For more than 15 years now, the Environmental Protection Agency (EPA) has clamped down on dioxin, a by-product of paper bleaching and of incineration of certain materials. Until it was banned as such, it was also a by-product in the manufacturing of some herbicides, including the notorious Agent Orange. Ever since the chemical was found to be horribly toxic to guinea pigs - albeit far less so to every other animal species tested, including other rodents - the EPA and other environmental organisations have relentlessly attacked it as they have no other chemical except for the pesticide DDT. Fear of dioxin contamination led to the evacuation of Love Canal near Niagara Falls in 1978 and of Times Beach, Missouri in 1983, and to telling veteran soldiers of the Vietnam War that they may be at extraordinary risk of disease. But while dioxin was long touted as "the most deadly chemical created by man", decades of scientific scrutiny have found that its only acute human effect is a form of acne (Neubert 1997). As dioxin expert Dr Michael Gough noted:

No human illness, other than the skin disease chloracne, which has occurred in highly exposed people, has been convincingly associated with dioxin. In short, epidemiologic studies in which dioxin exposures are known to have been high, either because of the appearance of chloracne or from measurement of dioxin in exposed people, have failed to reveal any consistent excess of cancer. In those studies that have reported associations between exposure and disease, no chloracne was reported, and there are no measurements of higher-than-background levels of dioxin in the people who are classified as exposed (Gough 1991).

The case against dioxin for threatening people is almost as suspect as that against DDT, but this hasn't deterred environmentalists. For years they charged that dioxin was a powerful human carcinogen known to man, to the most potentially damaging to unborn children, immune systems and hormones.

A recent dioxin assessment report by the EPA made the shift official. In addition to the old charge of dioxin being a possible human carcinogen - causing as many as one in 1000 human cancers - the EPA added two newer charges: that it might affect human children in the womb and that it could compromise immune systems at levels approaching those to which Americans are currently exposed. While those human exposure levels are infinitesimal compared with our exposure to many other chemicals, the EPA maintained that what causes illness in some animals at huge doses must also cause sickness in humans in tiny ones.

But several scientists at the meeting challenged the EPA's assumption, used in all its policy-making, that there is not a threshold below which a harmful chemical causes no harm. One was the University of Wisconsin's Alan Poland, widely known for his discovery of the "dioxin receptor", the molecule in cells to which dioxin must bind before it produces any affects. He said that 150 years of science contradicted the EPA no-threshold position.

Regarding dioxin, Dr Poland said that the normal level to which Americans are exposed - four molecules of dioxin per cell - is far below the number required to have an effect, considering that there are about 10 000 receptor molecules per cell. One EPA official complained that its science advisory board (SAB) meeting had unfairly been characterised as negative. In fact, he said, the only problems the SAB found were in the ninth chapter. Of the first eight, he was highly complimentary.

But that's just the point. The first eight chapters were written by scientists outside the EPA. Only the last chapter, the conclusive one, the one from which EPA was to draw its regulatory policy and from which the media drew the headlines, was the one written by the EPA itself. In that chapter, said Dr Poland at the meeting, "policy masquerades as science". This is probably the best data that the EPA will see in my lifetime", Dr Poland added, "yet, despite all of that, the first eight chapters are thrown away" (Food Chemical News 1995).

Advisory board members repeatedly accused the EPA of picking and choosing its data. For example, the largest, most heavily-studied group of persons with known high exposure to dioxin were the members of Operation Ranch Hand, the men who did the actual spraying of Agent Orange on the jungles of South Vietnam. The EPA report duly noted any possible minor abnormality in this group. But it neglected to say the Ranch Handlers were strapping specimens of healthy humanity. "The EPA didn't mention that there were no more cancers than would be expected, no effects on there were no more cancers than would be expected, no effects on the immune and nervous systems, no increase in deaths, and no increased birth defects in their children' SAB member and Office of Technology Assessment official, Michael Gough noted. "They mentioned nothing that didn't serve their purpose" (Food Chemical News 1995).

Also unmentioned were follow-up studies conducted in Seveso, Italy, where 37 000 people were exposed to high doses of dioxin following the explosion of an unattended chemical reactor. As the Institute of Occupational Health at the University of Milan found, there were "no increased birth defects due to dioxin exposure" (Bertazzi 1991). Furthermore, cancer mortality rates were inconclusive.

One SAB member, Dr Knute Ringen of the Center to Protect Workers' Rights in Washington DC, concluded: "I think that the agency has pretty much come to the end of the line with regard to producing useful decision-making information on dioxin, and that it's time to go on to something else" (Bertazzi 1991, Gribbler 1995, WHO/IPCS 1998).

References:

Bertazzi, P.A. (1991). Long-term effects of chemical disasters: lessons and results from Seveso
        Science of the Total Environment, 106:5.
Food Chemical news (1995). EPA Dioxin Assessment slammed for lack of science basis
        September 11, 37, 29.
Gough, M (1991). Human health effects: what the data indicate
        Science of the Total Environment, 104:129.
Gough, M (1991). Greenpeace press release, July 26 1991.
Gribble, G.W. (1995). Chlorine and Health
        (New York: American Council on Science and Health, August).
Neubert, D. (1997). Teratogenesis, Carcinogenesis and Mutagenesis, 17:157-215,
        on toxicity of dioxin to humans.
WHO/IPCS (1998). Review of TDI for dioxins (May - press release).

This article was previously published in Green & Gold Vol 09 No 2, February 1999.