Pressure treated lumber: another material to do your research on before you build

Newly milled redwood lumber. Redwood is naturally resistant to insects and decay.

Can you believe we were injecting arsenic into common building lumber all the way up until 2003?

It’s true. And not just any lumber, but more than half of the lumber that you’d find in stores like Lowe’s and Home Depot, and any other lumber yard. The arsenic, known as a wood preservative called CCA or Chromated Copper Arsenate, was injected to keep out fungi, termites and other pests that might destroy the wood over time. Unfortunately, it turns out that arsenic is toxic not just for termites but for us too. If lumber treated with arsenic comes into contact with anything acidic (cleaners, chlorine, acid rain, fertilizers) or certain common building materials (aluminum siding or galvanized nails) it will cause the arsenic to be released into the air. Exposure to arsenic causes many health problems.  Arsenic accumulates over time in the human body making it hard to detect as a cause when people are affected by it.

The dangers of using wood treated this way was known as early as 1968, though it wasn’t until 2003 after rising public awareness and activism that the wood preservation industry got their act together and voluntarily decided to stop using it and replace it with other preservatives that were more “environmentally and health friendly”. Ummm… why did Stephen put it in quotes? Read on and find out…

I knew this bit about arsenic when I was going into my home renovation project. I knew that arsenic had more or less been phased out of preserved lumber and I knew that it was replaced by some more “eco-friendly” methods. Well, it wasn’t until recently that I decided to get off of my sustainable wood quest and do some research on how wood is actually preserved. What I found will likely be surprising to some, and to others who are reading this will likely be not much of a surprise at all.

It turns out that modern-day methods of preserving aren’t all that much better than what we were doing 10 years ago. If we had a toxic scale from 1 to 10, where 10 was using arsenic, we’re down to, I’d say probably a 9 now. Not that much better.

But rest assured, I’m going to tell you all about what I’ve found out in detail, so you have all the info you need. And I’m even going to recommend some less-common alternatives to preserving wood from being eaten by termites, fungi, or other types of damage from the elements and give some options that meet building code.

Today’s common preservatives

Now that CCA is restricted (note: I just found out it’s not actually banned) the two most common preservatives today are called alkaline copper quaternary (ACQ) and copper azole (CA). There are also variations of these preservatives called MCQ and MCA that you’ll sometimes see in lumber yards.


ACQ wood uses copper as the main fungicide and something called a quaternary ammonium compound that acts as both an insecticide and a fungicide.

And let’s just get right into it.  Here’s what wikipedia says about quaternary ammonium compound:

Quaternary ammonium compounds can display a range of health effects, amongst which are mild skin and respiratory irritation up to severe caustic burns on skin and gastrointestinal lining (depending on concentration), gastrointestinal symptoms (e.g., nausea and vomiting), coma, convulsions, hypotension and death.

They are also thought to cause an allergic reaction called Anaphylaxis that affect the immune system in up to 2% of the population. (That’s 6 million people in America.) And that percentage is purportedly rising, especially in young people.

Quaternary compounds are a generic term used for a class of substances.  One of the specific quaternary compounds frequently used in ACQ is Didecyl Dimethyl Ammonium Chloride. One thing I’m learning through much of my research is that anytime something has “chlorine” or “chloride” or any word that begins with “chlor-” you generally don’t want to inhale, drink, touch, or otherwise be around it. Chlorinated chemicals are one of the most notorious polluters of our environment and our health in modern day, affecting our living spaces and even our drinking water. Yet, they’re so widespread.


A Weathershield label found on a 2x6 at Home Depot. Weathershield is another common brand that uses CA as a preservative. It's labeled as "Environmentally Preferable". Not by me!

The other common preservative CA is similar to ACQ except instead of using a quaternary compound it uses something called an azole biocide. When hear the term Wolmanized it’s actually referring to a specific brand of preserved wood that uses CA.

An example of an azole biocide that is used is called tebuconazole. After a little research on tebuconazole I found that the USDA believes that it may pose a health risk. Tebuconazole is a possible carcinogen (i.e. it “possibly” causes cancer) according to the EPA in the United States. The World Health Organization believes that it is “slightly hazardous”. The European Union’s studies on tebuconazole found that it’s an endocrine disruptor and they’ve considered removing it from the market for that reason.

The endocrine system is one of the most important systems that run the human body.  Our endocrine system relates closely with our chakras, which regulate how the energy we derive from our food and other sources gets distributed throughout our body.  A functioning endocrine system is necessary for everything from having a working immune system to regulating how emotional we feel on a given day.  An endocrine disruptor can cause physical issues such as cancerous tumors and birth defects, and other developmental disorders including learning disabilities, attention deficit disorder, brain development problems….. the list goes on.

