Weapons of Mass Destruction, Detection
█ K. LEE LERNER/
Weapons of mass destruction are weapons that cause a high loss of life within a short time span. Nuclear, chemical, and biological weapons fit this definition.
An atomic bomb exploded over a densely populated city could kill hundreds of thousands of people instantaneously and, as the lethal effects of radiation exposure take hold, causes many more deaths within days or weeks. Chemicals such as Ricin that disrupt nerve function are lethal upon exposure. Agents such as mustard gas can cause life-threatening burns. Chemical weapons can affect a wide geographical area because the chemicals are dispersed in the air.
Biological weapons take longer than nuclear and chemical weapons to cause damage. Because infections can subsequently spread through a population far from the site of contamination, and because the population may not be protected by vaccination or natural immunity to the microorganism responsible for the infection, the eventual death toll from an organized biological attack, however, could reach into the millions. Relevant modern day examples of biological weapons of mass destruction are anthrax (caused by Bacillus anthracis ), plague (caused by Yersinia pestis ), and smallpox (caused by the variola virus).
The damage from weapons that are less powerful or toxic can be minimized. For example, buildings can be fortified to withstand assaults from conventional explosives such as grenades. Thus, for such weapons, damage prevention can be the priority rather than detection. However, the damage from a weapon of mass destruction cannot be minimized once the weapon has been unleashed. Rather, the weapons need to be detected before they are used.
Detection of Chemical and Nuclear Weapons of Mass Destruction
Chemical and nuclear weapons are often delivered to their target in missiles. Sophisticated open-air launch facilities and large pieces of equipment are required for launch, and it is difficult to conceal such facilities from aerial surveillance. Planes, unmanned drones, and even satellites positioned over a region will all reveal the presence of a missile installation. Underground chemical storage facilities can also be revealed by the use of ground penetrating radar.
The materials that are commonly used in the construction of chemical and nuclear weapons can be detected. For example, an instrument called the Dual-Use Analyzer uses the phenomenon of eddy current. An electrical current is passed through a sample, and the conductivity of the metal produces a characteristic signal. If another metal is present, such as those used in chemical and nuclear weapons, another signal is produced. The rogue signal can be compared to a databank of signals produced by metals that are typically used in weapons.
Light or radiation. The airborne release of chemical weapons can be detected using light. Specifically, the scattering or absorption of a directed beam of laser light, or
the development of fluorescence when the aerosol cloud contacts laser or ultraviolet light, can detect a chemical cloud at a distance. This sort of detection is not specific. The identity of the compound in the aerosol cloud cannot be determined. But detection can provide some time for preparations (i.e., evacuation gathering in an airtight facility). Specific detection methods, however, are possible. Chemical groups behave in distinctive ways when exposed to different kinds of light or radiation. The measurement of the chemical behavior is called spectroscopy. The machines that perform the analysis are called spectrometers.
In mass spectroscopy, the mass (or molecular weight) of proteins is determined. The molecular weight is an important means of identifying a protein. In turn, the identification of a protein can provide a clue as to what chemical agent is present. Raman spectroscopy relies on the change in the shape and frequency of the wave of light (i.e., the wavelength) as it passes through a sample to identify the chemical groups that cause the wavelength change. In neutron spectroscopy, neutrons interact with the chemical groups of the sample. The patterns of these interactions can be measured and used to identify chemical groups. Neutron spectroscopy is especially adept at detecting plutonium, and thus is useful in the detection of nuclear weapons. Finally, optical spectroscopy relies on the use of ultraviolet and infrared light. The absorption of the light energy by sample chemical groups, and the giving off of light of a different wavelength by the groups, is used to identify compounds, particularly compounds present in certain explosives.
A Geiger counter is a traditional portable radiation detection device. Here, a tube of gas becomes charged when neutrons pass through the tube. The charged particles are converted to an electrical signal that produces a read-out of the intensity of the radiation.
The U.S. Department of Energy's Argonne National Laboratory has developed a portable device that can detect nuclear weapons. The heart of the device is a small wafer made of gallium arsenide—a material that is similar to silicon—that is coated with boron or lithium. The coated wafer can detect neutrons that are given off by radioactive sources like plutonium 239 and uranium 233 . Another portable sensor detects alloys like zirconium, which are typically used in nuclear weapons. The United Nations (U.N.) weapons inspectors in Iraq utilized this sensing technology during inspections in 2003.
