Toxicology is the study of the harmful effects of chemicals on living organisms. All substances can be toxic depending on dose, with even something essential like vitamin A becoming poisonous at high enough levels. Common routes chemicals enter the body include ingestion, inhalation, and dermal contact. Factors like dose, formulation, and individual susceptibility determine a substance's toxicity. Pesticides aim to control pests but can also harm nontarget species like humans if exposed, so their use requires minimizing risks to human and environmental health.

1. Write down the definition and scope
of toxicology.-5
Support the statement, “ All
substances are a potential poison”.-
3

2. • Define toxicity of xenobiotics. What are the
factors that affect toxicity. 5
• Define clinical toxicology. 3

3. TOXICOLOGY
• Toxicology is the study of the adverse
effects of chemical, physical or biological
agents on living organisms and the
ecosystem, including the prevention and
amelioration of such adverse effects.
• The study of adverse effects of
xenobiotics.

4. • Xenobiotics are chemicals found but not
produced in organisms or the environment.
• They are foreign or exogenous compound

5. • Toxicology deals with the study of the harmful
effects of chemicals on living beings.
• In Greek and Roman civilizations, such
substances or chemicals with poisonous
effects were used in various activities like
hunting, defence, wars. Killings or suicides.

6. • Poisoning and knowledge of poisons have long been
known to humans
• Even the cave dwellers had the knowledge of
substances that can cause harm…
• ‘Socrates’ & ‘Cleopatra’ are two famous victims of
poisoning in history

7. Histo
ry Socrates was forced to drink Hemlock for
corrupting the youth of Athens
 Cleopatra committed suicide through the bite of
an asp; a poisonous snake
 In 15thCentury in Italy, Cesar and Lucrezia Borgia
assassinated many of their political rivals by
poisoning with arsenic, copper and phosphorus
 Lead caused poisoning in hundreds of thousands
from the time of Roman era till 17thand 18thcentury as
it was used in pottery, cosmetics, paints and in
automobile fuels

8. Histo
ry
 Mustard Gas and other poisonous gases were used
in many wars started from WW-I in 1914 by
Germans
 Newer versions are Neurotoxins, Sarin, Tabun
and VX
 Chemical toxicities has caused disasters too, like in
Bhopal, India in 1984 where release of methyl
isocyanate killed many thousands

9. Paracelsus (1493-1541)—Swiss
Physician
All substances are poisons;
there is none which is not a poison.
The right dose differentiates a poison from a
remedy.
Paracelsus (Father of Toxicology): determined
specific chemicals responsible for the toxicity
of plants and animals (dose-response
relationship)

10. Poisons are chemical/physical agents that
produce adverse responses in biological
organisms
Any substance can be toxic if introduced in a
dose capable of disturbing the normal
physiological homeostasis of the exposed
body.

11. Toxicants: are toxic substances from
chemicals
Toxic – the chemical/physical agent/substances
having the characteristic of producing an
undesirable or adverse health effects.

12. •Toxicity– the ability of a toxic to
cause adverse effects in living organisms.

13. