Chapter 8 Toxicology: Poisons and Alcohol

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 Kendall/Hunt Publishing Company 2

Toxicology and Alcohol

A quantitative approach to toxicology.

The danger of using alcohol.

Students will learn:


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.

Students will be able to:

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Was Paracelsus Right?

Hormesis —refers to the concept promoted by Paracelsus: that substances that kill at high doses are actually beneficial at low doses— the poison is in the dosage.This appears to be true for many substances:

oxygen, water, aspirin, alcohol, etc.

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Historical Perspective of Poisoners

Olympias—a famous Greek poisoner Locusta—personal poisoner of Emperor Nero Lucretia Borgia—father was Pope Alexander VI Madame Giulia Toffana—committed over 600

successful poisonings, including two Popes. Hieronyma Spara—formed a society to teach women

how to murder their husbands Madame de Brinvilliers and Catherine Deshayes—

French poisoners.AND many others through modern times.


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.


Toxicology

Toxicology —the study of the adverse effects of chemicals or physical agents on living organisms.

Types: Environmental Toxicology—air, water, soil Consumer Toxicology—foods, cosmetics, drugs Medical (Clinical) Toxicology—prescription

medication Forensic Toxicology —use of toxicology to aid in the

investigation of death, poisoning and drug use.


Forensic Toxicology

Postmortem—medical examiner or coroner

Criminal—motor vehicle accidents (MVA) Workplace—drug testing Sports—human and animal Environment—industrial, catastrophic,

terrorism

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Toxins

Toxin—a substance that causes injury to the health of a living thing on contact or absorption, typically by interacting with enzymes and receptors. (Usually a naturally produced substance that kills rapidly in small quantities)



Toxic Substances

Toxic substances may:Be a cause of deathContribute to deathCause impairmentExplain behavior

Poison hemlock is a plant related to the carrot. It containsalkaloids that negatively affectthe nervous system


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”


Elements of Toxicity

Dosage many substances are only lethal in high dosages

The chemical or physical form of the substance Arsenic is not very poisonous in its natural form (metal);

but arsenic trioxide or arsenic gas is very poisonous.

The mode of entry into the body some substances are most poisonous if swallowed;

others must be injected, inhaled or absorbed

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Body weight and physiological conditions of the victim, including age and sex Blood alcohol content is directly related to body weight Infants and elderly are more susceptible to most toxins

The time period of exposure Sometimes small amounts ingested over time create a

tolerance for the toxin Chronic exposure (larger amounts over time) can create serious

medical problems Acute toxicity—very large dose causing immediate problems,

including death


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The presence of other chemicals in the body or in the doseSynergism: combination of two chemicals

increases the effects of both in the systemEx: antihistamine and alcohol

Antagonism: combination of two chemicals decreases the effects of both in the systemEx: Chelating agent and arsenic



Lethal Dose

LD50 —refers to the dose of a substance that kills half the test population, usually within four hours

(Note: test population is usually mice or rats)

Expressed in milligrams of substance per kilogram of body weight. A correlation is then made to humans based on the body weight data.

However, estimating lethal doses for humans is often complicated by the fact that resistance to certain chemicals can differ greatly between species


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

Chapter 8

LD50 Update

Because a single test may kill as many as 100 animals, the U.S. and other members of the Organization for Economic Cooperation and Development agreed in December 2000 to phase out the LD50 test in favor of alternatives that greatly reduce (or even eliminate) deaths of the test animals.



Federal Regulatory Agencies

To ensure public safety, the federal government has created several regulatory agencies related to toxic substances: Food and Drug Administration (FDA)—deals with

pharmaceuticals, food additives, and medical devices

Environmental Protection Agency (EPA)—works with agricultural and industrial chemicals released to the environment

Consumer Product Safety Commission—concerned with toxins in consumer products

Department of Transportation (DOT)—watches shipment of toxic chemicals

Occupational Safety and Health Administration (OSHA)—concerned with exposure to chemicals in the workplace


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


Critical Informationon Poisons

Form Common color Characteristic odor Solubility Taste Common sources Lethal dose Mechanism Possible methods of administration Time interval of onset of

symptoms.

Symptoms resulting from an acute exposure

Symptoms resulting from chronic exposure

Disease states mimicked by poisoning

Notes relating to the victim Specimens from victim Analytical detection methods Known toxic levels Notes pertinent to analysis of

poison List of cases in which poison was

used

—John Trestrail from “Criminal Poisoning”


To Prove a Case

Prove a crime was committed Motive Intent Access to poison Access to victim Death was caused by poison Death was homicidal


Forensic AutopsyLook 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


Human Specimens for Analysis

Blood

Urine

Vitreous Humor of Eyes

Bile

Gastric contents

Liver tissue

Brain tissue

Kidney tissue

Hair/nails


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 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% is done in the liver at a rate of about

0.015% per hour. About 5% is excreted unchanged in breath, perspiration and urine


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


BACBlood Alcohol Content

Expressed as percent weight per volume of blood Legal limits in all states is 0.08% (0.08 grams of pure

alcohol for every 100ml of blood) Parameters influencing BAC:

Body weight Alcoholic content Number of beverages consumed Time between consumption


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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Sample Problem

What would be the approximate BAC of a 185 pound man who has consumed three shots (1.5 oz.each) of Jack Daniels (80 proof = 40% alcohol) in an hour?

BACmale = 0.071 x 4.5 x 40 = 0.07

185



Henry’s Law Henry’s Law provides the scientific basis for the breath test check for

sobriety. 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. In other words 1 ml of blood will contain nearly the same amount of alcohol as 2100 ml of breath.


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.


The Breathalyzer Invented in 1954 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


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.


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.


More Information

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

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

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Chapter 8 Toxicology: Poisons and Alcohol

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