Toxicology

Chapter 9

Introduction• Toxicology – • Detect and identify drugs and poisons in body fluids,

tissue, & organs• Used in legal settings – CSI and ME• Used in medical settings – hospitals and health facilities• Examples – blood tests, urine tests

History of Toxicology• Earliest record of use of poison – 339BC• Socrates’ execution• Extract of hemlock

• During European Renaissance• Poisoning became an art• Common poisons – came from plants• Hemlock, monkshood, belladonna, arsenic….left no

trace!

• Forensic Toxicology• Developed in 19th Century• 1814 – Mathieu Orfila published book on poisons• 1836 – James Marsh developed test to detect arsenic in

body

Elements of Toxicology• Important parts of Toxicology• Dosage• The dose can be the poison! Aspirin, oxygen, water

• Chemical/physical form of substance• Solid, liquid, gas• Arsenic metal – not very poisonous; Arsenic compounds –

VERY poisonous; Arsenic gas – VERY poisonous

• How it enters body• Swallowed, injected, absorbed through skin, inhalation

• Body weight• Infants more susceptible to toxins than adults• Toxins – substance that causes injury to health

• Old age weakens body

Elements of Toxicology

• Physiological conditions of victim – age, sex• Time period of exposure• Chronic Exposure vs. Acute toxicity

• Whether other chemicals are present in body• Combination of chemicals can increase/decrease

individual effect• Synergism – combined effect exceeds sum of

individual effects• Antagonism – combined effect decreases individual

effects

Testing Process• Specimen collection (postmortem)

• Blood• Most important. Best relationship with concentration. Heart blood

preferred. Test for: alcohol, cyanide, CO, depressants• Urine• Large volumes, non-invasive. Test for: sugars, drugs

• Gastric contents• Highly toxic substances will remain in large quantities in stomach. Test

for: pills, capsules• Vitreous humor• Test for: Certain drugs, alcohol, sugar, iron, urea

• Bile, liver• Liver involved in metabolism; bile drains from liver. Test for:

morphine, methadone, other drugs• Hair• Long usage; date stamp. Test for: Chronic drug use/metal poisoning

• Adipose tissue• Fat. Test for: fat soluble drugs, pesticides, insecticides

Measuring Toxicity• Standardized animal tests (rats or mice)• LD50 (lethal dose)• Amount of substance needed to kill half the population,

usually within 4 hours• Given in milligrams (mg) of substance per kilogram (kg) of

body weight• Still very uncertain because of differences in species• Examples:• Nicotine – 0.9 mg/kg for humans

9.2 mg/kg for dogs53 mg/kg for rats

Material LD50 (mg/kg, rats, oral)

Sucrose 29,700

Vitamin C 11,900

Ethanol 7,060

Sodium Bicarbonate 4,220

Sodium Chloride 3,000

Arsenic Metal 763

Caffeine 192

Nicotine 53

Arsenic Trioxide 14.6

Sodium Cyanide 6.4

Mercuric Chloride 1

Ricin 0.020

Dioxin 0.020

Botulin Toxin 0.000005-0.00005

Regulatory Agencies• The Food & Drug Administration (FDA)

• Deals with pharmaceuticals, food additives, and medical devices

• The Environmental Protection Agency (EPA)• Works on agricultural and industrial chemicals released in

environment

• The Consumer Product Safety Commission• Toxins in consumer products

• The Department of Transportation (DOT)• Shipment of toxic chemicals

• The Occupational Safety & Health Administration (OSHA)• Exposure to chemicals in the workplace• MSDS – Material Safety Data Sheets• Includes facts on physical and chemical properties of a material• Health hazards• Other information as needed• Examples

Poisons• Lead• Pharmaceutical• Cyanide• Carbon Monoxide• Alcohols

Toxicology of Lead• Chronic exposure – serious health problem – esp

for children• Can cause brain damage• Most common way of exposure:• Lead based paint (banned in 1978)• Was common ingredient• Lead compounds taste sweet• Children (often teething) would put in mouth

• Leaded gasoline (banned in 1995)• Lead in soil• Lead pipes• Lead crystal/ceramics

Toxicology of Pharmaceuticals• Could be suicide, accidental• Focus is on drugs that are dangerous in very small

amounts• Common drugs used:• Opiods – pain killers• Morphine, codeine, Vicodin, OxyContin

