Outside of the Middle East, the concern about Sarin gas (or VX gas, which stays in the environment longer) is more about a targeted terrorist attack, such as the one that occurred in the Tokyo subway in 1995, where 12 people were killed and thousands were injured.

FORBES: Sarin Gas Is Deadly, But Fear Is More Powerful And More Deadly

Taking the witness stand on the first day of his trial, Dr Ovens recalled how Mr Railton had spoken of using VX nerve gas on a bus in Caterham.

BBC: Man 'planned poison attack on bus' in Surrey

But U.S. National Security Advisor Sandy Berger said Sunday that the United States has "physical evidence" that the factory was manufacturing a chemical used to make deadly VX nerve gas.

CNN: Sudan demands U.S. apology for missile attack