The U.S. chemical industry has spent more than $2 billion to increase security since the Sept. 11 attacks, but the risk of a terrorist strike on a plant can never be entirely eliminated, public and private sector officials said last week.

Many experts believe the odds for a chemical attack are relatively high, compared with biological or nuclear terrorism because of the widespread availability of raw materials including millions of military-grade chemical weapons scattered in at least a dozen countries.

Chemical and biological weapons falling into the hands of individuals or small bands of terrorists is as much a threat as nuclear weapons being developed by rogue states according to delegates at U.N. disarmament talks.

Gregg Easterbrook argues that U.S. threat scenarios of chemical and biological attacks are far less likely than a terrorist attack using a radiological or nuclear weapon.

The U.S. has received a credible report that Islamic extremists affiliated with al Qaeda took possession of a chemical weapon, possibly the nerve agent VX, in Iraq last month or late in October.

The U.S. government has spent $230 million trying to build a Russian plant to destroy thousands of tons of deadly chemical munitions from the old Soviet arsenal. This month, unless Congress acts, the Pentagon will begin closing down the project without laying a single brick ? or eliminating a single weapon.

A previously undisclosed study by the Army surgeon general concludes that as many as 2.4 million people could be killed or injured in a terrorist attack against a U.S. toxic chemical plant in a densely populated area.