F Summary of European Site Visit

From April 5 through 11, 1997, six members of the Committee on Marking, Rendering Inert, and Licensing of Explosive Materials traveled to Zurich, Switzerland, and London, England to learn from Swiss and British authorities about their experiences with the four areas specified in the committee's assigned task, especially the Swiss experience with tagging explosives and the British experience with controlling use of ammonium nitrate (AN) for large urban bombs. Perhaps the most valuable information gathered by the subcommittee related to the conclusions of the Swiss and the British about the efficacy of their strategies to control harmful and illegal uses of explosives. This information provided a basis for evaluation of the relevance of these strategies to addressing real and publicly perceived bombing threats in the United States.

VISIT TO SWISS SCIENTIFIC RESEARCH SERVICE1

Introduction

From April 7 to 9, 1997, the delegated members of the Committee on Marking, Rendering Inert, and Licensing of Explosive Materials2 met with Swiss Scientific

1  

 For additional information on the Swiss taggant program, see Schärer (1995).

2  

The delegated members were Edward M. Arnett, Alexander Beveridge, Robert B. Hopler, David W. McCall, Alexander MacLachlan, and Jimmie C. Oxley. Staff members Douglas J. Raber and Tracy Wilson also attended the site visits to support the committee.



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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors F Summary of European Site Visit From April 5 through 11, 1997, six members of the Committee on Marking, Rendering Inert, and Licensing of Explosive Materials traveled to Zurich, Switzerland, and London, England to learn from Swiss and British authorities about their experiences with the four areas specified in the committee's assigned task, especially the Swiss experience with tagging explosives and the British experience with controlling use of ammonium nitrate (AN) for large urban bombs. Perhaps the most valuable information gathered by the subcommittee related to the conclusions of the Swiss and the British about the efficacy of their strategies to control harmful and illegal uses of explosives. This information provided a basis for evaluation of the relevance of these strategies to addressing real and publicly perceived bombing threats in the United States. VISIT TO SWISS SCIENTIFIC RESEARCH SERVICE1 Introduction From April 7 to 9, 1997, the delegated members of the Committee on Marking, Rendering Inert, and Licensing of Explosive Materials2 met with Swiss Scientific 1    For additional information on the Swiss taggant program, see Schärer (1995). 2   The delegated members were Edward M. Arnett, Alexander Beveridge, Robert B. Hopler, David W. McCall, Alexander MacLachlan, and Jimmie C. Oxley. Staff members Douglas J. Raber and Tracy Wilson also attended the site visits to support the committee.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors Research Service (SRS) personnel Kurt Zollinger (head of the SRS), Konrad Schlatter (technical director of SRS), Jürg Schärer (head of the taggant program at SRS), Urs Hilfiker (scientific staff member involved in the taggant program at SRS), and Brigitte Hilfiker-Boller (support staff member involved in the taggant program at SRS), and with Claude Muller of the Swiss Federal Police in Bern, the agency that oversees the Swiss taggant program. For historical reasons,3 all explosives forensic services are provided by the 15-member staff at the SRS in Zurich, working closely with law enforcement officials. There are four analytical chemists and two laboratories equipped with atomic absorption, liquid chromatography, optical microscopy, differential scanning calorimetry, x-ray fluorescence, and high-performance liquid and ion chromatography instruments. The Swiss provided introductory briefings on their Federal Law on Explosive Materials and then responded, through roundtable discussion, to committee members' questions on detection taggants, identification taggants, rendering common chemicals inert, and imposing controls on precursor chemicals used to manufacture explosive materials. They also provided a tour of their forensic laboratory to demonstrate the steps in their taggant program, and they hosted a visit to the Schweizerische Sprengstoff AG Cheddite explosives plant in Isleten (see Box F.1). The Swiss are unique because of their long-standing use of taggants in explosives manufactured for use in Switzerland. From the subcommittee's 2-1/2-day visit it was apparent that the Swiss have learned valuable lessons related to implementing and carrying out their taggant program. Summarized below are the points that seemed most significant in relation to the committee's task. Background Switzerland has 7 million people and an area of 15,940 square miles (it is approximately the size of Massachusetts, Connecticut, and Rhode Island combined) and is composed of 26 cantons. Zurich is the largest city, with 350,000 people. Bern is the Swiss capital. The country is very mountainous—60 percent of it is in the Alps (in the south) and 10 percent is in the Jura mountains (in the north), with most of the population living in between. There are three official languages, with 70 percent of the population speaking German, 20 percent French, and 10 percent Italian. There are three explosives manufacturers in Switzerland: one that makes ammonium nitrate (AN)-based explosives only (Swiss Blasting AG, Bülach/ZH); one that makes AN-based explosives, pentaerythritol tetranitrate (PETN), and 3    Jakob Meier of Zurich initiated the use of bomb forensics in the 1960s.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors BOX F.1 Visit to Schweizerische Sprengstoff AG Cheddite Explosives Plant Hosts: Markus Sigrist (plant manager), with Urs Hilfiker, Jürg Schärer, and Brigitte Hilfiker-Boller The factory was founded in 1872 to build the St. Gotthard Tunnel. Alfred Nobel set it up on an island that had been the site of a paper plant and before that a prison. There was no road to access this plant, and transportation via boat was required until 1951. The factory made the blasting explosive cheddite (chlorate) during World War I, hence the plant's name. Today, the plant makes several products: 90 percent dynamites, 10 percent ammonium nitrate/fuel oil (ANFO), and small amounts of pentaerythritol tetranitrate (PETN)-based plastic explosive. (The PETN-based material does not require addition of the International Civil Aviation Organization (ICAO) markers because it is 50 percent PETN and 5 percent nitroglycerin (NG) and nitroglycol and is thus already detectable. PETN is supplied by another Swiss manufacturer. Although it is an explosive. PETN is not tagged because it is not used except as a mixture.) These materials are made at the rate of about 500 kg/month or 6 tons/year and used as mudcapping explosives to break up big boulders. Ammonium nitrate (AN) is usually purchased from Dyno Nobel Sweden (the committee members saw some French material as well), and nitrocellulose (NC) comes from the Czech Republic. NG and nitroglycol are made on site. The ratio of NG to nitroglycol depends on cost and use. Generally, glycerin is more expensive than glycol, and so a 50/50 or 25/75 mix is made. The committee viewed the continuous NG/nitroglycol manufacturing setup. Stainless steel containers were used, but an operator had to manually start, stop, and check hourly. plastic explosives that are 85 percent PETN (SSE Gamsen, Brig/VS); and the Schweizerische Sprengstoff AG Cheddite plant, which makes AN, dynamite, and plastic explosives that are 50 percent PETN. There is also one military explosives factory (Ems-Dottikon, Dottikon/AG), as well as one black-powder mill (Pulvermühle, Aubonne/VD). Switzerland uses 4,000 to 5,000 metric tons (8.8 million to 11 million pounds) of commercial explosives annually, of which 20 percent is dynamite. (Note: The United States uses approximately 5,000 million pounds of AN and 100 million pounds of dynamite annually.) The Swiss have virtually no mining industry. Bombing Threat in Switzerland In the 1960s, the Swiss recorded their first terrorist incident—a bombing by farmers. Then, from the late 1960s until the early 1980s, Switzerland experienced a number of terrorist incidents. In February 1969, an El Al plane was attacked by Palestinians with automatic rifles and hand grenades. They carried three improvised explosive devices (about 7 pounds each) but were unable to place them on