Sound. Sandi National Laboratories in Albuquerque New Mexico has developed a portable machine that can detect and identify 18 different chemicals in a vapor within a few minutes. This enables an on-the-spot detection of chemicals, which is applicable to the battlefield or to the detection of a planted chemical weapon. The compounds that can be detected can be present in chemical, nuclear, and biological weapons.
The basis of the detection is the acoustic wave sensor. A quartz surface can detect an electric signal and convert it to an acoustic signal. The acoustic signal then radiates over the quartz surface as a wave. As the wave moves, it encounters a film of material that has been coated onto the quartz. The chemical nature of the coatings determines what acoustic signal will register. The film slows down the speed of the acoustic wave, which can be used to identify the source of the wave.
The technique of acoustic resonance can reveal whether the interior of a missile is solid or whether it houses a liquid. The distinction is based on the resonance, or vibration, from inside a shell as the shell is vibrated by sound waves. Because different chemicals resonate at different frequencies of sound, the technique can even be used to determine the type of chemical housed in the shell. The device was first used by U.N. inspectors in Iraq in 1997.
Chemical reactions. Detection of chemical weapons can be accomplished by several methods. One means is by the use of detection paper. Dyes and pH indicator (an indicator of the concentration of hydrogen or hydronium ions in a solution) are incorporated into a cellulose paper. When a drop of liquid that contains a chemical warfare agent is spotted onto the paper, one of the indicators is dissolved (the particular indicator being dependent on the chemical agent present). The result is a color change. For example, mustard agent dissolves a red dye, and nerve agent dissolves a yellow dye. Other compounds like fat, oil, and fuel can also dissolve the dyes, which produces a false positive reaction. But, with careful use of the paper, the presence of chemical warfare agents can be detected.
Mustard gas can also be detected by sucking air through a tube containing an indicator compound. A reaction between the compounds produces a blue color when the tube is heated.
Detection of Biological Weapons of Mass Destruction
The identification of proteins by mass spectroscopy can be an efficient and rapid way to identify bacteria. An example is Matrix-Assisted Laser Desorption/Ionization Mass Spectroscopy (MALDI-MS). MALDI-MS can separate and detect different proteins in less than one second. The pattern that is produced is analyzed and the areas of the pattern that are unique to bacteria such as Bacillus anthracis (the cause of anthrax) and Yersinia pestis (the cause of plague) are identified.
Genetic technologies. The genetic detection of biological agents has become exquisitely sensitive. Gene probe sensors can detect and identify bacteria based upon the presence of a stretch of genetic material that is unique to the microorganism. An example is the use of the gene probe technology of the polymerase chain reaction (PCR). PCR detects a pre-determined sequence of genetic material and then produces copies of the target region. Millions of copies can be produced within a hour, allowing the sequence to be detected and studied using other tests (i.e., gel electrophoresis).
When PCR was first introduced, the equipment required dedicated space in a lab. Now, however, the equipment has been miniaturized so that it can fit into a standard briefcase. For example, the Lawrence Livermore Laboratory has developed the Handheld Advanced Nucleic Acid Analyzer (HANAA). The HANAA is about the size of a brick. The genetic probes that are used are designed to detect specific microorganisms. The microbes of interest are Bacillus anthracis and Yersinia pestis . The unit is being used in the 2003 inspection of Iraqi facilities by U.N. officials, an inspection that is designed to verify Iraqi's submitted list of biological weapons, and to reveal any expansion of the nation's biological warfare program since the Gulf War of the mid 1990s.
In contrast to the handheld detector, which operates periodically and under human control, the Autonomous Pathogen Detection System (APDS) is designed to operate continuously and without operator assistance. A fan pulls in air, and any biological material is used for PCR analysis. The APDS, which is about the size of a mailbox, is positioned where round the clock monitoring is critical. The unit can be programmed to sound an alarm when a chemical unique to bacterial spores (including anthrax spores) is present. As well another reaction causes the development of fluorescence. The intensity of the fluorescence is related to the number of spores present.