• Barbiturates – sleeping pills• Secobarbital, Pentobarbital

• OTC medications• Diphenhydramine

• Anti-depressant medication

Toxicology of Cyanide

• Highly toxic• Found in solid or gas forms (fastest acting = gas)• Many industrial chemicals metabolize to cyanide

• Production of paper, textiles, and plastics

• Found in cigarette smoke• Pest extermination• Some plant materials leads to production of cyanide in body

• Foods – lima beans, almonds, apricot pit, apple seeds

• Why dangerous?• Binds to iron ions in mitochondria• Interrupts electron transport chain; cells die• Death occurs quickly (energy is not produced)

• Antidote?• If exposed to large doses – beyond treatment• Small doses – can be saved• Antidote contains nitrite

Toxicology of Carbon Monoxide• Fires, faulty heaters• Stoves, charcoal grills, generators

• Binds to hemoglobin and it cannot carry O2

• Cells die

Toxicology of Alcohol• Legal OTC drug• Most heavily abused in Western countries• Facts:• In 2010, 10,228 people were killed in alcohol-impaired

driving crashes, accounting for nearly one-third (31%) of all traffic-related deaths in the United States.• Of the 1,210 traffic deaths among children ages 0 to 14

years in 2010, 211 (17%) involved an alcohol-impaired driver.• Of the 211 child passengers ages 14 and younger who died

in alcohol-impaired driving crashes in 2010, over half (131) were riding in the vehicle with the alcohol-impaired driver.• In 2010, over 1.4 million drivers were arrested for driving

under the influence of alcohol or narcotics.

Toxicology of Alcohol

• Alcohol = Ethyl alcohol (C2H5OH)• Colorless• Liquid• Normally diluted with water• Consumed as beverage• Depressant to CNS, especially the brain

1. Starts in forebrain (surface areas)2. Moves to central and rear portions3. Lastly – medulla (vital functions – respiration and heart activity)

Toxicology of Alcohol• Determine presence of alcohol in body?• Extremely variable! • Relies on body weight, rate of absorption, time elapsed• Absorption – passage of alcohol across organ tissue

into bloodstream• Best (most accurate) test – remove brain and test brain

tissue• Blood!• Circulates alcohol throughout body• Research proves that blood alcohol concentration is

directly proportional to concentration of alcohol in brain• THE accepted standard• Appears within minutes in blood

Path of Alcohol in Body• Absorption• Distribution• Elimination

Absorption of Alcohol• Many factors affect rate of absorption• Time taken to consume, amount, food present, alcohol

content• Beer absorbed more slowly because of carbs present• Absorbed faster on empty stomach• To reach maximum blood alcohol concentration:• May take anywhere from 30 min – 3 hours

Distribution of Alcohol• Will be distributed to all watery parts of the body• About 2/3 of body volume• Fat, bones, hair – little water, not useful in BAC• So…..if blood is not available…water rich organ or fluid

Distribution of Alcohol• Circulatory system• Basics:• Closed circulatory system• Artery – carries blood away from heart• Vein – Transports blood to heart• Capillary – Tiny blood vessel that interconnect arteries

and veins

Distribution of Alcohol• Movement through circulatory system:• Ingested• Moves to stomach (20% absorbed through stomach walls

into blood system)• Remaining passes into blood system through small

intestine• Carried to liver• Moves up to heart• Pumped up to lungs to replenish with oxygen

Distribution of Alcohol• Movement through Respiratory System:• Blood in capillaries comes in contact with alveoli at the

ends of the bronchial tubes• An oxygen-carbon dioxide exchange occurs here• CO2 and alcohol are expelled through nose and mouth

Distribution of Alcohol• Back to circulatory system:• Blood emerges from lungs (now oxygenated)• Moves back to heart by the pulmonary vein• Heart pumps into the arteries – carries throughout body

During absorption phase, arterial blood is always a higher BAC than venous blood!!! As soon as maximum absorption is reached, level equalize!!

Elimination of Alcohol• Two mechanisms:• Oxidation• Excretion

Average rate is 0.015% per hour!

