Download Introduction to Forensic Toxicology

Introduction to Toxicology
Larry Johnson
Partnership for Environmental Education
and Rural health (PEER)
Texas A & M University
Forensic Toxicology
- the study of the chemical and physical properties
of toxic substances and their physiological effect on
living organisms
What We’ve Learned So Far…
• A chemical’s shape helps determine its physical properties
like polarity
• The way a chemical passes through the human body has a
lot to do with its shape and physical properties
• We can identify a substance by how it reacts with a known
substance (White Powder Lab)
• We can identify a substance by the kind of light its absorbs
Three Primary Responsibilities
1. Postmortem Drug Testing
2. Workplace Drug Testing
3. Identification of Contraband Materials
Deaths Investigated by Toxicologists
1. Accidental Poisonings
2. Drug Abuse Cases
3. Suicidal Poisonings
4. Homicidal Poisonings
Toxicological Analysis of Tissue
a. Collect sample of all body fluids
b. Collect samples from organs and tissues
c. A forensic toxicologist cannot simply look for the presence of
a toxin or drug in a body, she must understand how the
body processes these molecules
d. Toxicological analysis must start as soon as possible after a
person’s death
General Classes of Poisons
1. Gases
2. Metallic Poisons
3. Volatile Organics
4. Non-volatile Organics
- the major category here is what is known as an alkaloid, a drug that
mimics human neurotransmitters or hormones and therefore interferes
with normal body chemistry
Alkaloids are derived from plants…
Alkaloids
Common Examples:
•
Amphetamines – stimulants that provoke euphoria; these drugs mimic
catecholamines in the human body (adrenaline, etc)
•
Cocaine – natural stimulant that acts as a mimic to catecholamines;
metabolites are detected in urine for as many as 3 days
•
Opiates – depressants that reduce muscle activity, heartbeat, respiration,
and the inclination to sleep; effective pain relievers and euphoria
producing; opiates mimic endorphins in the human body
•
Cannabinoids – fast acting plant alkaloid; body mimic is unknown;
metabolites can be detected in urine for months
Alkaloids
amphetamine
adrenaline
cocaine
serotonin
ecstasy
Methods of Detection
1. Color test
2. Microdiffusion test
3. Chromatography
a. thin-layer chromatography (TLC)
b. gas chromatography (GC)
c. high performance liquid chromatography (HPLC)
4. Spectroscopy
a. UV light
d. X-ray
b. visible light
e. infrared
c. microwave
Methods of Detection
1. Color test
2. Microdiffusion test
3. Chromatography
a. thin-layer chromatography (TLC)
b. gas chromatography (GC)
c. high performance liquid chromatography (HPLC)
4. Spectroscopy
a. UV light
d. X-ray
b. visible light
e. infrared
c. microwave
Example UV-vis Spectrum
Methods of Detection
1. Color test
2. Microdiffusion test
3. Chromatography
a. thin-layer chromatography (TLC)
b. gas chromatography (GC)
c. high performance liquid chromatography (HPLC)
4. Spectroscopy
a. UV light
d. X-ray
b. visible light
e. infrared
c. microwave
Example IR Spectrum
Methods of Detection
5. Mass Spectroscopy
6. Immunoassay
Methods of Detection
5. Mass Spectroscopy
6. Immunoassay
Interpretation of Findings
1. Is a drug or poison present? What substance?
2. How much of the substance is present? Is it’s
concentration in the body sufficient to cause
death?
3. How was the drug/poison administered?
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
Italian physician
Ramazzini (1713) published
“De Morbis Artificum”
(Diseases of Workers)
describing "asthma" in bakers, miners, farmers, gilders,
tinsmiths, glass-workers, tanners, millers, grain-sifters,
stonecutters, ragmen, runners, riders, porters, and
professors. Ramazzini outlined health hazards of the dusts,
fumes, or gases that such workers inhaled. The bakers and
horse riders described by Ramazzini would today probably
be diagnosed as suffering from allergen-induced asthma.
The lung diseases suffered by most of the other workers
would now be classified as "pneumoconiosis," a group of
dust-related chronic diseases.
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.
History
20th Century
Rachel Carson - alarmed public
about dangers of pesticides
in the environment.
Occupational and
Environmental Toxicology
Environmental toxicants (air
and water pollutants) are
substances harmful to the
environment and to humans.
