Consensus Study Report
HigHligHtS
Reducing the Threat of Improvised
Explosive Device Attacks by Restricting
Access to Explosive Precursor Chemicals
November 2017
A lack of visibility and oversight at the retail level makes it possible for mali-cious actors to acquire chemicals that could be used to make improvised explosive devices, this report inds. Bulk quantities of the chemicals, which have many legitimate uses, are tracked through much of the industrial supply chain but there is less visibility and oversight as smaller quantities move further along the supply chain to retail, especially for use by the general public. This report prioritizes precursor chemicals that can be used to make home-made explosives, examines current domestic and international regulation of the chemicals, considers the role of voluntary actions, and compares economic, security, and other tradeoffs among possible control strategies.
An improvised explosive device (IED) is a type of unconventional bomb that can cause loss of life, injury, and property damage in both military and civilian environ-ments. Terrorists, violent extremists, and criminals (collectively referred to in this report as malicious actors) often choose IEDs because the ingredients, components, and instructions required to fabricate them are readily accessible. In many cases, the explosives in IEDs are made with chemicals that can be purchased legally from hardware, drug, and garden supply retailers, in brick-and-mortar stores, or online. How-to guides and videos for making homemade explosives and constructing IEDs are also widely available and transmitted on the internet.
Precursor chemicals have played an important role in past terrorist attacks in the United States, some involving large-scale IEDs, such as the truck bombings of the World Trade Center in 1993 and the Alfred P. Murrah Federal Building in Oklahoma City in 1995, and others involving smaller-scale, person-borne IEDs. After the Oklahoma City bombing, Congress placed attention on ammonium nitrate, a chemical principally used as an agricultural fertilizer, but also used in that attack. Numerous federal agencies (including the Department of Homeland Security, the Department of Justice, and the Environmental Protection Agency), state agencies, and voluntary programs managed by private organi-zations, oversee precursor chemicals in some capacity, but the majority do not focus on retail-level sales. In 2008, Congress called on the U.S. Department of Homeland Security to develop a plan to regulate the sale and transfer of ammonium nitrate to prevent its misappropriation or use in an act of terrorism and in 2011 the Department published a notice of proposed rulemaking for that purpose that remains under contention. However, ammonium nitrate is just one of several precursor chemicals that have been used in IEDs.
At the request of the U.S. Department of Homeland Security, the National Academies of Sciences, Engineering, and Medicine assembled a committee of experts to
consider opportunities to reduce the threat of IED attacks by restricting access to
precursor chemicals that can be used to make homemade explosives. The resulting report prioritizes the precursor chemicals that can be used to make homemade explo-sives, analyzes the movement of those chemicals through the domestic supply chain, and identiies potential vulnerabilities. The report’s authoring committee exam-ined current domestic and international regulation of the chemicals, considered the role of voluntary actions, and compared economic, security, and other tradeoffs among possible control strategies.
Precursor chemicals used to make
homemade exPlosives
The committee developed a prioritized list of precursor chemicals according to three criteria: (1) whether the pre-cursor chemical could be used in both vehicle-borne IEDs and person-borne IEDs, (2) whether the precursor chemi-cal had a history of use in IED attacks, and (3) whether the precursor chemical can be used to make homemade explosives independent of the presence of another spe-ciic chemical. On that basis, the committee established three groups of precursor chemicals—Groups A, B, and C—by order of priority (see Table 1). With one exception, chemicals that satisied all three criteria were placed in Group A, indicating the highest priority. Chemicals that satisied two of the three criteria were placed in Group B; and chemicals that satisied one of the three criteria in Group C. The committee stressed the importance of reevaluating the groupings periodically to address shift-ing threats and precursor chemical use.
Although this report focuses solely on precursor chemi-cals used to make homemade explosives, the majority of bombing incidents in the United States involve certain explosives—such as smokeless powder, black powder, lash powder, and pyrotechnic illers—likely due to their ease of legitimate acquisition. Thus, no strategy for restricting access to precursor chemicals can eliminate the threat of IED attacks as long as these other explosive materials remain accessible.
domestic chemical suPPly chains
The available data suggest that a malicious actor can acquire enough precursor chemicals to manufacture homemade explosives through legal purchases at retail outlets. The precursor chemicals sold at retail have legiti-mate uses, generally fall below regulatory thresholds in non-agricultural environments, and, as a consequence, are subject to little or no oversight as a security matter.
The committee concluded that retail-level sales present a substantial vulnerability in the supply chains under consideration. Retailers, especially those selling through internet commerce, have not been a major focus of federal regulation or of voluntary programs, except in a limited number of speciic circumstances and sectors, such as agriculture. Internet commerce presents additional challenges because of the anonymity of pur-chasers, ease of sharing information, and large volume of transactions.
Binary exploding target kits, which are used as targets for irearms practice, are also available from brick-and-mor-tar and online retailers and represent another noteworthy vulnerability. These kits contain precursor chemicals in the proper weights and physical forms—and instructions for use—to create an optimized homemade explosive that does not require either a commercial detonator or any other primary explosive to detonate.
international regulations
The report’s authoring committee assessed the regula-tions in place to restrict access to precursor chemicals in Australia, Canada, Singapore, the United Kingdom, and the European Union (EU) for insight into possible control strategies. Although the beneits of security regulations are dificult to track, authorities in the EU believe their
restrictions on access, which have included retail bans, licensing, and registries, have reduced the threat of attacks using IEDs made with precursor chemicals, albeit at some cost to commerce.
assessing PossiBle control
strategies
While the United States has not experienced an attack with a large-scale IED since the 1990s, the commit-tee stressed that deliberative thinking about possible control strategies is more effective than event-driven policy making in the aftermath of a crisis. Using the lessons learned from international regulations on precursor chemicals and related domestic policies in other arenas, the committee assessed possible control strategies that could include different combinations of mandatory and voluntary policy mechanisms, directed at retail sales to noncommercial end-users (i.e., the general public).
