Blood agents
Blood agents are a category of chemical agents that primarily exert their toxic effects through absorption into the blood. These agents are significant in forensic investigations, particularly in cases of homicides or suspicious deaths, due to their potential use in criminal activities and terrorist attacks. Blood agents can be either cyanide-based, such as hydrogen cyanide and cyanogen chloride, or arsenic-based, like arsine. Known for their fast-acting and lethal properties, these agents can exist as volatile gases or in solid forms, and their effects can be particularly dangerous in confined spaces.
Exposure typically occurs through inhalation or ingestion, leading to severe respiratory failure and rapid death if not treated immediately. Symptoms of exposure vary with concentration, ranging from dizziness and nausea at lower levels to convulsions and coma in severe cases. Detection of blood agents can be challenging, but certain indicators, such as the distinct color of the blood in poisoned individuals, may assist forensic investigators. Understanding blood agents is crucial for public safety and effective law enforcement response, given their potential for misuse in harmful scenarios.
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Subject Terms
Blood agents
DEFINITION: Chemical agents that affect the body by being absorbed into the blood.
SIGNIFICANCE: Forensic investigators must be aware of the signs and symptoms of the presence of blood agents when these chemical substances are involved in homicides or other deaths. The possibility that such agents may be used in terrorist attacks is also of concern to law-enforcement agencies.
Chemical agents are toxic substances that are classified by their primary sites of effect; blood agents are thus chemical agents that exert their primary effects in the blood. Known blood agents are either cyanide- or arsenic-based. Examples of cyanide-based blood agents include hydrogen cyanide and cyanogen chloride. Arsine is an example of an arsenic-based blood agent.
Characteristics
Blood agents are fast-acting, potentially deadly chemicals. Cyanide can be a highly volatile colorless gas, such as hydrogen cyanide or cyanogen chloride, or can exist in crystal forms, such as sodium or potassium cyanide. Cyanogen chloride is slightly less volatile than hydrogen cyanide. Arsine exists as a colorless gas. As gases, blood agents are lighter than air and quickly dissipate. Consequently, these agents are more toxic in confined areas than in open areas.
Blood agents typically have a slight odor detectable at higher concentrations. Cyanide gas, for example, may have a smell of peach kernels or bitter almonds, but the odor can be faint and many people cannot detect it—only about half of all persons have the ability to smell cyanide gas. Arsine has a mild garlic odor that can be detected only at concentrations greater than those that are fatal.
Exposure Routes
Blood agents are difficult to detect, volatile, and fast-acting, features that render such compounds potentially useful in chemical warfare. When these agents are used as chemical weapons, they are typically disseminated as aerosols, and inhalation is one of the deadliest exposure routes.
Cyanide occurs naturally in the environment, and small amounts are present in certain foods and in cigarette smoke. Both cyanide and arsine are used in various manufacturing processes, so some people may be exposed at their workplaces. Cyanide is present in the chemicals used to make paper, textiles, and plastics and to develop photographs; it is also used in metallurgy, electroplating, and mining. Because cyanide gas can be released when synthetic fabrics and polyurethane burn, cyanide poisoning may contribute to fire-related deaths.
Cyanide gas has been used to exterminate pests. Arsine, which was developed initially as an insecticide, is used in the manufacture of computer chips. Arsine gas forms when arsenic encounters an acid, and most common reports of arsine exposure have resulted from accidental formation of arsine in the workplace.
Effects
Blood agents poison the blood quickly and can result in very rapid death. Often, powerful gasping for breath occurs, followed by violent convulsions. Death from cyanide poisoning is painful, and it takes a few minutes to die from blood agent poisoning.
Blood agents are taken into the body either by ingestion or by inhalation. Cyanide-based blood agents irritate the eyes and respiratory tract. Arsine, in contrast, is nonirritating. Respiratory failure is usually the cause of death. Blood agents interfere with oxygen utilization at the cellular level by preventing exchange of oxygen and carbon dioxide between blood and tissues, causing cells to suffocate from lack of oxygen. Arsine works by damaging red blood cells, which also impairs the ability of cells to deliver oxygen throughout the body. The lack of oxygen to tissues and cells can quickly lead to death unless the victim is immediately removed from the toxic atmosphere.
Symptoms of blood agent exposure depend on concentration and duration. Breathing in or ingesting very small amounts of cyanide may have no effects, whereas exposure to somewhat higher concentrations may result in dizziness, weakness, and nausea. If removed from exposure, the person generally will begin to feel better. Over time, exposure to low concentrations can produce mild symptoms followed by permanent brain damage and muscle paralysis. Moderate exposure can result in headache, dizziness, and nausea, symptoms that can last for several hours, and may be followed by convulsions and possible coma. Higher concentrations or longer exposure may also result in convulsions and coma. With very high concentrations, severe toxic effects begin in seconds, and death occurs rapidly.
Detecting Blood Agents as Causes of Death
Because blood agents prevent adequate utilization of oxygen, the blood of persons exposed to these chemicals is a rich red rather than blue-red. Cyanogen chloride injures the respiratory tract, which results in severe congestion and inflammation in the lung. A smell of bitter almonds may be detected. The presence of thiocyanate or cyanide in the blood can also be used to detect cyanide poisoning. Arsine may leave a garlic smell on the victim’s breath, but no specific tests have been developed to determine arsine poisoning.
Investigators have struggled to identify blood agents, for example, several foes of Russian president Vladimir Putin have died or fallen ill. Some methods of administering the poisons, investigators say, include putting substances in drinking water bottles and applying them to surfaces such as doorknobs.
Bibliography
Banks, Daniel E. Medical Management of Chemical Casualties Handbook. 5th ed., Department of the Army, 2014. eBook Collection (EBSCOhost), search.ebscohost.com/login.aspx?direct=true&db=nlebk&AN=937533&site=ehost-live. Accessed 3 Jan. 2017.
"Chemical Warfare Agents." US Environmental Protection Agency, 26 Jan. 2024, www.epa.gov/emergency-response/chemical-warfare-agents. Accessed 12 Aug. 2024.
Crippen, James B. Explosives and Chemical Weapons Identification. Boca Raton, Fla.: CRC Press, 2006.
Ellison, D. Hank. Handbook of Chemical and Biological Warfare Agents. 2d ed. Boca Raton, Fla.: CRC Press, 2007.
Hoenig, Steven L. Compendium of Chemical Warfare Agents. New York: Springer, 2011.
Litvinova, Dasha, and Emma Burrows. "Nerve Agents, Poison and Window Falls. Kremlin Foes Have Been Attacked or Killed Over the Years." Associated Press, 16 Feb. 2024, apnews.com/article/russia-kremlin-enemy-navalny-prigozhin-litvinenko-skripal-958c2ed6b8d60ecc4f64092fc1f9ceb5. Accessed 12 Aug. 2024.
Wecht, Cyril H., ed. Forensic Aspects of Chemical and Biological Terrorism. Tucson, Ariz.: Lawyers & Judges Publishing, 2004.