Transcript Unit 10-Toxicology

Forensic Science
Unit 10-Toxicology
Toxicology
What is toxicology? The study of the effects of poisons.
Poisonous substances are produced by plants, animals, or
bacteria.
Phytotoxins
Zootoxins
Bacteriotoxins
Toxicant - the specific poisonous chemical.
Xenobiotic - man-made substance and/or produced by but not
normally found in the body.
Introduction
Toxicology is arguably the oldest scientific discipline, as the
earliest humans had to recognize which plants were safe
to eat.
Most exposure of humans to chemicals is via naturally
occurring compounds consumed from food plants.
Humans are exposed to chemicals both inadvertently and
deliberately.
You Know ?
92% of all poisonings happen at home.
The household products implicated in
most poisonings are: cleaning
solutions, fuels, medicines, and other
materials such as glue and cosmetics.
Certain animals secrete a xenobiotic
poison called venom, usually injected
with a bite or a sting, and others
animals harbor infectious bacteria.
Some household plants are poisonous to
humans and animals.
History
2700 B.C. - Chinese journals: plant and
fish poisons
1900-1200 B.C. - Egyptian documents
that had directions for collection,
preparation, and administration of
more than 800 medicinal and poisonous recipes.
800 B.C. - India - Hindu medicine includes
notes on poisons and antidotes.
50-100 A.D. - Greek physicians classified over
600 plant, animal, and mineral poisons.
History
50- 400 A.D. - Romans used poisons for
executions and assassinations.
The philosopher, Socrates, was executed
using hemlock for teaching radical
ideas to youths.
Avicenna (A.D. 980-1036) Islamic authority on
poisons and antidotes.
1200 A.D. - Spanish rabbi Maimonides writes
first-aid book for poisonings,
Poisons and Their Antidotes
History
Swiss physician Paracelsus (14931541) credited with being
“the father of modern toxicology.”
“All substances are poisons: there is
none which is not a poison. The
right dose differentiates a poison
from a remedy.”
The Dose Makes the Poison
An apparently nontoxic chemical
can be toxic at high doses. (Too
much of a good thing can be
bad).
Highly toxic chemicals can be life
saving when given in appropriate
doses. (Poisons are not harmful
at a sufficiently low dose).
Lethal Doses
Approximate Lethal Doses of Common Chemicals
(Calculated for a 160 lb. human from data on rats)
Chemical
Lethal Dose
Sugar (sucrose)
3 quarts
Alcohol (ethyl alcohol)
3 quarts
Salt (sodium chloride)
1 quart
Herbicide (2, 4-D)
one half cup
Arsenic (arsenic acid)
1-2 teaspoons
Nicotine
one half teaspoon
Food poison (botulism)
microscopic
Source: Marczewski, A.E., and Kamrin, M. Toxicology for the citizen, Retrieved August 17, 2000
from the World Wide Web: www.iet.msu.edu/toxconcepts/toxconcepts.htm.
History
Spanish physician Orfila (1815) established
toxicology as
a distinct scientific discipline.
History
20th Century
Paul Ehrlich –developed staining procedures to observe
cell and tissues and pioneered the understanding of how
toxicants influence living organisms.
Toxicology Terms
Toxicity - The adverse effects
that a chemical
may produce.
Dose - The amount of a
chemical that gains
access to the body.
Toxicology Terms
Exposure – Contact providing
opportunity of
obtaining a
poisonous dose.
Hazard – The likelihood that the
toxicity will be
expressed.
Routes of Exposure
Ingestion (water and food)
Absorption (through skin)
Injection (bite, puncture, or cut)
Inhalation (air)
Duration & Frequency of Exposure
Duration and frequency are also important
components of exposure and contribute to dose.
Acute exposure - less than 24 hours; usually entails a
single exposure
Repeated exposures are classified as:
– Subacute - repeated for up to 30 days
– Subchronic - repeated for 30-90 days
– Chronic -repeated for over 90 days
What Do Forensic Toxicologists
Do?
Forensic toxicologists study the
application of toxicology to the law.
They use chemical analysis to
determine the cause and
circumstances of death in a
postmortem investigation.
.
Forensic Toxicology
• Definition:
– The science of detecting and identifying
the presence of drugs and poisons in body
fluids, tissues, and organs.