The committee considered trade-offs among secu-rity, economic, and other factors associated with a small set of possible control strategies. It assessed the strategies qualitatively in relation to three goals: (1) restricting malicious actors’ access to precursor chemicals, (2) gathering and disseminating informa-tion to prevent or respond to terrorist incidents, and (3) minimizing the burdens on legitimate commerce and use. In deference to the third goal, the committee did not consider restrictions on access for commercial end-users; in each case, a commercial purchaser, such as a housecleaning, pool, or spa service or beautician, would only be expected to provide evidence of com-mercial status to complete a transaction.
The committee considered four general types of control strategy, three of which featured a new control—either a ban, licensing, or a registry—and one which would not feature a new control, but would augment any existing controls with supplemental measures and activities, such as outreach, training, and reporting.
Overall, no single strategy emerged as a clear “best choice” during the committee’s deliberations on security, economic, and other tradeoffs. For example, the committee found the beneits of stringency might come at the price of forgone sales and use, displace-ment to other forms of terrorism, and commercial disruption. The committee lacked the time, resources, and directive from DHS to conduct a comprehensive and detailed analysis of policy options. Thus, this report constitutes a starting point, not an ending point for evaluating possible control strategies.
recommendations
The report’s authoring committee detailed six recom-mended courses of action and four research areas that merit future attention. The committee emphasizes the essential role of Congress in developing and imple-menting appropriate risk-reducing control strategies. Congress could, for example, be particularly instru-mental in ensuring that crisis-driven interests do not unduly inluence new laws or regulations.
Priority Precursor Chemicals
recommendation 1: Federal, state, local, and private-sector entities attempting to reduce
Copyright 2017 by the National Academy of Sciences. All rights reserved.
For More Information . . . This Consensus Study Report Highlights was prepared by the Board on Chemical Sciences and Technology based on the Consensus Study Report Reducing the Threat of Improvised Explosive Device Attacks by Restricting Access to Explosive Precursor Chemicals (2017). The study was sponsored by the Department of Homeland Security. Any opinions, indings, conclusions, or recommendations expressed in this publication do not necessar-ily relect the views of any organization or agency that provided support for the project. Copies of the Consensus Study Report are available from the National Academies Press, (800) 624-6242; http://www.nap.edu or via the Board on Chemical Sciences and Technology web page at http://www.nationalacademies.org.
Division on Earth and life Studies
the threat of IED attacks by restricting access toprecursor chemicals should focus on both person-borne and vehicle-person-borne IEDs.
recommendation 2: Federal, state, local, and private-sector entities attempting to reduce the threats from person-borne and vehicle-borne IEDs should consider multi-chemical, rather than single-chemical, strategies.
Strategies at the Retail Level
recommendation 3: Federal, state, local, and private-sector entities attempting to reduce the threats from person-borne and vehicle-borne IEDs should focus on retail-level transactions of precur-sor chemicals, especially e-commerce.
recommendation 4:Federal, state, local, and private-sector entities should explore strategies for harmonizing oversight of the sale and use of commercially available kits that contain precursor chemicals that are speciically designed to be com-bined to produce homemade explosives.
Analysis of Control Strategies
recommendation 5: U.S. Department of Homeland Security should engage in a more comprehensive, detailed, and rigorous analysis of speciic provisions for proposed mandatory and
committee on reducing the threat oF imProvised exPlosive device attacks
By restricting access to chemical exPlosive Precursors
victoria a. greenield (Chair), George Mason University; robert g. Best, Defense Threat Reduction Agency – JIDO; leo e. Bradley, LE Bradley Consulting LLC; John c. Brulia, Austin Powder Company (Retired); carrie l. castille, Independent Consultant; david g. delaney, University of Maryland; arthur g. Fraas, Resources for the Future; William J. hurley, Institute for Defense Analysis; karmen n. lappo, Sandia National Laboratories;
Becky d. olinger, Los Alamos National Laboratory; Jimmie c. oxley, University of Rhode Island; kevin F. smith, Sustainable Supply Chain Consulting; kirk yeager, Federal Bureau of Investigation; camly tran (Study Director), samuel m. goodman (Postdoctoral Fellow), Jarrett i. nguyen (Senior Program Assistant), National Academies of Sciences, Engineering, and Medicine
voluntary policy mechanisms to restrict access to precursor chemicals by malicious actors.
Voluntary Measures, Activities, and
Programs
recommendation 6:The federal government should provide additional support for voluntary measures, activities, and programs that can con-tribute to restricting access by malicious actors to precursor chemicals used to manufacture IEDs.
Research Priorities
In addition to the aforementioned recommenda-tions, the committee identiied several areas of research that could provide additional pathways for limiting access to precursor chemicals or designing appropriate regulations. Major topics for future research include:
