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Wood Preservatives - Low Toxicity

Same benefits of conventional wood preservatives, with fewer health concerns

A stack of 2 by 4 lumber treated with low toxicity preservatives

Because of its increased resistance to rot and infestation, preservative-treated wood has been widely used for many residential applications, including decks, outdoor furniture, wood foundations, and a host of other purposes. Chromated Copper Arsenate (CCA), the most commonly used preservative, has been effective and economical, but the chromium and arsenic in this formula has also generated concerns over possible health risks from exposure or leaching.

In February of 2002, the Environmental Protection Agency (EPA) announced a voluntary decision by the wood-treating industry to phase out the use of CCA preservatives for residential building products by the end of 2003. The EPA will not permit the manufacturers of materials containing CCA for residential use after that date. Several manufacturers have already developed arsenic- and chromium-free preservatives, marketing them as low-toxicity alternatives to traditional treated lumber. Although not widely available at the time of the EPA announcement, arsenic-free preservative-treated products are expected to become common as the industry develops new products.

Pressure-infused preservatives in lumber, plywood, and other wood-based products add decades to the predicted service life of these materials in exterior applications, especially where ground contact is required. Chromated copper arsenate (CCA) is the preservative used in about 90% of the pressure-treated materials sold through 2001. However, concerns about CCA have focused mainly on the possible environmental and health effects of arsenic through contact or chemical leaching. Since arsenic is also a common, naturally-occurring element in soil, it has been difficult to establish a consensus on whether there is any existing or potential harm.

There are several alternative preservatives to CCA. Some were developed to treat wood species that did not treat well with CCA, but they may also contain arsenic. Others have been designed specifically to provide less-toxic alternatives to conventional treating chemicals. Given the controversial nature of CCA, manufacturers felt that the industry and consumers alike would be better served by voluntarily surrendering licenses to use CCA, so that production of alternative materials could be stepped up quickly. A list of products available as of this writing is shown below:

Ammoniacal Copper Quat (ACQ-A, B, C) - The preservative effects of copper are combined with a low toxicity co-biocide to achieve durability levels equivalent to copper/arsenic preservatives, with no impact on the mechanical properties of wood. A preservative containing ACQ-A is marketed under the brand name ACQ Preserve, by Chemical Specialties, Inc. (CSI)

Amine Copper Quat (ACQ-D) - This product contains active ingredients similar to ACQ-A, B, C, but uses ethanolamine instead of ammonia as the solution carrier. Lumber treated with this preservative is marketed as NatureWood by Osmose, Inc.

Copper Azole-Type A (CBA-A) - This new generation preservative contains copper and boron, and is marketed as Wolmanized Natural Select by Arch Wood Protection (formerly Hickson).

Manufacturers believe that these preservatives intended for ground contact will provide similar durability as conventional CCA.

Borate Oxide (SBX) - Boron compounds are well known, non-toxic preservatives, but are water soluble. Wood products treated with SBX are not recommended for direct ground contact, but can effectively preserve wood for other applications like deck surfaces or furniture. Brand name products include AdvanceGuard lumber by Osmose, Inc.and SmartGuard products from Louisiana Pacific.


Environmental Performance

Many of these preservatives offer a formula that is not as dangerouse to humans and the environment, in the situation that they leach into the ground or become airborne.

Quality and Durability

These preservatives allow the wood to resist rot and infestation form insects, allowing for a longer-lasting structure or apparatus.


Easy

Check the manufacturers' recommendations on the suitability of various products for specific projects. Specially designed products may be needed where ground contact occurs, or for wood foundations, poles, pilings or other applications highly susceptible to decay. As with conventional pressure-treated wood, special products may also be needed for finishing. A drying period may be required, and generally high quality oil-based, semi-transparent stains are recommended. Latex products usually do not penetrate as well, and may wear or blister more readily.

As of this writing, low-toxicity products are available only in very limited areas. As the industry gears up production, these products will be sold throughout the United States.


Products made from low-toxicity preservatives are expected to cost 10 to 20% more than CCA-treated lumber.


Not Applicable


The latest generation of wood preservatives contains no chemicals that fall under regulation of the Toxic Substances Control Act (TSCA), and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Dust from any wood source, treated or untreated, is considered a carcinogen by the International Agency for Research on Cancer, and carcinogenic warnings are required on treated wood products shipped into California. When cutting or sawing any type of wood, it is recommended that a mask and goggles be worn for personal protection. The EPA also recommends cutting outdoors, washing hands, and laundering clothes separately after use. Low-toxicity treated wood can be disposed of in the normal waste stream or as advised by your local waste regulatory authority.

The chemical components of low-toxicity preservatives are EPA-registered, general-use pesticides that are less toxic than chemicals in conventional wood preservative systems. American Wood Preserver's Association (AWPA) has a standard for ACQ. It is also listed by the International Conference of Building Officials (ICBO).


Not Applicable


The general construction methods, sawing, shaping, and fastening techniques for working with wood materials will not change. Since treated wood is likely to be used in harsh, exterior environments, corrosion-resistant hot-dipped galvanized, or stainless steel fasteners are recommended. As with other wood products, using eye protection and a dust mask is advised.


Most manufacturers offer a limited lifetime warranty against structural damage due to fungal and infestation decay and rot for the entire period the original purchaser owns the property on which the product is installed.


Alternative preservatives should provide the same benefits as conventionally treated wood, while avoiding perception problems and any potential risks from arsenic and other metals that may leach into soils.

Disclaimer: The information on the system, product or material presented herein is provided for informational purposes only. The technical descriptions, details, requirements, and limitations expressed do not constitute an endorsement, approval, or acceptance of the subject matter by the NAHB Research Center. There are no warranties, either expressed or implied, regarding the accuracy or completeness of this information. Full reproduction, without modification, is permissible.