Introduction to 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
Postmortem Drug Testing Workplace Drug Testing Identification of Contraband Materials

Deaths Investigated by Toxicologists
Accidental Poisonings Drug Abuse Cases Suicidal Poisonings Homicidal Poisonings

Toxicological Analysis of Tissue
Collect sample of all body fluids Collect samples from organs and tissues 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 Toxicological analysis must start as soon as possible after a person’s death

General Classes of Poisons
Gases Metallic Poisons Volatile Organics 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 Color test Microdiffusion test Chromatography
a. thin-layer chromatography (TLC) b. gas chromatography (GC) c. high performance liquid chromatography (HPLC) Spectroscopy a. UV light d. X-ray b. visible light e. infrared c. microwave

Example UV-vis Spectrum

Methods of Detection Color test Microdiffusion test Chromatography
a. thin-layer chromatography (TLC) b. gas chromatography (GC) c. high performance liquid chromatography (HPLC) Spectroscopy a. UV light d. X-ray b. visible light e. infrared c. microwave

Example IR Spectrum

Methods of Detection Mass Spectroscopy Immunoassay

Interpretation of Findings
Is a drug or poison present? What substance? How much of the substance is present? Is it’s concentration in the body sufficient to cause death? 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
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. 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 ) 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 (1493-1541) 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) quarts Alcohol (ethyl alcohol) 3 quarts Salt (sodium chloride) 1 quart Herbicide (2, 4-D) one half cup Arsenic (arsenic acid) 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:

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)

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)

- 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.

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.

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.

1961 - Society of Toxicology
Modern Toxicology 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
Dose-Response Relationships Is there such a thing as a ‘safe’ dose?? Agent A Agent B Response “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 days Chronic -repeated for over 90 days

Exposure to chemicals may come from many sources:
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 Hydrophilic (parent compound) (metabolite) Metabolism Decrease biological activity 2) Increase excretability Phase I Phase II (oxidative) (synthetic) Metabolites Metabolites size ionization water solubility Increase excretability Bioactivation Detoxification polarity functionality Detoxification

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)

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.

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 The Center for Environmental and Rural Health Partnership for Environmental Education 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, post-mortem 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 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

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 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
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:

Alcohol Detection

Field Sobriety Testing
Two reasons for the field sobriety test: Used as a preliminary test to ascertain the degree of the suspect’s physical impairment 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 cell-based 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

Introduction to Toxicology

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