A scientific paradox

Seveso also produced a paradox about the use of scientific knowledge in the policy process. Although there was undoubted physical and psychological illness among people, together with the deaths of many animals, dread consequences for human health have been elusive (Mastroiacovo et al. 1988; Regione Lombardia 1989; Mocarelli et al. 1991). In this respect it could be said that Seveso is a disaster that has not yet produced identifiable disastrous consequences. Even the most recent epidemiological results, while showing an increase in some sorts of rare cancers, do not provide firm evidence for a generally increased cancer risk to the monitored population (Bertazzi et al. 1993)

In the Seveso case, dread was associated with the perceived toxicity of dioxin. Once it was realized that the population had been subjected to dioxin contamination, the accident became, by definition, a disaster with severe psychological, social, and economic effects. However, in this case, scientific certainty about the extreme toxicity of dioxin gradually dissipated. No established scientists have argued that Seveso's population continues to suffer significant health effects.⁷ So the recent accusations (Chronology 1992, 1993) that dioxin was a component of the factory's production would, paradoxically again, amount to evidence that the substance was less toxic to humans than was initially believed.

A visitor to Seveso now finds a park where the factory once stood; some say that Seveso is now the least polluted place in Italy. Of course, the history of illness, dread, and disruption cannot be undone. But the recovery of the community proceeded smoothly; only the stigma of the town's name survives as a present source of harm. So Seveso has become, simultaneously, a symbol of an industrial disaster and a monument to relevant ignorance in science (Keynes 1921). But such ignorance is not absolute and it need not be paralysing for decision-making. At Seveso, monitoring continues, and the lessons of this relevant ignorance are being assimilated into our understanding of the place of science in the modern world.

Seveso now functions partly as an experiment, along with other monitored disaster sites such as Hiroshima. Data from the affected Seveso population are used as evidence in other, less straightforward, pollution cases and also for the ongoing review of regulations. Every experiment exists in a particular context, and inferences from its data depend on an assumption of similarity between the experimental setup and that of the other case in question (Funtowicz, MacGill, and Ravetz 1989a, 1989b, 1989c). The extent to which Seveso, with its single event of atmospheric contamination (and later contact with contaminated objects), is an appropriate model for situations of long and continuous contamination will be debated among scientists and policy makers.

Toxicology necessarily makes inferential leaps - from animals to humans, from large doses to small, and from acute to chronic doses. In turn, these inferences underlie the dose-response models that are used to define "safe limits." Thus, toxicological models have large inherent uncertainties, and large-scale accidents with good subsequent monitoring can provide less unrealistic sources of data (Funtowicz and Ravetz 1995).⁸

The very classic status of Seveso as a dioxin disaster could possibly lead to the use of its data in a paradoxical way. As we have seen, Seveso was an immediately perceived disaster, but one where the long-term health consequences have up to now been accepted as far from disastrous. We may be tempted to make a simple inference: Seveso was a harmless dioxin disaster; therefore, other dioxin releases need not be harmful. Such an argument was recently made in Arkansas, where the evidence of Seveso has been used in arguments supporting the safety of a proposed toxic waste incinerator that would emit dioxin in a similar quantity to that estimated for Seveso (Schneider 1992). Thus, we have the scientific paradox of Seveso: an event at first accepted as a disaster (with great consequences for regulatory policy) is now being used as evidence for safety. The symbol of Seveso may now be becoming increasingly complex: its original connotation of dread is challenged by one of reassurance. Paradoxically, the excellence of the recovery of Seveso could be used for the assertion of limited liability, with possible consequences for litigation and impeded recovery elsewhere.

However, as scientists know, it needs only a single long-delayed pathological condition to appear in the monitoring process for the original negative resonance of Seveso to be restored. And then the recovery of Seveso, apparently so complete at this time, could suddenly be thrown into question. Even the complete absence of conclusive evidence of cancer among chloracne victims and others in the most exposed zone A might be explained in terms of "the small population size, youth of the subjects, and short follow-up period" (Bertazzi et al. 1993)