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Forensic toxicology Forensic department Luyang Tao
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.
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
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.” History
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 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. Approximate Lethal Doses of Common Chemicals (Calculated for a 160 lb. human from data on rats) ChemicalLethal 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 Nicotineone half teaspoon Food poison (botulism)microscopic
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. History
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. Toxicology Terms
Threshold Effects for Dose Is there such a thing as a ‘safe’ dose?? Agent A Agent B Dose Response “NOEL” (No Observable Effect Level) Dose-Response Relationships
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
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.
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?
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.
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.
For certification as a toxicologist, an individual must possess a Ph.D. or doctorate in one of' the natural, sciences. Undergraduate degrees must also be in these areas (biology or chemistry, usually). Certification is bestowed by the American Board of Forensic Toxicology, and the expert may use the title of “Diplomate” which must be renewed every three years.
A forensic toxicologist is normally presented with preserved samples of body fluids, stomach contents, and organ parts.A forensic toxicologist is normally presented with preserved samples of body fluids, stomach contents, and organ parts. They will have access to the coroner's report which should contain information on various signs and symptoms as well as other postmortem data.They will have access to the coroner's report which should contain information on various signs and symptoms as well as other postmortem data. The toxicologist needs a through knowledge of how the body alters or metabolizes drugs because few substances leave the body in the same state as they entered.The toxicologist needs a through knowledge of how the body alters or metabolizes drugs because few substances leave the body in the same state as they entered.
SCREENING TESTS Physical tests--boiling point, melting point, density, and refractive index Physical tests--boiling point, melting point, density, and refractive index Crystal tests--treatment with a chemical reagent to produce crystals Crystal tests--treatment with a chemical reagent to produce crystals Chemical spot tests--treatment with a chemical reagent to produce color changes Chemical spot tests--treatment with a chemical reagent to produce color changes Chromatography (thin-layer or gas)--used to separate components of a mixture Chromatography (thin-layer or gas)--used to separate components of a mixture
Forensic Toxicology Forensic department Shizhong bian
Poisons "All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy." Paracelsus (1493-1541) Toxicology
TOXICOLOGY “ Science of poisons ” Studies chemical effects on life forms –Involves exposure of life forms to outside agents and recording subsequent effects Exposures can be –occupational or non-occupational gas station attendant; gas station customer –intentional or non-intentional cigarette smoker, non-smoker & 2nd hand smoke toxicology studies involve intentional exposures
PRIMARY ROUTES OF EXPOSURE Ingestion Inhalation Absorption Injection
ROUTES OF EXPOSURE Organisms can be “ dosed ” in 4 ways, Inhalation - breath most common, important OELs based on this Ingestion - oral, gastrointestinal poor hygiene often the cause we “ dose ” ourselves by ingestion often Skin absorption/contact through skin, mucous membrane contact Injection - through break in skin
Ingestion ORAL DOSE –mouth to stomach Generally to the small intestine. Examples employee who eats lunch in the work area and ingests inorganic lead that has contaminated a sandwich. Curious child who puts a toxic substance in his or her mouth out of curiosity ingestion of residue from chemicals added to our food to kill germs or parasites.
FOOD CHAIN (ingestion)EXPOSURE Depending on the chemical, we could potentially eat toxic food.
Absorption DERMAL EXPOSURE Entering the body through the skin. Substances that absorb through the skin sometimes further assimilate into the blood system. some chemicals are not absorbed easily unless the skin is cut others are absorbed quite readily regardless of the skin’s condition use of proper gloves prevents skin contact/absorption through the skin
Inhalation Breathing what is in the air which travels to the lungs. lungs are rich in blood vessels substances inhaled into the lungs often absorbed into the bloodstream –or may cause problems in the lung itself Warning properties are sensory clues (odor, irritation) –let us know a chemical’s presence in the atmosphere--“rotten egg” smell of H2S –some substances have no warning properties carbon monoxide
Injection Direct chemical access under the skin Ex. - medical shots, needle sticks Injection can also occur accidentally. –skin cut by a contaminated can or a piece of glass. –Needle sticks Powerful means of exposure –contaminant enters the bloodstream immediately.
DOSE - RESPONSE 1 Defines a chemical ’ s toxic potency Related to Amount of chemical (dose) that enters or contacts the body That elicits a given response, or reaction occurring after exposure For a given exposure duration –time is an important factor Human (or animal) variability (bell curve)
8The Occupational Environment -- Its Evaluation and Control Dose-Response (D-R) Relationship The relationship between the degree of exposure (dose) and the magnitude of the effect (response ).
