Occurrence and Assessment of Drug Residues in Wild-Life Fish Caused by Unintentional Contamination with Sewage Effluents: The Zero Tolerance Dilemma

Tuesday, September 22, 2009: 2:20 p.m.
Thomas Heberer, Ph.D. , Food Institute Oldenburg, Lower Saxony Federal State Office of Consumer Protection and Food Safety (LAVES), Oldenburg, Germany
Andrea M. Schuetze , Institute for Fish and Fishery Products, Lower Saxony Federal State Office of Consumer Protection and Food Safety (LAVES), Cuxhaven, Germany
Residues of malachite green (MG) and crystal violet (CV), two compounds used as veterinary drugs for the antifungal and antiparasitic treatment of fish, were found in German wild-life eels resulting from a contamination by municipal sewage discharges but not from intentional treatment. 

MG and its metabolite leucomalachite green (LMG) were detected with total concentrations up to 0.765 µg kg-1 fresh weight in the tissues of 25 out of 45 eels caught from different lakes, a river and a canal in Berlin,  Germany. Residues of CV were found in 35 of these samples with leucocrystal violet (LCV) being the dominant residue with total concentrations up to 6.7 μg kg–1 fresh weight in tissues of the eels. In all cases, the occurrence of the residues could directly be linked to the presence of discharges by municipal STPs into the receiving surface waters. MG and CV are multiple-use compounds with various legal uses including applications to color materials such as textiles, uses as paints and in printing inks.

MG, CV and/or their leuco metabolites have been classified as genotoxic and/or carcinogenic. Thus, it is not possible to establish an acceptable daily intake (ADI) and to derive a maximum tolerance level (MRL) either for MG or CV residues. The available data on the toxicity is also not sufficient for to establish tolerable daily intakes (TDI’s) for any of these compounds. According to EU law, zero tolerance applies to residues of both compounds in food for human con­sumption as both compounds are not registered for use as veterinary drugs with food producing animals. Zero tolerance means that such compounds should not occur at any concentration in food for human consumption. Legally, zero tolerance also applies if residues in fish are not caused by illegal treatment but by unintentional contamination via municipal sewage effluents.