Role of the Toxicologist
• Must identify one of thousands of drugs and
poisons
• Must find nanogram to microgram
quantities dissipated throughout the entire
body
• Not always looking for exact chemicals, but
metabolites of desired chemicals (ex. heroin
 morphine within seconds)
Color Tests
• Marquis Test:
– Turns purple in the presence of Heroin, morphine,
opium
– Turns orange-brown in presence of Amphetamines
• Scott Test: Three solutions
– Blue then pink then back to blue in the presence of
Cocaine
• Duquenois-Levine:
– Test for marijuana –turns purple
More Analytical Tests
• Microcrystalline Tests: Identifies
drug by using chemicals that reacts to
produce characteristic crystals
• Chromatography: TLC, HPLC and
gas – separate drugs/tentative ID
• Mass Spectrometry: chemical
“fingerprint” no two drugs fragment
the same
Toxicology of Alcohol
• Alcohol is absorbed through the
stomach and intestine
• Once absorbed, alcohol is:
– Oxidized- in liver by alcohol
dehydrogenase—turned into acidic acid
– Excreted- by breath, perspiration, and
kidneys—turned into carbon dioxide and
water
Toxicology of Alcohol
• Alcohol intoxication depends on
– Amount of alcohol consumed
– Time of consumption
– Body weight
– Rate of alcohol absorption
Fate of Alcohol
• Alcohol is absorbed into the
bloodstream.
• Distributed through-out the
body’s water.
• And finally eliminated by
oxidation and excretion.
Fate of Alcohol Con’t
Oxidation is the combination
of O2 and alcohol to produce
new products by the liver.
Elimination is removing alcohol from the
body in an unchanged state; normally
excreted in breath and urine.
Factors that Affect Alcohol
Absorption
• Time of
consumption
• Type of alcoholic
beverage
• Presence of food in
stomach
Alcohol in the Circulatory System
• Measuring the quantity of alcohol in
the blood system determines the degree
to which someone is drunk
• Two methods of making this
measurement
– Measurement of alcohol content in
blood
– Measurement of alcohol in breath
Circulation Con’t
• Note: If alcohol is present, it will be passed from
the blood into the alveoli where it will be passed
on to the mouth and nose during the act of
breathing.
• Evidence has shown that the ratio of alcohol to
alveoli air is approx. 2100 to 1—This is a basis for
relating breath to blood-alcohol concentration.
Parts of the brain affected by Alcohol
• Alcohol 1st
affects the
forebrain
and moves
backward
• Last
affected is
medulla
oblongata
Field Sobriety Testing
• Two reasons for the field sobriety
test:
1. Used as a preliminary test to
ascertain the degree of the suspect’s
physical impairment
2. To see whether or not an evidential
test is justified.
Field Sobriety Testing Methods
• Field sobriety testing consists of a
series of psychophysical tests and a
preliminary breath test (typically done
with a handheld fuel cell tester)
• These tests are preliminary and nonevidential in nature—they only serve
to establish probable cause requiring a
more thorough breath or blood test.
Field Sobriety Tests
• Horizontal Gaze Nystagmus
– Involuntary eye jerk as eye moves horizontally
• Walk and Turn (divided attention tasks)
• One-Leg Stand
Breath Tests
• A breath test reflects the alcohol
concentration in the pulmonary artery.
• One instrument used for breath tests is
called The Breathalyzer.
• The Breathalyzer is a device for
collecting and measuring the alcohol
content of alveolar breath.
The Breathalyzer Con’t
• The Breathalyzer traps 1/40 of 2100
milliliters of alveolar breath.
• Since the amount of alcohol in 2100
milliliters of breath approximates the
amount of alcohol in 1 milliliter of
blood—the Breathalyzer in essence
measures the alcohol concentration
present in 1/40 of a milliliter of
blood.
Breathalyzer Con’t
• Once the alveolar breath is trapped it is allowed to undergo a
chemical reaction:
• 2K2Cr2O7 + 3C2H5OH + 8H2SO4  2Cr2(SO4)3 +
2K2SO4 + 3CH3COOH + 11H2O
Potassium
dichromate
Ethyl
alcohol
Sulfuric
acid
Chromium
sulfate
Potassium
sulfate
Acetic
acid
Dihydrogen
oxide
• The Breathalyzer indirectly determines the quantity of alcohol
consumed by measuring the absorption of light by potassium
chromate before and after its reaction with alcohol, using the
principle of spectrophotometry
The Breathalyzer
Infrared-Breath Test
• Uses the principle that infrared light is absorbed
when shined on alcohol
• Essentially, the infrared light passes through a
chamber where it will interact with the alcohol and
cause the light density to decrease.
• The decrease in light intensity is proportional to
the concentration of alcohol present in the
captured breath
Fuel Cell—Breath Test
• A fuel cell converts a fuel and an
oxidant into an electrical current.
• In this test, the breath alcohol is the
fuel and atmospheric oxygen acts as
the oxidant.
• Alcohol is converted, generating a
current that is proportional to the
quantity of alcohol present in the
breath.
Infrared and Fuel Cell Breath Tests
• Infrared Breath Test
uses infrared wavelengths
to test for alcohol or other
interferences in the breath
• Fuel Cell Test
converts fuel
(alcohol) and oxygen
into a measurable
electric current
Alcohol
and the Law
• 1939-1964:
intoxicated =
0.15% BAC
• 1965:
intoxicated =
0.10% BAC
• 2003:
intoxicated =
0.08% BAC
At least we don’t live
in France, Germany,
Ireland, or Japan
(0.05%) or especially
Sweden (0.02%)!