How can zero tolerances be controlled? The case study of Nitrofurans

Nitrofurans comprise a group of antibiotic substances that have been used widely in the past in intensive farming of pigs, poultry, fishes, and shrimps. Studies in the late 1980s and early 1990s have proven that they are metabolised shortly after administration and form persistent residues that could be detected in the tissues of treated animals for weeks after administration. Both the nitrofurans as well as special metabolites have been classified as genotoxic compounds. No maximum residue limit (MRL) could be fixed either due to a lack of data or because the toxicological data did not support the derivation of an acceptable daily intake (ADI). Therefore, nitrofurans are listed in Annex IV of Council Regulation EEC No. 2377/90. From a regulatory point of view, any exposure to those substances is deemed a hazard to human health. Consequently Annex IV substances are controlled with zero tolerances.