CCA CONCERNS

for

PERMANENT WOOD FOUNDATION USE

On February 12, 2002 the EPA (Environmental Protection Agency) announced the VOLUNTARY decision by the wood preserving industry to move consumer use of specified kinds of residential uses of treated lumber products away from pressure treated wood that contains arsenic by December 31, 2003. Arsenic is a known human carcinogen and any reduction in the levels of potential exposure to arsenic is desirable. Among the residential uses to be dropped are play-structures, decks, picnic tables, landscape timbers, residential fencing, patios and walkways and boardwalks. NO specific mention was made to include Permanent Wood Foundations.

 Historically, the wood preservative most commonly used for the above mentioned uses, including  permanent wood foundations, is chromated copper arsenate (CCA). It has been successfully in use since the 1940’s with no ill effects being reported and confirmed involving humans and animals. EPA has NOT concluded that CCA-treated wood poses unreasonable risks to the public for existing CCA-treated wood being used around or near their homes or from wood that remains for sale in stores and lumber yards. EPA does NOT believe there is any reason to remove or replace existing CCA-treated structures, including decks or playground equipment. EPA is NOT recommending that existing structures or surrounding soils be removed or replaced.

 Since CCA was introduced over 60 years ago it has become a commodity. It is being used for nearly every conceivable use for pressure treated wood, and has been in great demand by consumers as safe treated wood products. Competition among sellers of CCA pressure treated wood products has forced very competitive prices and lowered profit margins. It seems that this “voluntary” decision by the wood preserving industry to move consumption of CCA pressure treated residential uses away from CCA in favor of newer more highly priced preservatives (10 to 25%) is more self-serving than an environmental concern. Profit margins for the wood preserving industry will be enhanced at the cost of the consumer.

CCA is a chemical compound mixture containing inorganic arsenic, copper and chromium. It is a water-soluble mixture (in the form used in a treating plant), and in solution, it is forced into the wood under high pressure. Type C is the most commonly used formula. This is: Hexavalent chromium as CrO3  – 47.5%; Copper as CuO – 18.5%; and Arsenic Acid as As2O5  - 34.0%. This is the only form of arsenic used in wood preservation (in CCA).

The molecular weight of As2O5  is (2 x 75) + (5 x 16) = 230. The arsenic is 2 x 75 = 150. Therefore, the Arsenic is 150 / 230 = 0.652 or 65.2% of the molecule.

Wood foundation lumber and plywood is pressure treated to a retention of 0.60 pounds per cubic foot of wood treated. In one cubic foot of wood there is 0.60 x 0.34 = 0.204 lbs. of As2O5. The Arsenic amounts to 0.204 x 0.652 = 0.133 pounds per cubic foot of wood.

 Other residential uses, such as decks and play structures, are pressure treated to a retention of 0.40 lbs. per cu. ft. of wood treated. In one cubic foot of wood there is 0.40 x 0.34 = 0.136 lbs. of As2O5 . The Arsenic in this case amounts to 0.136 x 0.652 = 0.089 lbs. per cu. ft. of wood.

The cross-section of a 2 x 6 is 1 ½ “ x 5 ½” = 8.25 sq. inches x 12” = 99 cu. ins. In one linear foot. 99 / 1728 = 0.0573 cu. ft. per linear foot. By dividing 1 by 0.0573 it is found that it would take.

17’ 5 3/8” of 2 x 6 to equal one cubic foot of wood. Put another way at a 0.60 retention it would take a 2 x 6 – 17’ 5 3/8” to hold 0.133 pounds of arsenic. One would have to eat the whole 2 x 6 – 17’ 5 3/8” to get this much arsenic. The splinters would prove to be much more troublesome than the arsenic. If the retention were 0.40 lbs. per cu. ft., then only 0.089 lbs. of arsenic would be present in a 2 x 6 – 17’ 5 3/8”.

 Upon pressure treating into wood, CCA undergoes complex chemical reactions during the treating process; whereby the active ingredients, copper, chromium, and arsenic are fixed in the wood cell cavities as an insoluble precipitate. Wood is composed of + or - 150 natural extractives, most of which are soluble in water and toxic to some degree. These extractives protect the trees as living organisms from attack by insects and fungi and they are stored by the tree in the heartwood. This is why the heartwood is more naturally durable than the sapwood of the same species. The extractives are natural toxic preservatives. Where they are high in volume and toxicity, as in redwood and the cedars, the heartwood of these species are naturally durable.

In the presence of hexavalent chromium, all the active ingredients in CCA react with the extractives to form an insoluble in water precipitate in the cell cavities of the wood. They cannot leach out. However, the chemical reaction is time / temperature dependent. The higher the temperature at the time of treating: the shorter the time to accomplish fixation. Under most conditions 99% of the active ingredients are fixed within 6 days. It would be very unusual if any CCA treated lumber and plywood is not completely fixed after treating and kiln drying. After fixation arsenic or other active chemicals cannot leach into the environment.

 The biggest danger is a large amount of sawdust or chips from CCA treated wood that might be generated in a manufacturing process. In some cases scraps are ground into a treated bedding for use in playgrounds. This should not be done. Cutoffs and pieces of scrap can be disposed of in an ordinary landfill, but treated sawdust and chips are a hazardous waste and must be disposed of in a hazardous waste facility. The small amount of sawdust generated at a constructing site is not a problem. The active ingredients in CCA can be released when the treated wood is ground into sawdust or chips, but as long as the treated wood remains whole, there is little danger of any of the active ingredients being released.

 The arsenic atom exists in two states: the trivalent state and the oxidized pentavalent state. The latter is the only state found in CCA. Pentavalent arsenicals are readily excreted by humans, are essentially non-toxic, and unlike the trivalent form, do not accumulate in mammalian tissues. Furthermore, animals studies have not shown arsenic compounds to be carcinogenic. There are no reports linking inorganic pentavalent arsenic compounds, as in CCA, with human cancer. Arsenic is naturally found in most soils, plants, and water to varying degrees. Did you know that clams contain an average of 11.6 ppm of arsenic, and common table salt contains 2.7 ppm.? The dose makes the poison, and the dose from arsenic in CCA treated wood is not likely ever to be over 5 ppm.. So why the fuss over eliminating CCA from residential use? It must be money or politics. It has very little to do with safety or cancer risk.

For more information, E-mail us at woodbasement@comcast.net

Note: Panel foundations can be site built or made in a shop. When made so it cover up items that need inspection by the Building Inspector. Third Party Inspection may be required. (inspect for grade stamps, treatment stamps, stud spacing, insulation, nailing, dip of saw cuts, plywood requirments are some of the item that a third party inspection will note.

All Panel Wood Foundations must be designed and installed in accordance with:
All current Building Codes Standards

While wood foundations are easy to build, this is only true if one is building from an accurate well designed plan. When such a plan is incorrect, or if something is left out of the plan or absent, or if a design is made using a guide manual (these are not design manuals); major mistakes can be made during the construction process. These errors cause problems for the owner, builder, and the building department.

Woodbasement.com a service of Permanent Wood Foundation System (PWF), supported by Southern Pine lumber users affiliated with the training and installation of wood foundations.
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