“Among building materials, wood is ideal: beautiful, strong, easily shaped. And it’s renewable. Its one big flaw is vulnerability to decay and insects. For centuries, builders resorted to oily smelly solutions like creosote to make wood more durable. Then in the 1930's, scientists found a way to infuse wood with a solution that included copper (toxic to the fungi that cause rot) and arsenic (then the most common insecticide). To ensure the protection would last, and builders and the environment wouldn’t be hurt, they also added chromium. It triggered a chemical reaction that locked the pesticides into the wood.”1 “The raw lumber is placed in a pressure cylinder where a vacuum sucks air and water from the wood cells. The cylinders are then filled with a mixture of water and pesticides and pressure is increased to refill the wood’s cells with the mixture. As the wood dries, the chemicals are trapped inside.”2
“The formula became known as chromated copper arsenate, or just CCA. But the industry called it pressure treated because the chemicals were injected under great pressure. The wood dried with a green tint because of the copper, but otherwise it was similar to ordinary lumber, except that it stood up to even the dampest, warmest climates.”1 during the pressure treatment up to 250 liters of CCA solution per cubic meter of wood is applied, resulting in copper (CU), chromium (CR), and arsenic (AS) concentrations in the range of 1000-5000 mg/kg. In the United States more than 10 million cubic meters of CCA treated wood is produced each year.3
|Table 1 Composition of CCA-Type A, B, and C (AWPA, 1996)4|
|CCA-Type A||CCA-Type B||CCA-Type C|
|Chromium as CrO3||65.5%||35.3%||47.5%|
|Copper as CuO||18.1%||19.6%||18.5%|
|Arsenic as As2O5||16.4%||45.1%||34,0%|
|Table 2 Retention Requirements for CCA-Treated Wood (AWPA, 1996)4|
|Applications|| Retention Value
|Above ground: lumber, timber, and plywood||0.25|
|Ground/Freshwater contact: lumber, timber, plywood||0.4|
|Salt water splash, wood foundations: lumber, timber, and plywood
|Foundation/Freshwater: pilings and columns||0.8|
|Salt water immersion: pilings and columns||2.5|
“CCA-treated wood was first used in India in 1933 and was approved by the American Wood Preservers Association for use by Bell Telephone Co. in 1950.”2 “Stakes pounded into a termite-infested field at a federal laboratory in Mississippi in the late 1930's remain intact “and some of them will probably last 100 years,” says Jerrold Winandy, a research wood scientist with the U.S. Department of Agriculture’s Forest Products Laboratory in Madison, Wisconsin.
For many decades, pressure-treated wood remained a specialty product; people built porches, decks and fences of untreated redwood, cedar or fir. But as the price of wood soared, marketers of plantation- grown Southern Pine seized on pressure treating as a way to convert their product into one that would command a premium. Sales of the greenish lumber ballooned from practically nothing in the early 1970's to 467 million cubic feet last year-nearly a fifth of all softwood boards and timbers sold.”1
Even the smallest of pressure treated decks - 8x10 feet - has four pounds of toxic metals in its 1 ½ -inch-thick platform. The recipe for this amount of chromated copper arsenate calls for 1.9 pounds of red crystals (chromic acid), 1.36 pounds of white powder (pentavalent arsenic) and .74 pounds of copper.1
“CCA preservative is used almost exclusively in the pressure treatment of timber, although it can be used for the sap replacement of hardwood fence posts. Freshly treated timber should be held on the treatment plant premises for a sufficient period to ensure fixation of the preservative and surface dryness. It is recommended that this period be two weeks.
Where treated timber is to be used for playground equipment or log cabin construction, a storage period of four to six weeks is recommended before distribution. All treated lumber intended for this use should also be washed prior to distribution to remove surface build-up of dried salts.”5
“A study at the University of Turin in Italy found exposure of CCA-treated wood sawdust to rain water resulted in significant release of the chemicals and was potentially hazardous.
A 1984 study of the biological impact of CCA-treated wood on honeybees found that the bees had elevated arsenic levels and poorer winter survival when kept in CCA-treated hives.
A 1991 study by researchers at Rutgers University found leaching of CCA-treated wood in seawater retarded the growth of fiddler crabs and algae, and resulted in higher death rates for fish and snails.
The leaching research of David E. Stilwell, an analytic chemist at the Connecticut Agricultural Station of New Haven, Conn. found elevated levels of copper, chromium and arsenic in soil samples under seven wood decks built with CCA-treated wood.”2
Burning of the wood also releases these toxins in the smoke and the wood ash is even more dangerous containing around 80% of the toxins. The arsenic in wood ash is highly “leachable” and poses a serious threat to the environment and is capable of causing health damage and death to both humans and animals.
In a question and answer sheet published by the Connecticut Department of Health we read, “Doesn’t pressure-treatment lock pesticides into the wood.” Their answer, “ Not completely. During treatment, the boards are dipped into a CCA bath under high pressure. This forces arsenic into the wood but it doesn’t seal the wood against the weather. Once in the environment, rainwater can penetrate into the wood and dissolve arsenic, bringing it back up to the surface. Cracking of the wood as it ages speeds up the leaching process. New boards may also have surface residue of arsenic-containing pesticide that had not penetrated into the wood during the treatment process. The amount that leaches is enough to contaminate soil immediately below and next to the wood structure, and to leave a residual coating of “dislodgeable” arsenic on the wood surface.”6
Alan Wilbur, a spokesman for the American Wood Preservers Institute is
quoted as saying, “As in any product line, there are good and not so good manufacturers.
There may be folks who take shortcuts. That’s not appropriate, and we
do not condone that, but we have no policing powers.”2
In a publication by the European Commission we read this statement concerning the safety of CCA, “The authors indicate that they base their risk assessment on the assumption that “best current practice” is followed at all stages of the manufacture, use and disposal of CCA and CCA- treated wood. To the extent to which the technical specifications for various procedures are imposed by regulatory statutes to which compliance is compulsory, this is a reasonable position.
However, it appears that some of the “best practice” guidelines assumed in the Report to be in general operation are guidelines recommended by professional or other organizations and rely upon voluntary cooperation for their application. Given the well documented problems related to the environment or human exposure arising from past practices, especially at wood treatment sites, it would be important to have an indication of the extent to which such guidelines are indeed employed in practice.”7
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