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors Step 1. Last run's (2 runs a week; 4 tons/day) spent mixed acid is stirred and cooled, and glycerin/glycol mix is added dropwise. Step 2. Top fraction is allowed to run into a wide, fast mixer. The organics are 1.5 g/cc, and the spent acids (H2SO4, 10% HNO3) are 1.6 g/cc. Steps 3 and 4. Top fraction of organics runs into first wash station, where it is washed with Na2CO3 and water; then into the second wash station for water wash. Compared with pure water, the organic layer is denser and goes to the bottom. Step 5. The organics flow into a wide washer where the pH is checked; if it is not between pH 6 to 8, an alarm is set off. Step 6. Finally the product goes to a mixer where it is emulsified with water so that it does not flow out of the building as a pure material. In the next building there is a three-story distillation apparatus to separate spent acids. At the top, the acids are heated to 130 °C to decompose any remaining organics; then H2SO4 and HNO3 are separated and stored for sale to other manufacturers (nitric acid to the military munitions factory). Water/NG/nitroglycol emulsion is separated and hung in large stainless steel tanks (2 tons each in 3 tanks). Then pure material is taken (by hand or buggy) to the mixing house for processing. To mix dynamite, NG/nitroglycol mix is first put into a mixing bowl, and nitrocellulose is added and stirred to give a pre-gel. Then wood meal, aluminum, and any other component are added, and then AN. Finally tags are added. They add about 0.13 SFr/kg or about $0.08/kg to the cost of the explosives. Tagging dynamite requires about 3 hours per 2 months and adds about 5 percent to the price of the dynamite, which sells for 2 to 4 SFr. Tagging ANFO adds about 13 percent to the cost of these products, which sell for 1 to 2 SFr/kg. the plane. Then, on February 21, 1970, a bomb blew up on a Swiss Air flight leaving Zurich. The plane attempted to return to the airport but did not make it due to the smoke from the explosion; 40 people died. The police found an altimeter and dynamite traces as residues of a bomb. In Switzerland in the 1970s, a group protesting nuclear power used high explosives in an attack on a nuclear information center and on many power transmission poles. In one case the device used four sticks of dynamite and two alarm clock timers set up so that the timers would be destroyed. There was also an Armenian separatist movement that set off four bombs in four days (July 19-22, 1981, in Bern, Zurich, Lausanne, and Geneva). The devices were composed of 150 grams of plastic explosive with lighter-fluid strapped around it to create a fireball. Finally, on April 21, 1980, an intact bomb was found at the airport of Zurich during the check-in to an El Al flight. Because the man with the suitcase had a passport with a Boston stamp but obviously knew nothing about Boston, he fell under suspicion and a detailed search of his suitcase was conducted. The x-ray showed wires and detonating cord hidden under the lining. During the render-safe

