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Animal Products: Random Residue Monitoring
Background
Sources of residues
Residues and drought feeding
Useful definitions
Background
Currently the NRS carries out random residue testing on 11 meat products, honey, egg and three fish products. Details of the 2006–2007 monitoring projects and their results are summarised on the 2006–2007 in brief page, or in more detail in the appropriate section of the National Residue Survey Annual Report 2006–2007.
The random monitoring program supports the market access of participating industries to their principal export markets, and also provides information to domestic consumers of the residue levels in these animal-based commodities. The broad-based testing approach of the residue monitoring projects further provides evidence of good practice in the usage of agvet chemicals by the participating animal production industries. To address the specific residue monitoring requirements of importing countries, some chemicals are monitored that are not registered for use - nor are likely to be used - in Australian animal production systems.
The animal products program designs sampling regimes in consultation with participating industries, organises sample collection and coordinates the dispatch of the samples to the relevant laboratories for appropriate analysis.
Sample collection
Sample collection rates are based on production levels of the agricultural commodity in Australia, or are as directed to accommodate overseas market access requirements if the commodity is to be exported. Sample requests are generated by NRS and forwarded to sample collection points.
Authorised government officers at export abattoirs and quality control staff at domestic abattoirs collect meat samples for residue monitoring. They are then are sent from collection points to a central receival and dispatch facility within NRS, where they are sorted into batches and forwarded to appropriate laboratories for testing.
In the sampling plan for random monitoring of meat, the allocation of samples to abattoirs is affected by the numbers and species of animals being slaughtered at each abattoir. The distribution is designed so that the probability of an abattoir being selected for sampling is proportional to the commodity throughput of that abattoir. Sample requests are sent to abattoirs each month, specifying the kind of product required and the production period during which samples are to be taken. Animals for sampling are then selected at random along the slaughter chain.
Honey samples are collected by officers of state and territory government authorities at appropriate stages of the production chain and are sent directly to laboratories for analysis.
Poultry and egg samples are collected by quality assurance officers at the relevant establishments and are forwarded either to the NRS central receival and dispatch facility or are sent directly to the laboratories.
Samples for the fish (wildcaught) random monitoring project are collected from fish establishments by officers from the Australian Quarantine and Inspection Service (AQIS), NRS staff or state or territory government authorities. The samples are forwarded to the NRS central receival and dispatch facility, or are sent directly to the relevant laboratories by AQIS.
Chemical–commodity selection
Chemical–commodity combinations are selected on the basis of risk profiles. Combinations that show the likelihood of highest risk of residues occurring are identified for inclusion in NRS residue monitoring projects. In developing risk profiles, the main factors to be considered are:
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international and/or domestic perceptions of the chemical–commodity combination as a possible public health hazard
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the likelihood of residues occurring in the product (potential for misuse; persistence in the crop, animal or environment; extent of use; and use patterns)
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the extent and results of previous monitoring for the chemical–commodity combination
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the Australian Standards for residues and market access requirements of trading partners
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factors such as the availability of suitable sampling and analytical methods.
Importing countries sometimes require analyses for particular chemicals of concern in their country. Consequently, in its residue monitoring projects NRS may test for chemicals not registered for use in Australia.
Choice of matrix for analysis
The matrix (tissue or material) expected to contain the highest concentration of a residue is usually selected for analysis. The matrix may be inedible, and does not necessarily represent the part most likely to be eaten (eg. fat is analysed for pesticides; kidney is analysed for antibiotics; liver is analysed for metals; and, for some hormonal growth promotants, the matrix chosen for testing is urine or faeces). The levels of chemicals detected in such material are usually much higher than in meat (muscle).
Sources of residues
The results of NRS residue monitoring help to audit the use of currently registered agvet chemicals in Australia. At present, chemicals that may be detected include:
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antibiotics used to control microbial diseases in animals
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anthelmintics used to control internal parasites in animals
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hormonal growth promotants used as veterinary medicines or to improve growth in livestock
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fungicides used to control fungal diseases in plants and plant products
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insecticides and acaricides used to control insect and mite pests in crops, to protect grain, and to control external parasites on animals
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fumigants used as grain protectants, and to sterilise soil, storage sheds, animal houses and bee hives
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herbicides used to control weeds in crops.
