THE SIGNIFICANCE OF PENTACHLOROPHENOL-TREATED WOOD AS A SOURCE OF DIOXIN RESIDUES IN UNITED STATES BEEF

Authors: Fries, George; Feil, Vernon; DAVISON, KENNETH - 5442-05-05 (RETIRED)

Submitted to: Organohalogen Compounds
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The U.S. Environmental Protection Agency reassessment of dioxins and related compounds (chlorinated dibenzo-p-dioxins and dibenzofurans) indicated that animal products are important contributors to the human background exposure to these compounds. Human exposure pathways involving beef are considered particularly important because of the potential animal exposure by deposition of combustion emissions to the atmosphere on pastur and forage crops. Another point of entry of dioxins into the food chain was as contaminants in chlorophenol-based products, but the manufacture and use of these products have been curtailed or restricted since 1980. Two surveys of United States beef carried out since the reassessment indicate that the relative concentrations of the 17 toxic dioxins and furans resemble contaminants of the wood preservative, pentachlorophenol, rather than combustion emissions. Follow-up observations were made to evaluate the presence of treated wood and other potential environmental sources of dioxins and furans at several locations identified as having higher than average residue concentrations in beef. One or more wood samples that had concentrations of dioxins compatible with pentachlorophenol contamination were identified at each location. No feed sample contained sufficient residues to account for the animal residues. The frequent use of pentachlorophenol-treated wood, the propensity of animals to lick or chew wood, and the compatibility of congener profiles lead to the conclusion that pentachlorophenol-treated wood may be an important source of dioxin residues in animal products.

Technical Abstract: The results of a statistical survey of United States beef, and a focused survey of beef from 12 institutional herds were examined to determine the distribution profiles of the chlorinated dibenzo-p-dioxins (CDD) and dibenzofurans (CDF) with the 2,3,7,8 chlorine substitution pattern. Congeners that occurred with the greatest frequency and highest concentrations were 1,2,3,6,7,8-CDD, 1,2,3,4,6,7,8-CDD, and 1,2,3,4,6,7,8,9-CDD. Profiles dominated by these congeners are typical of the contaminants of pentachlorophenol, a wood preservative. Follow-up collections of environmental samples were made at several locations with higher than average residue concentrations in beef. Samples included wood from fences, buildings, and feed bunks; hay and pasture grass; soils; and road surface material. One or more wood samples that had high concentrations of CDDs compatible with pentachlorophenol contamination were eidentified at each location. The congener profiles in the beef fat samples were compatible with the profiles in wood samples adjusted for differential congener absorption by animals. No other feed or environmental sample contained sufficient CDD residue to account for the animal residues. Pentachlorophenol-treated wood was used extensively for animal housing confinement facilities before its use was restricted after 1980. This use of pentachlorophenol, the propensity of animals to lick or chew on wood, and the compatibility of congener profiles lead to the conclusion that pentachlorophenol-treated wood is an important, if not the most important, source of CDDs and CDFs in animal products.