Five years ago, in the aftermath of the attack on the World Trade Center, anthrax was found in the mail in several locations in the United States. The discovery heightened fears that the country was vulnerable to bioterrorist attack. Subsequently, the federal government has, according to the Center for Arms Control and Non-Proliferation in Washington DC, spent a staggering $36 billion on biosafety-related activities.

Criticism of this approach was muted back in 2001, but five years on it is surging in the communities designated to host biosafety labs. Despite protests, however, the government is accelerating its investment in the biodefence complex that is now taking shape.

Last May, residents of Boston's Roxbury district sued the Boston University Medical Center and the National Institutes of Health (NIH) to try and block the construction of a $178-million biodefence laboratory there. The lab, which will be equipped to perform experiments at biosafety level 4 — the highest classification of confinement — is already under construction. Last month, a district-court judge declined to halt the building work, but reserved the right to stop the project later on, subject to the results of an environmental review that the NIH has already agreed to perform.

The proliferation of such labs begs the broader question of how much biodefence is too much.

The court's ruling suggests that the NIH and Boston University failed to adequately assess the environmental consequences of building such a lab in the middle of a large conurbation. A similar omission appears to have been made by the Department of Energy, which wants to construct a biosafety level 3 lab at the Lawrence Livermore National Laboratory in California — a site virtually surrounded by suburban sprawl. An appeal court there ruled last month that the energy department has yet to conduct a sufficiently thorough assessment of the laboratory's risks, particularly regarding the risk of a terrorist attack on the site itself.

These cases follow protests against a new biosafety level 4 lab being built by the Department of Homeland Security (DHS) at Fort Detrick, Maryland, as part of a $105-million National Biodefense Analysis and Countermeasures Center. And they offer a taste of what's to come with another DHS project, a planned $450-million National Bio and Agro-Defense Facility, as yet unlocated.

These objections have concentrated on local questions, but the proliferation of such labs begs the broader question of how much biodefence is too much. In the febrile climate of 2001, the Bush administration wasn't pressed sufficiently to explain why such proliferation of knowledge is in the national interest. Five years on, the time has come for it to do so.