Dieldrin and DDT soil contamination
Dieldrin belongs to a group of chemicals known as organochlorines (OCs) that include DDT. These are man-made chemicals used widely as insecticides and pesticides.
OCs were used to protect crops, livestock, buildings and households from the damaging effects of insects. Most uses of these chemicals were phased out by the 1990s.
It was found that these chemicals could contaminate soil for decades. They can accumulate in agricultural produce including livestock that grazed on affected land.
International standards have been set that define the level of acceptable chemical residues in produce. If unacceptable residues are detected in our farm produce, valuable domestic and export markets are put at risk.
Risks to livestock
Cattle, and other stock (including free-range pigs, poultry, and ratites), can accumulate dieldrin and DDT residues in their body fat, when ingesting soil as they graze on affected land.
Absorption of these chemicals via the gastrointestinal tract and accumulate in:
- body fat of the grazing stock,
- eggs produced by free-ranging poultry.
The chemicals are also excreted in the milk produced by lactating animals.
The health and productivity of cattle is not affected. To prevent animals with residues entering the food chain, farms must be managed effectively.
Historical use of these chemicals resulted in detections of unacceptable residues in exported beef. This led to the imposition of trade restrictions in the late 1980s.
The Victorian Government has undertaken extensive monitoring to identify properties with OC contamination. Working with the livestock industry, the government manages the risk of residues transferring into beef products.
Testing of soil samples will verify if soil is contaminated with OCs. Discuss soil sampling procedures with an agricultural consultant or a testing laboratory. Ensure appropriate tests be carried before any commitment is made to purchasing the land.
Farms with contaminated soil residues
Owners of properties with known contamination have been advised of the status. Farmers were advised of the risks associated with grazing cattle on contaminated land. A property management plan was established by the Victorian Government for property owners wishing to continue cattle production on affected land. Plans are now audited under the industry operated Livestock Production Assurance (LPA) program.
The beef industry and state and territory governments collaborate on a chemical residue monitoring program under the National Residue Survey (NRS) that includes monitoring for organochlorine residues in beef. Random testing of livestock from properties with a known contamination status may be conducted.
Residue monitoring is a requirement that supermarkets place on their horticultural growers, which is further complimented by residue monitoring programs conducted by Agriculture Victoria and the Commonwealth government.
All primary producers are responsible for ensuring that they do not sell contaminated produce. Regulatory action may be taken against producers who are not effectively managing the residue risks.
Experience has demonstrated that farmers raising livestock or growing crops under a property management plan are unlikely to experience any issues with soil residues being detected in their produce.
How can I find out if my farm or one I am thinking of purchasing is contaminated?
The Section 32 (S32) statement that persons selling land must complete is designed to protect buyers.
Vendors must provide the purchaser any notices, property management plans, reports or orders that have been issued in relation to livestock disease or land affected by contamination from agricultural chemicals.
Agriculture Victoria can search for and release information on any known land use restrictions. This can only be released to the landowner or another party with permission from the landowner. To make an application please contact our customer service centre on 136 186.
It should not be assumed that land is free from chemical contamination or physical defect, even in the absence of land use restrictions listed in the S32. The only way to determine this, is to undertake appropriate tests on the land before any commitment is made to purchasing it.
Past soil test results
Past test results for farms may only tell part of the story as organochlorine residue levels will vary across paddocks, between paddocks on the same farm, and from farm-to-farm.
Organochlorines are generally persistent in the environment. In some cases, soil residue levels have reduced over time, however residue levels continue to be detected in soils where these chemicals were used. Organochlorine residue levels in these soils fall slowly and may be detectable for decades.
I grow produce on the Bellarine Peninsula — how can I reassure consumers that it is safe?
Chemical residue monitoring programs under the NRS and by Agriculture Victoria demonstrate a very high level of compliance with residue standards in Australian produce.
Many producers take part in Quality Assurance programs and routinely undertake chemical residue testing of their produce to provide assurance to themselves, and their customers, that their produce is not contaminated.
You may wish to undertake testing of your soil if you have reason to believe organochlorines have been used on your property. Testing may provide more assurance to you or your customers that your property is free of organochlorine residues.