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors procedure, the device exploded. The reconstruction showed an estimated charge of 1.6- to 1.8-kg PETN detonating cord. During this period, Germany was having severe terrorist problems. Switzerland was criticized for its lax approach to the sale and storage of explosives, which neither farmers nor commercial companies were required to lock up. (Most other countries had instituted laws around 1880 requiring that explosives be stored in secure magazines.) Today, terrorism is only a minor problem in Switzerland, due largely to the absence of internal or external militant groups with grievances against the government. Each year, the SRS conducts approximately 500 ''actions" involving explosives. These include testing explosives for manufacturers, finding explosives, and recovering stolen explosives, among others. The actual number of bomb attacks is quite small (Table F.1).4 The Swiss have had neither car bombings nor use of a large fertilizer-based bomb. Over the 5-year period from 1989 to 1994, one person was killed by a bomb. As in the United States, shooting powders and pyrotechnics are the major formulations used in bombing incidents; the targets in such events are usually mailboxes, phone booths, safe crackings, or single acts of revenge. The estimated annual cost for mailbox and phone booth damage is 200,000 to 500,000 Swiss Francs (SFr) (approximately $135,611 to $339,0295). Swiss Laws to Control Explosives On March 25, 1977, the Swiss passed the Federal Law on Explosive Materials, and on March 26, 1980, they passed the enabling regulations, the Order Concerning Explosive Materials. The law put into effect several measures, including the following: Licensing for purchasers and users of various explosives, Requirements to make storage for explosives secure, and Introduction of identification taggants into various explosives. The main changes in the law and regulations included (1) making all purchasers and users of explosives take an explosives course and pass an examination6 to 4    Safe crackings using explosives are counted in the data, but modern safes are made without keyholes and thus are no longer cracked by explosives. 5    At the exchange rate in February, 1998, of 1.4748 SFr to $1 U.S. 6    Private companies certified by the Federal Bureau of Education (BIGA), rather than the police, give the training course. The price of 900 to 2,500 SFr drove many small users such as farmers away from using explosives on their own. Specialty courses are also offered on topics such as metal working and destruction, big-borehole blasting, underwater explosives, and building demolition, with prices ranging from 600 to 1,900 SFr.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors obtain a license,7,8 and mandating that explosives be purchased in the local canton and that sales records (name and signature required) be kept for 5 years;9 (2) mandating that all storers of explosives lock them up in magazines (large users) or day boxes (small users)10—this law intentionally reduced the number of explosives retailers from 200 or 300 to fewer than 50; and (3) requiring that materials manufactured for use as explosives (dynamites, slurries, water gels, ammonium nitrate/fuel oil (ANFO), black powder for blasting) be tagged.11 Neither military materials nor exported explosives are tagged, but imported explosives are.12 7    The license is good for a lifetime. A license is valid for purchase of explosives only in the canton where it is issued. When a customer buys explosives, he must specify a reason for use and when the explosive will be used. When that date has passed, the material must be returned. There are three levels of licensing: (1) for surface blasting in less endangered areas with a limited number of charges (maximum 5) and amount of explosives (maximum 5 kg) and other restrictions; (2) for surface and underground blasting in areas with little risk and with a limited number of charges (maximum 19) and amount of explosives (maximum 10 kg) and other restrictions; and (3) for operations involving planning, carrying out, or allowing the carrying out of blasting jobs with no restrictions on numbers of charges and amount of explosives, in areas with high risk and under the supervision of a blasting expert (articles 22 through 26). 8    No license is required to buy black powder for shooting. In fact, retailers are not allowed to ask for identification, only for a name and address. The Swiss speculated that with no requirement to ask for identification, the retailer has no responsibility. (Smokeless powder has not played any significant role in explosive incidents in Switzerland. Asked if they would like shooting black powder tagged, the Swiss said no, primarily because of technical problems.) 9    When a customer wants to buy explosives, he takes his license to the canton police with a request form. The police verify the license and approve the application. The purchaser takes the application to the explosives retailer, who fills the order and sends a slip with the name of the customer, material, and amount purchased back to the canton police. The retailer does not specify the date-shift code of the explosive on the receipts. The retailer is required to keep sales records for 5 years (as is the manufacturer); the police have their own requirements to follow. However, the SRS assumes that all will keep records longer so that if taggants found in an explosive are identified as having come from a particular manufacturer roughly 10 years ago, it may be possible to find the retailer who received it and thus all buyers of the product. This system is not designed to provide information on a chain of custody such as that kept on paper in the United States or Canada (Canada also indicates chain of custody on the original packaging). 10    The first time a license is used, the canton police inspect the storage facility. 11    The law also specifies what does not have to be tagged: (1) materials requiring air or oxygen to detonate, (2) materials made only transiently as intermediates to some other product, and (3) materials that are explosives but are not manufactured with the intent that they be explosive. Thus, smokeless powder, black powder for shooting, ammonium nitrate fertilizer, and AN-based explosives mixed on site are not tagged, nor are explosive precursors or pyrotechnics. However, a farmer using fertilizer-grade AN to blow up stumps is violating the law. 12    The manager of the explosives plant that the delegation visited (see Box F.1) reported that he sent the taggant he wanted used to the non-Swiss company from which he purchased explosives.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors TABLE F.1 Details on Bombings in Switzerland, 1989-1994   1989 1990 1991 1992 1993 1994 Total Bombings 10 10 5 31 23 7 Persons Killed 0 0 0 0 1 0 Energetic Material Used             Flammable liquid 0 1 0 1 0 0 Dynamite             Untagged 3 4 4 4 5 1 Tagged 0 2 3 2 2 1 Black powdera             Untagged 7 7 9 15 13 10 Tagged 0 0 1 0 0 0 Smokeless powder 2 0 1 3 1 0 Pyrotechnics 20 19 26 3 4 2 Chemicals 5 12 1 4 1 0 Blasting agents 2 0 1 0 0 0 Military explosives (including grenades) 4 4 2 3 3 3 Target             Residential 8 9 7 2 4 2 Commercial 10 7 11 7 8 2 Vehicles 1 2 3 5 6 2 Mailboxes 13 15 11 3 1 2 Utilities 7 14 11 13 5 1 Form of Explosive             Pipe bomb 10 10 6 9 9 7 Dynamite sticks 1 5 4 4 0 0 Bottles 1 2 1 3 1 3 a Black powder for blasting purposes is tagged; black powder for sport shooting is not. Although the regulations for controlling explosives are administered at the federal level, the cantons control the details of licensing, storage, transport, and enforcement. Following the implementation of these regulations, the incidence of high-profile bombings in Switzerland fell to zero. Nuisance bombings (e.g., of mailboxes and individual automobiles) continued, but at a reduced level. Markers for Detection Military explosives are not tagged; the Swiss military was strongly against such a requirement, and criminal use of stolen military explosives has never been much of a problem in Switzerland. In 1991 the International Civil Aviation