Environmental toxicants are both natural and
man made.
Public perception that man-made ones are more
serious than natural ones - Reality: both
are serious.
5,000,000 yearly deaths worldwide due
to bacterial toxicants (Salmonella, E. coli)
Occupational and
Environmental Toxicology
Many examples of diseases associated with specific
occupations were recorded in antiquity, but they were
not considered serious because the health of the
workers was not a societal concern.
-
Paracelsus - Miner’s Disease (1533)
Hill & Pott (1761 &1775)
Radium dial painters, “aniline dye” workers (1900)
Shoe salesmen (1950s)
Industrial chemical workers (1940-present)
Occupational and
Environmental Toxicology
- Paracelsus - Miner’s Disease (1533) came from
inhaling metal vapors, foundation for the
field of chemotherapy.
- Hill (1761) linked tobacco (snuff)
to cancer.
- Pott (1775) linked scrotal cancer
and soot (benzo(a)pyrene) in
chimney sweeps.
Occupational and
Environmental Toxicology
- Radium dial painters,
“aniline dye” workers (1900)
painters licked their brushes
to pull it to a point.
- Shoe salesmen (1950s)
shoe-fitting fluoroscopes:
radiation of feet in shoes
of children and repeated
exposure for salesmen.
Occupational and
Environmental Toxicology
- Industrial chemical workers
(1940-present)
Workers typically are exposed to
a greater number of carcinogens
for longer periods of time.
Occupations with high risk of cancer :
Health care workers, pharmaceutical and
laboratory workers, refinery workers, rubber
workers, furniture makers, and pesticide workers.
Modern Toxicology
1961 - Society of Toxicology
1970s - EPA, FDA, and NIOSH
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.
Threshold Effects for Dose
Response
Dose-Response
Relationships
Is there such a thing
as a ‘safe’ dose??
Agent A
Agent B
“NOEL”
(No Observable Effect Level)
Dose
Fundamental Rules of
Toxicology
Exposure must first occur for the chemical to present a risk.
The magnitude of risk is proportional to both the potency of
the chemical and the extent of exposure.
“The dose makes the poison” (amount of chemical at the
target site determines toxicity).
Exposure Concepts
Different toxic responses may arise from
different:
– Routes of exposure.
– Frequencies of exposure.
– Duration of exposure (acute vs. chronic).
Routes of Environmental
Exposure
Ingestion (water and food)
Absorption (through skin)
Injection (bite, puncture, or cut)
Inhalation (air)
Chemicals, Chemicals Everywhere
Everything in the environment is made of chemicals. Both
naturally occurring and synthetic substances are chemical in
nature.
People are exposed to chemicals by
eating or swallowing them,breathing
them, or absorbing them through the
skin or mucosa.
People can protect themselves by
blocking these routes of exposure.
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
Exposure Concepts
Exposure to chemicals may come from many sources:
–
–
–
–
–
–
Environmental
Occupational
Therapeutic
Dietary
Accidental
Deliberate
Children & Poisons
Individual Responses Can Be
Different
The variety of responses among organisms that get the
same dose of chemical is due to individual susceptibility.
Dose and individual susceptibility play roles in all situations
involving chemicals, including those making medicine
and caffeine.
Introduction to Xenobiotics
*Recall: Foreign chemicals are
synthesized within the body are
termed xenobiotics (Gr.Xenos
meaning “strange”)*
• Xenobiotics may be naturally
occurring chemicals produced by
plants, microorganisms, or animals
(including humans).
• Xenobiotics may also be synthetic chemicals produced by
humans.
Poisons are xenobiotics, but not all xenobiotics are poisonous.
How Does the Body Prevent the
Actions of Xenobiotics ?
1) Redistribution
2) Excretion – (primarily water soluble compounds)
- kidney and liver
3) Metabolism – the major mechanism for terminating
xenobiotic activity, and is frequently the single most
important determinant of the duration and intensity of
toxic responses to a xenobiotic.
