The most ambitious definition of health is that proposed by WHO in 1948: “health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.” but,
Practical definitions of health and disease are needed in epidemiology, which concentrates on aspects of health that are easily measurable and amenable to improvement.
Definitions of health states used by epidemiologists tend to be simple, for example, “disease present” or “disease absent”
1. HARAR HEALTH SCIENSE COLLEGE
Course Title: Applied Toxicology
Chapter 1- Introduction to Toxicology
For 3rd Year Medical laboratory science Student
By:-MENBERE DEBELE
(BSc. C/Nurse, B.Pharm)
1
2. Outline
Introduction to Toxicology
Definition, areas of toxicology, scope, application,
and the medical laboratory scientist role in
toxicology
Nature of toxic responses, routes of poisoning
Potential causes of toxicity
2
3. Learning objectives
At the end of this chapter you will be able to:
Define toxicology & commonly associated
terms
Differentiate the sub-disciplines of
toxicology
Describe the classifications of toxic agents
Explain Nature of toxic responses, routes of
poisoning
Mention Potential causes of toxicity
3
5. Definitions
What is Toxicology?
Derived from Greek word, toxikon and logos
Toxicology is the study of the adverse effects of
xenobiotics
Toxicology is the study of how natural or man-made
poisons cause undesirable effects in living
organisms
5
6. Definitions…
What are harmful or adverse effects?
Harmful or adverse effects are those that are
damaging to either the survival or normal function of
the individual
What is Toxicity?
The word “toxicity” describes the degree to which a
substance is poisonous or can cause injury
The toxicity depends on a variety of factors:
• Dose, duration & route of exposure, nature of the
chemical, & individual human factors
6
7. Definitions…
Poison- a chemical that may harm or kill an organism
What is a Toxicant?
A toxicant is any chemical that can injure or kill living
organisms
The term “toxicant” is used when talking about toxic
substances that are produced by or are a by-product
of human-made activities
What is a Toxin?
The term “toxin” usually is used when talking about
toxic substances produced naturally
7
8. Definitions…
What is a Toxic Symptom?
This term includes any feeling or sign indicating the
presence of a poison in the system
e.g feeling and being sick, diarrhoea, stomach pain,
drowsiness, dizziness or weakness, high
temperature….etc
What are Toxic Effects?
This term refers to the health effects that occur due
to exposure to a toxic substance; also known as a
poisonous effect on the body
8
9. Definitions…
What is Selective Toxicity?
“Selective toxicity” means that a chemical will
produce injury to one kind of living matter
without harming another form of life,
eventhough the 2 may exist close together
9
10. Definitions…
How does toxicity develop?
Before toxicity can develop, a substance must
come into contact with a body surface such
as skin, eye or mucosa of the digestive or
respiratory tract
The dose of the chemical, or the amount one
comes into contact with, is important when
discussing how “toxic” a substance can be
10
11. Definitions…
What is a dose?
The dose is the actual amount of a chemical that
enters the body
The dose received may be due to either acute
(short) or chronic (long-term) exposure
• An acute exposure occurs over a very short period of
time, usually 24 hrs
• Chronic exposures occur over long periods of time
such as weeks, months, or years
The amount of exposure & the type of toxin will
determine the toxic effect
11
12. Definitions…
What is dose-response?
Dose-response is a relationship b/n exposure &
health effect that can be established by measuring
the response relative to an increasing dose
This relationship is important in determining the
toxicity of a particular substance
Usually, the larger or more intense the dose, the
greater the response, or the effect
• “the dose makes the poison”
12
13. Definitions…
What is the threshold dose?
Given the idea of a dose-response, there should
be a dose or exposure level below which the
harmful or adverse effects of a substance are
not seen in a population
• That dose is referred to as the ‘threshold dose’
• This dose is also referred to as the no observed
adverse effect level (NOAEL), or the no effect
level (NEL)
13
14. Definitions…
What is meant by ‘individual susceptibility?’
This term describes the differences in types of
responses to hazardous substances, b/n
people
Each person is unique, & b/c of that, there may be
great differences in the response to exposure
Exposure in one person may have no effect, while
a second person may become seriously ill, & a
third may develop cancer
14
15. Definitions…
What is a “sensitive sub-population?”
