Plant Products: Random Residue Monitoring
Background
Sources of residues
Useful definitions
Outlook
Background
During 2008–09, samples were collected from 21 grain commodities and products, pulses and oilseeds, and from five horticultural commodities. For detailed information and results of random residue testing, please see the NRS Annual Report.
Sample collection
Sampling procedures and numbers of samples for analysis are agreed upon through consultation between NRS and industry. Sample collection rates are determined in consultation with peak industry bodies. Sample requests are generated by NRS and forwarded to sample collection points.
In the random monitoring project for plant-based commodities, authorised government officers, NRS staff and industry quality-control staff collect grain and horticulture samples at appropriate locations (eg. export grain terminals, domestic grain establishments, flour mills, processing plants, produce packing houses, oilseed crushers and wholesale markets). Arrangements for sample collection vary with the commodity being tested, but NRS methods always include procedures to minimise any bias in sampling.
Export grain is sampled at terminals as ships are loaded. Each sample is collected, usually using automatic sampling equipment, as bulk grain is loaded. Samples of wheat due to be milled (and the products derived from this process) are collected from domestic flourmills on randomly selected consignments. Milled flour and bran samples are derived from sampled wheat so that the results provide information on the relative concentration of residues in each grain fraction. Other millable products such as maize, soybean and their derivatives are also included in the program. Grain is also sampled on delivery to domestic end users such as stock feed manufacturers, maltsters, feedlots, oilseed processors and processors of oats for human consumption.
Grain and horticulture samples are boxed and freighted overnight directly to the appropriate laboratory. Up to two different laboratories may conduct the various grain and horticulture analyses. The first laboratory is responsible for sample registration and forwarding samples to the other laboratory (if relevant).
Chemical–commodity selection
Chemical–commodity combinations are selected on the basis of risk profiles. Those combinations of highest risk are identified for inclusion in NRS residue monitoring projects. In developing risk profiles, the main factors considered are:
- international and/or domestic perceptions of the chemical–commodity combination as a possible public health hazard
- the likelihood of residues occurring in the product (potential for misuse; persistence in the crop or environment; extent of use; and use patterns)
- the extent and results of previous monitoring for the chemical–commodity combination
- the Australian Standards for residues and market access requirements of trading partners
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.
Sources of residues
The results of NRS residue monitoring programs help to audit the use of currently registered agricultural and veterinary (agvet) chemicals in Australia. At present, chemicals that may be detected in plant commodities include:
- fungicides used to control fungal diseases in plants and plant products
- insecticides and acaricides used to control insect and mite pests in crops and to control insects in facilities and machinery
- fumigants used as grain protectants, and to sterilise soil and storage sheds
- herbicides used to control weeds both pre-sowing and during crop growth
- post-harvest horticultural products such as scald inhibiters.
Pesticides
A range of pesticides is used either in-crop or to protect grain and horticultural produce post-harvest. A multi-residue screen is used to detect residues of such chemicals registered for use in Australia, as well as some chemicals of concern to industry that are registered in overseas markets. The principal groups of pesticides covered are organophosphate insecticides, synthetic pyrethroid insecticides, carbamate insecticides, insect growth regulators, other insecticides, and some fungicides and herbicides.
Organochlorines
This test covers a range of chemicals (once widely used in agriculture and horticulture) that are known to persist in the environment. In addition to detecting these older organochlorine pesticides, the test methods may cover endosulfan and dicofol, two relatively non-persistent organochlorine products that are still registered for use with some crops under specialised conditions.
Environmental contaminants
Tests for a range of environmental metal contaminants are conducted on a proportion of the samples.
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 owner and 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 misuse has occurred. NRS is notified of traceback activities and findings.
Useful definitions
Maximum level
The maximum level (ML) is the maximum concentration of a contaminant (e.g. 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
The 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.
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.
Export harvest interval
The export harvest interval is the minimum suggested time interval that should elapse between the last application of a product to a crop, vegetation or food commodity of plant origin and:
- further testing for residue levels in that crop, vegetation or food commodity of plant origin
- the harvesting or sale/supply of that crop, vegetation or food commodity of plant origin.
Outlook
The NRS grains program expanded in 2007–08 with the addition of a further 13 commodities, through agreement with grain growers. Levies are now established for these commodities and this means that all tradeable grains are now tested as part of the NRS random residue testing program.
For further information contact the Plant Program Manager:
Phone: 02 6272 3436
Fax: 02 6272 4023