- LIVER, kidney, lung, GI, and others
Note: 1) and 2) are highly dependent upon 3)
Xenobiotics at Work
TOXICOKINETICS
Xenobiotic
Excretion
General Scheme of Xenobiotic Metabolism
Lipophilic
(parent compound)
Metabolism
Phase I
(oxidative)
Bioactivation
Detoxification
Hydrophilic
(metabolite)
1) Decrease biological activity
2) Increase excretability
Metabolites
polarity
functionality
Phase II
(synthetic)
Detoxification
Metabolites
size
ionization
water solubility
Increase excretability
How Xenobiotics Cause Toxicity
Some xenobiotics cause toxicity by disrupting normal cell functions:
– Bind and damage proteins (structural, enzymes)
– Bind and damage DNA (mutations)
– Bind and damage lipids
– React in the cell with oxygen to form
“free radicals” which damage lipid, protein,
and DNA
Types of Toxic Effects
Death - arsenic, cyanide
Organ Damage - ozone, lead
Mutagenesis - UV light
Carcinogenesis - benzene, asbestos
Teratogenesis - thalidomide
Target Organ Toxicity
Central Nervous System – lead
Immune System - isocyanates
Liver - ethanol, acetaminophen
Respiratory Tract - tobacco smoke,
asbestos, ozone
Eye - UV light (sunlight)
Kidney - metals
Skin - UV light, gold, nickel
Reproductive System –
dibromochloropropane
Mechanistic Toxicology
How do chemicals cause their toxic effects?
What Do Toxicologists Do?
Most toxicologists work to develop a
mechanistic understanding of how
chemicals affect living systems:
– Develop safer chemical
products
– Develop safer drugs
– Determine risks for chemical
exposures
– Develop treatments for chemical
exposures
– Teach ( e.g. other toxicologists,
graduate students, and youth)
What Do Toxicologists Do?
Mechanistic toxicologists study how a chemical
causes toxic effects by investigating its absorption,
distribution, and excretion. They often work in
academic settings or private industries and develop
antidotes.
Descriptive toxicologists evaluate the toxicity of
drugs, foods, and other products. They often perform
experiments in a pharmaceutical or academic setting.
Clinical toxicologists usually are physicians or
veterinarians interested in the prevention, diagnosis,
and treatment of poisoning cases. They have
specialized training in emergency medicine and
poison management.
What Do Toxicologists Do?
?
Forensic toxicologists study the
application of toxicology to the law. They
uses chemical analysis to determine the
cause and circumstances of death in a
postmortem investigation.
Environmental toxicologists study the
effects of pollutants on organisms,
populations, ecosystems, and the
biosphere.
Regulatory toxicologists use scientific
data to decide how to protect humans and
animals from excessive risk.
Government bureaus such as the FDA
and EPA employ this type of toxicologist.
Regulatory Toxicology
Use data from descriptive and mechanistic toxicology to
perform risk assessments.
Concerned with meeting requirements of
regulatory agencies.
Industry/government interactions.
Review
Toxicology is the science that studies the harmful effects of
overexposure to drugs, environmental contaminants, and
naturally occurring substances found in food, water, air, and
soil.
– Main objectives are to establish safe doses and
determine mechanisms of biologic action of chemical
substances.
A career in toxicology involves evaluating the harmful effects
and mechanisms of action of chemicals in people, other
animals, and all other living things in the environment.
– This work may be carried out in government, private
industry and consulting firms, or universities and other
research settings.
Toxicologists routinely use many sophisticated tools to
determine how chemicals are harmful.
(e.g.) computer simulations, computer chips, molecular
biology, cultured cells, and genetically-engineered
laboratory animals .
What Is the Risk?
People can make some choices about chemical exposure;
however, some exposure is controlled at a level other than
an individual one. Collective groups of people, such as
communities and governments, seek to control chemical
exposure on a community or global level.
Animals in
Research
“Virtually every medical
achievement of the last
century has depended
directly or indirectly on
research in animals.”
U.S. Public Health
Service
Summary
Toxicology is a fascinating science that
makes biology and chemistry interesting
and relevant.
Understanding HOW (i.e. mechanism)
something produces a toxic effect can lead to new ways of
preventing or treating chemically-related diseases. Animal
use in research is essential for medical progress.
Many diseases are the result of an interaction between our
genetics (individual variability) and chemicals in our
environment.
Toxicology provides an interesting and exciting way to apply
science to important problems of social, environmental,
and public health significance.
