Contaminants and Residues


Agricultural products and animals have a wide range of microbes on, or in, them at harvest/slaughter, whose type vary with commodity, geographic region, and production and harvesting/slaughtering methods. Some of these microbes (bacteria, yeasts, moulds) can grow on the food causing spoilage, which is a common cause of rejection at import. Other pose a hazard to man through illness, having the capacity to infect the consumer, or to intoxicate if they have multiplied in the food and/or elaborated a toxin (enterotoxin or exotoxin).

The levels of microbial contamination of food are influenced by harvesting / slaughtering technologies and by the processes applied during food manufacture. With current technologies it is impossible to guarantee the absence of pathogenic microorganisms on raw foods, both of plant and animal origin. Widespread and increasing incidence of foodborne diseases and the resultant social and economic impact on the human population have brought food safety to the forefront of public health concerns. Foodborne illness occurs in every country in ever increasing frequency. Many outbreaks are the consequence of a failed process, or inappropriate storage conditions (usually temperature abuse) during distribution, food service or by the consumer. There are also examples of sporadic outbreaks of illness attributed to raw products eaten unprocessed (e.g. lettuce, melons, raw fish). Foodborne illness has long been linked primarily to foods of animal origin, but in recent years many outbreaks of foodborne illness have been associated with fruits, vegetables and other foods.

There are also examples of imported foods causing human illness, exported from both developed and developing countries. Consequently there is widespread concern that food in international trade carries pathogenic microorganisms that could result in outbreaks of illness. Importing countries have sometimes responded to this concern with measures which are neither scientifically based nor statistically sound, and may be an impediment to fair trade.

The microbiological safety of food can never be achieved by end-product testing, which only detects that a failure has occurred and can only contribute indirectly to identification and control of the cause of the problem. Also, no sampling plan can ensure the absence of pathogen in a food, and testing products at point-of-production, port-of-entry, or in the retail distribution chain cannot guarantee food safety. All too frequently, industry has become aware of microbiological problems in its products as the result of spoilage in the marketplace or from reports of illness. Control measures are then applied as a response to an existing problem. Furthermore, the isolation of a bacterial pathogen from a food does not mean that the food necessarily is dangerous, e.g. the food may be cooked before consumption. Hence preventive approaches are required, often as simple as control of storage time and temperature. Nevertheless, microbiological testing, used appropriately, is one of the measures that can be used to achieve microbiological safety. Food irradiation if one of the tools the FEP promotes among Member States for the prevention/control of food-borne pathogenic micro-organisms as well as food food spoilage (hence foods loss/waste) and exposure to and insect pests.


Pesticides are important in modern farming and will remain indispensable for the foreseeable future. Without them it would be practically impossible to produce the required quantities of food - in most parts of the world and farming practices - to feed the world's growing population. However, since pesticides are hazardous substances, there is increasing concern about the safety and quality of food from such farms and in the surrounding environment. Thus, pesticides include many hazardous substances. They must be applied with utmost care in the most efficient manner to protect crops and farm animals, while leaving the lowest possible residues in food and the environment.

As the use of pesticides has not relented but increased governments have introduced measures to restrict and regulate their use to protect the users of pesticides, consumers, domestic animals and the environment at large. Analytical laboratories play a critical role in the regulation and educating farmers of use. Registering the use of a pesticide is based on the assessment of the results of very extensive research work on the toxicity and the fate of active ingredient, its metabolites and degradation products, together with data on the magnitude of residues obtained from supervised trials. The conditions of use specified in the registration document or use permit "Good Agricultural Practice" guide food safety stakeholders in ensuring that foods (and environment) are free of unsafe pesticide levels. FEP supports various Member States in the developing/enhancing capabilities to control of pesticide residues in foods and the environment (including pesticide registration and use) and ensuring good agricultural practices for the benefit of public health and trade.

Veterinary Drugs

An increase in the use of veterinary drugs, including growth promoters, is a predictable consequence of expanded food animal production efforts. Residues of these drugs in foods present health risks and trade restrictions hence the need for regulation. Unfortunately, many developing countries lack necessary/effective regulatory control of their use. In the developed world, national legislation and international trade agreements dictate required withdrawal periods before slaughter and/or maximum permissible residue levels (MRLs) for the consumable parts (meat, milk, etc.) for an increasing number of veterinary drugs. The use of hormonal growth promoters and beta-agonists is either prohibited (European Union) or strongly regulated (e.g. USA, Canada and Australia).

Producer compliance with these regulations is monitored by national testing laboratories according to nationally or internationally accepted sampling protocols and assay methods. Within the European Union, a group of European Union Community Reference Laboratories have responsibility for the effectiveness of the analytical residue control programmes (methods, materials). This responsibility is directed towards both the EU Member States and countries trading with the EU. In order to ensure a safe and saleable food product for both local consumption and international trade, developing countries also require the capacity to operate quality assured testing programmes for detection of these regulated residues in food animals and their products.

Like many other contaminants, while assays of veterinary drugs can be performed using a number of techniques at different stages of production, the ante-mortem or at-slaughter testing of livestock or livestock products (milk, meat, cheese, etc.) provides the most practical avenue for large-scale analysis both for home consumption or for export purposes.

