least for the timber here) and a special profile bit for the boards to flush finish the screw heads.

P.S. Our house is mainly untreated hardwood with hoop pine for internal flooring. It predates Federation by a few decades. Hardwood can be very long lasting.


There are two systems in use (why?).

Durability class 1 to 4 (highest to lowest)

and the other way round

Hazard ratings H1 to H4 (lowest to highest)

As you can see if you read the description they are more or less the same scale but reversed.

As others have said you can get un-treated hardwood that will do the job but it cost more. I have fence posts that are expected to last 30-40 years in an area which can be waterlogged and where white ants are endemic. Even if you don’t have white ants wood rot is a problem everywhere.

If thinking of a DIY consider if your skills are up to doing hardwood. It is much heavier to lift and more difficult to work, you need sharper and more powerful tools. It is usually worked semi-green, if fully cured it is even more demanding, the heavier sorts are impossible to drive a nail into then. On the plus side you can use thinner timbers in some cases as hardwood is stronger.

If you are contracting this to a builder or landscaper get them to specify the quality of timber in writing.

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We have a treated pine domestic jetty in a marine environment as have all the property owners surrounding a man made salt lake. Fish life appears unaffected over 20 plus years and even clams and seaweed grow in prolific confusion. This leads me to feel that statements of the impact of CCA treated timber on life forms is more a guideline than an actual threat to health.
The non use in playgrounds is sensible as children are inclined to taste anything they can lay their hands on even though there are few recorded examples of poisoning. CCA powder often leaches to the surface of pine, so children might taste it out of curiosity. The older treatments of coal tar would be of more concern to me and these are still available (creosote) and I know where we used rural posts treated with coal tar they stank for years unlike the CCA posts. Creosote is a known carcinogen.
I have used CCA treated pine in many situations from sleepers to structural building uses. Like any building product, building with CCA needs to be done with care. Sleepers are sold wet so should be handled with gloves. The builder needs to avoid breathing sawdust and should hand treat any cut surfaces otherwise protection is lost. Fittings need to be cold galv (not zinc plated) or 416 grade stainless (expensive) or monol. Galv stirrups are better for use in the soil even if the H5 level treatment is recommended for use in soil. Better to use all H5 for structural components and H3 for decking. After weathering for a couple of months, the construction needs to be washed and treated with oil based products and retreated before summer and winter forever. In my opinion, this locks in the CCA treatment as well as maintaining the weathering qualities and appearance of treated pine.
I would be more concerned about the new plastic decking made with recycled product which contains all manner of noxious material, rather than CCA timber. But like any product, you need to be sensible and understand the risks.

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As are Arsenic and Chromium (the hexavalent form used in CCA).


At our first home, my wife’s late father and I built a post-and-rail fence using bushmill rough-sawn red stringybark sleepers for the posts and yellow stringybark planks for the rails.

Although we had been told that stringybark was naturally termite resistant, we painted the posts and rails with 3 coats of Creosote and poured more Creosote into the post holes as the electricity board used to do with their power poles.

About 10 years later when we replaced the fence with a treated pine picket fence when we had a swimming pool installed, we discovered around half of the posts had been eaten by termites to the point where a couple of posts simply fell to pieces after removal.

A little over 20 years ago, we needed to construct a retaining wall at our previous home so my son and I built it using Cypress Pine sleepers for the posts and the horizontal rails.

Despite Cypress Pine being claimed to be termite proof, we took the precaution of painting every sleeper with 3 coats of Creosote.

Some years later whilst our pest control contractor was carrying out the annual inspection, he pointed out how some of the sleepers were just eaten-out shells. He used some chemical that killed the termites which prevented any further damage.

I have used CCA treated pine for all outdoor timber requirements since those unhappy experiences.


Yes, I should have clarified that creosote as a volatile carcinogenic product at low temperatures may be readily inhaled, whereas the compounds of CCA require high temperatures produced in combustion to create similar risks. Coal tar is the base for creosote and is made usable by the addition of low temperature volatiles. Coal tar fumes killed miners until ventilation was improved which illustrates how lethal are those fumes. CCA Pine is plastered with warnings about burning the product, but until burnt it is relatively stable. All compounds of both products occur naturally in the soil, but it’s the packaging that renders their risk profiles somewhat different.
I was trying to answer the original poster’s question by comparing the old compounds with the modern compounds and pointing out they all have risks which must be managed if we are to use them safely. Hence my point on the working with product guidelines and the ongoing maintenance requirements. Thanks for picking me up.