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors Organization (ICAO) mandated use of detection markers, and the Swiss, like the United States, chose to use 2,3-dimethyl-2,3-dinitrobutane (DMNB) for military and sheet explosives and para-mononitrotoluene (p-MNT) as a possible marker for commercial plastic explosives. As part of an ICAO experiment, the Swiss used detection markers in emulsion explosives but detected explosives workers and people using heart medicine, not criminals. (Two individuals caught coming into Switzerland with unassembled plastic explosives strapped to their bodies were caught because they acted suspiciously, not because of a detection system.) Taggants for Identification By law, identification taggants used in Switzerland must have fluorescent and magnetic marking and must indicate manufacturer and period of manufacture. However, other taggant concepts could be acceptable provided that they could be found and analyzed postblast. Three identification taggants are used in Switzerland by domestic explosives manufacturers and by foreign manufacturers who import explosives into the country: The Microtrace (formerly 3M) taggant—a fluorescent, magnetic, melamine resin, 9-layered particle in 7 colors; A Swiss version of the above taggant (developed by Swiss Blasting AG, Bülach, Switzerland), called HF6 (with 5 layers); and A Swiss-developed taggant (produced by Plast Laboratory, Bulle, Switzerland) called Explotracer that consists of orange polyethylene chunks permeated with fluorescent markers, imbedded iron particles, and rare-earth oxides. The taggant is analyzed via x-ray fluorescence and by its melting point. This is cheaper, but more taggant is needed because it is less capable of survival. It cannot be used in plastic explosives or explosives that have high heats of detonation. All three are about the same size (16 mesh, 1,190 microns).13 The United States has used a taggant concentration of 0.05 percent, but the Swiss use 0.025 percent in commercial dynamite and AN-based materials and 0.05 percent in commercial plastic explosives (PETN-based). In some cases up to 0.1 percent is used. For example, Microtrace taggants in plastic explosive are used at concentrations of 0.05 percent because fewer survive in such a high-temperature event. 13    16-mesh taggants provide 3 million particles per pound; the smaller 80-mesh (180-micron) size yields 15 million taggants per pound, thus providing more detectable material at the same concentration. (AN prills are between 8 and 20 mesh.)

