WASHINGTON -- Additives that improve detection of explosives before detonation or determine their origins after a blast are not yet practical enough for broad use in the United States, concludes a committee of the National Research Council in a new report. Nor is there a practical method available to neutralize the explosive properties of ammonium nitrate, a commonly available fertilizer that was used in the 1995 Oklahoma City bombing.
Instead, voluntary commercial controls and regulatory action, together with wider use of present methods for detecting explosives, offer the best means of reducing the threat from illegal bombings until better technologies can be developed, says the report, Containing the Threat From Illegal Bombings.
"Some of the proposed concepts for altering explosive materials are technically feasible, but their safety, effectiveness, cost, and environmental effects must be addressed before implementation can be recommended," said committee co-chair Marye Anne Fox, vice president for research and Waggoner Regents Chair in Chemistry, University of Texas at Austin. "The findings to date support the use of chemical markers only to improve detection of plastic and sheet explosives, which pose a considerable risk in facilities such as airports. Limiting criminal access to explosive materials and developing better methods to detect explosives are important strategies to deter would-be bombers and increase the chances they will be caught."
One key strategy is prohibiting the retail sale of the types of packaged ammonium nitrate fertilizers that can be detonated, unless consumers produce identification and retailers keep accurate records of transactions, the committee said. Although many common chemicals potentially can be used to make explosives into terrorist bombs, ammonium nitrate is by far the most accessible ingredient. It is produced in enormous quantities for fertilizer and for blasting agents used in mining and other industries.
In the wake of the 1993 World Trade Center and 1995 Oklahoma City bombings, the threat of terrorist attacks has become an issue of national concern. Congress asked the National Research Council to investigate technologies for tagging or physically altering explosive materials, and to examine the feasibility of controlling access to these materials to prevent terrorist attacks.
Explosive materials may be altered by mixing additives to make them more difficult to detonate, or by adding detection markers or identification taggants so their origins can be traced before or after detonation. Detection markers, such as chemical additives, can help law enforcement officers find explosives before a blast. Identification taggants -- for example, particulate additives containing coded information -- are used to determine a bomb's origins before or after detonation.
About 2,000 illegal bombings occur annually in the United States, but only a small percentage involve loss of life, injuries, or significant property damage. Although seldom used in such bombings, commercial "high explosives" -- which include dynamite and ammonium nitrate mixed with fuel oil -- can have devastating consequences, particularly in large bombs. The most frequently used materials are commercial "low explosives," such as gunpowder and fillers commonly found in fireworks. (Black and smokeless powders -- low explosives which are used in about one-third of all illegal bombings -- were excluded from the committee's study and are being similarly assessed by another National Research Council committee.)
A Strategy for Controlling Illegal Use of Explosives
The problem of illegal bombings is difficult to address from a policy perspective, the report notes. About 5 billion pounds of commercial high explosives are used annually in the United States for legitimate purposes, but the quantity used in illegal bombings is small. Policy measures that attempt to address the illegal use of explosives will inevitably impinge on everyday commerce, the committee said. Complying with new regulations also could be costly for the private sector and consumers. But if terrorist bombings were to increase substantially, the savings in lives, property damage, and enhanced security could justify the costs.
Given these concerns, the committee called for the federal government to sponsor research to develop safe taggants for possible future use and to be ready to adopt progressively stronger measures to deter terrorist bombings, based on federal policy-makers' assessments of threats to public safety. "The keys to this strategy are flexibility, and conducting rigorous testing and development of tagging technologies now rather than later," said committee co-chair Edward M. Arnett, Reynolds Professor of Chemistry Emeritus, Duke University, Durham, N.C. "Some policy measures could be put into practice at the present time, but others should be adopted only if the level of threat increases."
At Current Levels of Threat
After examining a variety of technologies for marking explosives using either detection markers or identification taggants, the committee recommended against broad-based implementation of a taggant program at the present time. However, it affirmed a recommendation by the United Nations' Council of the International Civil Aviation Organization (ICAO), which called for the use of chemical detection markers in plastic and sheet explosives to allow for better detection by currently available commercial equipment. After the 1988 downing of Pan Am Flight 103 over Lockerbie, Scotland, 34 countries, including the United States, ratified a convention requiring the marking of these explosives. The international convention must be approved by one more nation to enter into force, but already has been implemented by the United States.
The committee also recommended deploying explosive detection equipment more widely -- and developing better equipment to detect unmarked explosives -- in facilities other than airports, such as federal courthouses, large public buildings, and power plants. Cost, effectiveness, and assessed level of threat are factors that should determine the extent of installation throughout the country.
Although detection markers are being added to plastic and sheet explosives, the committee said further research on both markers and identification taggants is needed before implementation occurs in other types of commercial explosives, such as dynamite. Both approaches, while technically feasible, must undergo further testing to address concerns about long-term effects to the environment, economic costs, and safety issues.
Despite considerable international efforts to make fertilizer-grade ammonium nitrate less explosive or render it inert, the committee found that currently there is no practical method that would make the material considerably less explosive without seriously affecting its use as a fertilizer. More research is needed to develop such methods. Meanwhile, the government should develop standard tests to evaluate the extent to which any proposed additives can render ammonium nitrate-based fertilizers inert.
A federal licensing program should be adopted for restricting the purchase of commercial explosives, the committee said. Greater enforcement of existing regulations for securely storing explosives is necessary as well. State controls for purchasing explosives vary widely and federal regulations are lax compared with some countries.
In addition, the "Be Aware for America" program -- developed by the fertilizer industry and coordinated with the Bureau of Alcohol, Tobacco, and Firearms for sales of bulk nitrate fertilizers -- should be strengthened, the report says. This voluntary program, which encourages sellers to report suspicious fertilizer purchases, would benefit from more rigorous implementation and greater involvement with local and national law enforcement authorities.
Options if the Threat Increases
The committee also outlined actions that should be taken if the level of threat to public safety increases. Given an escalation of terrorist attacks against the public or the U.S. government, tagging some explosives, such as detonators, with detection markers may be a suitable emergency control. A program should then be implemented that utilizes the best available taggant technology. In addition, buyers would need to show identification to make bulk purchases of ammonium nitrate fertilizers and chemicals, such as sodium chlorate and potassium perchlorate, that can be used to make explosives. Vendors would need to keep records of such purchases.
If the threat of terrorism were to increase greatly, other measures should be considered, such as adding ultra low-level, radiation-emitting detection markers to plastic explosives and detonators and establishing a program using the best available technique for making fertilizer-grade ammonium nitrate less explosive or completely inert. Both approaches, however, would require considerable research and development before they could be workable. Increased controls on commerce would be necessary as well. Sellers would need licenses and buyers would need permits to purchase nitrate-based fertilizers and chemicals such as sodium nitrate and potassium chlorate.
In parallel with this strategy of progressively stronger measures for tagging and regulating explosives and making them inert, the report also recommends instituting a single national databank to record incidents involving stolen explosives and criminal bombings. Federal and law enforcement agencies already collect some of these data, but a single source with uniform, detailed information would be valuable in developing a broad-based approach to suppressing illegal bombings nationwide.
The study was funded by the U.S. Department of the Treasury. The National Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering. It is a private, non-profit institution that provides science and technology advice under a congressional charter.
*Copies of Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors are available from the National Academy Press; tel. (202) 334-3313 or 1-800-624-6242. The cost of the report is $45.00 (prepaid) plus shipping charges of $4.00 for the first copy and $.50 for each additional copy. Reporters may obtain a copy from the Office of News and Public Information at the letterhead address (contacts listed above).