DOSE - RESPONSE 2 Dose-response designations - XY Z (generic) X = response, effect –L = lethal (death) –T = toxic (toxic effect) –E = effective (a given effect is seen) Y = method of administration –D = dose (ingested, injected) –C = concentration (inhaled) Z = magnitude of effect; % of subjects affected –may also be a word such as “ lo ” (lowest dose to affect) –5 or 50 = 5% or 50% of test animals Example: LC 50 = inhaled dose at which 50% of subjects died
11 Dose-Response Terms 2 TD lo Toxic dose low lowest dose (not inhaled) for effect except radiation TC lo Toxic concentration low lowest toxic concentration via inhalation LD lo Lethal dose low lowest dose to kill 10% of the test population (LD 10 ) LD 50 Lethal dose 50% administered dose that kills 50% of the test population LC lo Lethal concentration low in air lowest inhaled concentration to kill a test animal LC 50 Lethal concentration 50% concentration that kills 50% of the test population
7The Occupational Environment -- Its Evaluation and Control Dose Units Quantity of chemical per unit mass of body weight (i.e., mg/kg) Quantity of chemical per unit area of skin surface (mg/m 2 )
12The Occupational Environment -- Its Evaluation and Control LD 50 The dose of chemical that causes death in 50 percent of the test animals. –Approximate oral LD 50 in rats often used PROBABLE ORAL LETHAL DOSE TOXICITY RATINGfor a 70 kg PERSON (154 lb) 6 SUPER TOXIC< 5 mg/kgA TASTE (< 7 dps) 5EXTREMELY TOXIC5-50 mg/kgBETWEEN 7 dps AND 1 tsp 4 VERY TOXIC50-500 mg/kgBETWEEN 1 tsp AND 1 oz 3 MODERATELY TOXIC0.5-5 g/kgBETWEEN 1 oz - 1 pt (1 lb) 2 SLIGHTLY TOXIC5-15 g/kgBETWEEN 1 pt - 1 qt 1 PRACTICALLY NONTOXIC > 15 g/kgMORE THAN 1 qt (2.2 lb)
LETHAL DOSE - LD 50 LD50 for a substance is established by repeated experiments with animals substance’s effect on humans is extrapolated to determine what the LD50 would be for humans. results are adjusted to apply to human body weight and similar characteristics. tests on animals cannot predict the exact effect that the substance will have on a human population –toxic substance often has different effects on different species In addition, scientists study the effect of a substance on human populations wherever statistics are available. Another uncertainty - most LD50 data is from acute exposure (single dose) rather than chronic testing
TOX. STUDY LIMITATIONS Use of animal data to predict human response Use of acute exposure data to infer chronic responses in some cases Unpredictability of D-R relationships So Safety factors are applied to no-effect dose to determine OELs –1/10, 1/100, or 1/000 of NOEL –What if response is immediate?
8.1The Occupational Environment -- Its Evaluation and Control Dose-Response Relationship Dose (mg/kg) % Mortality Gray Region The dose- response relationship (from C.D. Klaassen, Casarett and Doull’s Toxicology, 5th ed., New York: McGraw-Hill, 1996; reproduced with permission).
9The Occupational Environment -- Its Evaluation and Control D-R Assumptions Chemical reacts with reactive site to produce effects Response related to concentration of agent at reactive site Concentration at site relates to administered dose.