Elimination of Alcohol• Oxidation• Combining oxygen to alcohol• Produces CO2 and H2O

• About 95-98% of alcohol consumed is oxidized• Occurs in liver (contains an enzyme to aid in this process –

alcohol dehydrogenase)• Alcohol acetaldehyde acetic acid CO2 and H2O

Elimination of Alcohol• Excretion• Eliminated unchanged• Breath, urine, perspiration• Concentration of alcohol in breath is directly proportional

to BAC

Alcohol Testing• Breath Test• Test alcohol in pulmonary artery• Very useful• Easily obtained from suspect• Rapid, accurate result

Alcohol Testing• Breath Test• First successful breath-test device – 1954 – R.K.

Borkenstein – called the Breathalyzer• Blow into a disposable mouthpiece• Trapped breath in a cylinder• Measures the quantity of alcohol in breath through several

chemical reactions (color change; orange to green)

Alcohol Testing• Breath Test• Breathalyzer phased out in 1970s• Replaced with computerized instruments – still measure

alcohol content in breath• Free of chemicals• Use IR to detect and measure alcohol

Alcohol Testing• Blood tests• Gas Chromatography (GC) • Most widely used• High degree of accuracy

• Spectrophotometer• Measures conversion of alcohol to acetaldehyde

Collection of Blood• Sterile environment• Qualified individual• Add anticoagulant and preservative• Now it can be stored in an air-tight container!!• Anticoagulant – Prevent clotting• Preservative – inhibits growth of bacteria

• Store in refrigerator• Failure to do so = substantial decline in alcohol

concentration

• Storage time• Longer time = reduced blood alcohol levels

Collection of Blood• Postmortem• Collect many from different sites!• Ethyl alcohol may be produced because of

decomposition

Blood Alcohol Content (BAC)

• BACmale = 0.071 x [vol consumed, oz] x [% alc]

body weight

• BACfemale = 0.085 x [vol consumed, oz] x [% alc]

body weight

Alcohol and the Law• Operation of Motor Vehicles:• 1939-1964• 0.15%

• 1965• 0.10%

• 1972• 0.08%

CDL – 0.04%

Alcohol and the Law• Internationally:• Many countries – 0.08%• Canada, Italy, Switzerland, UK

• Some – 0.05%• Finland, France, Germany, Ireland, Japan, the

Netherlands, Norway• Sweden – 0.02%

Blood Alcohol Content (BAC)• Example:• What would be the approximate BAC of a 185 pound man

who consumed 3 shots (1.5 oz each) of Jack Daniels (40% alcohol)?• Can he legally drive home?

Alcohol and the Law• Implied Consent Law• If you do not comply to a breath test if asked, you will

automatically lose your license – usually for 6-12 months• This is to combat the possibility of using the 5th amendment

defense!

• Schmerber vs California, 1966• Schmerber was arrested for DUI at a hospital after a car accident

while being treated• Physician took blood sample at direction of police even though

Schmerber refused.• Schmerber argued that his 5th amendment rights were violated• Court ruled that physical evidence like blood is not covered under

the 5th amendment; only testimonial evidence• Taking of blood was deemed an emergent situation and therefore

a warrant was not needed – did not violate 4th amendment rights either

Toxicological Techniques• There are many drugs/poisons to look for• Must develop analytical scheme to ultimately

identify• Possible methods:• Screening• Confirmation

Toxicological Techniques• Screening (presumptive tests)• Likelihood a specimen contains the drug• Narrows down possibilities• Positive results are tentative and preliminary (may be

present)• Most used methods:• Color tests• TLC• GC• Immunoassay (antigen-antibody reaction)• UV Spectroscopy

Toxicological Techniques• Confirmation• GC-MS (Gas Chromatography/Mass Spectrometry) • Most used method of choice• One step confirmation test• Identifies drug• Produces “fingerprint” of drug

• IR Spectroscopy

Case Study• Georgi Ivanov Markov• September 1978• Markov defected to London from Bulgaria• Markov worked in broadcasting and was a writer• One day – standing at bus stop – felt sharp jab in thigh.

Turned to see an apologetic man standing with umbrella• Next morning – admitted to hospital with high fever and

vomiting• Died three days later• During autopsy found small pellet in thigh – believed to be a

poison pellet fired by umbrella• Determined pellet to contain ricin (LD50 = 0.020 mg/kg)

• Very close to major blood vessels which sped process up!• Bulgarian secret service responsible! Victim of the cold war!