A sensitive sub-population describes those persons who
are more at risk from illness due to exposure to
hazardous substances than the average, healthy
person
• Usually include the very young, the chronically ill,
& the very old
• It may also include pregnant women & women of
childbearing age
Depending on the type of contaminant, other factors
(e.g., age, wt, lifestyle, sex) could be used to describe
the population
15
17. History of toxicology
A. Antiquity
The Ebers papyrus (circa 1500 B.C.)
describes many recognized poisons-
hemlock, aconite, opium, lead, copper,
antimony, digitalis, belladonna alkaloids
Theophrastus (370–286 B.C.), a student of
Aristotle, wrote De Historia Plantarum
Socrates (470-399 B.C.) received poison as
part of state execution
17
18. History of toxicology…
Demosthenes (385– 322 B.C.) and Cleopatra’s (69–
30 B.C.)
Voluntary took poison
King Mithridates (134-63 B.C.) of Pontus
Poisoned many criminals in his experiments to
identify antidotes
Epidemic Poisonings in Rome lasted from 4th -1st
century B.C
Dioscorides (Greek physician) 60 A.D.
Described many poisons, devised categorization system (plant,
animal, mineral)
18
19. History of toxicology…
B. Middle Ages
Moses Ben Maimon (Maimonides 1135–
1204 A.D.)
• Wrote poisoning and their Antidotes
Renaissance Italians brought poisoning to a
zenith
Catherine de Medici
Catherine Deshayes ( “La Voisine” )
19
20. History of toxicology…
C. Age of Enlightenment
Paracelsus led the change from the science of
Hippocrates and Galen to that of the 17th century
giants
Championed the “toxicon,” as a chemical entity and
the following principles:
• Experimentation is essential in the examination of
responses to chemicals
• Therapeutic and toxic properties of chemicals
• Therapeutic and toxic properties are often
distinguishable by dose
• Specificity can be achieved for the therapeutic versus
toxic properties of chemicals
20
21. History of toxicology…
D. The Modern age
Exponential growth parallels the World
War II with greatly increased
production of drugs, pesticides,
organic chemicals
During this period, the use of “patent”
medicines was prevalent, and there
were several incidents of poisonings
from these medicaments
21
23. Branches of Toxicology
The field of toxicology can be further divided into
the following sub-disciplines or subspecialties:
Mechanistic Toxicology
Descriptive Toxicology
Regulatory Toxicology
Environmental Toxicology
Occupational (Industrial) Toxicology
Food Toxicology
Clinical Toxicology
Forensic Toxicology
Analytical toxicology
23
24. Branches of Toxicology…
Mechanistic Toxicology
It makes observations on how toxic substances
cause their effects
Descriptive Toxicology
It is concerned with gathering toxicological
information's from animal experimentation
These types of experiments are used to establish
how much of a chemical would cause illness or
death
24
25. Branches of Toxicology…
Regulatory Toxicology
It gathers & evaluates existing toxicological
information's to establish conc-based standards of
“safe” exposure
• The std is the level of a chemical that a person can
be exposed to without any harmful health
effects
Analytical toxicology
It identifies the toxicant through analysis of body
fluids, stomach content, excrement, or skin
25
26. Branches of Toxicology…
Environmental Toxicology
It is concerned with the study of chemicals that
contaminate food, water, soil, or the atmosphere
It also deals with toxic substances that enter
bodies of waters such as lakes, streams, rivers,
& oceans
26
27. Branches of Toxicology…
Occupational (Industrial) Toxicology
It is concerned with health effects from exposure
to chemicals in the workplace
Food Toxicology
It is involved in delivering a safe & edible supply of
food to the consumer
All of the additives added during processing are
studied to determine if & at what amount, they
may produce adverse effects
27
28. Branches of Toxicology…
Clinical Toxicology
It is concerned with diseases & illnesses
associated with short term or long term exposure
to toxic chemicals
Forensic Toxicology
It is used to help establish cause & effect
relationships b/n exposure to a drug or chemical
& the toxic or lethal effects that result from that
exposure
28
29. Scope and Application of Toxicology
In forensic toxicology
establishing the cause of death and elucidating
its circumstances in a postmortem investigations
Economic or industrial toxicology
in drugs, pesticides, food additives,
containers(like cans and packing materials)
Environmental toxicology
Pollutional studies, resedue analysis
Industrial hygiene and occupational health
29
31. Toxicokinetics & Toxicodynamics
Toxicokinetics
It is the quantitation of the time course of
toxicants in the body during the processes of
ADME of toxicants
It is a reflection of how the body handles
toxicants as indicated by the plasma conc of
that xenobiotic at various time points
The end result of these toxicokinetic processes
is a biologically effective dose of the toxicant
31
33. Toxicokinetics & Toxicodynamics…
Toxicodynamics
Refers to the molecular, biochemical, &
physiological effects of toxicants or their
metabolites in biological systems
These effects are result of the interaction of the
biologically effective dose of the ultimate (active)
form of the toxicant with a molecular target
33
35. Spectrum of toxic dose
“What is there that is not poison? All things are
poison and nothing [is] without poison. Solely the
dose determines that a thing is not a poison.”
