Monitoring and regulating chemical residues and contaminants

What are chemical residues?

Chemical residues in food and fibre are those chemicals and their metabolites which are present due to their use in food and fibre production systems.

Residues of agricultural or veterinary chemicals can occur due to direct chemical treatment of the plant or animal from which the product is derived.  Residues may also occur because there has been a chemical treatment of some other material that is then taken in by the plant or animal.  For example, residues in meat or milk could result from indirect chemical exposure if animals are fed grain or forage that has been treated with a pesticide.  Unacceptable chemical residues should not occur if approved label instructions or permit conditions are strictly observed when the chemical is used.

What are chemical contaminants?

Contaminants are substances within the environment which end up by accident in food and fibre products and may be undesirable at certain levels.  Examples are remnants of no longer used persistent organochlorine pesticides such as dieldrin, DDT or heptachlor; heavy metals such as cadmium, lead or mercury; naturally occurring toxins of certain plants such as aflatoxins and alkaloids; and contaminants following industrial processes such as dioxins, which also occur naturally.

Biosecurity Queensland, part of the Department of Primary Industries and Fisheries (DPI&F), in conjunction with other government agencies, develops and implements monitoring, detection and management programs to manage the risks posed by chemical residues.

The importance of managing chemical residues and contaminants

On occasions residues are detected above the level set in legislation, however the residue levels are not high enough to affect human health.  Residues, even at minute levels, can affect trade and often impact on market access in countries where different residue standards may apply.

Surveys of Australia´s agriproducts undertaken under the National Residue Survey (NRS) and by Food Standards Australia and New Zealand (FSANZ) show a high rate of compliance with Australian food standards.  

Agriculture in Australia, as with other countries, generally relies on chemicals for effective pest and disease control.  Whenever chemicals are used there is a risk that they will be misused and unacceptable residues will result.  This risk needs to be managed.  Biosecurity Queensland assists this process by undertaking activities which include:

• monitoring of food products for residues
• building innovative detection systems for environmental contaminants and residues
• supporting quality management systems
• traceback and investigation of residue detections.

How are limits for residues established?

International standards setting

The Codex Alimentarius Commission (Codex), attached to the Food and Agriculture Organization of the United Nations and the World Health Organization, sets international standards for food commodities.  Codex standards aim to protect the health of consumers and ensure fair practices in the food trade arena.  These standards include maximum residue limits (MRLs) for agricultural and veterinary chemical residues, maximum permissible concentrations (MPCs) for heavy metals such as cadmium, lead and mercury and extraneous residue limits (ERLs) for some of the environmental contaminants in foods.  Standards are established for all types of raw or unprocessed foods and some processed foods.  These foods may be of either plant or animal origin, and be for consumption by humans or farm animals.  

National standards

The Australian Pesticides and Veterinary Medicines Authority (APVMA) establishes and revises MRLs for agricultural and veterinary chemicals in food and feed commodities during the registration process, after evaluating data submitted by registrants.  APVMA MRLs are published in the MRL Standard.  .

Food Standards Australia and New Zealand maintains a list of MRLs for food commodities as Standard 1.4 within the Food Standards Code.  Standard 1.4 is used by state health departments in administering food standards under food regulations.

Queensland legislated standards

Both the Chemical Usage (Agricultural and Veterinary) Control Regulation 1999 and the Stock Regulation 1988 set residue limits for agricultural and veterinary chemicals and for contaminants in foods using the MRL Standard published by APVMA.  The Stock Regulation 1988 also sets residue limits for metals and polychlorinated biphenyl in animal tissues which are listed in part 1.4.1 Contaminants and natural toxicants of the Australia New Zealand Food Standards Code.

Monitoring

FSANZ conducts the Australian Total Diet Survey every 2 years.  The Total Diet Survey monitors residues and contaminants in table-ready foods and estimates human dietary exposure to these chemicals.  

The National Residue Survey monitors the residues in food commodities destined for human consumption within Australia or for export.  State, territory, retailer and grower groups also monitor residue levels in food commodities.

Targeted chemical residue programs administered by the National Residue Survey

The National Residue Survey, a program administered by the Australian Government Department of Agriculture, Fisheries and Forestry (DAFF), is involved in support programs designed to specifically assess the residue status of some commodities from areas or farms that have a higher risk of chemical residues.  The program is funded by industry.   DPI&F is involved in the implementation of these programs within Queensland.  The current programs are the:

• National Organochlorine Residue Management (NORM) Program
• National Antimicrobial Residue Minimisation (NARM) Program
• Endosulfan Management Program.

