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Chapter 8 Toxicology: Poisons and Alcohol

Chapter 8 Toxicology: Poisons and Alcohol

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Chapter 8 Toxicology: Poisons and Alcohol

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  1. Chapter 8Toxicology:Poisons and Alcohol “All substances are poisons. There is none which is not. The right dose differentiates a poison and remedy.” —Paracelsus (1495-1541). Swiss physician and chemist

  2. Toxicology and Alcohol • A quantitative approach to toxicology. • The danger of using alcohol. We will learn:

  3. Toxicology and Alcohol Goals: • Discuss the connection of blood alcohol levels to the law, incapacity, and test results. • Understand the vocabulary of poisons. • Design and conduct scientific investigations. • Use technology and mathematics to improve investigations and communications. • Identify questions and concepts that guide scientific investigations. • Communicate and defend a scientific argument.

  4. Toxicology Definition—the study of the adverse effects of chemicals or physical agents on living organisms. Types: • Environmental—air, water, soil • Consumer—foods, cosmetics, drugs • Medical, clinical, forensic

  5. The Severity of the Problem “If all those buried in our cemeteries who were poisoned could raise their hands, we would probably be shocked by the numbers.” —John Harris Trestrail, “Criminal Poisoning”

  6. People of Historical Significance Mathieu Orfila—known as the father of forensic toxicology, published in 1814 “Traite des Poisons” which described the first systematic approach to the study of the chemistry and physiological nature of poisons.

  7. Aspects of Toxicity • Dosage • Chemical or physical form of the substance • Mode of entry into the body • Body weight and physiological conditions of the victim, including age and sex • Time period of exposure • The presence of other chemicals in the body or in the dose

  8. Lethal Dose • LD50 — refers to the dose of a substance that kills half the test population, usually within four hours • Expressed in milligrams of substance per kilogram of body weight

  9. Toxicity Classes

  10. Symptoms of Various Typesof Poisoning Type of PoisonSymptom/Evidence • Caustic Poison (lye) Characteristic burns around the lips and mouth of the victim • Carbon Monoxide Red or pink patches on the chest and thighs, unusually bright red lividity • Sulfuric acid Black vomit • Hydrochloric acid Greenish-brown vomit • Nitric acid Yellow vomit • Phosphorous Coffee brown vomit. Onion or garlic odor • Cyanide Burnt almond odor • Arsenic, Mercury Pronounced diarrhea • Methyl (wood) or Nausea and vomiting, unconsciousness, Isopropyl (rubbing) alcohol possibly blindness

  11. Forensic Autopsy Look for: • Irritated tissues • Characteristic odors • Mees lines—single transverse white bands on nails. Order toxicological screens • Postmortem concentrations should be done at the scene for comparison • No realistic calculation of dose can be made from a single measurement

  12. Blood Urine Vitreous Humor of Eyes Bile Gastric contents Liver tissue Brain tissue Kidney tissue Hair/nails Human Specimens for Analysis

  13. Alcohol—Ethyl Alcohol (C2H5OH) • Most abused drug in America • About 40% of all traffic deaths are alcohol-related • Toxic—affecting the central nervous system, especially the brain • Alcohol appears in blood within minutes of consumption; 30-90 minutes for full absorption • Detoxification—about 90% in the liver • About 5% is excreted unchanged in breath, perspiration and urine

  14. Rate of Absorption Depends on: • amount of alcohol consumed • the alcohol content of the beverage • time taken to consume it • quantity and type of food present in the stomach • physiology of the consumer

  15. BACBlood Alcohol Content • Expressed as percent weight per volume of blood • Legal limits in all states is 0.08% • Parameters influencing BAC: • Body weight • Alcoholic content • Number of beverages consumed • Time between consumption

  16. BAC • Burn off rate of 0.015% per hour but can vary: • Male BAC male = 0.071 x (oz) x (% alcohol) body weight • Female BAC female = 0.085 x (oz) x (% alcohol) body weight

  17. Henry’s Law • When a volatile chemical is dissolved in a liquid and is brought to equilibrium with air, there is a fixed ratio between the concentration of the volatile compound in the air and its concentration in the liquid; this ratio is constant for a given temperature. • THEREFORE, the concentration of alcohol in breath is proportional to that in the blood. • This ratio of alcohol in the blood to alcohol in the alveolar air is approximately 2100 to 1. • 1 ml of blood will contain nearly the same amount of alcohol as 2100 ml of breath.

  18. Field Tests • Preliminary tests—used to determine the degree of suspect’s physical impairment and whether or not another test is justified. • Psychophysical tests—3 Basic Tests • Horizontal gaze nystagmus (HGN): follow a pen or small flashlight, tracking left to right with one’s eyes. In general, wavering at 45 degrees indicates 0.10 BAC. • Nine Step walk and turn (WAT): comprehend and execute two or more simple instructions at one time. • One-leg stand (OLS): maintain balance, comprehend and execute two or more simple instructions at one time.

  19. The Breathalyzer • More practical in the field • Collects and measures alcohol content of alveolar breath • Breath sample mixes with 3 ml of 0.025 % K2Cr2O7 in sulfuric acid and water 2K2Cr2O7 + 3C2H5OH+ 8H 2SO4  2Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11 H2O • Potassium dichromate is yellow, as concentration decreases its light absorption diminishes so the breathalyzer indirectly measures alcohol concentration by measuring light absorption of potassium dichromate before and after the reaction with alcohol

  20. Generalizations • During absorption, the concentration of alcohol in arterial blood will be higher than in venous blood. • Breath tests reflect alcohol concentration in the pulmonary artery. • The breathalyzer also can react with acetone (as found with diabetics), acetaldehyde, methanol, isopropyl alcohol, and paraldehyde, but these are toxic and their presence means the person is in serious medical condition. • Breathalyzers now use an infrared light absorption device with a digital read-out. Prints out a card for a permanent record.

  21. People in the News John Trestrail is a practicing toxicologist who has consulted on many criminal poisoning cases. He is the founder of the Center for the Study of Criminal Poisoning in Grand Rapids, Michigan which has established an international database to receive and analyze reports of homicidal poisonings from around the world. He is also the director of DeVos Children’s Hospital Regional Poison Center. In addition, he wrote the book, Criminal Poisoning, used as a reference by law enforcement, forensic scientists and lawyers.

  22. More Information Read more about Forensic Toxicology from Court TV’s Crime Library at: http://www.crimelibrary.com/criminal_mind/forensics/toxicology/2.html