Paracelsus (1493–1541)
35
36. 36
Table 1, which shows the dosage of chemicals needed to
produce death in 50 percent of treated animals (LD50)
38. The medical laboratory scientist
role in toxicology
Clinical toxicology can be defined as the
analysis of drugs and toxins in body fluids
for the purpose of patient care.
The mission of the clinical toxicology laboratory
is to effectively utilize available laboratory
resources and expertise to provide clinically
useful toxicology tests to support the needs of
the patients.
38
39. role in toxicology cont’d
Most poisoned patients can be treated
successfully without any contribution from
the laboratory other than routine clinical
biochemistry and haematology.
This is particularly true for those cases where
there is no doubt about the poison involved
and when the results of a quantitative analysis
would not affect therapy.
39
40. role in toxicology cont’d
However, toxicological analyses can play a
useful role if the diagnosis is in doubt, the
administration of antidotes or protective
agents is contemplated, or the use of active
elimination therapy is being considered.
40
41. Basic information necessary for toxicology
laboratory
Close communication b/n clinical & laboratory
personnel is essential.
Suspected agent(s), suspected dose, time of
ingestion & sampling, clinical presentation &
location of the victim are very important basic
information necessary for toxicology laboratory.
41
43. Nature of toxic responses
The resulting biologic effect of combined exposure to
several agents can be characterized as:
Synergism
when the effect of two chemicals is greater than the
effect of individual chemicals Example: 2 + 2 = 20
e .g carbontetrachloride + alcohol= more toxic to the liver
than the sum of the individual drugs.
43
44. Nature of toxic responses cont’d
Additive effect-
when the total pharmacological action of two or
more chemicals taken together is equivalent
to the summation of their individual
pharmacological action
Example: 2 + 3 = 5
Organophosphorus pesticides ⇒ Cholinesterase
inhibiters
44
45. Nature of toxic responses cont’d
Potentiation effect
when the net effect of two chemicals used together is
greater than the sum of individual effects (the capacity
of a chemical to increase the effect of another chemical
without having the effect alone) Example: 0 + 2 = 10
Isopropanol is not hepatoxic, but enhance carbon
tetrachloride induced hepatoxicity
Antagonism - is the phenomenon of opposing actions of
two chemicals on the same system Example: 4 + 0 = 1
Dimercaprol (BAL) chalets with metal ions, As, Pb….
45
46. Nature of toxic responses cont’d
RELATIVE TOXICITIES
Standard toxicity ratings that are used to describe
estimated toxicities of various substances to humans
Their values range from one (practically nontoxic) to
six (supertoxic)
In terms of fatal doses to an adult human of average
size, a “taste” of a supertoxic substances (just a few
drops or less) is fatal
46
48. Nature of toxic responses cont’d
Parameters
Median lethal dose (LD50) – is the dose which is
expected to kill 50% of the population in the particular
group.
Median effective dose (ED50) –is the dose that
produces a desired response in 50% of the test
population when pharmacological effects are plotted
against dosage.
Median toxic dose (TD50) – is the dose which is
expected to bring toxic effect in 50% of the population
in the particular group
48
49. Nature of toxic responses cont’d
REVERSIBILITY AND SENSITIVITY
a) Reversibility Vs. Irreversible
Sub lethal doses of most toxic substances are eventually
eliminated from an organ system.
If there is no lasting effect from the exposure, it is
said to be reversible
However, if the effect is permanent, it is termed
irreversible
49
50. Nature of toxic responses cont’d
Irreversible effects of exposure remain after the
toxic substance is eliminated from the
organism
For various chemicals and different subjects,
toxic effects may range from the totally
reversible to the totally irreversible
50
51. Nature of toxic responses cont’d
b)Hypersensitivity vs. Hyposensitivity
In some cases hypersensitivity is induced
After one or more doses of a chemical, a subject may
develop an extreme reaction to it
This occurs with penicillin, for example, in cases where
people develop such a severe allergic response to the
antibiotic that exposure results in death if
countermeasures are not taken
51
52. Nature of toxic responses cont’d
Hyposensitivity
hyposensitivity is induced by repeated exposures to a
toxic substance leading to tolerance and reduced
toxicities from later exposures
Tolerance can be due to a less toxic substance
reaching a receptor or to tissue building up a
resistance to the effects of the toxic substance
example, with repeated doses of toxic heavy metal
cadmium
52
54. Routes of poisoning
• A route of administration in pharmacology and
toxicology is the path by which a drug, fluid,
poison, or other substance is taken into the
body.
