title: Chronic effects of polychlorinated dibenzofurans on mink in laboratory and field environments.
abstract: Mink are often used as a sentinel species in ecological risk assessments of chemicals such as polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs) that cause toxicity mediated through the aromatic hydrocarbon receptor. Considerable toxicological information is available on the effects of PCBs and PCDDs on mink, but limited toxicological information is available for PCDFs. Thus, exposure concentrations at which adverse effects occur could not be determined reliably for complex mixtures in which PCDFs dominate the total calculated concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent (TEQ). Two studies were conducted to evaluate the potential toxicity of PCDFs to mink. The first was a chronic exposure, conducted under controlled laboratory conditions, in which mink were exposed to 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF) concentrations as great as 2.4 x 10(3) ng 2,3,7,8-TCDF/kg wet-weight (ww) diet or 2.4 x 10(2) ng TEQ(2006-WHO-mammal)/kg ww diet. In that study, transient decreases in body masses of kits relative to the controls was the only statistically significant effect observed. The second study was a 3-y field study during which indicators of individual health, including hematological and morphological parameters, were determined for mink exposed chronically to a mixture of PCDDs and PCDFs under field conditions. In the field study, there were no statistically significant differences in any of the measured parameters between mink exposed to a median estimated dietary dose of 31 ng TEQ(2006-WHO-mammal)/kg ww and mink from an upstream reference area where they had a median dietary exposure of 0.68 ng TEQ(2006-WHO-mammal)/kg ww. In both studies, concentrations of TEQ(2006-WHO-mammal) to which the mink were exposed exceeded those at which adverse effects, based on studies with PCDD and PCB congeners, would have been expected. Yet in both instances where PCDF congeners were the sole or predominant source of the TEQ(2006-WHO-mammal), predicted adverse effects were not observed. Taken together, the results of these studies suggest that the values of the mammalian-specific toxicity equivalency factors suggested by the World Health Organization overestimate the toxic potency of PCDFs to mink. Therefore, hazard cannot be accurately predicted by making comparisons to toxicity reference values derived from exposure studies conducted with PCBs or PCDDs in situations where mink are exposed to TEQ mixtures dominated by PCDFs.
authors.affiliation: Department of Animal Science, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Zwiernik
authors.forename: Kerrie J
authors.initials: KJ
authors.lastname: Beckett
authors.forename: Steve
authors.initials: S
authors.lastname: Bursian
authors.forename: Denise P
authors.initials: DP
authors.lastname: Kay
authors.forename: Ryan R
authors.initials: RR
authors.lastname: Holem
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Moore
authors.forename: Behzad
authors.initials: B
authors.lastname: Yamini
authors.forename: John P
authors.initials: JP
authors.lastname: Giesy
mesh_terms: D000818:Animals; D001572:Benzofurans / Q000737:chemistry / Q000633:toxicity*; D000072338:Dibenzofurans, Polychlorinated; D004305:Dose-Response Relationship, Drug; D017753:Ecosystem; D004785:Environmental Pollutants / Q000737:chemistry / Q000633:toxicity*; D005260:Female; D008297:Male; D008824:Michigan; D008907:Mink; D011157:Population Dynamics; D013997:Time Factors
chemical_list: D001572:Benzofurans; D000072338:Dibenzofurans, Polychlorinated; D004785:Environmental Pollutants; C014211:2,3,7,8-tetrachlorodibenzofuran