Citation: This article was published as Sharon Beder, 'Dioxin still on the menu', Engineers Australia, August 2000, p. 30.

This is a final version submitted for publication. Minor editorial changes may have subsequently been made.

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Moves by the US government to classify dioxin as a "known" human carcinogen have been challenged in the courts by a group of New York restaurant owners who say that the classification will cause them economic harm.

The main source of dioxin for the general public is in meat, poultry, fish and dairy products. The plaintiffs argue that these products form the 'centerpieces' of their menus and if dioxin is classified as a known human carcinogen and this is publicised then they will "be forced into the Hobson's choice of either (a) serving food products that the nation's leading health agency has declared are responsible for 90 percent of human exposure to a known carcinogen, (b) somehow locating 'dioxin-free' supplies of these foods, which would involve extraordinary transportation and certification costs and other business disruption, or (c) changing their menus and foregoing high revenue-dishesÉ"

The dangers of dioxin have long been disputed because of the economic interests associated with dioxin production. Dioxins are by-products of many industrial processes including waste incineration, chemical manufacturing, pesticide production, chlorine bleaching of pulp and paper, and smelting. In fact any process in which chlorine and organic matter are brought together at high temperatures can create dioxin.

Dioxins have been studied more than any other chemical. They have been found to be toxic to all animal species tested. However, the assumption that these tests can be extrapolated to humans is hotly contested. The reliance on animal experiments is necessitated by the inability to experiment on humans.

In 1997 the World Health Organisation's International Agency for Research on Cancer evaluated the evidence and decided that there was enough evidence to say that the most toxic form of dioxin, TCDD, was a known human carcinogen. It found that although human studies were limited, the animal studies--combined with evidence that the mechanism by which dioxin causes cancer in animals also applies to humans--were enough to confirm it as a human carcinogen.

Subsequently the US National Toxicology Program (NTP) reviewed its own classification for TCDD dioxin, which had previously been "reasonably anticipated to be a human carcinogen". In 1999, when it became apparent that the NTP intended to change that to "known to be a human carcinogen", it was challenged in the courts.

The plaintiffs are led by Jim Tozzi, president of Multinational Business Services, and include the Empire State Restaurants Association, representing 20,000 businesses, and a manufacturer of medical products containing PVC. They claim that there is not enough evidence from human studies to reclassify dioxin. They say that the human studies are based on occupational exposure to dioxin rather than dietary exposure and that animal studies, in conjunction with studies of mechanisms by which cancer is caused, is not sufficient to make the case for a substance to be a known carcinogen.

As a result of the law suit the NTP published its biennial report on carcinogens in May 2000 without the change in dioxin's classification. It hopes to add an addendum when the court case is settled. Other substances added to the known carcinogen category in this report included tobacco smoke, resulting from passive and active smoking and UV solar radiation, from the sun and from sun lamps.

The US EPA which has been working on a risk assessment for dioxin for several years, is planning to publish a final report which recommends TCDD dioxin be classified as a known human carcinogen. It states that people who eat large amounts of fatty foods, such as meats and dairy products, could have a 1 in 100 chance of getting cancer as a result.

However the EPA has noted in an earlier draft that non-cancer effects from dioxin can be even more significant for humans, "including disruption of the endocrine, reproductive, and immune systems, as well as dioxin’s impact on the developing fetus".

Dioxin is not a problem that is limited to any one part of the world. Penguins in Antartica have been found to be contaminated with dioxin. The latest research, published in the prestigious journal, The Lancet, finds that dioxin contamination reduces the number of boys born and this may account for the falling male birthrate worldwide.