The term "nuclear, biological or chemical weapon of mass destruction" applies to "any substance that is designed or has the capability to cause death or serious injury and ... is or contains toxic or poisonous chemicals or their immediate precursors."
And now there's this gem, showing that, in fact, this is Fatherland Security's favored approach, rather than just some loophole being attempted by an insane prosecutor: New Terror Laws Used Vs. Common Criminals:
"Within six months of passing the Patriot Act, the Justice Department was conducting seminars on how to stretch the new wiretapping provisions to extend them beyond terror cases," said Dan Dodson, a spokesman for the National Association of Criminal Defense Attorneys. "They say they want the Patriot Act to fight terrorism, then, within six months, they are teaching their people how to use it on ordinary citizens." [...]
Stefan Cassella, deputy chief for legal policy for the Justice Department's asset forfeiture and money laundering section, said that while the Patriot Act's primary focus was on terrorism, lawmakers were aware it contained provisions that had been on prosecutors' wish lists for years and would be used in a wide variety of cases.