Dieldrin and DDT soil contamination
In the 1940s, a group of man-made insecticides/pesticides called organochlorine chemicals were introduced into Australia. Two such chemicals were Dieldrin and DDT (dichlorodiphenyltrichloroethane).
They were widely and commonly used to protect crops, livestock, buildings and households from the damaging effects of insects. The use of organochlorines was largely phased out by the 1980s-90s.
It was later found that these chemicals could contaminate soil for decades and accumulate in agricultural produce, and in livestock that grazed on affected land.
This page contains commonly asked questions about dieldrin, DDT and related organochlorines.
What is dieldrin?
Dieldrin belongs to a group of chemicals known as organochlorine chemicals that include DDT (dichlorodiphenyltrichloroethane). These are man-made chemicals that were used widely as insecticides/pesticides.
What were dieldrin and related organochlorines used for in agriculture?
Dieldrin and the related organochlorine chemical DDT (dichlorodiphenyltrichloroethane) were used in agriculture to protect crops, livestock and buildings from insect pests.
In Victoria, they were used specifically for the control of insect pests in potato, tobacco, pasture, grass seed, grain and fruit production, as well as for termite control and for the control of external parasites on livestock.
DDT was used as a 'broadacre' insecticidal spray on a range of horticultural crops, including apples and tobacco, and as a treatment for termites and livestock.
Dieldrin was used in a similar manner and was also applied with fertiliser to root vegetable crops, particularly potatoes.
When were these chemicals used in agriculture?
Dieldrin and DDT were first used in Australia in the 1940s. Their use in horticulture and as parasiticides in livestock was phased out from the early 1960s, and tobacco in the 1970s.
Where were these chemicals used for agriculture?
The distribution of dieldrin and DDT affected land in Victoria reflects the past widespread use of these chemicals, particularly on farms producing tobacco, and some producing apples and potatoes. The historical use in Victoria includes the Bellarine Peninsula, north east Victoria and areas on the eastern outskirts of Melbourne.
Why are these chemicals potentially a problem for agriculture?
Dieldrin and DDT persist in the environment for long periods and can accumulate in the body of living things such as animals and plants (i.e. they bio-accumulate).
These chemicals are persistent in soil for decades and can accumulate at variable rates in agricultural produce, and in livestock grazing affected land.
If unacceptable residues are detected in our farm produce, valuable domestic and export markets are put at risk. International standards have been set that define the level of acceptable chemical residues in produce.
What are the risks to livestock?
Cattle, and other stock including free-range pigs, poultry and ratites, can accumulate dieldrin and DDT residues in their body fat, mainly through ingestion of soil as they graze on affected land.
These chemicals are absorbed from the gastrointestinal tract and accumulate in body fat of cattle or other grazing stock, as well as in eggs in free-ranging poultry. They are also excreted in the milk produced by lactating animals.
While the health and productivity of cattle is not affected, active management at a farm level is required to prevent cattle with residues entering the food chain.
Why was soil testing undertaken on farms?
Historical use of these chemicals resulted in detections of unacceptable residues in exported beef and the imposition of trade restrictions in the late 1980s.
Since then the Victorian Government has undertaken extensive monitoring to identify properties with contamination and, working closely with the livestock industry, to manage the risk of residues transferring into beef products.
How are farming properties that are known to have soil residues managed?
Properties with a known organochlorine contamination have been formally advised of the contamination status and the risks associated with grazing cattle. 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 that includes monitoring for organochlorine residue occurrence in beef. Properties with a known status may be randomly selected for testing at abattoirs.
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 risk of residues.
Experience has demonstrated that farmers raising livestock in accordance with a property management plan or growing crops 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 statement that persons selling land must complete is designed to protect buyers.
Vendors on their Section 32 statement must provide the purchaser under a contract for the sale of land detail of whether there are any notices, property management plans, reports or orders in respect of the land issued by a government department or public authority in relation to livestock disease or contamination by agricultural chemicals affecting the ongoing use of the land for agricultural purposes.
Agriculture Victoria can search for and release information on any known land use restrictions. However, in accordance with privacy and data protection principles this can only be to the landowner or to another party with permission of the landowner.
The absence of any land use restrictions must not be interpreted as confirmation that the land is free from chemical contamination or physical defect, or that the land is suitable for raising livestock. The only way to determine this is to undertake appropriate tests on the land before any commitment is made to purchasing the land.
To make an application please contact the Agriculture Victoria customer service centre on 136 186.
What can past soil test results for a property tell me?
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.
Organochlorine chemicals 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.
If you are concerned that agricultural land may be contaminated by organochlorine chemicals, it may be possible to determine whether any such substances are present or absent by a program of soil sampling and testing. It is suggested that you discuss soil sampling procedures with an agricultural consultant or a testing laboratory, and if necessary, that the appropriate tests be carried out on the land before any commitment is made to purchasing the land.
I grow produce on the Bellarine Peninsula – how can I reassure consumers that it is safe?
Chemical residue monitoring programs under the National Residue Survey and by Agriculture Victoria demonstrate a very high level of compliance with residue standards in Australian produce.
Many producers participate 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 organochlorine chemicals may have been used on your property or if you feel this would provide additional assurance to you or your customers.
As a consumer, how do I know agricultural produce I am purchasing is safe?
The Victorian Government has undertaken extensive monitoring to identify properties with organochlorine contamination and, working closely with the livestock industry, has managed the risk of residues transferring into beef products. Experience has demonstrated that farmers raising livestock in accordance with a property management plan or growing crops are unlikely to experience any issues with soil residues being detected in their produce.
Agriculture Victoria undertakes regular monitoring of fresh Victorian grown fruit and vegetables for chemical residues and other contaminants. The results from many years of residue monitoring demonstrate to consumers that Victorian produce is clean. Agriculture Victoria has analysed almost 1,800 samples of agricultural produce since 2015 and found a 100% compliance rate when measured against relevant standards for organochlorine residues.
The National Residue Survey tests selected animal and plant products for residues of agricultural and veterinary chemicals and environmental contaminants on behalf of participating industries. This includes a specific program which focuses on monitoring for organochlorine residue occurrence in beef. The results of the programs demonstrate a very high compliance rate and the safety of produce.