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Forensic Science Unit 10-Toxicology Toxicology What is toxicology? The study of the effects of poisons. Poisonous substances are produced by plants, animals, or bacteria. Phytotoxins Zootoxins Bacteriotoxins Toxicant - the specific poisonous chemical. Xenobiotic - man-made substance and/or produced by but not normally found in the body. Introduction Toxicology is arguably the oldest scientific discipline, as the earliest humans had to recognize which plants were safe to eat. Most exposure of humans to chemicals is via naturally occurring compounds consumed from food plants. Humans are exposed to chemicals both inadvertently and deliberately. You Know ? 92% of all poisonings happen at home. The household products implicated in most poisonings are: cleaning solutions, fuels, medicines, and other materials such as glue and cosmetics. Certain animals secrete a xenobiotic poison called venom, usually injected with a bite or a sting, and others animals harbor infectious bacteria. Some household plants are poisonous to humans and animals. History 2700 B.C. - Chinese journals: plant and fish poisons 1900-1200 B.C. - Egyptian documents that had directions for collection, preparation, and administration of more than 800 medicinal and poisonous recipes. 800 B.C. - India - Hindu medicine includes notes on poisons and antidotes. 50-100 A.D. - Greek physicians classified over 600 plant, animal, and mineral poisons. History 50- 400 A.D. - Romans used poisons for executions and assassinations. The philosopher, Socrates, was executed using hemlock for teaching radical ideas to youths. Avicenna (A.D. 980-1036) Islamic authority on poisons and antidotes. 1200 A.D. - Spanish rabbi Maimonides writes first-aid book for poisonings, Poisons and Their Antidotes History Swiss physician Paracelsus (14931541) credited with being “the father of modern toxicology.” “All substances are poisons: there is none which is not a poison. The right dose differentiates a poison from a remedy.” The Dose Makes the Poison An apparently nontoxic chemical can be toxic at high doses. (Too much of a good thing can be bad). Highly toxic chemicals can be life saving when given in appropriate doses. (Poisons are not harmful at a sufficiently low dose). Lethal Doses Approximate Lethal Doses of Common Chemicals (Calculated for a 160 lb. human from data on rats) Chemical Lethal Dose Sugar (sucrose) 3 quarts Alcohol (ethyl alcohol) 3 quarts Salt (sodium chloride) 1 quart Herbicide (2, 4-D) one half cup Arsenic (arsenic acid) 1-2 teaspoons Nicotine one half teaspoon Food poison (botulism) microscopic Source: Marczewski, A.E., and Kamrin, M. Toxicology for the citizen, Retrieved August 17, 2000 from the World Wide Web: www.iet.msu.edu/toxconcepts/toxconcepts.htm. History Spanish physician Orfila (1815) established toxicology as a distinct scientific discipline. History 20th Century Paul Ehrlich –developed staining procedures to observe cell and tissues and pioneered the understanding of how toxicants influence living organisms. Toxicology Terms Toxicity - The adverse effects that a chemical may produce. Dose - The amount of a chemical that gains access to the body. Toxicology Terms Exposure – Contact providing opportunity of obtaining a poisonous dose. Hazard – The likelihood that the toxicity will be expressed. Routes of Exposure Ingestion (water and food) Absorption (through skin) Injection (bite, puncture, or cut) Inhalation (air) Duration & Frequency of Exposure Duration and frequency are also important components of exposure and contribute to dose. Acute exposure - less than 24 hours; usually entails a single exposure Repeated exposures are classified as: – Subacute - repeated for up to 30 days – Subchronic - repeated for 30-90 days – Chronic -repeated for over 90 days What Do Forensic Toxicologists Do? Forensic toxicologists study the application of toxicology to the law. They use chemical analysis to determine the cause and circumstances of death in a postmortem investigation. . Forensic Toxicology • Definition: – The science of detecting and identifying the presence of drugs and poisons in body fluids, tissues, and organs. Role of the Toxicologist • Must identify one of thousands of drugs and poisons • Must find nanogram to microgram quantities dissipated throughout the entire body • Not always looking for exact chemicals, but metabolites of desired chemicals (ex. heroin morphine within seconds) Color Tests • Marquis Test: – Turns purple in the presence of Heroin, morphine, opium – Turns orange-brown in presence of Amphetamines • Scott Test: Three solutions – Blue then pink then back to blue in the presence of Cocaine • Duquenois-Levine: – Test for marijuana –turns purple More Analytical Tests • Microcrystalline Tests: Identifies drug by using chemicals that reacts to produce characteristic crystals • Chromatography: TLC, HPLC and gas – separate drugs/tentative ID • Mass Spectrometry: chemical “fingerprint” no two drugs fragment the same Toxicology of Alcohol • Alcohol is absorbed through the stomach and intestine • Once absorbed, alcohol is: – Oxidized- in liver by alcohol dehydrogenase—turned into acidic acid – Excreted- by breath, perspiration, and kidneys—turned into carbon dioxide and water Toxicology of Alcohol • Alcohol intoxication depends on – Amount of alcohol consumed – Time of consumption – Body weight – Rate of alcohol absorption Fate of Alcohol • Alcohol is absorbed into the bloodstream. • Distributed through-out the body’s water. • And finally eliminated by oxidation and excretion. Fate of Alcohol Con’t Oxidation is the combination of O2 and alcohol to produce new products by the liver. Elimination is removing alcohol from the body in an unchanged state; normally excreted in breath and urine. Factors that Affect Alcohol Absorption • Time of consumption • Type of alcoholic beverage • Presence of food in stomach Alcohol in the Circulatory System • Measuring the quantity of alcohol in the blood system determines the degree to which someone is drunk • Two methods of making this measurement – Measurement of alcohol content in blood – Measurement of alcohol in breath Circulation Con’t • Note: If alcohol is present, it will be passed from the blood into the alveoli where it will be passed on to the mouth and nose during the act of breathing. • Evidence has shown that the ratio of alcohol to alveoli air is approx. 2100 to 1—This is a basis for relating breath to blood-alcohol concentration. Parts of the brain affected by Alcohol • Alcohol 1st affects the forebrain and moves backward • Last affected is medulla oblongata Field Sobriety Testing • Two reasons for the field sobriety test: 1. Used as a preliminary test to ascertain the degree of the suspect’s physical impairment 2. To see whether or not an evidential test is justified. Field Sobriety Testing Methods • Field sobriety testing consists of a series of psychophysical tests and a preliminary breath test (typically done with a handheld fuel cell tester) • These tests are preliminary and nonevidential in nature—they only serve to establish probable cause requiring a more thorough breath or blood test. Field Sobriety Tests • Horizontal Gaze Nystagmus – Involuntary eye jerk as eye moves horizontally • Walk and Turn (divided attention tasks) • One-Leg Stand Breath Tests • A breath test reflects the alcohol concentration in the pulmonary artery. • One instrument used for breath tests is called The Breathalyzer. • The Breathalyzer is a device for collecting and measuring the alcohol content of alveolar breath. The Breathalyzer Con’t • The Breathalyzer traps 1/40 of 2100 milliliters of alveolar breath. • Since the amount of alcohol in 2100 milliliters of breath approximates the amount of alcohol in 1 milliliter of blood—the Breathalyzer in essence measures the alcohol concentration present in 1/40 of a milliliter of blood. Breathalyzer Con’t • Once the alveolar breath is trapped it is allowed to undergo a chemical reaction: • 2K2Cr2O7 + 3C2H5OH + 8H2SO4 2Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2O Potassium dichromate Ethyl alcohol Sulfuric acid Chromium sulfate Potassium sulfate Acetic acid Dihydrogen oxide • The Breathalyzer indirectly determines the quantity of alcohol consumed by measuring the absorption of light by potassium chromate before and after its reaction with alcohol, using the principle of spectrophotometry The Breathalyzer Infrared-Breath Test • Uses the principle that infrared light is absorbed when shined on alcohol • Essentially, the infrared light passes through a chamber where it will interact with the alcohol and cause the light density to decrease. • The decrease in light intensity is proportional to the concentration of alcohol present in the captured breath Fuel Cell—Breath Test • A fuel cell converts a fuel and an oxidant into an electrical current. • In this test, the breath alcohol is the fuel and atmospheric oxygen acts as the oxidant. • Alcohol is converted, generating a current that is proportional to the quantity of alcohol present in the breath. Infrared and Fuel Cell Breath Tests • Infrared Breath Test uses infrared wavelengths to test for alcohol or other interferences in the breath • Fuel Cell Test converts fuel (alcohol) and oxygen into a measurable electric current Alcohol and the Law • 1939-1964: intoxicated = 0.15% BAC • 1965: intoxicated = 0.10% BAC • 2003: intoxicated = 0.08% BAC At least we don’t live in France, Germany, Ireland, or Japan (0.05%) or especially Sweden (0.02%)!