Increasingly the approach is to use screening assays (such as radio-immuno/receptorassay, ELISA, thin layer chromatography etc) followed by confirmatory methods such as high pressure liquid chromatography HPLC/MS (MS) on suspected positive samples. The FEP supports Member States in establishing/strengthening their residues monitoring programs.


Mycotoxins are toxic metabolites produced by different genera of fungi (Aspergillus, Fusarium, Penicillium, Claviceps, etc.) that can contaminate a wide range of foods and feeds. These fungi are ubiquitous and wide-spread at all levels of the food chain. They are present in food produced at all latitudes exept the polar regions. Under favourable conditions (such temperature and humidity) these fungi grow on certain foods (grains, cereals, oilseeds, edible nuts, dried fruits) producing mycotoxins as secondary metabolites to which consumers are at a risk of exposure. Over 300 mycotoxins produced by some 350 fungal species have been identified although the most agriculturally important ones include aflatoxins, deoxynivalenol, nivalenol, T-2 toxin, zearalenone,ochratoxin, fumonisins, and patulin. Mycotoxins can also be metabolized by animals fed contaminated grains and pass into milk, eggs and other organs thus entering the food chain.

The presence of mycotoxins is considered unavoidable and it is not possible to predict or prevent entirely their occurrence during cultivation, harvest, storage, and processing operations by current good agronomic and good manufacturing practices. Medical consequences of mycotoxins have been known since historical records exist. They are some of the most toxin natural contaminants known to man such as Aflatoxin a potent carcinogen. Ergotism, a vaso-constricting disease with severe neurological alterations, caused by ergot alkaloids produced by the fungal genus Claviceps, has been extensively described since the Middle Ages. Additional mycotoxicological effects/manifestations may may include immunosuppression, mutagenicity and estrogenic gastrointestinal, urogenital, vascular, kidney and nervous disorders.

In many countries (especially the developing) mycotoxins also have profound economic implications including loss of grain and reduced animal productivity as well as losses of markets by non-tariff barriers due to mycotoxin level restrictions. According to FAO estimates, world losses of foodstuffs due to mycotoxins are in the range of 1000 million tonnes per year.

Thus there is a continuous need to protect the health of local humans and susceptible animals as well as preserving/securing markets by limiting their exposure to mycotoxins. A number of countries regulate the mycotoxins against national or international maximum limits. Many countries regulate for or suggest permitted levels of mycotoxins in foods and feed because of the public health significance and commercial consequences.

For governments to routinely monitor their domestic and imported products for acceptable mycotoxin levels, laboratories with trained/competent staff and sensitive, accurate and precise methods of analysis and sampling meeting national/international standards are required. FEP supports Members States in this regard, especially promoting use of nuclear analytical techniques alone or with other complimentary tools.


Foods and feed can become contaminated by radionuclides due to various causes and processes even though all food and drinking water naturally contains radioactivity. Contamination generally has a negative impact on the quality of the food or feed and may imply a risk to human or animal health or a barrier to trade. Contamination levels in foods shall be as low as reasonably achievable.

Actions to prevent or to reduce contamination of foods and feeds in an emergency may be found under Emergency Preparedness & Response. Compliance of food and feed contaminant levels to internationally accepted maximum levels for particular uses has to be demonstrated by monitoring and survey programmes, following measurement principles and procedures subjected to international acceptance. Moreover, the correct application of those principles and procedures in practical situations will have to be demonstrated by an appropriate quality assurance system, involving the use of validated analytical procedures, adequate reference materials for equipment calibration and the participation to inter-comparison exercises for independent capability assessment.

In contrast to the routine monitoring programmes, contamination occurring as the consequence of an accidental release of radionuclides into the environment, will generate pressure on the laboratories to provide a rapid survey of the situation in order to provide the data for matching the emergency response and the corrective actions to the risk represented by the event. Because the contaminant levels will then generally be different from the levels routinely measured and the response time will be shorter, rapid methods dedicated to and developed for accidental situations should be available and should be maintained operative by regular exercises and practice.

The Agency/FEP helps Members States monitor radionuclides in foods and in collaboration with other international organizations, helps set necessary standards.

Methods of analysis

The FEP provides assistance and support to developing Member State analytical laboratories (including availing analytical methods) in their efforts to ensure the safety and quality of food and agricultural commodities, thereby safeguarding the health of consumers and facilitating international trade. Assistance can be through training at or transfer of technology (including adaptable research) from the sections’s food and environmental protection Laboratory (FEPL) focusing on various food and environmental contaminants or through regular/extra- budgetary programs with local training conducted in Member States or elsewhere. This is in addition to capacity building programs under technical cooperation projects. T.

Analytical methods are developed or adapted and validated for transfer to Member States for application in regulatory and research laboratories. Emphasis is placed on simple, multi-residue methods to improve cost-effectiveness and applicability, whilst meeting the performance requirements necessary for use as regulatory methods for international trade. Radiolabelled compounds, when available, provide a comparative advantage as a quality control tool during method development.

The Food and Environmental Protection Subprogramme assists the Joint FAO/WHO Codex Alimentarius Commission in the elaboration of Codex standards and guidelines related to pesticide and veterinary drug residues and food safety.

The FEP also hosts The Food Contaminant and Residue Information System (FCRIS), a database of method protocols and information on methods of analysis for various veterinary drugs and pesticides provided by Member States, collaborating institutions and the FAO/IAEA Food and Environmental Protection Laboratory. The database can be accessed at FCRIS.