Conventional agricultural systems in Australia use a wide range of agricultural chemicals to boost the yield and quality of produce and to control weeds, insect pests and disease.
While recognizing the important role these chemicals play, growers should be mindful that consumers are becoming increasingly concerned with the level of chemical residues in produce.
What are chemical residues?
Chemical residues are the traces of a chemical or its breakdown products that remain in or on treated produce after a particular time.
Residues can occur via directly treating produce with a chemical product as well as from exposure to chemicals (e.g. off-target drift, persistent chemicals in soil).
The main concern is when chemical residues are detected at unacceptable levels (i.e. above the maximum residue limit (MRL)), which indicates that chemicals may not have been used in accordance with good agricultural practice (GAP).
Managing chemical residues is essential. Growers are responsible for ensuring that chemicals are used correctly to minimise any chance of unacceptable chemical residues occurring.
Chemical residues in crops and produce
Chemical residues will generally remain in a crop or its produce for a period of time after it has been treated with an agricultural chemical. The rate at which a chemical accumulates and degrades in a plant can be difficult to predict and depends on a range of factors, including:
- the rate and frequency used
- the formulation and properties of the active consistent in the chemical product
- adjuvants added to the chemical product or/at application
- equipment used
- climactic conditions after and during application
- crop characteristics and growth stag
- crop growth after application
- the rate of chemical breakdown in plants, soil or water and resulting products from the breakdown.
Maximum residue limits (MRLs)
The maximum residue limit (MRL) is the maximum concentration of a chemical residue that is legally permitted to be present in a food, agricultural commodity or animal feed. This concentration is expressed in milligrams per kilogram (mg/kg) of the food.
MRLs are first established by the Australian Pesticides and Veterinary Medicines Authority (APVMA) under their MRL Standard After a period of time, these MRLs are then adopted into Food Standards Australia New Zealand's (FSANZ) Food Standards Code.
Meeting MRL standards demonstrates GAP in the use of farm chemicals. When a product is used according to label directions, it should not cause residues in food over the MRL.
Minimising unacceptable chemical residues
Residues are deemed unacceptable when they exceed the MRL set. Using a chemical product according to the label directions minimises the risk of unacceptable chemical residues occurring because the use has been tested by the product manufacturer.
Crops or produce with residue levels below the MRL are considered to have been grown according to GAP and are acceptable for sale and consumption. If there is no corresponding MRL for a chemical, any detectable residue will be unacceptable.
Residue standards may differ across countries. If you're supplying an export market, it's important that you comply with their requirements.
There is a greater likelihood that produce treated off-label will contain unacceptable residues, which is why off-label chemical users are particularly at risk, as any residual effect from using the chemical off-label may be unknown.
There are significant penalties that may be imposed on growers that are found to be selling produce that is contaminated with unacceptable chemical residues.
Analytical chemical testing can be used to detect unacceptable chemical residues in produce.
Know your responsibilities with regards to withholding periods and sale of products after chemical application.
Post-harvest treatment of agricultural produce
Owners of agricultural produce are responsible for the chain of custody and must give permission for their produce to be treated.
Produce monitoring programs
Find out about the National Residue Survey and how Agriculture Victoria monitors fresh fruit and vegetables for chemical contamination.
Residue information for veterinarians
Withholding period and export slaughter interval information for Vets.
Chemical residue resources
Information notes, templates and advice to further help you monitor and manage chemical residues. Includes information notes on how to take samples of soil, fruit, vegetable, grains and bees for residue testing.