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Public acceptance of bioremediation to address New Zealand's DDT problem

Find out what New Zealanders think about using a genetically modified bacterium to breakdown toxic DDT residues in the soil.

DDT is a pesticide that was used on New Zealand farms in the 1950s and 1960s to kill insects, particularly grass grub. DDT residues stay in the soil for many years - they are still in our soil 50 years on. What do New Zealanders think about the use of bioremediation to help clean up DDT in our soils?

The DDT problem

DDT was initially used to control grass grub. Grass grubs are a native insect that eat the roots of many grasses, especially ryegrass. Ryegrass is one of the most common grasses on farms.

In 1970, DDT was banned from use on farm land, but unfortunately DDT residues stay in the soil for many years. When animals accidentally eat DDT contaminated soil while eating grass or feed crops, the DDT residues build up in their fat tissue. This causes the contamination of the animal's meat and milk. Fonterra will not collect milk if the DDT residues are 1mg/kg milk fat or more. Land with high levels of DDT residues is therefore not good as farm land.

A possible solution

A genetically modified bacterium has been created that breaks down DDT residues in the soil. This would help remove the DDT residues from New Zealand soil, decreasing the risk they pose to our exports of milk and meat.

What New Zealanders think?

In focus groups conducted by Lincoln University's Agribusiness and Economics Research Unit (AERU) it was found that public opinion is divided over whether this application of biotechnology is acceptable or unacceptable. There were a total of 117 people surveyed in these focus groups.

People were concerned that putting these bacteria in the ground would be an irreversible step. As one person commented: "There is no way you can say, 'That doesn't work, take it out of the ground'." This would be especially problematic if there were unforeseen circumstances, such as the genetically modified bacteria "gobbling up" other beneficial bacteria in the soil, or becoming pathogenic to humans, other mammals, or organisms living in the soil.

Soil was recognised as one of New Zealand's most important resources, for a variety of reasons. People were supportive of taking measures to look after it. Cleaning up DDT residues was seen to have economic benefits for New Zealand. Opinion was divided about whether using the genetically modified bacteria is the best way to do it.

Survey respondents felt the need to right a wrong, but this was balanced by a concern not to create another problem.

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