Should conventional terrorist bombings be considered weapons of mass destruction terrorism?

Since weapons of mass destruction (WMD) are typically thought of as chemical, biological, radiological, or nuclear (CBRN) weapons, the designation of conventional bombings as WMD terrorism under US law has generated controversy and can affect how policymakers plan for future attacks. Using quantitative data on terrorist attacks, federal planning documents, and the academic literature, we argue that placing the conventional terrorist bombings in the same legal category as CBRN terrorism confuses two distinct terrorist threats with different risks of occurrence, casualty profiles, consequences, and emergency response requirements. We explore the logical and practical reasons why such threat conflation could create policy problems. We conclude that the current definition of WMD terrorism under US law that aggregates conventional terrorist bombings with CBRN terrorism should be revised.