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors (Particles do crack during detonation, but tend to crack across the grain of the color code, leaving it intact, rather than breaking off pieces of the code.) For the Microtrace and HF6 taggant, the code is easily read with a microscope in the laboratory; for the Explotracer, differential scanning calorimetry shows whether the chunk is high-or low-density polyethylene, and x-ray fluorescence identifies the rare-earth elements. The Microtrace taggant is the most expensive of the three, and the smallest batch size available is 3.75 kg (10 lb). There is no price break for large-volume purchases.14 The SRS uses three tests of survivability to evaluate the taggants in new batches of explosives. One is to detonate 100 g of cartridged product 50 cm in the air with a 25-m2 polyethylene sheet under it. There must be 10 tags on the sheet within 1 m2 of the center of the explosion. Occasionally, the SRS finds a wrong tag (owing to the batch changes at 6-month intervals), but 1 out of 10 is acceptable. Every time the tag changes or a new product is run, the manufacturer collects a sample of each product and ships these to the SRS. The SRS opens up the cartridge, takes out a sample, extracts it with acetone, and recovers multiple taggants. These are examined to see if they agree with the manufacturer's records, and then the tags are preserved. A portion of the cartridge is stored in a screw-cap glass jar, and the cartridge wrapper is also saved; the rest of the cartridge is stored in a magazine elsewhere. No safety problems have been attributed to the use of taggants. Introduction of the taggants caused a price increase for tagged explosives of about 10 percent, but never more than 20 percent. The postblast information provided by the taggant is the manufacturer of the explosive and the date (period) of manufacture. One of the important lessons learned by the Swiss from their long-standing taggant program is that it is best to do the taggant search and analysis in a well-equipped laboratory.15 Thus, the police do not look for taggants at the scene of a bombing; instead, SRS personnel ask to be invited to the site of a large bombing, and they use a standard collection protocol. If they do not find taggants—they must find at least 10—they conclude that an untagged explosive (pyrotechnic, military, improvised, old explosive) was used. Reports are then sent to the canton police for use in finding the criminals or helping the prosecutors. At detonation, light materials such as paper wrapping and taggants are sucked into the bomb crater by a rarefaction wave. Heavy materials like timer parts are ejected far away. The SRS personnel collect samples near the crater center (3- to 14    The manufacturer of both the Microtrace and HF6 indicated that the price would not be lower if there were fewer colored layers. 15    However, they gave two examples of taggants having been found at the scene by the SRS. In the first, involving an explosive set off in a fountain, the taggants' fluorescence helped in locating them. In another case, a transformer was blown up and a magnet had to be used to find the taggants in the liquid phase.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors 5-m radius), vacuuming right at the center and sieving remains into four fractions ("riddles"). The smallest riddle is separated by magnetic attraction, and the magnetic portion is put into a density-controlled solution. Microtrace and HF6 float in saturated ZnCl2 solution, whereas Explotracer floats in saturated NaCl solution. After separating the Microtrace or HF6 tag, the SRS personnel put the tag under a microscope and read the code. The SRS checks its records and explosives sample and asks the manufacturer to whom that batch was sold. Chemical analysis of residue is also done. Analytical chemistry is done using thin-layer chromatography, high-performance liquid chromatography, ion chromatography, spot tests, and atomic absorption, as well as capillary electrophoresis. The Swiss SRS forensic staff are accustomed to using the Microtrace taggants and like the fact that reading the code is as simple as using a microscope. The Explotracer taggant requires more analysis: differential scanning calorimetry must be run to obtain the melting point of low-or high-density polyethylene (112 °C or 130 °C) and x-ray fluorescence must then be used to identify the rare-earth element. Also the design of the Explotracer tag allows for fewer possible permutations and thus has a lower maximum information content than the Microtrace tag. The SRS does not preclude the use of other approaches,16 but all taggant concepts must have well-thought-out collection, isolation, and analytical protocols worked out as a system. Manufacturers maintain records from tagging for 5 years, but the SRS maintains samples of actual explosives for 15 years, along with the corresponding records. Swiss taggant regulations require only information on the manufacturer and the 6-month interval during which the explosive was manufactured. The interval may also be determined by the volume of explosive material produced, ending after 150 to 300 tons of manufacture, and thus may be shorter.17 Within the period of time or the volume of production mentioned, many different types and forms of explosives may have been manufactured with the same taggants. Early in the taggant implementation period, the Swiss specified that each type of explosive be uniquely identified but found that manufacturers could not accurately deal with this complexity—often, they ended up with two different tags in one product—and so dropped this requirement after 2 years. The Swiss authorities apparently work closely and cooperatively with their manufacturers. Reference was often made to arriving at "gentlemen's agreements" as details of the taggant program were worked out over the years. 16    The SRS tests new taggants, products, formulations, and imports to see if taggants survive. There is no charge for this service. 17    Importers can bring in 10 to 15 tons with one taggant, changing tags with the next shipment. Imported explosives are generally tagged by lot. The next lot will have a different tag. It was reported that this procedure may soon become a written revision to the Swiss regulations.