ways the larger social, economic, and political context affects how human health risk is defined, remedied, or contested. Another perspective on the anthrax attacks of 2001 can be found in P.S. Brachman’s thorough commentary, Bioterrorism: An Update with a Focus on Anthrax (2002).

A successful decontamination project will require the following:

• Removal of the threatening agent to the greatest extent feasible.

• Certification that the property is as safe as it was before contamination occurred.

• Public or stakeholder acceptance of the credibility of those who have certified the safety of the property.

Those three elements are both technical and social, and they are all difficult to achieve. But without all three elements, in the case of a real-world decontamination effort, the answer to “How clean is safe?” would likely be, “Cleaner than you claim.”

Consider, for example, the hypothetical situation of an anthrax contamination of a major metropolitan airport, San Francisco International (SFO). Decades of practical work in decontaminating laboratories at Fort Detrick, Maryland, and elsewhere, demonstrate convincingly that cleanup and reoccupation of buildings are achievable. But even if those same techniques used at Fort Detrick were applied at SFO, at the end of the project, someone must say, “It is safe to go back into the airport.”

Were that announcement marred by uncertainty about residual contamination, or about the decision-making process regarding safety, it is unlikely that SFO would reopen. If decision makers stated that scientists think they may have decontaminated SFO, stakeholders would not likely be convinced that the airport is safe. And yet, officials would not be able to claim with certainty that no spores remained after cleanup. “Zero spores,” after all, is an undetectable quantity. Policymakers must be able to state, with credibility and defensibility, that they have used the most conservative science available and that they have used proven decontamination techniques (Hsu et al., 2002). Decision makers also will need the public to see their decisions as legitimate. Legitimacy can not be commanded, and it does not flow automatically from competent science.

There is no documented threshold for cleanup of B. anthracis—especially in its weaponized form—below which no health effects would occur. Raber and colleagues (2003) noted that uncertainties surrounding B. anthracis contamina-