Hazards of Pressure Treated Wood

Advice on safety precautions when using treated wood. October 25, 2006

From Professor Gene Wengert, forum technical advisor:
Wood is treated under pressure and vacuum with a variety of chemicals that are insecticides and fungicides. Such wood is called pressure treated wood. In past years, almost all PT wood had a green color from the copper used; the treatment chemical was called CCA. Political pressure and poor technical information stopped widespread use of this chemical a few years ago. Your local home store or lumberyard is now selling lumber treated with amine copper quat (ACQ) and copper azone (CA). CCA is still being used in certain marine and industrial applications since it is still the best preservative available at the present time.

Special concerns:
The sawdust from PT pressure-treated wood is an irritant to the nose, eyes, and skin. Use of a dust mask and eye protection is highly recommended. Avoid contact with the skin as much as possible. Wash hands before eating. Wash clothes after use.
Try to collect as much of the sawdust as possible for disposal. Do your cutting in one specified location, and lay a heavy disposable plastic tarp under the sawing area. Use of a tarp is especially valuable if you must cut in an area that you cannot easily sweep, such as a lawn. Do not allow dust to get into the soil where children may play, etc.
Pressure-treated wood should not be burned under any circumstances. The fumes can be toxic and the ash is very toxic.
Do not use pressure-treated wood for making cutting boards, or for any food preparation surface. Picnic tables made of pressure-treated wood are fine to use for the purpose they were intended... to serve food on (or play cards on), not to prepare food on! But can you count on this?
Pressure-treated wood is intended for outdoor use and a few situations (such as sill plates) in home construction.

Building hints:
Predrill any nail or screw holes within an inch of the end of the board.
Use screws, nails, joist hangers, etc. that are galvanized (or stainless) and designed for pressure-treated wood.
Do not allow ACQ treated wood to contact aluminum.
Do not allow any space between boards when laying in a deck floor.

Pressure-treated wood will not rot, even if buried, making it ideal for fence, mailbox, and light posts. Check with your local building inspector to see if code allows burial of pressure-treated deck posts in your area, or if the concrete footing must be exposed above ground level.
Use the proper material... "above ground" (0.25) or "ground contact" (0.40). Some are also water repellent.

From contributor W:
Why do you not allow any space between the boards when decking?

From Professor Gene Wengert, forum technical advisor:
The wood is normally quite wet when installed and it will shrink 1/4" or more as it dries in place. So, if you leave a 1/4" space initially, you will potentially have a 1/2 gap when the wood dries.

From contributor R:
Have there been any long term studies/case histories of proven illness or deaths resulting from repeated exposure to pt lumber? Any class action lawsuits from groups of deck installers, factory workers, daycare centers, etc.?

From Professor Gene Wengert, forum technical advisor:
There are a half dozen stories about someone getting sick and relating that illness to a new CCA deck that was installed at their home at the same time. The problem is that their illness would require exposure to a very high level of arsenic or chromium. So these stories all include that statement that the wood was exceptionally heavy and it oozed sap for a long time, and so on. Naturally, these people are suing for damages and so on. There are also some other stories that are circulated but without any information that can be used to verify the validity. Here are three.

In 1983 two workers building picnic tables for the forestry service found out what working with this wood can do. One lost seven pints of blood and the other had many symptoms, which left them unable to work for many months.

A man building a CCA dock became partially paralyzed after working with the wood. He recovered, but not fully and received a large settlement from the company involved.

A woman claims to have lost two fingers on her hand from CCA wood splinters. Naturally, what we really have to do is find someone who also lost two fingers to splinters that was not exposed to CCA wood to prove that it was indeed CCA that caused the problem, if indeed this story is actually true.

It is very hard to prove "cause and effect" in these cases, but jury emotions can really be important instead of relying on the facts. In one case they talk about their deck being made of CCA treated jack spruce... That is a new species to me and I did not find that on the Internet either. Many of these reports have other errors, but they all seem to have the idea that it is a severe illness with many symptoms and tremendous losses. None had mild problems. We each have to be the judge of what is truth in these cases.

From Professor Gene Wengert, forum technical advisor:
I should add that several cases involve breathing fumes when burning the wood and a large number involve inhaling and skin contact with sawdust and sanding dust in a closed room for many days.

The comments below were added after this Forum discussion was archived as a Knowledge Base article

Comment from contributor A:
There are some comments I would like to touch upon. The concept of burying PT lumber and it not rotting is a slight misnomer. The comment below regarding the use categories of Above Ground and Ground Contact doesn't seem to me to do a good enough job explaining this. PT that is buried should be treated to a minimum rating of Ground Contact, and if in areas where it is a critical structural member, like poles in pole barns or piling in marine use, should be treated to Severe Service Ground Contact. Generally, the Above Ground application has run into issues of misuse, and is generally being done away with. The newest chemical, which is a Micronized Copper product, is actually fine for indoor or outdoor use. This MCA treated wood utilizes a copper and azole for its chemicals. Both are utilized in many other forms for human contact. Copper is used in cookware and plumbing, and azoles in fungal infections both inside and outside the body. The MCA can be used in picnic tables and garden beds without concern. This newest chemical MCA can be placed into contact with Aluminum in residential situations. CCA contains Arsenic in the form of Arsenate, and in the chemical change that happens during the burning process, produces Arsenite, which is when the large hazard exists with CCA exposure, and you will not find CCA approved for residential use anymore. Farm fencing and marine use, however, still being used. With this being said, still don't burn PT wood, the newer chemicals may be safer, but there is no guarantee your deck wasn't resurfaced and still contains CCA as part of the joists or support timbers or that the current chemicals won't be found to be harmful during the burning process. Splinters - there is nothing more irritating to me than to hear someone complain that a splinter from PT caused an infection, especially the newer chemicals. The chemicals used are in many ways, antibiotic by nature. Chances are, the splinter pushed in dirt and grime (microbes) on your hand to inside your hand. Additionally, any foreign body like a splinter is going to cause a systemic reaction, and your body is going to react - whether this be PT or wood or metal. The PT splinter might actually be safer as it will have at least helped to kill the microbes that were introduced by the splinter. At the end of the day, pull it out, clean it well, and keep an eye open for infection. Lesson - wear the proper PPE when handling any sort of building material - like gloves, glasses, and mask where appropriate. Happy building!