1 Answer

What is the chemical preservative used, and is it dangerous?

Until 2003, the preservative most commonly used in residential pressure-treated lumber was chromated copper arsenate (CCA), an extremely toxic chemical. Remember "Arsenic and Old Lace"? How about that old box of rat poison you have lurking in the garage? CCA is so toxic that the Environmental Protection Agency, over 20 years ago, imposed strict guidelines regarding the manufacturing practices of companies using CCA.

However, one must distinguish between the toxicity of the chemical and the toxicity of the wood product in everyday use. Extensive studies were done since the mid 1980's concerning the potential dangers of pressure-treated wood, and rightfully so! Large volumes of CCA were being used, and the treated wood products were beginning to be widely distributed, justifying the need for some hard research.

The research was mixed, but the typical hysteria ensued as attorneys and plaintiffs lined up to claim damages from exposure to CCA. In the end, the industry agreed to voluntarily eliminate use of CCA for residential use. CCA is still being used in certain marine and industrial applications since it is still the best preservative available at the present time.

The new alternatives to arsenic-based preservatives.

Your local home store or lumberyard is now selling lumber treated with less toxic alternatives... amine copper quat (ACQ) and copper azole (CA)... though you may find other chemical combinations in specific areas. The reason these new copper-based alternatives are considered safer than arsenic-based preservatives is based on the human body's inability to absorb these poisons. Inorganic arsenic is readily absorbable by the body.

Whether these new chemicals will turn out to be less hazardous in the long term is anyone's guess, but all indications are that they will be. Fingers crossed!