In 2002, the PCR technology was successfully adapted to allow the detection of the smallpox virus within a few minutes. As of 2003, the rapid test for smallpox is still being refined in the laboratory. However, it will doubtless not be long before the smallpox test is portable enough for use in the field.
Microorganisms can also be rapidly detected using antibodies that have been produced to certain components of the organisms. The binding of the antibody to the corresponding antigen can identify Bacillus anthracis in 15 minutes, for example. The same technology can be used with antibodies to other bacteria (e.g., Clostridium botulinum and viruses (e.g., smallpox), as well as to chemicals such as ricin.
Electrophoresis and chromatography. If a sample is suspected of containing a biological threat, the genetic material (deoxyribonucleic acid; DNA) present in the sample solution can be extracted from the other materials and analyzed. The analysis involves cutting the DNA into a variety of pieces using enzymes that recognize specific sequences of nucleotides (the building blocks of the DNA). When the pieces of DNA are electrophoresed a series of bands results in the electrophoretic gel. The pattern of the bands is compared to patterns in a database. If an exact match is found, then the identify of the microorganism is established.
The various types of chromatography all distinguish different chemical groups from one another by the varying behaviors of the groups in certain environments. For example, one chemical group may move more slowly through a certain liquid than another chemical group. Thus, the two groups can be separated from one another. Furthermore, the pattern of their movements provides a fingerprint to identify the chemical natures of the compounds.
Microorganisms can be detected by a technique called gas liquid chromatography. The method detects fatty acids, which are a portion of the lipid molecules that make up the membrane(s) that surround microorganisms. This type of detection still requires a bulky machine and the use of specialized personnel. Nonetheless, if the need for detection is on the order of days rather than minutes, then fatty acid analysis is a useful and accurate technique.
Filters. Microorganisms like bacteria and fungi that are floating in the air can be detected by sucking the air through a filter. The filter traps the microorganisms. The filter is then placed in contact with a food source that encourages the growth and division of the bacterial or fungal cells. Within about 24 to 48 hours the microorganisms have grown and reproduced enough to form a visible clump of cells called a colony. This technology is also portable.
Detection of Weapons of Mass Destruction in Iraq
In November 2002, a team of 220 inspectors—with 50 more to join within weeks—began examining a variety of sites throughout Iraq for the presence of chemical, nuclear, and biological weapons of mass destruction. During the 1990s, Iraq acknowledged having such weapons and weapons development programs. However, Iraqi officials reported that these activities were ended.
The weapons inspection occurring in Iraq in 2003 utilized a variety of weapons detections technologies. Surveillance planes such as the unmanned Predator drone are equipped with high-resolution cameras and provided aerial views of the selected terrain. Detailed images from surveillance satellites placed in orbit over a selected part of the globe provided details of construction projects or the presence of equipment that might be used for weapons. Other cameras were utilized on the ground. Digital cameras can be left in place after an inspection is complete, to provide a longer-term monitoring of the site. Ground penetrating radar positioned on helicopters or unmanned drones was used to seek buried caches of missile components and bunkers that could house weapons. Finally, the portable sensors that have been described were used.
█ FURTHER READING:
Butler, Richard. The Greatest Threat: Iraq, Weapons of Mass Destruction, and the Crisis of Global Security. New York: Public Affairs, 2001.
Cirincione, Joseph, Jon B. Wolfsthal, and Jessica T. Mathews. Deadly Assaults: Tracking Weapons of Mass Destruction. Washington, D.C.: Carnegie Endowment for International Peace, 2002.
LeDuc, J.W., I. Damar, J.M. Meegan, et al. "Smallpox Research Activities: U.S. Interagency Collaboration 2001." Emerging and Infectious Diseases 8 (2002): 743–45.
Reeves, A. "Tracing Biothreats with Molecular Signatures." Los Alamos National Laboratory Research Quarterly Fall 2002: 15–17.
Lawrence Livermore National Laboratory. "Reducing the Threat of Biological Weapons." Chemical/Biological Nonproliferation Program. June 1998. < http://www.llnl.gov/str/Milan.html >(7 January 2003).