A Congener Specific Evaluation of Transfer of Chlorinated Dibenzo-p-dioxins and Dibenzofurans to Milk of Cows following Ingestion of Pentachlorophenol-Treated Wood

Abstract

Pentachlorophenol (PCP) treated wood has been hypothesized as an important source of dioxins in milk and beef. This phase of studies to evaluate the hypothesis involved the administration of PCP-treated wood to cows and measurement of the transfer of polychlorinated dibenzo-pdioxins (PCDD) and dibenzofurans (PCDF) to milk. The 3 g/day dose of ground wood was administered to four cows for 56 days. This dose provided a PCP intake of 4.8 mg/ day and PCDD/F intakes in the range of 0.3 µg/day for 2,3,7,8-TCDD to 17 000 µg/day for 1,2,3,4,6,7,8,9-OCDD. Steady state with respect to excretion in milk was reached because concentrations of PCDD/Fs in milk fat were reasonably constant from day 28 through day 56. The PCDFs without chlorine in the 4 and 6 positions were metabolized and not transported to milk. The other PCDFs and all PCDDs had intake adjusted concentrations in milk that were inverse to the number of chlorines. Variations among cows in concentrations of specific congeners were small and were not related to body weight, dry matter intake, or production of milk and milk fat. The transfer coefficients calculated for the PCDD/Fs in this study provide tools for reducing uncertainty in risk assessments.

Carry-over of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in dairy cows fed smoke contaminated maize silage or sugar beet pulp

“…Various studies have been published in which the carry-over of PCDD/Fs in dairy cows was studied, including studies with single doses of pure (radiolabelled) standards (Jensen and Hummel, 1982;Jones et al, 1987Jones et al, , 1989Olling et al, 1991), or repeated doses of contaminated chemicals like pentachlorophenol (Firestone et al, 1979;Fries, 1999), grass containing background levels (McLachlan et al, 1990;McLachlan and Richter, 1998), grass contaminated by sewage sludge (McLachlan and Richter, 1998), or contaminated feed materials like citrus pulp (Traag et al, 1998) or minerals (Huwe and Smith, 2005). Other studies followed up the depletion of PCDD/Fs on affected farms after removal of the source, like citrus pulp (Malisch, 2000), minerals (Brambilla et al, 2008) or potato peels with kaolinic clay .…”

Travis and Arms revisited: a second look at a widely used bioconcentration algorithm

“…Specifically, challenges to the Travis and Arms equations include that they: 1) do not predict concentrations appropriately for high log K ow chemicals; (2) fail to accurately predict concentrations for rapidly metabolizing chemicals; (3) were derived based on data that are not steady state; (4) underestimate beef BTFs because they include data for lactating animals; and (5) assume constant chemical intake rates for beef cattle. The first criticism is based on studies published subsequent to 1988 demonstrating that concentrations in beef and milk actually decrease with increasing log K ow for high log K ow chemicals (i.e., log K ow > 6) (McLachlan, 1993;Thomas et al, 1998;Fries et al, 1999). The Travis and Arms equations are based on six chemicals having a log K ow greater than 6 and no chemicals having a log K ow greater than 6.9, and predict that concentrations continue to increase as log K ow increases.…”

Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans in cattle raised at agricultural research facilities across the USA and the influence of pentachlorophenol-treated wood

“…It has been seen that exposure to pentachlorophenol (PCP)-treated wood produced a distinctive residue pattern in animals (Fries et al 1999, Feil et al 2000. This pattern showed little or no tetra-or penta-congeners but high amounts of 1,2,3,6,7,8-HxCDD, 1,2,3,4,6,7,8-HpCDD and OCDD (figure 3), somewhat resembling the PCP formulation used to treat the wood.…”

“…Seven treated-wood samples that tested positive for PCP (> 300 mg g À1 ) in this study had an mean ratio of 1,2,3,6,7,8-HxCDD to 1,2,3,7,8,9-HxCDD equal to 5.3 AE 3.1. The bioconcentration or carry over of each of the HxCDDs into cows' milk has been shown to be equivalent (Fries et al 1999) and may be expected to be equal in beef adipose tissue. Because of this, the ratio of HxCDDs reflected in the mean and median beef patterns and also in the patterns from animals with low TEQs suggests that a source, such as PCP-treated wood with an isomeric excess of 1,2,3,6,7,8-HxCDD, was common for many of the animals in this survey.…”