Other sources of residues include those from the unintended exposure of plants and animals to chemicals that are no longer registered for use in Australia. Such chemicals include some organochlorine (OC) pesticides and polychlorinated biphenyl (PCB) compounds. These can remain in the soil for long periods, and livestock can accidentally ingest or come into contact with residual amounts of these chemicals and become contaminated.
Environmental contaminants
The term ‘environmental contaminant’ refers to those chemicals in the natural environment that may contaminate agricultural produce. Such chemicals include some metals, some naturally occurring mycotoxins and some persistent organic pollutants. In NRS work, the results for OCs are included with the pesticide results, as although they can be considered environmental contaminants, their presence in the environment is the result of past use as a pesticide.
Traceback of samples
Standards are set for allowable levels of residues in foods. When a sample is detected with a residue that is above an Australian Standard or defined residue action level, the laboratory immediately notifies NRS, which then informs the relevant state or territory government authority. State or territory government authority staff then trace the sample back to its property of origin. Subsequent actions depend on both the chemical detected and the commodity in which it is found, and are specified by state or territory government authority legislation. Action varies from simple advice in the case of a minor problem, to quarantining the property concerned, or prosecution where serious contamination has occurred. NRS is notified of traceback activities and findings.
Residues and drought feeding
The use of unusual feeds during times of drought may have serious implications for levels of residues found in animal products. For example, plant material not normally used for animal feed may have been treated with insecticides or herbicides that could lead to residues in animal-derived products following ingestion. Producers are advised to exercise caution, and to check with their state or territory residue officers. Further web information about drought feeding and residues can be accessed through the NRS "Drought Feeding and Residues" page.
Useful definitions
Maximum level
The maximum level (ML) is the maximum concentration of a contaminant (eg. a metal, natural toxicant or agvet chemical that is no longer used in agriculture but can persist in the environment) in or on a food, agricultural commodity or feed. The concentration is expressed in mg/kg (milligrams per kilogram or parts per million) of a commodity.
Maximum residue limit
Maximum residue limit (MRL) is defined as the maximum concentration of a residue that is legally permitted or recognised as acceptable in or on a food, agricultural commodity or animal feed. It results from the officially authorised safe use of an agricultural or veterinary (agvet) chemical. The concentration is expressed in mg/kg (milligrams per kilogram or parts per million) of the commodity. If an MRL is not set for a residue in a particular matrix, generally there is zero tolerance for that residue.
Extraneous residue limit
An extraneous residue limit (ERL) is the maximum permitted limit of a pesticide residue arising from environmental sources other than the use of a pesticide directly or indirectly in or on a food, agricultural commodity or animal feed. The concentration of the residue is expressed in mg/kg (milligrams per kilogram or parts per million) of the commodity. There are ERLs for selected commodities for several organochlorine pesticides no longer in use in Australian agriculture for example, DDT and dieldrin.
No observable effect level
The no observable effect level (NOEL) is the highest dose of a substance in experimental animal studies that does not cause any detectable toxic effects. The NOEL is expressed in milligrams of the substance per kilogram of body weight per day.
Withholding period
The withholding period (WHP) is the minimum period which must elapse between the last administration or application of an agricultural or veterinary chemical product (including treated feed), and the slaughter, collection or harvesting for human consumption or use of the animal commodity. The WHP is a statutory requirement.
Export slaughter interval
The export slaughter interval is the minimum suggested time interval that should elapse between the last application of a product to an animal, or administration of a product to an animal, or feeding of livestock to an animal and:
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further testing of that animal for residue levels
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slaughter of that animal for a particular export market, and/or
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the use or sale of milk, eggs or other produce from that animal for a particular export market.
For further information contact the Animal Products Program Manager.
Phone: (02) 6272 4019
Fax: (02) 6272 4023