Preservative Treatment of Wood Poles
Treatment of utility poles represents 93 percent of the remaining uses of pentachlorophenol. After crossties, poles are the largest wood product still treated with creosote. Forty-two percent of wood poles are treated with inorganic arsenicals and 13 percent are treated with creosote. As mentioned above the sole purpose of these chemicals is to preserve by killing living organisms. Because they easily move in air, water and soil, they threaten human life.
In addition to causing both short- and long- term health effects -- from extreme irritation to nerve damage to spontaneous abortions to death, penta and creosote are linked to disruption of the endocrine system.
This means that they can disrupt the basic messages of life, affecting fertility, reproduction and the functioning of the nervous and immune systems and have been linked to breast and prostate cancer. Regarding environmental impacts, these chemicals contaminate the soil, leach into groundwater and move through the air.
Because of these effects, in many contexts the use of these chemicals is severely restricted or banned in the U. Twenty-six countries around the world have prohibited the use of penta.
Wood Pole Preservative | Wood Preservative | Preschem
Furthermore the Province of Labrador in Canada has certain distance requirements buffers for chemically treated poles that are in proximity to water supply areas and the City of Seattle prohibits treated wood poles in wetlands and sees composite reinforced fiberglass poles as an alternative solution. Chemically-treated poles are used in virtually every community in the U.
Nearly 12 percent of all wood preservatives are used to treat utility poles. The rest is used on lumber and timber, plywood, fence posts, crossties and switch and bridge ties. In most cases, the poles, soaked in wood preservatives, are placed adjacent to property lines, or in backyards, front yards and playgrounds. The utility or telephone poles coated with a dark brown or oily substance --penta or creosote-- give off a petroleum odor. Other poles appear lighter, sometimes greenish, in color with no odor.
These are treated with arsenicals. To maintain preservation of a pole over time, they are often pumped full of fresh chemicals, especially at the base where the wood meets the soil. In addition to the environmental and health issues related to the use of wooden poles, they present a serious roadside hazard due to the large number of poles located in close proximity to the roadways and the unforgiving nature of existing pole designs.
Anomalous leaching or dislodging characteristics of wood preservatives, diffusion and solubilizing processes under decreased pH, and the presence of organic acids, salts and fertilizers in leached water have further aggravated the already existing concern and controversy. The climate and the surface water characteristics low pH and presence of humic acids in Newfoundland are a most favourable host environment for leaching of chemicals used in different types of wood preservatives. In recent years, the use of treated timber utility poles in this province has become an issue of increasing public concern especially in protected water supply areas.
Section 39 of the Water Resources Act prohibits all activities in a protected water supply area which have potential to impair water quality. In response to public concern and requests from the utility companies, policy guidelines have been proposed under the provisions of the Water Resources Act for application in protected water supply areas. These guidelines are designed to minimize the adverse impact of treated poles on drinking water quality.
Remedial Timber Treatment Products
The Department of Municipal Affairs and Environment requires that the following guidelines be followed by all utility companies in this province in order to minimize the risk of water quality impairment and possible impact on public health:. Existing treated wooden utility poles will be permitted to remain as long as they are not located within the high water mark of the intake pond, or in the case of a river intake, within one kilometre upstream of the intake provided they are not impacting water quality.
Existing treated wooden utility poles which are located within the high water mark shall be replaced with untreated wooden, concrete or steel structures. During the design of any new transmission line, or the placement of any new poles, the following options shall apply in decreasing order of preference:.
Wood Utility Poles and Preservative Choices
Option 3. If this option is approved, poles shall not be placed within the following buffer zones from the high water mark of any body of water:. If the poles in question cannot be located outside the above specified buffer zones, then only untreated wood steel or concrete poles be used. The utility companies are required to submit a detailed plan for any new transmission line, or the placement of new poles to be located in a water supply area, to this department for approval before undertaking any work.
The plan should also include a written letter of consent from the concerned council s that they have no objection to the proposed work. Controlled studies have shown that wood preservation enhances the lifetime of wood by a factor of 5 to 15, depending on the wood species and the efficacy of treatment. It has also been estimated that if wood were not treated with preservation chemicals, timber requirements in some industrial applications would increase by three- to six-fold Konasewich and Henning, Unfortunately, long-term environmental and public health hazards associated with the use of treated wood have not been considered in assessing the value of wood preservation.
