Persistent organochlorines in beluga whales ( Delphinapterus leucas) from the St Lawrence River estuary-I. Concentrations and patterns of specific PCBs, chlorinated pesticides and polychlorinated dibenzo- p-dioxins and dibenzofurans

Abstract

Blubber samples from beluga whales ( Delphinapterus leucas) in the St Lawrence River estuary were analysed for PCB congeners (ortho- and non-ortho-substituted) and other persistent organochlorines as well as chlorinated dibenzo-dioxins/furans (PCDD/Fs). Major individual components (mean concentrations > 1 μg g −1) were 4,4′-DDE, -DDD and -DDT, T12 (a toxaphene-related compound), trans-nonachlor, oxychlordane, mirex, HCB, tris( p-chlorophenyl) methane and dieldrin. Concentrations of ∑PCBs (8.3–412 μg g −1), ∑DDT (3.36–389 μg g −1) and mirex (0.18–6.8 μg g −1) were particularly elevated relative to other odontocetes in Canadian waters. ∑DDT, PCBs (as Aroclor), mirex and T12 concentrations were positively correlated with age of adult females (> 10 years) but only weakly, or not significantly, correlated with age of adult males. PCDD/Fs were present at low ng kg −1 levels and consisted mainly of penta- and hexachlorofurans, and hepta- and octachlorodioxin. CB126 (3,3′,4,4′,5-PCB) was the most prominent non-ortho-substituted PCB congener in beluga blubber. Total TCDD toxic equivalents averaged 330 ng kg −1 in females and 1400 ng kg −1 in males and were dominated by CB126, and the mono-ortho-substituted congeners CB105 and CB118. Biomagnification factors (BMFs) for mirex and ∑PCB from fish to beluga ranged from 11 to 16, and were similar to BMFs in Arctic animals, indicating that elevated levels in St Lawrence animals are a consequence of relatively high levels of recalcitrant organochlorines in prey of the beluga in the St Lawrence river system.