National Institute of
Environmental Health
Sciences
Texas Rural Systemic
Initiative
Partnership for
Environmental
Education and Rural
Health
The Center for
Environmental and
Rural Health
College of Education,
Texas A&M
University
College of Veterinary
Medicine at Texas
A&M University
Port-Mortem Toxicology
PM Toxicology
• Following death there can be rapid changes in cellular biochemistry as
autolysis proceeds, and drugs and other poisons may be released from
their binding sites in tissues and major organs, also unabsorbed drug
may diffuse from the stomach.
• Special care should always be taken in the selection of blood and
tissue sampling site(s), the method of collection of samples, and the
labelling of sample containers. There is substantial published evidence
to show that for most drugs and poisons, including alcohol, there are
important differences in their concentration in blood according to the
time of specimen collection after death, choice of sampling site,
method of sampling and volume of blood collected (Pounder and
Jones 1990; Pounder 1993).
PM Toxicology
• It is common to observe tenfold differences in the concentration of
certain drugs and some chemical poisons in post-mortem blood taken
from different sites. Specimens taken from "central" sites e.g. heart
tend to give particularly "high" values for most analytes. Moreover,
certain commonly used "peripheral" sites such as subclavian, may
sometimes give results closer to "central" sites such as the heart.
• The most consistent quantitative findings are obtained in blood taken
from the femoral vein, which is the recommended site of specimen
collection. It is also possible to observe differences in the
concentration of certain drugs obtained from different tissue sampling
sites for liver and lung.
PM Toxicology
• Parts of the body extracted and tested for toxicology, postmortem
– Blood and urine
– Bile from the duodenum and/ or liver
– Entire liver in some cases
– Stomach contents and the entire stomach may be
extracted
– Liquid from the Vitreus Humour (eye)
– Part of the brain and lungs may be extracted and tested
– Hair, fingernails, and sometimes bone
• Refer to http://www.toxlab.co.uk/postmort.htm for more
information about why each element is extracted
PM Toxicology
• Factors that prevent accurate manner of death due to toxins
or drugs:
– Person’s weight and metabolism
– How long the person was dead
– Where sample was extracted from body post mortem
– Differing expert testimonials
– In the case of drugs, deceased’s addiction level and
tolerance to suspected drug
Forensic Toxicology
Forensic Toxicology
• Definition:
– The science of detecting and identifying the presence of
drugs and poisons in body fluids, tissues, and organs.
Forensic Toxicology
• The role of the forensic toxicologist is limited to matters
that pertain to violations of criminal law
– Variability in in who conducts toxicology service in the
U.S.
• Crime lab staff member, government health
agencies, private lab facilities
• Whatever facility is doing the testing, the prevailing
popularity of the drug will determine the types of cases the
toxicologist will see
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)
The Role of The Toxicologist
• Once the forensic toxicologist ventures outside the analysis
of alcohols the methods for analysis become more complex
• Determining if the victim died from drugs can be a
daunting task, especially if they have only the body and or
organs and know external clues
– No symptoms
– Examination of personal effects
The Role of The Toxicologist
• With out any indicating evidence the toxicologist is forced
to start with general screening procedures in hopes of
narrowing the thousand possibilities
• Note that the concentration levels once processed by the
body may vary dramatically from that of the non-induced
form
• In order to detect these traces a toxicologist must
understand how the drug metabolizes
– Transforming a chemical in the body to another
chemical for the purpose of facilitating its elimination
from the body
Establishing Toxicity
• Once the obstacle of detecting the drug is overcome, the
toxicologist must then determine the toxicity of the drug
• With a deceased person many tests can be run on various
organs to determine the precise concentrations
• Living subjects are more difficult, due to the limited
samples (blood and urine)
Techniques Used in
Toxicology
• The three most widely used drug screening tests are
– Thin-layer chromatography
– Gas chromatography
– Immunoassay
• Confirmation tests is usually Gas Chromatography coupled
with Mass Spectrometry
Immunoassay