The wood preservation process deposits or fixes chemicals in the wood, and the toxic nature of the chemicals effectively prevents the attack of living organisms on the wood.
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The choice of wood preservatives depends upon the character of the wood to be treated, the required service, and the properties of the chemical or formulation. In general, the wood preservation formulations must meet the following requirements:. The chemicals used for wood treatment are generally divided into two major groups: i organics - these are oil-born chemical formulations, consisting of an organic preservative dissolved in a suitable petroleum oil carrier and ii inorganics - these are water-borne chemical formulations, consisting of inorganic compounds dissolved in a water as a carrier.
In Canada, the registered chemicals most often used for wood preservation are:. The first two chemicals belong to the organic group and the remaining two to the inorganic group. Other major chemicals used commercially for wood protection in Canada include: Sodium-tetra and pentachlorophenate, copperquinolinolate Cu-8 and 2- thio-cyanomethylthio benzothiazole TCMTB. Some of the main characteristics of these preservatives are briefly outlined below:.
The "Wolmanized" branded CCA pressure treated wood products are most popular. The components of CCA copper, chromium, and arsenic were selected for wood preservation use because of their biocidal properties and their ability to be retained within the wood for long-term protection. The fixation mechanism of CCA within wood is complex and the reactions involved depend on the preservative formulation and concentration, wood species, and temperature Konasewich and Henning, According to producers, the waterborne CCA preservative is permanently fixed in the wood by the full-cell pressure treatment process and soon after treatment, the chemicals are highly leach resistant, non-toxic to human and warm-blooded animals and vegetation if properly used.
However, leach resistant and non-toxic characteristics of CCA treated wood is an issue of controversy and debate due to unknown impacts of typical low-level exposure in drinking water on human health. Copper and arsenic, two active components of ACA, are used because of their biocidal properties and their ability to be retained by wood for long-term protection. Ammonium hydroxide is used as a solvent carrier for copper arsenate and once the ammonia evaporates from the wood the copper arsenate precipitates in the wood cells.
The resultant precipitate is reported to be highly resistant to leaching Konasewich and Henning, There is increasing concern about possible environmental contamination from leaching losses of chromium, copper and arsenic constituents from treated wood. It has been reported that solubilizing and diffusion processes are highly temperature and moisture dependent.
Thus, the climatic conditions of an area will have a great effect on leaching losses. The solubility of the fixed CCA and ACA components is also reported to increase with increased acidity decreased pH of the leaching water which implies that wood exposed to high rainfall under moderate annual temperature conditions will leach more than wood in colder and drier climates. The presence of other organic acids, such as humic acids and salt content or fertilizers in surface water in significant quantities, has also caused anomalous leaching effects.
In most of the cases, losses are highest during the initial years of installation. The organic compounds commonly used as wood preservatives include pentachlorophenol and creosote. PCP is prepared by reacting chlorine with phenol in the presence of a catalyst at high temperatures. Petroleum oils are used as carriers for PCP. PCP-oil mixtures are used for pressure treatment of wood products, such as telephone and other utility poles, railroad ties, posts and construction timbers.
In addition to functioning as a carrier of PCP, the oil also provides extra protection against moisture-content changes, providing more stability and resistance to splitting Konasewich and Henning, PCP, sold under the trade name Penta, is a registered commercial fungicide and bactericide produced by a few manufacturers worldwide.
Commercial preparations of pentachlorophenol contain varying percentages of related chlorophenols such as tetrachlorophenol and a range of chlorinated compounds including dibenzo-P-dioxins and dibenzo-furan micro-contaminants, some of which are highly toxic. There are potentially serious problems associated with dioxin contamination in the chlorinated phenols and creosote. Dioxins accumulate in the food chain, are slow to decay, cause reproductive problems in animals and are suspected of inducing cancer in humans. The most common use of PCP in Canada includes treatment of utility poles and unseasoned lumber.
Creosote is one of the oldest types of preservatives used for the protection of wood against all forms of wood destroying agents.
Creosote is a distillate of coal tar produced by high temperature carbonization of bituminous coal. Containing over compounds, creosote is primarily composed of liquid and solid aromatic hydrocarbons as well as some tar acids and tar bases which provides protection against destructive insects and organisms. Used in a mixture, creosote is blended with petroleum oil. Creosotes are traditionally specified by their physical properties density, water content, distillation intervals, etc.