National Organochlorine Residue Management (NORM) Program

The aim of the NORM Program is to reduce the occurrence of contaminants of organochlorine (OC) chemicals (such as dieldrin, DDT, heptachlor, and BHC) in beef products.  These OC chemicals were legally used in the past as pest control agents in agricultural production systems and for termite control in farm and domestic buildings.  They have been progressively banned from agriculture mainly because of their persistence in the environment and animals tissues.  Grazing animals such as cattle ingest soil either directly, or from soil particles attached to the plant material.  OC chemicals are absorbed through the diet of the animal, accumulate in the cattle´s fat and can be secreted in milk.  The presence of OC contaminates in animal tissues can prevent the trading of these commodities in international markets.  This necessitates the need to manage the risk of these contaminants.  

The NORM program functions by:

• preventing livestock with residues of OCs above the ERL from being sold for slaughter or trade
• assisting livestock producers to build and manage property residue minimisation plans - measures include restricting access of livestock to contaminated land or risk areas, remediating contaminated areas, and moving cattle that have grazed contaminated areas to clean areas for an extended period before slaughter
• auditing property residue minimisation plans
• allocating a risk status to each livestock property or grazing area based on history of previous use of OC chemicals and history of OC detections and analysing samples taken from livestock at slaughter with higher risk status.

NORM is a joint initiative of Cattle Council of Australia, Australian Lot Feeders Association, State Departments of Primary Industries (or equivalent) and DAFF.

National Antimicrobial Residue Minimisation (NARM) Program

The National Antimicrobial Residue Minimisation (NARM) Program has been established to reduce the threat to trade and public health of veterinary antimicrobial residues in meat.

NARM also is a joint initiative of Cattle Council of Australia, Australian Lot Feeders Association, State Departments of Primary Industries (or equivalent) and DAFF.

The program has three parts:

• education of the ivestock industry and individual producers about antimicrobial residues
• sampling and analysis of slaughter animals, particularly targeting groups such as calves and dairy cattle
• restricting sale of animals for slaughter if they have residues above the maximum residue limit (MRL).

Endosulfan Management Program

The aim of the Endosulfan Management Program is to ensure that the MRLs for endosulfan are not exceeded in meat.  Endosulfan is most commonly used on cotton but also on a wide range of horticultural crops.

The program involves:

• monitoring the use of endosulfan in the cotton growing areas - applications of the chemical and weather conditions are monitored closely to ensure that correct spray procedures are being followed in order to reduce the risk and severity of off-target spraydrift  
• sampling livestock at slaughter for residues.

These measures together with stricter controls over the use of endosulfan, and the recent low pest pressure on cotton crops has led to a dramatic decrease in the number endosulfan residue detections.

Other Queensland initiatives for residue management

Three programs undertaken by DPI&F support the programs administered by the National Residue Survey:

• Detector Dog Project
• Chemical Residues Surveillance
• Monitoring Stockfoods and Fertilisers.

 Detector Dog Project

This project trains and operates sniffer dogs to detect organochlorine chemical residues in the environment.  The project is very closely associated with the NORM Program.

A dog's sense of smell is up to a million times keener than the human sense of smell.  The sniffer dogs have been trained to detect less than one part per million of specific organochlorine chemicals in the environment.  The dogs are used in the field to identify contaminated sites on rural properties.  

Chemical Residues Surveillance - Agricultural produce

The aim of the Chemical Residues Surveillance program is to monitor and minimise chemical residues within plant produce from Queensland.

Biosecurity Queensland inspectors take selected samples of plant commodities for laboratory analysis.  The main focus of this program is on suspected misuse of agricultural chemicals, either identified by previous monitoring or reports from industry sources.

If a sample is found to contain chemical residues higher than the MRL or residues from the use of an unregistered chemical, the commodity is traced back to its source.  Further investigations are then undertaken to determine the cause of the unacceptable residues, including the degree of compliance with the instructions on the registered product label.

Tracebacks are also conducted on samples found to have residues at between half the MRL and the MRL, because residues at these levels can indicate that the farm practices being used are not in accordance with good agricultural practice.

Chemical Residues Surveillance - Animals

Biosecurity Queensland inspectors also initiate tracebacks of residue detections under the various National Residue Survey programs and respond to detections reported in export markets.  Inspectors also respond to suspected misuse of chemicals either identified in monitoring activities or reported through industry audit programs.

Monitoring Stockfoods and Fertilisers

Commodities such as commercial fertilisers and stockfoods are monitored to ensure they are free of prohibited ingredients, and contain below the maximum permitted concentrations of contaminants, for example cadmium, lead and mercury in fertilisers and ergots and aflatoxins in stockfoods.  Chemical contamination issues in these commodities can impact on both animal and plant industries.