“The Department of Homeland Security has preliminarily labeled more than 200 chemical facilities, including university laboratories, at highest risk for a potential terrorist attack. DHS has winnowed this number from a pool of about 7,000 facilities under review in its chemical plant security program. The agency had identified these facilities from a larger pool of 32,000 and ranked them according to a four-tier system. … C&EN has learned from several sources the breakdown of the notified facilities into the four-tier system: 219 in tier 1, the highest risk level; 756 in tier 2; and 1,712 and 4,319 in tiers 3 and 4, respectively.”
Chemical & Engineering News: Chemical Vulnerability
