Chapter 8 – Toxicology

Toxicology

the study of the adverse effects of chemicals or physical agents on living organisms

Mathieu Orfila –father of toxicology

Forensic Toxicology☠ Postmortem—medical examiner or coroner

☠ Criminal—motor vehicle accidents

☠ Workplace—drug testing

☠ Sports—human and animal

☠ Environment—industrial, air, water, soil catastrophic,

terrorism

☠Consumer – foods, cosmetics, over the counter drugs

Why we need forensics toxicologists

Death unattended by a physician or occurring under violent, unusual or sudden unexplained conditions happens in approximately 20% of the population and requires a medical/legal investigation

Forensic Toxicologist

☠ Determines if the toxin ☠ Caused the death – a lethal dose ☠ Contributed to death☠ Caused impairment☠ Explains behavior

If poison is suspected first step would be to take a blood sample

Homicide poisoning mimics medical situations, a heart attack or diabetic coma. This makes determining the cause of death difficult.

Things to consider

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

Presence of other chemicals in the body or in the dose

Toxicology Terms

Time of exposureChronic exposure – long period of time

Acute toxicity – immediate effects

Other chemicals/drugs in body Synergism – combination exceeds individual effects

Antagonism – combination decreases individual effects

Chelating agent – cancels out the poison - antidote

Toxicity Classification

To Prove a Case

Prove a crime was committed

Motive

Intent

Access to poison

Access to victim

Death was homicidal

Death was caused by poison

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.

Used for Analysis

Blood

Urine

Vitreous humor of eyes

Bile

Gastric contents

Liver tissue

Brain tissue

Kidney tissue

Hair/nails

Types of Poisoning

Arsenic

Cyanide

Carbon Monoxide

Ricin

Lead Poisoning

Mercury Poisoning

Arsenic

Claimed most victims

No odor, no taste

Fount in insecticides, pesticides and paints

Inhaled or swallowed – more than 90% absorbed into blood

Cyanide

Rapid acting – kills in minutes

Used in photo processing

Colorless gas

Stops cellular respiration and ATP synthesis

Cells cant use oxygen

Carbon Monoxide

Colorless, odorless, tasteless

Faulty heating systems, car exhaust, fires

Absorbed through lungs

Ricin

Twice as deadly as cobra venom, two-tenths of a milligram is a lethal dose.

Protein

Inhaled, injected, ingested

Potential terrorist – Al Queda

Death 36 – 72 hrs

Lead Poisoning

Lead compounds not highly poisonous, but chronic exposure can lead to health problems

Lead based paints – banned in ’78

Tastes sweet

Still 38 million houses with lead paint

Mercury Poisoningodorless, colorless, and tastelessDisturbances in sensations ("pins and needles" feelings, numbness) usually in the hands feet and sometimes around the mouth Lack of coordination of movementsImpairment of speech, hearing, walkingMuscle weakness, skin rashes, mood swing

Amalgam dental fillings

consume mercury-contaminated fish

exposed to spilled mercury

Alcohol Alcohol appears in blood within minutes of

consumption; 30–90 minutes for full absorption

About 5 percent is excreted unchanged in breath, perspiration, and urine

Rate of absorption Amount of alcohol consumed

The alcohol content ofthe beverage

Time taken to consume it

Quantity and type of food present in the stomach

Physiology of the consumer

Signs of Alcohol Poisoning

Cold, clammy, pale, or bluish skin

UnconsciousSlow or irregular breathingPuking repeatedly or

uncontrollably

BAC – Blood Alcohol Content

Expressed as percent weight per volume of blood

Legal limit in all states is 0.08 percent

Burn-off rate of 0.015 percent per hour, but can vary

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.

1 ml of blood will contain nearly the same amount of alcohol as 2,100 ml of breath.

Breathalyzer

Collects and measures alcohol content of breath

Breath sample mixes with 3 ml of 0.025 percent K2Cr2O7 in sulfuric acid and water:

2K2Cr2O7 +3C2H5OH + 8H2SO4 2Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2O

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.