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Pentachlorophenol is an organic chemical compound which is widely used in the timber industry. This chemical is also known as PCP, but this is different from the PCP which is used as a recreational drug. The chemical’s most common use is as a preservative for wood; however it has also been used historically as an insecticide, herbicide, and disinfectant. Due to concerns over pentachlorophenol toxicity, the sale of this chemical is restricted in many countries, including the USA and New Zealand. Both the production and use of the chemical is restricted in countries of the European Union. Some European countries have opted to ban it altogether.
PCP wood preservative is manufactured by adding chlorine to a chemical precursor called phenol. This process requires the addition of a catalyst to increase the speed of the reaction between chlorine and phenol. The catalyst added is either ferric chloride or anhydrous aluminum. When the reaction is complete, the resulting chemical mixture is up to 90% pure, with the remaining 10% of the mixture being a range of other phenol byproducts.
One of two methods can be used to treat wood products with pentachlorophenol. The first method is called the pressure process method. In this process, wood products are immersed in a chemical bath and pressure is applied to saturate the wood with the preservative. The second method is called the non-pressure process method, and involves wood products being soaked in or sprayed with the chemical without pressure being applied.
Pentachlorophenol exposure is a concern in industrial settings where the chemical is manufactured or used. This is because acute or chronic inhalation of air contaminated with solvent fumes, or contact with PCP-treated wood, can be toxic. In addition, exposure is a public health concern because ground water, soil, and even drinking water which has been contaminated with the chemical can also become a source of toxicity. This kind of toxicity is a risk particularly in locations near industrial facilities where the chemical is used, and near hazardous waste collection sites.
Symptoms of pentachlorophenol toxicity may differ depending on whether exposure to the chemical is chronic or acute. Short-term exposure to high concentrations of the chemical can damage the central nervous system, gastrointestinal tract, and organs such as the kidneys, liver, and lungs. Chemical vapor can seriously damage the eyes and mouth. Long-term low concentrations of the chemical cause also damage the central nervous system, kidneys, and liver. Long-term exposure is also thought to increase the risk of certain types of cancer.
The worry is that xylophene, which is used to spray wood, as in barns being refurbished, contains pentachlorophenols. France has not banned its use in wood preservatives, one of the reasons being they are trying to preserve their old buildings.
I cannot find out what the percentage of this is used in the manufacture of xylophene. They say it is OK after 48-72 hours, but it can take about 12 months to possibly vapourise to reduce it by 80 percent, and then there are other conditions involved.