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors TABLE F.2 Bomb Attacks in Switzerland, 1984-1994   Number of Cases Number Solved Percent Solved Total 254 54 21.3 Without Taggants 191 31 16.2 With Taggants 63 28 44.4 Note: The Swiss readily admit that the explosive materials employed 20 years ago by the external terrorist groups could not be stopped by taggants as used today in Switzerland. All those previous bombs used explosives made in the terrorists' sponsoring countries. The Swiss police are supportive of the use of taggants for forensic purposes. Taggant information is considered useful in the investigation of bombing incidents, particularly in identifying stolen explosives and connecting domestic, serial criminal bombing incidents that use commercial explosives. From 1984 to 1994 in Switzerland there were 187 incidents involving use of improvised explosive devices and 71 safe breakings. The Swiss Federal Attorney's office reported the successful resolution of 44.4 percent of the cases (23 involving improvised explosive devices and 31 safe breakings) in which tagged explosives were used, but only 16.2 percent of the cases involving untagged explosives (Table F.2). Changes or Improvements to Their Program Sought by the Swiss When asked what they would like to see changed or improved with respect to the taggant program, the SRS personnel listed the following: Reducing the cost of taggants so that a higher concentration can be used. The cost of tagging Swiss AN-based explosives is about 13 percent of the selling price. The Swiss would like to raise the concentration of taggant from 0.025 to 0.05 percent to make it easier to find in postblast residues. At the moment, they consider the current level marginal for effective taggant recovery; Requiring manufacturers and sellers to keep records as long as the police do, that is, 15 years; Requiring better record keeping by distributors (thus creating a chain of custody); Changing taggants more often—every 3 months, rather than every 6 months; Considering adding identification tags to military explosives. However, vapor-detection taggants have not yet been added to existing military explosives.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors The cost for this retrofit program is estimated at 3 million SFr. Military explosives do not appear to be a significant part of the criminal bombing problem, and so there is little incentive to support tagging of military explosives; Developing a method for tagging detonating cord so that taggant material survives the blast; Tagging detonators and fuses with a detection marker, like 60Co. However, this approach was reported to be publicly unacceptable; and Considering other tagging possibilities for gunpowder and propellants. Additional Observations Swiss law requires that safety fuse, detonating cord, and detonating flex (shock tube) be marked as to manufacturer and year and month of manufacture.18 Safety fuse (wrapped black powder) and detonating cord (wrapped PETN) have colored threads woven in that, although they never survive the functioning of detonating cord, do help identify found and stolen material. The Swiss do not make shock tubes (hollow plastic tubes coated with HMX/Al), although some are imported; there has never been any attempt to mark shock tube material. The law specifies that electric detonators and blasting caps shall also be marked as to manufacturer, and year and month of manufacture but the Swiss do not make these products either, and so this regulation is not enforced. The Swiss do not tend to use trinitrotoluene (TNT) or pentolite boosters, and so these also are not marked. During the subcommittee's visit it was reported that as part of pending revisions to their regulations for explosives, the Swiss may delete that part of the law requiring tagging of shock tubes. They might also add wording outlining the present "gentlemen's agreement" requiring that manufacturers use a given amount of taggant and that they change the tag they use on a given time scale. Rendering Explosive Materials Inert Switzerland's single ammonium nitrate plant makes fertilizer-grade AN. Explosive-grade AN is imported. There is no effort to render the AN inert, although a small percentage of material is added to suppress AN's fire hazard potential. Like the British, the Swiss do not sell pure AN (34 percent nitrogen), only AN fertilizer that is 27.5 percent nitrogen. There are no Swiss laws on this subject. The plant makes five types of solid AN and one liquid: AN + slate, AN 18    Packages of commercial explosives are marked with an expiration date. After expiration, the manufacturer is required to destroy the explosives but is occasionally given permission to rework the material. Thus, two different taggants may be mixed together during this process.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors + MgSO4, AN + dolomite (Mg, CaCO3), AN + limestone, and AN + sodium borate; the AN in solution with urea and water is 30 percent nitrogen. The SRS forensic group knew of only one bombing case involving AN fertilizer—20 years ago, a pipe bomb with 2 kg of AN mixed with aluminum paint was planted in Geneva by foreigners. Recently there were two TATP incidents involving students who were experimenting. Controls on Precursor Chemicals In the period from 1985 to 1995, 75 cases in Switzerland involved the use of improvised explosives or pyrotechnics. The SRS has no direct control over explosive precursors, but the Chemical Toxins Act provides for control of poisons. Under this act, chemicals are classified according to their LD5019 in one of five classes; the most lethal materials, those with the lowest LD50, like cyanides, are in class 1; nitric acid is in class 2. Class-1 and class-2 chemicals can be purchased, but the buyer must have a license and prove that he or she is trained. However, it sounded to committee members as if there was an exception for purchasing small amounts. Materials like the high-energy chlorates and permanganates are class-3 materials for which the name, signature, and address of the purchaser are required. However, no identity card is needed, and fraud would therefore be difficult to detect. Materials can be ordered by phone but then must be picked up. Nitrates (Na, K, NH4) and red phosphorus are class-4 chemicals; the only requirement for their purchase is that the person be responsible (e.g., not be a small child). Tracing the movement of explosives from purchaser to purchaser is not possible with the current level of Swiss documentation. VISIT TO THE BRITISH MINISTRY OF DEFENCE20 Introduction On April 10 and 11, 1997, the six-member delegation of the committee met with members of the British government, including the following: Sir David Davis (Chief Scientific Adviser to the Ministry of Defence), Jim Platt (Assistant 19    LD50 (lethal dose 50 percent) is a common measure of acute (single exposure) toxicity. The LD50 of a substance is the dosage (when given orally, injected, inhaled, or applied dermally) that will cause death in 50 percent of a set of test animals (usually mice or rats, but sometimes dogs, monkeys, or other animals). The amount required to kill individual animals is related, approximately, to their body weight. Therefore, LD50 figures are reported in milligrams of the test substance per kilogram of body weight of the test animal. The lower the number, the more toxic the substance. 