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Chemical management and fresh produce

Most farmers use agricultural chemicals at some stage of their production system as a management tool to control pests, disease, weeds or growth.  Even organic and biodynamic farmers use chemical substances (some commercial, others made on-site) that are allowed inputs under their management standards, to achieve production outcomes.

Regulation of chemicals

All commercial products marketed in Australia that claim to control a particular condition or have beneficial effects must be registered with the Australian Pesticides and Veterinary Medicines Authority (APVMA).  The APVMA is an Australian government statutory authority established in 1993 to centralise the evaluation and registration of all agricultural and veterinary chemical products that can be legally supplied, sold or used in Australia.

The APVMA also registers chemicals which are used in the household, such as insect sprays, personal insect repellents, products for treating pests and diseases in home gardens, and medicines for companion animals such as dogs, cats and horses.

There are over 10,500 different pesticides and veterinary medicine products sold in Australia.  Users need to know that products will not only work, but when used according to label directions they will not harm themselves, their family, crops, animals or the environment.

The APVMA also reviews older products that have been on the market for a significant period of time, to ensure they still do the job users expect and are safe to use.  They may also review a registered chemical when particular concerns are raised about their safety and effectiveness.  The review may result in the registration continuing unchanged, the registration continuing but with changes to the way the chemical can be used or the registration cancelled and the product taken off the market.

MRL =

Maximum Residue Limit

for chemicals in use

ERL =

Extraneous Residue Limit

for chemicals no longer in use

labels on chemicals are legal documents - label directions must be followed to comply with the law or fines may occur

Cadmium and Lead are the two heavy metals that vegetable farmers need to assess risks for

Food Standards Code Permitted MLs

Cadmium

leafy vegetables

= 0.1 mg/kg

Lead

Vegetables (except Brassicas)

= 0.1 mg/kg

Brassicas

= 0.3 mg/kg

go to APVMA website

search PUBCRIS chemical database for APVMA registered chemicals

go to Food Standards Code

go to MRL Standard 1.4.1

read this Final Report on how Australia is addressing the issues of Cadmium management in agriculture

click here to find out more about the FreshTest program

Maximum Residue Limits

The APVMA requires toxicological, residue and dietary exposure evaluations to be completed before a product can be registered for agricultural or veterinary use.  This is completed before a  Maximum Residue Limit (MRL) on foods is recommended to Food Standards Australia New Zealand (FSANZ).

The MRL is the maximum concentration of a residue that is legally permitted on produce after harvest. When registered chemicals are applied correctly and the withholding period required before harvest is observed, there should be no risk that any remaining chemicals will exceed the Maximum Residue Limit (MRL).

FSANZ sets the MRLs permissible in or on a food, agricultural commodity or animal feed.  FSANZ has established MRLs for fresh produce, which are published in Standard 1.4.2 in the Australia New Zealand Food Standards Code.

There can be a delay between the APVMA registering a chemical for agricultural and veterinary use and the processes for FSANZ to include the MRL in the Food Standards Code.

Exceeding the legal limits

Residues exceeding the MRL are unacceptable, but do not necessarily represent a food safety hazard to consumers because of the high safety margins (usually 100 times less than the No Observable Effect Level (NOEL) - see APVMA Fact Sheet above).  Where an MRL is not specified for a chemical on a produce type in Standard 1.4.2, no residues are permitted in the produce.

Farmers may be fined if there is any evidence that chemicals have not been used according to the label directions.  It is a legal requirement in NSW since 2003 that commercial users (e.g. farmers) keep records of their chemical applications - these are recorded within 24 hours of application, must be kept for three years and must be made available to regulatory authorities for inspection.

It has also been standard within the industry for many years that farmers complete Farm Chemical User training courses where they are kept up to date with the latest rules and regulations governing chemical registration, labelling and directions for use.

It has been a regulatory requirement in NSW since 2005 that any person using chemicals in their workplace must have completed the appropriate Australian Qualifications Framework (AQF) level training for their chemical use.

Persistent Chemicals

Chemicals that may remain in the soil for a long time are called ‘persistent chemicals’. Persistent chemicals belonging to the organochlorine (OC) and organophosphate (OP) groups may be present on farms due to past use, dumping or spillage.  How long chemicals persist in the soil will depend on soil type, climatic conditions and how they were used (e.g. cover spray, dip, dump site).

In Australia, Dieldrin is a common example of a persistent chemical.  Dieldrin is an organochlorine insecticide and although it has not been legally used since the 1980s, it was once applied routinely as an agricultural, industrial and domestic insecticide for the control of termites (white ants), household pests, ants and soil insects. Examples of some other persistent chemicals used in agriculture include DDT, Lindane, Chlordane, Aldrin, Endrin, BHC, Heptachlor, Methoxychlor, Hexachlorobenzene and Toxaphene.