• There are three major categories of route.
1)Enteral route
2)Parenteral route
3)Topical route
54
55. Routes of poisoning cont’d
Oral route – the GIT is the most important route of
absorption, as most acute poisonings involve ingestions
Dermal route – lipid solubility of a substance is an
important factor affecting the degree of absorption
through the skin
Inhalational route – toxic fumes, particulate and
noxious gases may be absorbed through the lungs
Intramuscular route – unreliable and varied from
patient to patient
Intravenous route – is the most reliable and provides
the most rapid clinical response
Rectal route – is generally considered to produce erratic
absorption
55
56. Routes of poisoning cont’d
Oral (commonest)
Inhalation: gas poison
Parenteral (IM, IV, Sub-Cutaneous, Intra-Dermal)
Natural Orifices other than mouth (Nasal, Rectal, Vaginal,
Urethral)
Ulcers, wounds and intact skin
The decreasing order of effectiveness in different routes is:
Intravenous, inhalation, intra-peritoneal, subcutaneous,
intramuscular, intra-dermal, oral, and dermal
56
57. Potential causes of toxicity
The potential causes of toxicities include:
Therapeutic agents
Industrial & house hold chemicals
Environmental contaminants
Animal & plant toxins
Drugs of abuse
Food preservatives
Traditional drugs
Fumes …..
57
59. Sources of toxic compounds
Given the enormous number of toxicants, it is difficult to
classify them chemically, either by function or by
mode of action, since many of them would fall into
several classes
Some are natural products, many are synthetic
organic chemicals of use to society, while others are
by-products of industrial processes & waste
disposal
It is useful, however, to categorize them according to:
The expected routes of exposure or their uses
59
60. Sources of Poison cont’d
Exposure classes
Include: toxicants in food, air, water, & soil as well as
toxicants characteristic of domestic & occupational
settings
Use Classes
Include: drugs of abuse, therapeutic drugs,
agricultural chemicals, food additives & contaminants,
metals, solvents, combustion products, cosmetics, &
toxins
• Some of these, such as combustion products, are the
products of use processes rather than being use
classes
60
61. Sources of Poison cont’d
Other classification
Domestic or household sources
Agricultural and horticultural sources
Industrial sources
Commercial sources
From uses as drugs and medicines
Food and drink
Miscellaneous sources - snakes bite poisoning,
city smoke, sewer gas poisoning etc.
61
62. Sources of Poison cont’d
Domestic or household sources - detergents,
disinfectants, cleaning agents, antiseptics, insecticides,
rodenticides etc.
Agricultural and horticultural sources- different
insecticides, pesticides, fungicides and weedicide
Industrial sources- In factories, where poisons are
manufactured or poisons are produced as by products
Commercial sources- From store-houses, distribution
centres and selling shops
62
63. Sources of Poison cont’d
From uses as drugs and medicines – Due to wrong
medication, overmedication and abuse of drugs
Food and drink – contamination in way of use of
preservatives of food grains or other food material,
additives like colouring and odouring agents or other
ways of accidental contamination of food and drink
Miscellaneous sources- snakes bite poisoning, city
smoke, sewer gas poisoning etc
63
64. Common poisons and drugs
Corrosive poisons
Irritant poisons
Analgesic, Hypnotic, Tranquilizer, and Narcotic poisons
Stimulants, Excitants, and Convulsants poisons
Paralytic, Anticholinesterase and Antihistamine poisons
Gaseous and Volatile poisons
Industrial gaseous and Volatile poisons
Poisons by Plants, flora, and fungi
64
65. Factors that influence toxicity
There are numerous factors which may modify the pt's
responses to the toxic agent
For examples;
Dose of toxicant
Route of exposure
Duration of exposure to toxicant: acute vs chronic
Toxicant’s properties: shape, structure, solubility,
stability, etc.
Individual factors, e.g. genetics, age, overall health,
etc
65
66. Major Factors that influence toxicity cont’d
Quantity:
A high dose of poison acts quickly and often resulting in
fatal consequences.