• The primary advantage of immunoassay is its ability to
detect small concentrations of drugs in body fluids and
organs
• This techniques is based on antigen-antibody recognition
• Essentially the drug is coupled with a protein carrier and
then injected into an animal
– This antigen stimulates antibodies in the animal
– The blood serum recovered from the animal now
contains antibodies that are specific for the drug
DRE
• The role of the toxicologist is based on knowledge,
– Once the drug is detected determining the effects on the
body must be done considering a number of variables
– Age, tolerance, metabolism
– Multiple drug, synergistic effect
• Before the medical examiner can determine the cause of
death he or she must rely on the interpretation of the
toxicologist
Toxicology Procedures
• 10mL of blood in airtight container
– Add anticoagulant
– Add preservative
• 2 consecutive urine samples
– Some drugs take a while to show up in urine (1-3 days)
• Vitreous humor
• Hair samples
Toxicology Procedures
• Screening– quick test to narrow down possibilities
– color tests, TLC, GC, immunoassay
• Confirmation– determines exact identity
– GC/Mass Spec
Note: TLC—thin layer
chromatography
Color Tests
• Marquis Test:
– Turns purple in the presence of Heroin, morphine, opium
– Turns orange-brown in presence of Amphetamines
• Scott Test: Three solutions (cobalt thiocyanate)
– Blue then pink then back to blue in the presence of Cocaine
• Duquenois-Levine:
– Test for marijuana –turns purple
• Cobalt Acetate/ isopropylamine test
– Barbiburates—turns red-violet
• P-Dimethlyamino-benzaldehyde (p-DMAB)
– LSD—turns blue
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
DRE
• Drug Recognition Experts are trained and developed for
standardization in procedures
• The process is designed so that each individual is tested in
the same fashion
• It is a twelve step process and evaluates for 7 categories of
drugs
– Central nervous system depressants
– Central nervous system stimulants
– Hallucinogens
– Phencyclidine
– Inhalants
– Narcotic Analgesics
– Cannabis
Why?
• Think of all the people that you have “heard” do drugs.
• US drug manufacturers produce enough barbiturates and
tranquilizers each year to give every person in the US 40
pills
• (that’s about 12 billion pills)
• 18,000 out of 44,000 annual traffic deaths are alcohol
related and send over 2 million people to the hospital
Toxicology of Alcohol
Toxicology of Alcohol; The fate of
alcohol in the body
• Alcohol is the most readily consumed drug among our
society
• It use coupled with automobiles have dictated the need for
reliable indicators of consumption
– Must be on evasive, reliable, meet the demands of legal
system
• Absorption is highly variable and dependant on a number
of factors
The fate of alcohol in the body
• The detection of alcohol, for determining an individual’s
impairment, focuses on the concentration of alcohol in the
blood
• Blood alcohol levels show a direct relationship to the
proportion of alcohol in the brain
• Alcohol is readily transferred into the circulatory system
minutes after it has been consumed
The fate of alcohol in the body
• Factors affecting rate of absorption
– Weight - the higher your weight, the lower your Blood Alcohol Content
(BAC) will be
– Gender - Men produce more of the enzyme that breaks down alcohol
– Food - the more food you eat, especially protein, before you drink, the
lower your Blood Alcohol Content (BAC) will be
– Emotional state - Alcohol is a depressant and will enhance your current
emotional state. For example, if you are upset before you start drinking at
the end of the night your mood will be lower than it was at the beginning
of the evening
– Drinking Rate - Chugging drinks and doing shots results in a large
amount of alcohol entering your body in a short amount of time. Your
body cannot process alcohol at a fast pace resulting in a higher BAC.
Elimination of Alcohol from the
Body
• Once alcohol begins to circulate in the bloodstream the
body begins the task of removing it, this is done in two
ways
– 1) Oxidation: The combination of oxygen with other
substances to produce new products.
• Nearly all alcohol consumed is eventually oxidized
to carbon dioxide and water
• Takes place in the liver, facilitated by the enzyme
alcohol dehydrogenase
• Alcohol + alcohol dehydrogenase = acetaldhyde,
then to acetic acid
Elimination of Alcohol from the
Body
• The second means by which the remaining alcohol is
eliminated from the body is
– 2) Excretion: Elimination of alcohol from the body in unchanged
state; is excreted in breath and urine, also perspiration.