Soil contamination of growing sites can lead to contamination of produce, with higher risks for root and tuber vegetables and crops grown near or in contact with the soil.  For crops grown above the ground, the risk of contamination is low, as only minute amounts of chemical may be taken-up through root absorption.

An Extraneous Residue Limit (ERL) is the maximum permitted level of a persistent chemical residue on food, as specified in Standard 1.4.2 .  For example, Dieldrin has no registered use so any small Dieldrin residue detected is assumed to arise from an environmental source.

Heavy metals

Examples of heavy metals are cadmium, lead and mercury.  Heavy metals occur naturally in soil or they can be introduced in small amounts through the use of fertilisers (especially phosphate) and soil additives (such as gypsum and animal manure), and from industrial uses (either past or present).

FSANZ has established acceptable limits for the presence of heavy metals in foods and the Maximum Levels (MLs) for fresh produce are published in Standard 1.4.1 of the Food Standards Code. Where produce is being exported to another country, a check of the appropriate importing country MLs should be undertaken.

Cadmium is the heavy metal of most concern to fresh produce.  Most cadmium (Cd) occurs naturally in the soil, is present at levels of 0.1-1.0 mg Cd/kg of soil and is in an insoluble form.  Uptake by plants is low.  However, cadmium is mobilised and uptake potential increases where soils are very sandy, saline or acidic, low in zinc or organic matter and if irrigation water is salty.

The potential risk of cadmium uptake varies with the type of produce.  The risk is higher for the following produce:

1. •root and tuber vegetables (defined as spinach, cabbage, raw watercress, lettuce and salad leaves (all varieties), fresh herbs (cilantro, basil, parsley), chicory
   

2. •leafy vegetables (e.g. Wombok, lettuce, spinach, silver beet)
   

3. •peanuts
   

These crops should be tested for cadmium levels if conditions favour uptake e.g. where soils are very sandy, saline or acidic, low in zinc or organic matter and if irrigation water is salty.

“Managing Cadmium in Vegetables”, is a publication developed by the National Cadmium Minimisation Committee (NCMC) in July 2003.  (Click the icons to the right to get more information about managing cadmium in vegetables)

Lead (Pb) is a heavy metal that can contaminate the growing site as a result of fumes from nearby heavy vehicle traffic, dumping of old paint or weathering of paint from buildings, and from previous use for storage or discharging of firearms (e.g. rifle range).  Lead can also be of concern if your growing sites are located near a smelter.  These factors need to be considered when assessing sites for growing fresh produce.

Spray drift management

Spray drift is the movement of agricultural chemicals away from the target area during or after ground or aerial spraying (in the form of droplets, particles or vapour).  Agricultural chemicals can drift long distances under certain weather conditions.

Spray drift or overspray can be a possible source of chemical contamination on produce.  One the main causes of this may be from spraying chemicals in unsuitable weather conditions.  Weather conditions impacting on the likelihood for spray drift include temperature, humidity, evaporation rate and droplet lifetime.

The Australian Pesticides and Veterinary Medicines Authority (APVMA) requires chemical label directions to include relevant weather information for avoiding spray drift.  Each chemical label should be read before spraying to check the suitability of weather conditions required for spraying the chemical.  A weather monitoring device should be used to measure the temperature, relative humidity and wind speed and direction and these details captured on the spray diary for each application of the chemical.

Neighbours also need to be aware of the potential for spray drift, and the effect it can have on adjacent properties.  Chemical users should talk to neighbours, discuss sensitive areas, and determine how the risk of spray drift between the properties can be managed.  Neighbours should also be asked to avoid spraying when drift is likely.

Click on the NSW Farmers’ Spray Drift Fact Sheet for further information and links or you can click here to purchase a comprehensive publication from the NSW DPI bookshop covering the principles and management of spray drift.

Produce chemical residue testing

HACCP-based food safety and quality assurance systems require chemical residue testing to verify that only registered chemicals are used, applied correctly and withholding periods are observed prior to marketing of fresh produce.  The frequency and type of testing requirements in these programs varies with the produce type, production systems, produce use plus any additional customer-perceived risks.

Freshtest is the largest fresh produce residue testing program in Australia, established by the Australian Chamber of Fruit & Vegetable Industries.  It is conducted through the major Central Markets in Australian cities and provides the most cost-effective option for farmers.

State Government Food Authorities also conduct chemical residue tests at wholesale or retail level to monitor chemical use patterns.

The National Residue Survey is a national levy-based residue testing service for a limited number of horticulture industries - established to facilitate export market access.

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