A field study in support of the monitoring of priority substances in German freshwater fish: derivation of fillet-to-whole fish conversion factors

Heinz Rüdel,Georg Radermacher,Anja Duffek,Annette Fliedner,Nina Lohmann

doi:10.1186/s12302-020-0295-9

Abstract

BackgroundBioaccumulating contaminants in surface waters are preferably monitored in fish for assessing the related risks to and via the aquatic environment. Consequently, the European Water Framework Directive (WFD) requires a monitoring of certain priority substances such as mercury, polybrominated diphenyl ethers (PBDE), perfluorooctane sulfonic acid and its derivatives (PFOS), hexachlorobenzene (HCB), hexabromocyclododecanes (HBCDD) and polychlorinated dioxins/dioxin-like compounds (dioxins) in freshwater and coastal fish. Tissue levels have to comply with biota environmental quality standards (EQSs) given in Directive 2013/39/EU. EQSs are justified either by risks for human health (assessed on the basis of fillet) or secondary poisoning of wildlife (based on whole fish). To support the practical implementation of the WFD biota monitoring in Germany, comparative investigations of target fish species caught at six sites were performed.ResultsAt each site, at least three fish species listed in a national guidance document were sampled (e.g., chub, roach, bream, perch). Beside biometric data, concentrations of seven priority substances were determined in pooled fillet and carcass samples and whole fish data were calculated. The EQSs for PBDE and mercury were exceeded in nearly all fillet and whole fish samples. PFOS was above the EQS at several sites especially in perch, while HCB exceeded the EQS only at one site (Elbe River). All fillet and whole fish samples complied with the EQSs for dioxins and HBCDD. Based on wet weight concentrations of a homogeneous set of 20 composite sample pairs of 3–5 year-old fish, the following fillet-to-whole fish conversion factors were derived: mercury 0.81, PBDE 5.4, HCB 3.6, PFOS 2.7, dioxins 5.3, and HBCDD 1.8.ConclusionsRecommendations on selection of target fish species, age or tissue given by EU and national guidance documents are practical and feasible. However, further adjustments of the samplings such as the determination of site-specific length–age relationships are required from both ecological and risk assessment perspectives. The derived conversion factors allow the translation of fillet-to-whole fish concentrations (and vice versa), and thus the EQS compliance assessment for the appropriate tissue (fillet for human health, whole fish for wildlife risks) if only one tissue is investigated.

Highlights

Bioaccumulating contaminants in surface waters are preferably monitored in fish for assessing the related risks to and via the aquatic environment
The Environmental quality standard (EQS) for polybrominated diphenyl ethers (PBDE), HCB, Polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) + Dioxin-like polychlorinated biphenyls (dl-PCB), heptachlor and heptachlor epoxide and perfluorooctane sulfonic acid and its derivatives (PFOS) are human health based while for HCBD, dicofol, HBCDD, and mercury the EQSs are based on the secondary poisoning of predators [5]
The focus of the present work was on the following questions: are the recommendations regarding the fish species applicable? Should fillet or whole fish be analyzed? How much fish tissue is required for the analysis? Do older fish have higher priority substances (PS) burden than younger ones? Which trophic level should the fish represent? Can factors be derived to convert fillet concentrations of contaminants into whole fish concentrations? Based on results derived from this study and additional literature data, the practical implications of the mentioned aspects for an appropriate surface water monitoring of contaminants in fish to determine EQS compliance are discussed

Summary

Introduction

Bioaccumulating contaminants in surface waters are preferably monitored in fish for assessing the related risks to and via the aquatic environment. The European Water Framework Directive (WFD) requires a monitoring of certain priority substances such as mercury, polybrominated diphenyl ethers (PBDE), perfluorooctane sulfonic acid and its derivatives (PFOS), hexachlorobenzene (HCB), hexabromocyclododecanes (HBCDD) and polychlorinated dioxins/dioxin-like compounds (dioxins) in freshwater and coastal fish. Nine of the biota-EQSs relate to fish, i.e., polybrominated diphenyl ethers (PBDE), hexachlorobenzene (HCB), chlorinated dioxins/furans and dioxin-like polychlorinated biphenyls (PCDD/F + dl-PCB), heptachlor and heptachlor epoxide, hexachlorobutadiene (HCBD), dicofol, hexabromocyclododecanes (HBCDD), perfluorooctane sulfonic acid and its derivatives (PFOS), and mercury (Hg). The objective of the WFD is a good status of water bodies and the protection of human health (risk of uptake of contaminated fish as food) and wildlife (risk of secondary poisoning of predators by feeding on contaminated prey) For these two protection goals quality standards were derived with the lower value being used as EQS [4]. When assessing EQS compliance, PS concentrations are usually evaluated by analyzing fillet for human health-based EQSs or whole fish for wildlife risk-based EQSs [5]

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