A moderate dose causes - acute poisoning
A low dose may have sub-clinical effects and causes-
chronic poisoning on repeated exposure
Very large dose of Arsenic may produce - death by
shock without dose irritant symptoms,
While smaller dose than lethal dose produces its -
therapeutic effects
66
67. Factors that influence toxicity cont’d
Physical form:
Gaseous or volatile poisons are very quickly
absorbed and are thus most rapidly effective
Liquid poisons are more rapid than solid poisons
Some poisonous vegetable seeds may pass through the
intestinal canal ineffective when taken intact due to
their impermeable pericarp
67
68. Factors that influence toxicity cont’d
Chemical form:
Chemically pure arsenic and mercury are not
poisonous because these are insoluble and
are not absorbed
But white arsenic (arsenic oxide) and mercuric
chloride are deadly poisonous
Barium sulphide is deadly toxic but barium
sulphate is non-toxic
68
69. Factors that influence toxicity cont’d
Concentration (or dilution):
Concentrated form of poison are absorbed more
rapidly and are also more fatal but there are
some exceptions too
69
70. Factors that influence toxicity cont’d
Condition of the stomach:
Food content presence of food-stuff acts as diluent of the
poison and hence protects the stomach wall
Dilution also delays absorption of poison.
Empty stomach absorbs poison most rapidly
In cases of achlorohydria, KCN and NaCN is ineffective
due to lack of hydrochloric acid, which is required for the
conversion of KCN and NaCN to HCN before absorption
70
71. Factors that influence toxicity cont’d
Route of administration:
Absorption rate is different for different routes. Eg. Based
on the Decreasing order
IV, inhalation, intra-peritoneal, subcutaneous, intramuscular,
intra-dermal, oral, and dermal
Age:
some poisons are better tolerated in some age groups
Opium and its alkaloids are tolerated better by elderly
subjects but badly by children and infants.
Belladonna group of drugs are better tolerated by children
than by adults
71
72. Factors that influence toxicity cont’d
State of body health:
A well built person with good health can tolerate the
action of poison better than a weak person.
Presence of disease:
In certain diseased conditions some drugs are tolerated
exceptionally well
e.g.: sedatives and tranquilizers are tolerated in very high
dose by manic and deliriant patients
72
73. Factors that influence toxicity cont’d
Intoxication arid poisoning states
In certain poisoning cases some drugs are well tolerated,
like, in case of strychnine poisoning, barbiturates and
sedatives are better tolerated.
Whereas in case of barbiturate poisoning any sedative or
tranquilizer will accentuate the process of death
73
74. Factors that influence toxicity cont’d
Sleep
Due to slow metabolic process and depression of
other body functions during sleep, usually the
absorption and action of the poison is also slow
But depressant drugs may cause, more harm during
the state of sleep.
Exercise
Action of alcohol on C.N.S. is slowed during exercise
because more blood is drawn to the muscles during
exercise
74
75. Factors that influence toxicity cont’d
Cumulative action of poisons:
Preparations of cumulative poisons (poisons which are
not readily excreted from the body and are retained
in different organs of the body for a long time) like lead
may not cause any toxic effect when enters the body in
low dose
But when such poisons enter over a long period of
time, may cause harm when their concentration in
different tissue reaches high level due to their
cumulative property
75
Editor's Notes
Extracts of Aconitum species have been given orally in traditional medicine to reduce fever associated with colds, pneumonia, laryngitis, croup, and asthma; for pain, inflammation, and high blood pressure; as a diuretic; to cause sweating; to slow heart rate; and for sedation.
What are common uses for hemlock?
Socrates, the ancient Greek philosopher, was given poison hemlock as a punishment for the crime of corrupting the youth and impiety
When the political climate of Greece turned against him, Socrates was sentenced to death by hemlock poisoning in 399 B.C
Overview. Eastern hemlock is a plant. The bark is used as medicine. People use eastern hemlock for conditions such as digestive disorders, diarrhea, a disease caused by vitamin C-deficiency (scurvy), and diseases of the mouth and throat, but there is no good scientific evidence to support these uses.
Opium was known to ancient Greek and Roman physicians as a powerful pain reliever. It was also used to induce sleep and to give relief to the bowels. Opium was even thought to protect the user from being poisoned. Its pleasurable effects were also noted.
Historia Plantarum is Latin and literally means History of Plants, although in reality it means something closer to "on plants" or "treatise on plants".
384-322 BC. Demosthenes was a Greek orator, speech-writer, and politician. He was known as a great champion of democracy and an advocate of the right of Greece to exist as a separate nation from Macedonia. Why is Cleopatra famous? While queen of Egypt (51–30 BCE), Cleopatra actively influenced Roman politics at a crucial period and was especially known for her relationships with Julius Caesar and Mark Antony. She came to represent, as did no other woman of antiquity, the prototype of the romantic femme fatale
Mithridates VI Eupator (120-63 B.C.) was a famous king of Pontus—a region on the Black Sea—who in the last century of the republic long defied the power of Rome. In a series of three wars, fought between the 80s and the 60s B.C., he engaged with such great soldiers of the day as Sulla, Lucullus and Pompey.
characteristic hyperactivity and dream-like hallucinations