Chapter 8

Toxicology: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

Chapter 8

Toxicology and Alcohol

A quantitative approach to toxicology.

The danger of using alcohol.

We will learn:

Chapter 8

Toxicology and Alcohol

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.

Goals:

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ToxicologyDefinition—the study of the adverse

effects of chemicals or physical agents on living organisms.

Types:Environmental—air, water, soilConsumer—foods, cosmetics, drugsMedical, clinical, forensic

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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”

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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.

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Aspects of ToxicityDosageChemical or physical form of the substanceMode of entry into the bodyBody weight and physiological conditions

of the victim, including age and sexTime period of exposureThe presence of other chemicals in the

body or in the dose

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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

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Toxicity Classes

LD50 (rat,oral) Correlation to Ingestion by 150 lb Adult Human

Toxicity

<1mg/kg a taste to a drop extremely

1-50 mg/kg to a teaspoon highly

50-500 mg/kg to an ounce moderately

500-5000 mg/kg to a pint slightly

5-15 g/kg to a quart practically non-toxic

Over 15g/kg more than 1 quart relatively harmless

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Symptoms of Various Typesof Poisoning

Type of Poison Symptom/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

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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

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Human Specimens for Analysis

Blood

Urine

Vitreous Humor of Eyes

Bile

Gastric contents

Liver tissue

Brain tissue

Kidney tissue

Hair/nails

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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

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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

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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

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BAC

Burn off rate of 0.015% per hour but can vary:

MaleBAC male = 0.071 x (oz) x (% alcohol)

body weight Female

BAC female = 0.085 x (oz) x (% alcohol) body weight

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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.

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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.

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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 water2K2Cr2O7 + 3C 2H5OH + 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

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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.

Chapter 8

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.

Chapter 8

More Information

Read more about Forensic Toxicology from Court TV’s Crime Library at:

http://www.crimelibrary.com/criminal_mind/forensics/toxicology/2.html