20    For additional information on the British experience and program, see also the following papers from the Compendium of Papers of the International Explosives Symposium (preliminary proceedings of the International Explosives Symposium hosted by the Bureau of Alcohol, Tobacco, and Firearms, Sept. 18-22, 1995, in Fairfax, Va.), Bureau of Alcohol, Tobacco, and Firearms, Washington D.C.: (1) "Overview of United Kingdom Research" by T.P. Donaldson, pp. 116-117; (2) "Research into the Deposition of Fertilizer Particulate" by T.P. Donaldson, pp. 118-121; (3) "UK Experience of Large Urban Vehicle Bombs on the UK Mainland and Measures Taken to Protect the Public Against Them" by Peter J. Hubbard, pp. 122-128; (4) ''A Review of Techniques Examined by UK Authorities to Prevent or Inhibit the Illegal Use of Fertiliser in Terrorist Devices" by Brian Foulger and Peter J. Hubbard, pp. 129-133; (5) "Post-Blast Analysis; the Forensic Response" by G.T. Murray, pp. 134-140; (6) "The Terrorist Development of Improvised Explosives in Northern Ireland" by G.T. Murray, pp. 141-144; and (7) "Additives to Aid Detection and Tracing of Explosives" by Brian Foulger, pp. 145-147.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors Director Science [Land], Ministry of Defence), Mark Stroud (Scientific Adviser for Counterterrorism, Ministry of Defence), and Bob Perry (Chief Scientist [Chemical], Defence Evaluation and Research Agency). The meeting on April 10 was primarily a courtesy call on Sir David Davis; the technical discussion with the other representatives on April 11 included British responses to questions that the committee had submitted before its visit. Bombing Threat in England and Northern Ireland Bombings in England and in Northern Ireland are predominantly the work of the Irish Republican Army, which currently operates via a form of rules of war; for example, warnings are provided, accompanied by a code that verifies their legitimacy. The intent is not to kill large numbers of people but rather to disrupt the life of British citizens as much as possible. This approach suits the goals of the organization and ensures continuing financial support from friendly countries, although the approach could change. The bombing campaign has been active since 1971. The bombs employed range from small devices fashioned from high explosives stolen or provided by foreign sources to large, improvised devices based on AN.21 Legislation was passed in 1972 to limit the nitrogen content of AN fertilizer to 27.5 percent in both Northern Ireland and in the Republic of Ireland, based on evidence that this degree of dilution (with limestone or dolomite) made AN difficult to use in the preparation of explosives. However, bombers found ways to convert the modified AN, called calcium ammonium nitrate (CAN), into bomb-making material. Detonators available through international sources as well as improvised detonators have been used. Ministry of Defence officials regard a decision to make explosives as a measure of the program's success in making commercial explosives too 21    Originally, the British problem was simpler; terrorists were using commercial explosives that were easy to detect because they contained EGDN or were small (with use of AN, the volume of explosive increased from beer-keg size to a lorry-full). The British believe that they have so effectively controlled commercial explosives that the terrorists are now forced to make their own.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors hard to buy or steal. They also think that their conversion of Irish agriculture from AN to CAN resulted in fewer bombing incidents. However, there is no denying that determined bombers have the capability to make and deliver bombs of considerable power. Aside from those of the Irish Republican Army, the British have few criminal bombings and at present no international terrorists targeting them. They do have some bombings on their soil by terrorist-sponsoring countries attacking their enemy embassies. The only other terrorists who rated mention were those in a loosely organized group called the Animal Liberation Front. Markers for Detection The British see little value in using any detection markers other than those endorsed by the ICAO for military plastic explosives. It is thought that improvements in detector performance are likely to make taggants less relevant. The British are concentrating their effort on trace detection of explosives rather than use of detection markers. Detection markers are difficult to implement against vehicle-borne bombs. However, a way to screen vehicles rapidly at a distance for AN would be useful if the level of certainty attainable were 100 percent. The British questioned the usefulness of markers, aside from political expedience, asking, for example, "What do you do with the information provided?" They believe that detection markers may require two types of detectors: one for the marked and one for the unmarked explosive. They also believe that vapor markers can be readily baked out of an explosive. Finally, 60Co marking schemes are said to be publicly unacceptable. Taggants for Identification Identification taggants have been studied in Britain but at this time are not part of the British program to control terrorist bombings. The Irish Republican Army is known to be a perpetrator of illegal bombings, and it can obtain large quantities of CAN from many sympathetic legal users for agricultural purposes in Northern Ireland. Thus, there is little incentive to initiate an expensive identification taggant program. Reportedly, AN residue is recovered in 50 percent of AN bombs. The others yield considerable device-specific debris; tags would not add significantly more information. Rendering Explosive Materials Inert Since the 1980s, the British have focused almost entirely on inerting AN—making it harder to initiate and propagate a detonation. However, efforts to make AN less sensitive have not stopped bombers from using the material as their

