Description of status quo, state of the art
Problems arise when new methods or technologies with enhanced capabilities are introduced without due notification of other interested parties. While this may not be significant for substances with a maximum residue limits (MRL), it can have a profound impact when it involves reporting limits (action levels) for residues of veterinary drugs without an MRL. Reporting limits are levels where the laboratory must report the presence of the analyte in the food matrix to the competent authority. For non approved compounds, the national regulatory authorities establish their action limits on the detection capability of the methods used in the laboratories responsible for the control of residues. The situation has worsened with the rapid acceptance of mass spectrometry (MS) and liquid chromatography-mass spectrometry (LC-MS) in those countries with resources to support the technology as the standard for analytical methods. Combined with changes in detector capabilities, this has resulted in a ten-fold increase in sensitivity since the early 1990s. There is no reason to believe that there won't be similar improvements in analytical method sensitivity in the future, resulting in a repetition of problems such as those encountered recently with residues of chloramphenicol and nitrofurans. These MS and LC-MS analytical methods have become the standard in major food importing countries. This has forced food exporting countries to work to match this technology to assure the acceptance of their exported food products.
Regulatory methods provided as part of registration packages are typically for the veterinary drug substances under consideration, while official regulatory laboratories rather use multi-analyte methods capable of detecting more than one drug. The best source multi-analyte drug residue methods are probably from counterpart regulatory laboratories in other countries. Therefore, transparency is a critical issue.
Analysis of gaps and identification of problems
Official regulatory laboratories are obliged under the SPS Agreement to make their methods and validation reports available to counterpart laboratories in other countries on request to facilitate routine implementation and promote equivalency of test capabilities between laboratories in importing and exporting countries. This does not always happen. Downsizing and cost-saving steps have caused some national authorities to partially or fully privatize analytical laboratories. In some cases, this has led to the specifications of regulatory analytical methods being considered to be proprietary. These laboratories may be unwilling to share validation, performance, and procedural information about the analytical method.
Rather than reflecting the level of risk associated with exposure of consumers to residues of veterinary drugs without MRLs, reporting limits only reflect the current analytical capabilities of analytical laboratories in that region of the world. Regional differences in the application of regulatory measures (e.g. analytical laboratory reporting limits, application of performance criteria for analytical methods, and other uncertainties) have created a profound impact on fair practice in the food trade.
Development of analytical methods does not consider the technical and resource limitations of developing countries frequently responsible for assuring the quality of exported food products derived from animals (including aquatic animals) treated with veterinary drugs. State of the art methodologies such as LC-MS are expensive to develop and maintain, particularly in the absence of the necessary technological infrastructure. As analytical method detection levels continue to improve there are increased cost associated with equipments and its maintenance, standards and consumables, staff training and retention, maintenance of quality assurance system and increased costs in avoiding cross contamination of the sample. The increased costs associated with increasingly sensitive analytical methods are incurred by both the importing and exporting countries.
Existing CODEX Volume 3 guidance on analytical method validation does not reflect the single laboratory validation approach but is currently being updated by the Codex Committee on Residues of Veterinary Drugs in Foods (CCRVDF).
Changes in analytical methodologies and knowledge can lead to changes in marker residue and target tissue resulting in rapid change in control strategy of a national authority. The communication of the laboratory result to the risk manager could be the source of misunderstanding in the absence of a clear communication procedure.
The matrix tested should be representative of the raw material from animal origin and the presence of material from other origins has been shown to be a source of confounding results. The lack of availability of rapid, cheap and validated screening tests for residues of banned substances in tissues remains a problem.
