Polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and dioxin-like polychlorinated biphenyls in Sydney Cockle (Anadara trapezia) from a subtropical estuary with an industrial legacy

Abstract

Polychlorinated dibenzo-p-dioxins, dibenzofurans, and dioxin-like polychlorinated biphenyls (hereafter collectively referred to as ‘dioxins’) are persistent organic pollutants that bioaccumulate through aquatic food webs, posing potential exposure-risks through seafood consumption. Sydney Harbour in south-eastern Australia is among the most dioxin-contaminated estuaries globally, due to its longstanding industrial legacy. Arcid cockles (Bivalvia: Arcidae) are harvested from estuarine habitats worldwide, yet little is known about dioxin accumulation by this group. This study provides the first published report of dioxin concentrations in Sydney Cockle (Anadara trapezia). Cockles were composited by body size and analysed for 29 dioxin congeners using high-resolution gas chromatography coupled with high-resolution mass spectrometry. Toxicity equivalency quotients (TEQs) were calculated following World Health Organization guidelines. Total dioxin concentrations were significantly higher in cockles from western Sydney Harbour (1.82 ± 0.07 (mean ± SE) pg TEQ g⁻¹ ) than those from eastern Sydney Harbour (0.74 ± 0.06 pg TEQ g⁻¹). All cockle TEQs were below the Australian seafood screening threshold of 6 pg TEQ_total g-wet-weight⁻¹. Cockle congener profiles were dominated by higher-chlorinated dioxins and mono-ortho-substituted dl-PCBs, largely corresponding with profiles of other invertebrates and the water column in previous studies. Monitoring programs utilising Sydney Cockle could provide a cost-effective means of tracking dioxin contamination and inform the periodic need for broader seafood sampling in Sydney Harbour.