Questions About Treated Lumber

What's the scoop on treated lumber safety? Read on to find out!

Recently a reader emailed me to ask about the safety of treated lumber. She and her mom (who has had breast cancer) live on boats, and the marina where she lives just replaced its docks with treated lumber. She also mentioned that her water (and that of the other dock-side residents) is delivered to their boats by hoses that are attached to the edge of the new dock. “Can the chemicals get into our water? How dangerous is this stuff? Should I move,” she asked?

The back story.

For decades the term treated lumber usually referred to CCA (chromated copper arsenate) pressure-treated wood. The process for treating wood with copper and arsenic to extend its life has been around since the 1930s when an Indian engineer injected copper and arsenic into the underground beams used to hold up the roofs of coal mines. The arsenic was poisonous to insects (including termites), while the copper was toxic to the fungi that caused dry rot. The addition of chromium helped bind the copper and arsenic to the wood. Over the years the wood industry learned how to thoroughly impregnate the wood with CCA by first drawing all the natural moisture and trapped air out of it with a vacuum, and then forcing the chemical mixture into the spaces previously occupied by water or air molecules with high pressure.

Beginning in the 1960s the use of CCA treated lumber grew exponentially as heartwood from old-growth hardwood (which is naturally resistant to rot and insect damage) disappeared and naturally rot resistant species (such as redwood) became more expensive. By the turn of this century, 80% of “treated wood” was the CCA-pressure-treated variety, and the other 20% or so was wood treated with pentachlorophenol (PCP) and/or creosote and/or flame retardants. Let’s look at these outliers before getting back to CCA.

Since 1980, PCP has been limited to use in railroad ties and utility poles due to its overall toxicity and concerns with it entering drinking water supplies, so unless you are exposed at work, you probably will never have much contact with it, though the folks at Beyond Pesticides are concerned that kids are often exposed from playing around poles.

For those who spend time around boats and marinas, you will definitely be exposed to creosote, which is one of the oldest wood preservatives. The name creosote actually refers to several different products, including wood creosote, coal tar creosote, coal tar, coal tar pitch, and coal tar pitch volatiles. Whichever type it is, creosote is a mixture of many naturally occurring chemicals created by high-temperature treatment of wood or coal, or from the resin of the creosote bush. Creosote is essentially the black goopy stuff seen on pilings and bulkheads around marinas, and it is also used to treat utility poles and railroad ties, as well as in other industrial applications. Of all the chemicals used to treat wood to withstand salt water immersion, creosote is less nasty from both the environmental and health angles.

CCA

We humans have long understand the toxicity of arsenic, chromium, and copper in acute, large doses, but it is only in recent history (say, since around the 1980s) that we’ve begun to understand that longer term and lower doses had a toxic impact. So it is understandable that we all got excited by using treated wood in so many applications: An inexpensive softwood board that would rot in a few years if left untreated, suddenly lasted a few decades. What a deal!

We began using treated lumber for decks, play grounds, picnic tables, garden applications... and by 2000, ninety percent of all outdoor wooden structures in the United States were made of CCA pressure-treated wood. But the evidence of long-term health impacts mounted, and in 2002 was enough to prompt the U.S. EPA and the lumber manufacturers to agree to a voluntary phase out of CCA treatment for lumber in these “residential” applications. However, that phase out didn’t affect non-residential uses, and marinas are considered a non-residential use, even if some people live on their boats. And, the phase-out did nothing about the CCA treated wood that was already all around us, though weathered lumber can still leach as much (or sometimes more) arsenic than newly treated boards. Children are particularly vulnerable, as they tend to crawl around more on hands and knees, and because those hands frequently end up in their mouths.

Arsenic is a known carcinogen, strongly associated bladder, lung and skin cancer, and to a lesser extent with other types of cancer. It is also implicated in a host of other illnesses ranging from diabetes and heart disease to fetal toxicity and congenital birth defects. Like arsenic, chromium is linked to a number of types of cancer (particularly brain and stomach cancer) and to dozens of other diseases and disorders. Copper, though less dangerous than arsenic and chromium, also has numerous health impacts. All three are associated with liver and kidney disease.

What can you do to protect yourself

Since CCA was banned for residential use, other preservatives are being used. (Treated lumber is stamped on the end of the board with a label that indicates what chemical was used to treat it.) The most common is ACQ, or Alkaline Copper Quaternary, which uses much heavier concentrations of copper in lieu of arsenic and chromium. Another is C-A, or Copper Azole. Are these alternatives really safe? Everything has some inherent dangers, but the newer preservatives are considerably safer than CCA. A note for anyone working with ACQ: it does cause galvanized nails or screws to fail due to corrosion, so use stainless steel fasteners. Of course, if you are getting ready to build or buy a new outdoor item yourself, such as deck or a picnic table, you have some excellent alternative options: consider using sustainably-harvested cedar or other rot-resistant wood, or use recycled plastic composites.

If you are stuck with existing CCA-treated wood, there are some things you can do. The greatest exposure comes from direct physical contact, and ingestion following physical contact. So, to minimize risks, follow these guidelines from the Environmental Working Group:

Seal the wood at least every six months with standard penetrating deck treatments.

Replace sections of potential high exposure like handrails, steps, or deck boards with non-arsenic alternatives.

Wash your hands and your children’s hands after every exposure to arsenic-treated wood, especially before eating.

Keep children and pets away from the soil beneath and immediately surrounding arsenic-treated wood structures.

Cover arsenic-treated picnic tables with a tablecloth before using.

Do not pressure wash to clean the surface of arsenic-treated wood. Instead use a soap and water solution, with disposable cleaning supplies. Pressurized water will blast off the upper surface of the wood and spray arsenic-contaminated particles over your yard.

Do not allow children to play on rough wood surfaces. Arsenic-treated wood splinters can be dangerous.

Never sand arsenic-treated lumber. If wood is smooth enough that splinters are not a risk, avoid sanding a deck to prepare the surface for sealing—use a simple soap and water wash instead. Wood dust formed by sanding contains arsenic that is easily ingested by a child, or can wash off the surface to contaminate the soil below.

Do not store toys or tools under the deck. Arsenic leaches from the wood when it rains and may coat things left there.

Do not use commercial “deck washing” solutions. These solutions can convert chemicals on the wood to a more toxic form.

As for the reader who initiated this post: Moving is obviously a big step, and finding anyplace that isn’t “dirty” is almost impossible (and I would guess that living on a boat has certain spiritually fulfilling aspects that might be really hard to give up on). If you opt to stay where you are, add don’t go barefoot on the dock to EWG’s list of suggestions. Your drinking water being supplied through a hose is also a big concern to me. The hose will leach phthalates and other chemicals, so consider investing in a reverse osmosis filter for your water supply.