• Alcohol exhaled by the breath is in direct proportion to the amount in
the blood
The fate of alcohol in the body
• The fate of alcohol in the body is relatively simple
– Absorption into the blood stream,
– Distribution throughout the body’s water,
– And finally elimination by oxidation and excretion
Alcohol in the Lungs
• It is in the lungs that the
respiratory system bridges with
the circulatory system
• Exchange of Carbon dioxide for
oxygen takes place, at the
Alveoli
• If while this exchange is taken
place, alcohol or any other
volatile substance, happens to
be in the blood, it too will pass
into the alveoli
Alcohol in the Lungs
• Henry’s Law:
– When a volatile chemical (alcohol) is dissolved in a
liquid (blood) and is brought to equilibrium with air
(alveolar breath) there is a fixed ratio between the
concentration of the volatile compound (alcohol) and
in air (alveolar breath) and its concentration in the
liquid (blood)
• This ratio is a constant for a given temperatures
Alcohol in the Lungs
• The temperature at which breath leaves the mouth is
normally 34 degrees Celsius
– At this temperature, experimental evidence has shown
that the ratio of alcohol in the blood to alcohol in
alveoli air is approximately
• 2,100 to 1
• 1 ml of blood will contain nearly the same amount
of alcohol as 2,100 ml of alveoli breath
Parts of the brain affected by
Alcohol
• Alcohol 1st
affects the
forebrain and
moves backward
• Last affected is
medulla
oblongata
Blood and Lungs
• Prior to completion of absorption the blood concentration
will be greater in the arteries than the veins
– Due to diffusion of alcohol into the tissues
• Breath tests reflect measurements in the pulmonary arteries
– During absorption phase breath test may be higher than
the blood test, taken from venous blood of arm
– Once absorption is complete blood and breath should
be of minimal difference
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%)!
Alcohol and the Law
•
Try the drink wheel: http://www.intox.com/wheel/drinkwheel.asp
Alcohol Detection
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
Infrared Technology
• Since the mid-1980s, infrared (IR) technology has been the primary
means of breath alcohol testing in the United States.
• Current technology uses infrared measurement systems that are made
more specific for alcohol by using several optical filters.
• You determine breath alcohol levels by passing a narrow band of IR
light, selected for its absorption by alcohol, through one side of a
breath sample chamber.
• By detecting emergent light on the other side, you can measure alcohol
concentration by using the well-known Lambert-Beers law, which
defines the relationship between concentration and IR absorption.
•
A major advantage of this technology is its ability to make real-time
measurements.
Infrared Technology
• One disadvantage of using IR technology is the high cost
of achieving specificity and accuracy at low breath alcohol
concentration levels.
• Also, the IR detector's output is nonlinear with respect to
alcohol concentration and must be corrected by
measurement circuits.
• Because of IR technology's expense, mechanical
components, and other limitations, breath alcohol
instrumentation manufacturers began a search for an
alternative.
• One technology, electrochemical cells, also known as fuel
cells, seemed to offer significant advantages.
Fuel Cell technology
• In the early 1800's a British scientist discovered the fuel
cell effect.
• He immersed two platinum electrodes in sulfuric acid
electrolyte and supplied hydrogen at one electrode and
oxygen at the other.
• The resulting reaction created a current flow between the
electrodes.
• There was no practical application of fuel cells at that time
because of high cost and technological problems.
• In the 1960s, researchers at the University of Vienna
demonstrated a fuel cell that was specific for alcohol.
• This evolved into the present-day cell used in all fuel cellbased breath alcohol measurement instruments.
Fuel Cell Technology
• In its simplest form, the alcohol
fuel cell consists of a porous,
chemically inert layer coated on
both sides with finely divided
platinum (called platinum
black).
• The manufacturer impregnates
the porous layer with an acidic
electrolyte solution, and applies
platinum wire electrical
connections to the platinum
black surfaces.
Fuel Cell Technology
• The manufacturer mounts
the entire assembly in a
plastic case, which also
includes a gas inlet that
allows a breath sample to
be introduced.
• Various manufacturers
employ numerous
proprietary nuances in
their construction.
Fuel Cell Technology
• The reaction that takes place in an alcohol fuel cell is
alcohol oxidation.
• In this chemical reaction a fixed number of electrons are
freed per molecule of alcohol.
• The oxidation occurs on the upper surface of the fuel cell.
Fuel Cell Technology
• The freed H+ ions migrate to the lower surface of the cell,
where they combine with atmospheric oxygen to form
water, consuming one electron per H+ ion in the process.
• Thus, the upper surface has an excess of electrons, and the
lower surface has a corresponding deficiency of electrons.
Fuel Cell Technology
• If you connect the two
surfaces electrically, a
current flows through this
external circuit to
neutralize the charge.
• This current is a direct
indication of the amount
of alcohol consumed by
the fuel cell.
• With appropriate signal
processing, you can
display breath alcohol
concentrations directly