Dioxins in Wood Preservatives

In the 1960s, paneling and other interior wood structures were treated with pentachlorophenol and gamma-hexachlorohexane for preservation purposes. Those preservatives contain trace quantities of polychlorinated diben-zo-p-dioxins and -furans that can volatilize into indoor air and impact the human immune system, particularly when the treated woods are being sanded and refinished, even many years after they were initially applied. 35  

---

Wolf N, Karmaus W. Effects of inhalative exposure to dioxins in wood preservatives on cell-mediated immunity in day-care center teachers. Environ Res 1995 68(2) 96 105. 

Cull MR, Dobbs AJ, Williams N. 1983. Polychlorinated dibenzo-p-dioxins (PCDDs) in commercial pentachlorophenol (PCP) used in wood preservation. Chemosphere 12 483-485. 

Arsenault, R.D. 1976. Pentachlorophenol and contained chlorinated dibenzo-dioxins in the environment a study of environmental fate, stability, and significance when used in wood preservation. Presented at the American Wood-Preservers Association Annual Meeting, Atlanta, Georgia, April 25-28. pp. 122-148. 

TCP), and pentachlorophenol (PCP), in order of abundance. Minor amounts of other trichlorophenols and dichlorophenols may also be present, as well as recalcitrant polychlorinated phenoxyphenols (PCPPs) and PCDD/Fs as impurities [75, 76]. In Finland, approximately 30,000 tons of CP products were used between 1934 and 1988, when they were banned because of their potential toxicity to humans and the environment [77, 78]. The careless manufacturing and application of wood preservatives together with the lack of suitable waste disposal caused massive contamination of river sediments and sawmill sites. For example, the river Kymijoki in southern Finland was identified as the largest source of dioxins accumulating in fish in the entire Baltic area. Similar products were used in other European countries, especially Nordic countries with a large forestry industry, such as Sweden [79]. 

Pentachlorophenol, a large-volume fungicide and wood preservative, contains relatively high levels of hexa-, hepta- and octachlorodibenzodioxins and essentially no tetrachlorodibenzo-p-dioxins [83-85] and polychlorodibenzo-p-dioxin incineration of materials containing chlorophenols readily produces mixtures of polychlorodibenzo-p-dioxins, but 2,3,7,8-tetrachlorodibenzo-p-dioxin is a minor component. On the other hand, the highly toxic 1,2,3,7,8-pentachloro isomer is a major component of polychlorodibenzo-p-dioxins and polychlorodibenzofurans usually produce mixtures of distinctly different relative component abundances [83], On the other hand, the preferential accumulation of certain isomers in animals may prevent source identification from analyses of biological samples. 

McKee P, Burt A, McCurvin D, et al. 1990. Levels of dioxins, furans and other organic contaminants in harbour sediments near a wood preserving plant using pentachlorophenol and creosote. Chemosphere 20(10-12) 1679-1685. 

Polychlorinated diphenyl ethers (PCDE) are common impurities in chlorophenol formulations, which were earlier used as fungicides, slimicides, and as wood preservatives. PCDEs are structurally and by physical properties similar to polychlorinated biphenyls (PCB). They have low water solubility and are lipophilic. PCDEs are quite resistant to degradation and are persistent in the environment. In the aquatic environment, PCDEs bioaccumulate. These compounds are found in sediment, mussel, fish, bird, and seal. PCDEs show biomagnification potential, since levels of PCDEs increase in species at higher trophic levels. PCDEs are also detected in human tissue. Despite the persistence and bio accumulation, the significance of PCDEs as environmental contaminants is uncertain. The acute toxicity and Ah-receptor-me-diated (aryl hydrocarbon) activity of PCDEs is low compared to those of polychlorinated di-benzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Due to structural similarity to thyroid hormone, PCDEs could bind to thyroid hormone receptor and alter thyroid function. Furthermore, PCDEs might be metabolized to toxic metabolites. In the environment, it is possible that photolysis converts PCDEs to toxic PCDDs and PCDFs. 

Pentachlorophenol (PCP) Users. PCP has been used as a wood preservative for many years. PCP contains octa-, hepta-, hexa-, and pentachlorinated dioxins. Since PCP was applied generally in an oil solution, spills and discharges from this operation have led to widespread migration of PCP and its impurities. The magnitude of these environmental discharges and possible remedial measures are being examined by U.S. EPA and responsible parties. 

Dibenzofuran, colourless, fluorescent crystals, mp 86°C, bp 287 C, occurs in coal tar. 2,3,7,8-Tetrachlorodibenzofuran and other polychlorodibenzofurans (abbreviated PCDFs) are extremely toxic and, like 2,3,7,8-tetrachlorodibenzo[l,4]dioxin (see p 371), belong to a group of compounds known as supertoxins [14]. The lethal dose for monkeys lies in the region of 0.07 mg/kg body weight. PCDFs are formed in traces during the industrial production of polychlorobenzenes, poly-chlorophenols and polychlorobiphenyls, as well as during the combustion or thermal decomposition of products which contain such compounds. Among these are pesticides, wood preserved with poly-chlorophenols, as well as transformer oils, e.g. ... 

Pentachlorophenol-contaminated air, rain, snow, surface waters, drinking waters, ground-waters, and aquatic biota are common in the United States. Residues of PCP in food, water, and mammalian tissues may result from the direct use of PCP as a wood preservative and pesticide or as a result of use of other chemicals that form PCP as degradation products - i.e., hexachlorobenzene and lindane. To confound matters, PCP was judged to be the source of dioxin and dibenzofuran contamination in chickens in Canada. More than 50% of all chickens sampled contained hex-achlorinated dibenzo-p-dioxins (hexa CDDs) at concentrations of 27.0ng/kg fat and higher ... 

PCP is frequently used as a wood preservative, herbicide and fungicide. It has additional uses in the leather and paper industry and an estimated 17,000 workers are exposed to PCP in the United States (O Malley et al. 1990). A retrospective review of 648 medical and personnel records from individuals manufacturing PCP between 1938 and 1978 demonstrated 47 cases of chloracne occurring in a 25-year period. These workers were exposed only to PCP for 2 years prior to their diagnosis. PCP was produced by direct chlorination of phenol, monochlorophenol, dichlorophenol and/or 2,4,6-trichlorophenol in the presence of an aluminum catalyst. During the commercial synthesis of PCP, varying amounts of polychlorinated aromatic by-products, including dioxins, are produced (O Malley et al. 1990). 

Organic compounds sought include naturally derived materials, such as mycotoxins and off-flavours (produced by rancidification or spoilage), and man-made/industrial chemicals, e.g. pesticides, veterinary drugs, environmental contaminants (such as polychlorodibenzo-p-dioxins, polychlorinated biphenyls, polynuclear aromatic hydrocarbons, etc.) and food tainting compounds (e.g. 2,4,6-trichloro-anisole, the compound responsible for musty cork taint in wine, arising from the inappropriate use of wood preservatives). GC-MS and HPLC-API-MS are widely used for these types of analyses. Desirable food components present at trace levels, such as nutrients, are also determined using these techniques. 

The chlorinated phenols, partieularly pentachlorophenol and the trichloro-phenol isomers, are signifieant hazardous wastes. These compounds are biocides that are used to treat wood to prevent rot by fungi and to prevent termite infestation. They are toxic, causing liver malfunction and dermatitis. However, contaminant polychlorinated dibenzodioxins ( dioxin ) may be responsible for some of the observed effects. Pentachlorophenol and other aromatic halides and aromatic hydrocarbons used as wood preservatives are encoimtered at many hazardous-waste sites in wastewaters and sludges. 

---