Following several major bombing incidents in the United States in the 1990s, most notably the bombing of the New York World Trade Center in February 1993 and of the Alfred P. Murrah Federal Building in Oklahoma City in April 1995, considerable discussion at the federal level has focused on ways to reduce the threat of illegal bombing attacks. In particular, there has been interest in the possibility of reducing the threat through some combination of introducing additives called detection markers or identification taggants¹ into explosive materials to facilitate detection or tracing of the materials (Box 1.1); decreasing the explosive potential of certain chemicals that might otherwise be used to manufacture explosives; and/or imposing licensing or other controls on explosive materials and/or their chemical precursors.

Currently, licensed manufacturers are required to place identifying markings on the packaging for explosives that can assist in tracing them for law enforcement purposes.² However, there is no requirement that the explosive themselves contain tracer elements—markers or taggants—that could be used to assist preblast or postblast law enforcement.