Insurers have always found it costly to ignore new exposures. Doing that in the case of terrorism, however, could literally bankrupt the industry. No one knows the probability of a nuclear detonation in a major metropolis this year (or even multiple detonations, given that a terrorist organization able to construct one bomb might not stop there). Nor can anyone, with assurance, assess the probability in this year, or another, of deadly biological or chemical agents being introduced simultaneously (say, through ventilation systems) into multiple office buildings and manufacturing plants. An attack like that would produce astronomical workers' compensation claims... We will not, for example, write coverages on a large number of office and apartment towers in a single metropolis without excluding losses from both a nuclear explosion and the fires that would follow it.