Tebuconazole is also a pesticide used for growing roses.  The rose growing community is also discussing whether they want to participate in Tebuconazole use.  The main issues here are the same as in the forestry industry:  On one hand lots of folks realize the danger of using a chemical like this.  On the other hand it just makes growing stuff so easy, especially when that thing doesn’t grow naturally in a certain area because of pests, climate, etc.  I especially liked this post by sammy in Oklahoma.


You may also here about treatments called MCQ and MCA. MCQ uses a quaternary compound system like ACQ. And MCA uses an azole biocide similar to CA. The only different between these products and their predecessor is how the copper is injected.

How to tell if you have treated wood in your home

The short answer is: It’s hard to tell.

If it’s new wood you can usually tell by a green hue that the wood takes on.  Though once the wood has sat for a while, especially outdoor wood that’s been exposed to UV rays from the sun, the color is harder to tell.

You also know you have treated wood if you see a notching pattern on a side of the wood.  This method is occasionally used to inject the preservative into the wood.  But it’s a less common method and just because a piece of wood lacks notches does not mean it hasn’t been treated.

If you don’t have new wood and it’s not notched, things get a little trickier.  Unfortunately there aren’t any over the counter test kits for sale.  The only options I found are to use a chemical kit called a PAN indicator which will change the wood a certain color if it finds copper in it, which all of the preservatives listed above including CCA use.  This chemical, however, is difficult to purchase based on restrictions to shipping to homes by most of the labs that produce it.

The only other option I found is to use an X-Ray gun called an XRF.  These guns cost over $20,000.

I’m hoping to find a way to offer testing for treated wood as a service in the near future to folks who want to know what types of materials they’re living near.

Why don’t more people know about what’s really in the wood they buy?

Most consumers are under the impression that treated woods are now safe. And retailers do little to dispel this notion.

Treated wood found in a hand railing at my new house. I could tell because one of the boards had notches.

These materials are being used for handrails and decks that people touch with their bare hands and feet. It’s also ubiquitous indoors.  Nearly all modern homes and buildings in the United States use preserved wood in some phase of the construction process. The building code requires it. The home and workplace are the places we sleep and spend the majority of our time. They’re enclosed spaces and so anything that ends up in the air becomes concentrated.

Preserved wood is also used for garden beds where people are growing food.  When the preserved wood breaks down the embedded chemicals go into the soil. Tebuconazole is known as a “mobile” chemical which means it travels through the soil when it rains or the grass and plants around it are watered. This means that once it’s released it’s now in the environment and very difficult to contain.  Plants will even pull some of the chemicals into the stems, leaves, and fruits of the plant while it is consuming the foods.

People also mistakenly burn these woods not realizing the chemicals that are contained within them, then releasing those chemicals into the air.

Earlier I mentioned how Tebuconazole affects our endocrine system.  There is a lot of new research about the effect of beneficial microbes on our endocrine system that led to an entirely new field called Microbial Endocrinology being created.  (Ever hear of probiotics?)  I’ve been wondering how living within the presence of toxic pesticides affects the health of beneficial microbes in our bodies?

I find it very misleading to the public that there is not more warning or education given to those who want to buy treated lumber and the retail store clerks who sell it.  Companies like Home Depot must assume that consumers will take the responsibility to research the hazards themselves and then decide whether they want to buy it.  But most people that I’ve talked to haven’t taken the time to do the research because they trust the retail stores would not sell them anything that would harm their health.

The only warning available for some CA wood I found at Home Depot. The warning is on a tiny sticker which is stapled to the side of the wood, warning side down.

Stacks of treated wood at Home Depot available for anyone to go right up and grab. There is no warning to tell customers about the hazards of handling or building with this wood.


Non-toxic alternatives

Phew… So now that we know all about today’s common ways of preserving wood what are our choices? It turns out there are a few. Not many, but a few.


Boric acid is a non-toxic preservative that has been used as a wood preservative for some time. It’s affective against insects, fungi, and decay. It is also allowed to be used for structural purposes by the building code. It leaches out, however, when exposed to water, so it can only be used indoor scenarios where it will not be exposed to water.

Naturally durable species

Certain species of trees are naturally able to prevent insects and decay. It looks like the building code (at least in some states) allow the following species to be used in many situations that would otherwise require treated lumber: redwood, cedar, black locust, and walnut. In certain applications though, such as wood that makes direct contact with the ground, the building code requires treated wood only.