ACUTE vs CHRONIC 1 Acute Acute dose/exposure –short-term, limited duration usually high level Acute response/effects –immediate or nearly so Chronic Chronic dose/exposure –over time, usually lower level Chronic response/effects –latent, delayed, long term
EXPOSURE LIMITS Concentrations at or below which it is assumed most healthy workers will not have adverse health affects Some chemicals/agents may have no safe level –NIOSH position on carcinogens (NPG Appx A) OELs per chemical may differ--WHAT IS SAFE? OELs may change with more studies, info Different types of OELs consider different effects Look up your chemical ’ s different OELs, recording source(s)
CHEMICAL INTERACTIONS Combinations of chemicals can alter the usual effect of the individual chemicals Additive1 + 1 = 2 –toxic chemicals affecting the same organ/system Synergistic1 + 1 > 2 –toxic chemicals enhance each other ’ s effects Potentiation1 + 0 > 1 –non-toxic chemical increases the toxic effect of a toxic chemical Antagonism1 + 1 < 2 –chemicals hinder the toxic effect(s) of one another or both (i.e., antidote)
TOXIC EFFECTS Grouped according to target organ, action &/or other factors Local vs systemic effects –site of contact vs. bloodstream entry, target organ/system Acute vs chronic effects –now vs. later Reversible vs irreversible effects –may change w/ exposure duration Allergic and sensitization effects –antibody development; not D-R dependent Vary with route & rate of entry, individual characteristics
REPRODUCTIVE TOXINS, EFFECTS Teratogens physical defects in embryo/fetus mother is exposed but not necessarily affected Mutagens “ mutate genes ” ; permanent DNA changes inheritable changes (future generations) exposure to mother or father usually also carcinogens
14The Occupational Environment -- Its Evaluation and Control Threshold Response Non-Threshold NOELNo-observed effect-level –the highest dose in an experiment which did not produce an observable effect doesn ’ t mean there was no effect LOELLowest observed effect level –the lowest dose which produced an observable adverse effect
15The Occupational Environment -- Its Evaluation and Control Influencing Factors Concentration Duration and frequency of exposure Route of entry Interspecies variation Intraspecies variation Environmental factors Chemical combinations
Intraspecies Variation Age and maturity Gender and hormonal status Genetic makeup State of health Overt and covert factors that make us all different, individual, also can affect the way our body responds to exposure
19 Concentration Units Mass Per Volume mg/m 3 milligrams per cubic meter /m 3 micrograms per cubic meter g/m 3 nanograms per cubic meter Ratio, % volume (ppm = % x 10,000) PPM- Parts of a substance per million parts of air –(e.g.: 1 inch in 16 miles), 1 minute in 2 years PPB- Parts of a substance per billion parts of air –(e.g.: 1 inch in 16 000 miles), 1 second in 32 years PPT- Parts of a substance per trillion parts of air –(e.g.: 1 inch in 16 million miles, 1 second in 320 centuries
21 The Occupational Environment -- Its Evaluation and Control Exposures that Reduce Life Expectancy by 8 Min. Smoking 1.4 cigarettes Living 2 months with a cigarette smoker Eating 100 charcoal-broiled steaks 1 X-Ray (in a good hospital) Eating 40 tablespoons of peanut butter Drinking 10,000 24-ounce soft drinks from banned plastic bottles Drinking 30 12-ounce cans of diet soda containing saccharin Living 20 years near a polyvinyl chloride plant Living 15 years within 30 miles of a nuclear-power plant Wilson, R.: "A Rational Approach to Reducing Cancer Risk." New York Times, July 7, 1978.
TOX. SUMMARY Toxicology continues to evolve, increase in importance Researching chemical effects Occupational Environmental Medical Often “ educated guesswork ” Essential to continuing health of humanity
CIRCULATORY SYSEM RESPIRATORY SYSTEMS HEART STOMACH LIVER & KIDNEY INTESTINE THE BRAIN TOXINS IN OUR BODY
History of Forensic Science Chinese medicine-6 th Century 1839-MJB Orfila, toxicology Late 1800s-Alexandre Lacassagne, ballistics and bloodstain patterns 1910-Edmund Locard, exchange principle 1924-August Vollmer, LAPD crime lab 1932-FBI Laboratory, fingerprints
Forensic Science in USA and china Federal State Local Private
Information from Physical Evidence Corpus delicti Modus operandi Linkage – Locard Exchange Principle Disproving/Supporting Witnesses ’ Statements Identification of suspects/victims Provide for investigative leads
Forensic Testing Methods Comparison Testing UnknownKnown or Standard Evidence “Origin or Source” Class Characteristics vs. Individualizing Characteristics
Types of Physical Evidence Various definitions “ Animal, vegetable or mineral ” Chemical, biological, or microscopic
Specific Areas of Forensic Science Impression Evidence –Fingerprints –Footwear/Tires Trace Evidence –Hairs –Fibers –Paint –Glass Chemical Evidence –Drugs –Accelerants Biological Evidence Other Areas –Toxicology –Anthropology –Odontology
Real CSI …. CS Investigators Physical Evidence Forensic Science
Teaching Forensic Science Available resources Specific useful resources Practical exercises- Generally Today