Poison Poles — A Report About Their Toxic Trail and Safer Alternatives The Toxic Trail
Chemical Treatment of Wood
In 1995, the wood preserving industry reported $3.65 billion in annual gross sales. In the same year, total volume of treated wood produced reached 578,874,000 cubic feet.19 The largest use of pentachlorophenol and other oilborne solutions is in the treatment of utility poles. Of the 32,764,000 cubic feet of all wood treated with penta and oilborne solutions, 93 percent, or 30,617,000 cubic feet, is used in the production of utility poles. Of the 450,596,000 cubic feet of all wood treated with arsenicals, six percent, or 29,215,000 cubic feet, go into utility poles. In other words, the vast majority of pentachlorophenol is used on utility poles.20 Nevertheless, the treatment of utility poles are almost evenly split between penta and CCA, with 45 percent treated with penta, 42 percent with CCA and 13 percent with creosote. More Info: |
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Treatment processPoles must be prepared before the chemical is applied. The preparation may include peeling, drying, conditioning, incising, cutting, and framing. These processes enable the preservative to penetrate the wood better. The different types of wood treating plants, including pressure treating and thermal non-pressure treating, use varying degrees of pressure, vacuum and temperature.24The pressure-treating process involves placing the wood in a pressure-treating vessel where it is immersed in the preservative and then subjected to applied pressure. The excess penta is vacuumed from the vessel and the treated wood is removed, inspected, stored, and shipped. In the non-pressure process, which is used for short-term wood protection in construction where the wood will be protected from exposure to soil or weather through brick or cement barriers, penta is applied to the surface of wood by spraying, brushing, dipping, and soaking. This process is also used to control sapstain fungi by passing green lumber through a spray tunnel or by dipping the wood.25
Toxic releases from treatment sitesWood preservative treatment facilities have contributed greatly to the ranks of Superfund cleanup sites. On the National Priority List (NPL) of sites identified by EPA:
Maps: Wood Preserving Plants (number per state) and National Priority List Sites Contaminated with Penta, Creosote, Chromium orDepending on the process used by the treatment plant, wastes from plants include debris from clean-out of pressure cylinders and sumps, filters and removed from bag filters, sludge and wastewater, used personal protection equipment such as respirator filters. In a survey conducted for a Canadian government study, volumes of penta waste in treatment plants using the chemical varied from 0.03 to 0.94 kg solid wastes/m3 (solid wastes per cubic meter of) treated wood.31 The study assumes a 6% concentration of penta in solid waste from treatment facilities.32 The study's analysis of the content of solid wastes from CCA treatment facilities establishes a range of toxic material content: for arsenic 2.0 to 5.7%; chromium from 0.7 to 1.7%; and copper from 1.0 to 1.6%.33 Drip residues is considered "one of the major potential sources of air-borne CCA components in treatment plants."34 Penta treated wood, "particularly immediately after treatment, emits PCP to the air and the wood may exude excess preservative."35 Worker exposureExposure to wood preservative chemicals is highest among workers at wood treatment facilities.36 So much illness has resulted from worker exposure to pentachlorophenol that it is seen as a significant source of income for attorneys pursuing toxic torts.37 One study found that mean pentachlorophenol levels in the blood of workers using penta ranged from 83 to 57,600 parts per billion.38 Exposure to pentachlorophenol at maximum air concentrations allowed by Occupational Safety and Health Administration (OSHA) are estimated to produce blood levels one hundredth as high as the maximum found in this study.39 EPA estimated the lifetime cancer risk of a worker in a wood treatment plant using inorganic arsenicals as ranging from two in 100 to more than one in ten. Cancer risk for workers using penta were based on the dioxin contaminant, rather than all the ingredients. Nevertheless, cancer risk was estimated to range from seven in 1,000 to more than one in 100. EPA did not perform a quantitative risk assessment for workers exposed to creosote.40 Back to Chemical Production | Contents | On to Storage of Treated Poles |