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Dichlorodiphenyltrichloroethane, commonly known as DDT, has a normative half-life of 2-15 years. This means it can take 15 years for 50% of the chemical to break down.
DDT was banned in Aotearoa in 1989. 21 years after it was first banned by Hungary; 27 years after the publication of Silent Spring.
30 years later, 25% of the DDT used in 1989 can still be detected in the soil.
DDT is colourless, tasteless and mostly odourless.
When DDT breaks down it forms Dichlorodiphenyldichloroethylene (DDE) and Dichlorodiphenyldichloroethane (DDD).
While DDD is classed a probable human carcinogen, the main issue is DDE.
DDE is fat-soluble so it builds up in animal tissue. In this way it is like the lead in lead petrol and the fallout from atomic bombs. Unlike other poisons (i.e. 1080) which break down naturally, the only time DDE is removed from the body is when it is passed to the animal’s young via breast milk.
DDE and DDT are stored in bodyfat and when one animal eats another the substance is transferred. This results in what is termed ‘biomagnification,’ meaning each level of the food-chain accumulates more of the substance.
Biomagnification threatens predators most, especially apex predators like native birds.
In 1948, Paul Hermann Müller was awarded the Nobel Prize in Physiology and Medicine for his discovering the insecticide properties of DDT.
The success of DDT led to the expansion of the pesticide corporations, famously Monsanto, which also produced 2,4–D, an ingredient in Agent Orange.
Many fungi are hyperaccumulators. They soak up the toxins and can later be removed from the soil.
Rachel Carson’s Silent Spring led to the formation in the USA of the Environmental Protection Agency.
There are ongoing efforts throughout Aotearoa to deal with DDT contamination, though more and more pesticides with long half-lives are entering awa, roto, moana and groundwater through agricultural runoff.
In 2016, 60% of Aotearoa’s monitored rivers were unsafe to swim in.
February 6, 2020
Rhys Feeney lives & teaches in Te Whanganui-a-Tara. His work has appeared in Mimicry, Starling, elsewhere, & Sponge. His debut chapbook will be published as part of the AUP New Poets in 2020. You can follow him at @rhysfeeneybot