PCDD/Fs and PCBs in seafood species from Moreton Bay, Queensland, Australia

Abstract

Previous studies have identified elevated levels of polychlorinated dibenzo-p-dioxins (PCDDs) in sediments and megafauna (dugongs and green turtles) in the marine environment of southeast Queensland, Australia. Little information exists, however, regarding the levels of PCDDs, polychlorinated dibenzofurans (PCDFs) and related polychlorinated biphenyls (PCBs) in seafood from this area. This study aims to establish baseline information on PCDD/F and PCB contamination in a range of seafood species from Moreton Bay and to investigate contaminant variability due to harvesting season, size, habitat location and trophic level. In addition, different seafood extraction methods were tested to evaluate their impact on lipid yields and contaminant concentration. Overall, the median TEQ_DF&PCB levels in seafood from Moreton Bay were elevated compared to background levels in Australian marine/estuarine and retail fish. However, TEQ_DF&PCB levels of most seafood analysed were below the respective EU maximum limits. High inter- and intraspecies variability was observed, which could be partially attributed to differences in trophic level, season harvested and habitat location.

Introduction

Persistent organic pollutants (POPs), such as PCDD/Fs and PCBs, are ubiquitous in the environment due to their emission from numerous sources, high persistency and a propensity to be transported long distances. These compounds are well known to bioaccumulate in animal tissue, biomagnify through the food web and have been shown to elicit adverse effects at relatively low concentrations (US EPA, 2004). For the general population, dietary intake contributes approximately 90% of the total human exposure to POPs (Liem et al., 2000). The majority of this dietary exposure results from consumption of lipid rich products, including seafood. To date, very limited information exists on the levels of these contaminants in commonly consumed seafood species from Australia. An Australian national study on pooled seafood (of unknown origin) from supermarkets suggested that TEQ_DF&PCB levels are generally low in purchased seafood (0.023–80 pg/g lipid, median 1.35 pg/g lipid; n = 19) (FSANZ, 2004). The 80 pg/g lipid result represents an extreme outlier with all other retail samples TEQ_{DF& PCB} ranging from 0.023 to 5.1 pg/g lipid (FSANZ, 2004). For fish originating from the Australian marine system, a national dioxins survey in 2004 recorded similarly low TEQ_DF&PCB background levels ranging from 0.72 to 68 pg/g lipid (median 3.9 pg/g lipid; n = 20) (Mueller et al., 2004). An examination of PCB and organochlorine pesticide contamination in a range of foodstuffs from various metropolitan locations within Australia showed that fish sourced locally, including coastal waters, were generally the most contaminated, with PCBs ranging in total concentration from 18 to 130,000 ng/g lipid (average 6900 ng/g lipid; n = 37) (Kannan et al., 1994).

Previous studies in the Australian north-eastern state of Queensland have identified widespread and elevated levels of PCDDs, particularly OCDD, in marine sediments along the coastline (Gaus et al., 2001, Hermanussen et al., 2004) and elevated PCDD TEQ levels were observed in lower trophic, nearshore marine biota (dugong and green turtles) (Gaus et al., 2004, Hermanussen et al., 2006). These findings suggest that other marine biota from Queensland, and in particular higher trophic seafood sourced near the mainland, may contain considerably higher levels of PCDDs and/or other POPs compared to seafood purchased from supermarkets and fish caught from offshore locations. Local seafood may be consumed by individuals as part of recreational, subsistence and commercial fishing. Consequently, information on the levels of POPs in seafood caught from Queensland’s nearshore marine environment, together with seafood consumption data, will provide information on the contribution of such activities to human exposure levels with respect to the subpopulation groups involved.

Bioconcentration and biomagnification processes and the resulting tissue levels of POP contaminants are influenced by numerous and complex interactions between biological, seasonal, geographical and other factors (Porte and Albaiges, 1993, Mackay and Fraser, 2000, Kiviranta et al., 2003, Mormede and Davies, 2003). This results typically in high variability of contaminant levels within and between species which can span several orders of magnitude. Understanding the extent and cause of contaminant variability in seafood provides an important basis for evaluating their levels, as well as potential human exposure and risks.

This study represents a component of a broader investigation into the pathways and processes of seafood contamination in tropical marine systems and resulting human exposure from consumption of locally caught seafood. The key focus of this initial component presented here was to provide baseline information on the distribution of PCDD/Fs and PCBs in individual seafood within a marine nearshore environment. Various factors that may influence the tissue levels of these contaminants were considered in order to provide an initial insight into their significance and potential contribution to seafood contamination.