The events of September the 11th have focused attention on the vulnerability of nuclear installations to attack and the possibility of the terrorists using radioactive material for “dirty bombs”—where radioactive material is dispersed by conventional explosives. Helfand and colleagues (p 356) estimate that in a nuclear explosion in New York city 52 000 people would die immediately and fallout from radiation would kill a further 200 000. They call for stricter control of nuclear materials and the abolition of nuclear weapons. 
The “Doomsday Clock” first appeared on the cover of the Bulletin of the Atomic Scientists in 1947 as a symbol of nuclear danger. Since then the hands have moved 16 times reflecting varying international tensions and the perceived threat of nuclear war. (www.bullatomsci.org/clock.html) In a commentary to Helfand's paper Bhutta and Nundy (p 358) draw attention to the horrifying possibility of nuclear war between India and Pakistan. They conclude that this has brought the hands of the clock closer to midnight.