Transcript Science Fair Project

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
Toxicology and Alcohol
We will learn:
 A quantitative approach
to toxicology.
 The danger of using
alcohol.
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Toxicology and Alcohol
Goals:
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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.
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
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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”
Chapter 8
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.
Chapter 8
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
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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
Chapter 8
Symptoms of Various Types
of Poisoning
Type of Poison
Symptom/Evidence
 Caustic Poison (lye)
Characteristic burns around the lips and
mouth of the victim
Red or pink patches on the chest and thighs,
unusually bright red lividity
Black vomit
Greenish-brown vomit
Yellow vomit
Coffee brown vomit. Onion or garlic odor
Burnt almond odor
Pronounced diarrhea
Nausea and vomiting, unconsciousness,
possibly blindness
 Carbon Monoxide
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Sulfuric acid
Hydrochloric acid
Nitric acid
Phosphorous
Cyanide
Arsenic, Mercury
Methyl (wood) or
Isopropyl (rubbing) alcohol
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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
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 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
 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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BAC
Blood Alcohol Content
 Expressed as percent weight per volume of
blood
 Legal limits in all states is 0.08%
 Parameters influencing BAC:
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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:
 Male
BAC 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.
Chapter 8
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.
Chapter 8
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 + 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/forensic
s/toxicology/2.html
Chapter 8