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What is dioxin?

Page - December 6, 2006
Dioxins and furans are a class of chemical compounds widely recognised as some of the most toxic chemicals ever made by humans. Generally just referred to as dioxins, dioxins and furans have no useful purpose and are produced as the unwanted by-products of industrial processes such as the manufacture of PVC, pesticide production, incineration, pulp and paper bleaching with chlorine, and the smelting and recycling of metals.

Dioxin (dioxin and furans) is one of 12 persistent organic pollutants (POPs), known as the "dirty dozen", which have been targeted for elimination under an international toxics treaty called the Stockholm Convention.

The dirty dozen includes:

  1. Chemicals deliberately produced by industry; eight pesticides: aldrin, endrin, toxaphene, chlordane, dieldrin, heptachol, mirex, and DDT industrial chemicals: hexachlorobenzene and PCBs.
  2. Chemicals released as unwanted industrial by-products: PCB's, hexachlorobenzenes, dioxin and furans.

Once released into the environment, dioxin can be transported vast distances along air and ocean currents. As dioxin travels throughout the global environment it builds up, or bioaccumulates, and can take decades to break down. Because of this globe trotting ability, dioxin is a global contaminant.

Dioxin dissolves easily in fats and as a result can build up in the fatty tissues of animals and humans. So animals with high fat contents, such as humans, whales, polar bears and dolphins, are particularly susceptible to the build up of dioxin. As it travels up the food chain - if an animal with dioxin in its body tissue is eaten by another animal, for instance - dioxin biomagnify, or multiply in concentration. Animals at the top of the food chain, humans, polar bears, beluga whales, will accumulate the highest levels of dioxin.

In 1997, the International Agency for Research on Cancer (IARC) classified the most toxic dioxin as human carcinogens. It is associated with a wide range of other health impacts including:

  • Altered sexual development
  • Male and female reproductive problems
  • Suppression of the immune system
  • Diabetes
  • Organ toxicity
  • Effects on a wide range of hormones

One of the most disturbing aspects of dioxin toxicity is the effect it can have on the developing foetus, which is far more susceptible than adults. Humans are exposed to dioxin mainly through the food we eat, especially meat, fish and dairy products. Dioxin levels are generally higher in people living in industrialised countries, such as the US, Europe and Japan, where they are already at - or near - the level where health effects may occur. However communities with a high fish or sea mammal diet, like the Indigenous Peoples of the Arctic, are also at a high risk from dioxin effects.

According to World Health Organisation figures, a piece of dioxin the size of a small grain of rice, if distributed equally and directly to people, is equivalent to the "allowable" yearly dose for one million people.

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