Glass wood and Sodium Silicate

This is an amazing technique! Unfortunately it’s not widely available and not written into the national building code yet.

Glass wood is a process wherein tiny bits of glass are injected into the lumber and then the lumber is heated. This causes a molecular change in the wood binding the sodium silicate to the wood fibers surrounding them with glass.  This makes the wood extremely hard, nearly fireproof, and resistant to decay and insects.

TimberSIL holding up to fire test.

After the process of glassifying it, the hardness of the wood rivals even cedar and redwood. This makes it difficult for organisms to penetrate the wood. It also makes it nearly fireproof. It’s so fireproof that some areas in the Southwest which are prone to forest fires have written it into the code so that roofs can be built out of it. Imagine roofs being built out of wood to prevent fire!

The final wood is completely non-toxic. It’s even non-toxic to fungi and insects. Whereas other methods allow the critters to eat it and then kill them with a pesticide, this method makes the wood so hard the critters don’t recognize the wood as a food source in the first place.

The main bottleneck with this technique is it’s availability. I found two companies manufacturing glass wood: TimberSIL and Kebony.  TimberSIL, which seems to be the more popular of the two companies, still has very limited distribution. I spoke with Rick Dixon, TimberSIL’s vice president of business development, on the phone about this. Rick told me that they’re specifically trying to be a “specialty item” and they’re not targeting big box stores like Lowe’s and Home Depot. He didn’t say why. There wasn’t anywhere in the Western Pennsylvania, Ohio, West Virginia region that carries this product. But Rick directed me to a small retail store called Wehrungs Homes Center near Philadelphia that used to carry it and still might have stock left.

When I called Wehrungs the woman I spoke to confirmed they did once carry it and don’t anymore. When I asked why she told me they really loved the product. It sold well and they still get people coming in and asking for it. The main issue for them was in the distribution. They had to go (to Texas) and pick up the wood themselves. And they were the only retailer in the region which was selling it. So they were making deliveries as far away as Connecticut. (That’s when I told her I was calling from Pittsburgh.) They weren’t able to keep up with the demand.

Since contacting Wehrungs I’ve expanded my search for TimberSIL to the entire Northeast.  I’ve found a couple of leads of retail stores that may carry it and am waiting for phone calls back.  The stores were recommended to me by the Northeast TimberSIL distributor, but when I called the stores (one in New Jersey and one in Connecticut) the lumber sales person hadn’t heard of the product.  They both said they’d search around and get back to me.  I’ll keep you updated.

Linseed oil

Linseed oil, make from flax seeds, is a way of preserving the wood by enveloping it (painting the outside) rather than injecting material into it. This allows the end user to buy untreated wood and treat it themselves. While not allowed by code in the United States, this method is catching on in Australia and New Zealand as a non-toxic alternative to chemically-preserved wood. Some products sold as linseed oil actually do contain chemicals, so it’s important when buying to seek out only the pure linseed oil varieties. Also, linseed oil does not protect against UV rays, so might not be as strong as other preservatives in outdoor, sun-exposed environments.

My choices

After more than two months… I don’t know yet.

In order to meet code I need to use some sort of structurally sound, insect-resistant wood for at least some of the wood I’m using.  TimberSIL seems like an amazing product but I can’t find it anywhere nearby.  The only other option would be to use a borate injected type of wood, which I haven’t searched for yet.  Or I could find a naturally durable hardwood, which would likely be quite expensive and possibly not grown sustainably.

In addition to seeking out a non-toxic wood I’d love to find a wood that’s sustainably and locally grown as well.  But this is looking very unlikely.  My personal priorities for this project are to find, first: a non-toxic, non-polluting product, and second: sustainably grown and harvested.  That means, if I found a product that was sustainably grown and doused in chemicals, I’d skip it.  But if it didn’t carry a sustainability certification but was non-toxic, structurally sound, and there were no other options short of driving myself to Texas, I’d use it.  We all have a line drawn somewhere.  The line for the type of material I’d use is pretty far to one side, relatively, but there’s still a line.  I hope writing about my experience and what I’ve learned helps raise awareness and shift the landscape…  and by landscape I mean both the forest and the way business is done.

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3 Responses to Pressure treated lumber: another material to do your research on before you build

  1. Stephen, 
    There is another kind of cool thing you can do to preserve wood – shou sugi ban. It’s a Japanese technique for burning wood to make it resistant to insects AND fire. You can google it. Just something to consider. 

  2. I really don’t think it is for structural lumber, more for siding. It looks really cool though. 

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