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors primary oxidizer, although such efforts may have discouraged some amateur bombers or reduced the extent of property damage. The British started by asking if the Irish needed to use AN as a fertilizer at all and whether they could use urea instead. However, political, economic, and agricultural factors, such as the demand for a single-substance fertilizer (which can be mixed as needed), led to the present solution: ammonium nitrate sold in Ireland is diluted with dolomite. This product was already being sold in the Irish market as a basic substance, since dolomite was good for the acidic Irish soil. Even the magnesium content of dolomite was thought to improve the grass for the major Irish crop—ruminant animals. Despite its degree of dilution, CAN is the favored material for bombs, even though pure ammonium nitrate can be obtained in Great Britain. Controls on Precursor Chemicals In Northern Ireland the sale of seven substances has been restricted (AN, sodium chlorate, sodium chlorite, nitrobenzene, potassium nitrate, sodium nitrate, and sodium nitrite). Dilute nitric acid can be purchased and concentrated. Acetone, methanol, peroxides, formaldehyde, and other precursors are available.22 However, in Great Britain there is no overt program to control precursor chemicals for explosives, although most chemical supply houses have voluntary programs that are generally effective in controlling precursors for drugs and explosives. Some substances are controlled for safety reasons under a "poisons list"; others are controlled via commercial requirements such as the need for a company to obtain a general operating license. For the purpose of fire suppression, sodium chlorate sold in Great Britain is a 50/50 mixture with the unoxidized sodium chloride; amateur bomb makers who attempt to use this material get poor explosive yields. With the major bombing problem being large devices made with CAN, it is believed that controls on precursors would not likely be a major deterrent. Further Observations British authorities have evolved a sophisticated intelligence system to obtain early warnings of terrorist activities. It works well because British citizens are strongly supportive of antiterrorist efforts, but authorities do not want details of how the system works made public. They also have developed many techniques for thwarting bombers and have responded to repeated terrorism by taking protective 22    TATP was used in a bombing of the Israeli embassy in London. The precursor chemicals used to make TATP are not controlled.

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Containing the Threat from Illegal Bombings: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors measures: controlling lorry access and parking, installing special curtains to protect against window glass fragmentation, and so on. The British view their approach to preventing bombings as one of making bombing increasingly inconvenient. They try to stay one step ahead of bombers in technology and also try to make the materials even harder to use. They acknowledge that this is only a delaying tactic and cannot prevent determined bombers from succeeding on occasion. Modifying AN fertilizer to make it less explosive requires much more than finding a workable technique. Fertilizer use is a complex subject involving economics and soil and crop characteristics. Different crops need to be supplied with different nutrients, and fertilizer must be adjusted to match crop requirements to soil type. As a result, an increasing trend in the fertilizer industry is to tailor compound fertilizers to meet a farmer's specific needs. One approach is to encourage this trend, licensing a limited number of wholesalers to store (securely) undiluted AN and sell it only compounded and made to order.