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Toxicology

Toxicology. Toxicology — 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. Forensic Toxicology. Postmortem — medical examiner or coroner

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Toxicology

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  1. Toxicology • Toxicology—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

  2. Forensic Toxicology • Postmortem—medical examiner or coroner • Criminal—motor vehicle accidents (MVA) • Workplace—drug testing • Sports—human and animal • Environment—industrial, catastrophic, terrorism

  3. Toxicology Toxic substances may: • Be a cause of death • Contribute to death • Cause impairment • Explain behavior

  4. Historical Perspective of Poisoners • Olympias—a famous Greek poisoner • Locusta—personal poisoner of Emperor Nero • Lucretia Borgia—father was Pope Alexander VI • Madame GiuliaToffana—committed over 600 successful poisonings, including two popes • HieronymaSpara—formed a society to teach women how to murder their husbands • Madame de Brinvilliers and CatherineDeshayes—French poisoners.

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

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

  7. Lethal Dose • LD50refers 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

  8. Toxicity Classification

  9. Federal Regulatory Agencies • Food and Drug Administration (FDA) • Environmental Protection Agency (EPA) • Consumer Product Safety Commission • Department of Transportation (DOT) • Occupational Safety and Health Administration (OSHA)

  10. Lead Poisoning: • Lead compounds are not highly poisonous. But chronic exposure to lead poses a real health problem. • Most common exposure is contact with lead-based paints (Banned in 1978). • Lead-based paints taste sweet. A teething child will often lick and chew the paint.

  11. Symptoms of Various Types of Poisoning

  12. To Prove a Case • Prove a crime was committed • Motive • Intent • Access to poison • Access to victim • Death was homicidal • Death was caused by poison

  13. 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.

  14. Human Specimens for Analysis • Blood • Urine • Vitreous humor of eyes • Bile • Gastric contents • Liver tissue • Brain tissue • Kidney tissue • Hair/nails

  15. Alcohol - Ethyl Alcohol (C2H5OH) • Most abused drug in America • About 40 percent of all traffic deaths are alcohol-related • Toxic—affecting the central nervous system, especially the brain • Colorless liquid, generally diluted in water • Acts as a depressant • Alcohol appears in blood within minutes of consumption; 30–90 minutes for full absorption • Detoxification—about 90 percent in the liver • About 5 percent is excreted unchanged in breath, perspiration, and urine

  16. 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

  17. BAC: Blood Alcohol Content • Expressed as percent weight per volume of blood • Legal limit in all states is 0.08 percent • Parameters influencing BAC: • Body weight • Alcohol content • Number of beverages consumed • Time since consumption

  18. BAC Calculation Burn-off rate of 0.015 percent per hour, but can vary: Male BAC = 0.071  (oz)  (% alcohol) body weight Female BAC = 0.085  (oz)  (% alcohol) body weight

  19. 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 2,100 to 1. In other words, 1 ml of blood will contain nearly the same amount of alcohol as 2,100 ml of breath.

  20. Field Tests • Preliminary tests—used to determine the degree of suspect’s physical impairment and whether or not another test is justified • Psychophysical tests—three basic tests:

  21. 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.

  22. Nine-step walk and turn (WAT): comprehend and execute two or more simple instructions at one time

  23. One-leg stand (OLS): maintain balance; comprehend and execute two or more simple instructions at one time

  24. The Breathalyzer • More practical in the field • Collects and measures alcohol content of alveolar breath • Breath sample mixes with 3 ml of 0.025 percent K2Cr2O7 in sulfuric acid and water: 2K2Cr2O7 +3C2H5OH + 8H2SO42Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2O • 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.

  25. During absorption, the concentration of alcohol in arterial blood is higher than in venous blood. • Breath tests reflect alcohol concentration in the pulmonary artery. • The breathalyzer also can react with acetone (as found in 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 readout. Prints out a card for a permanent record.

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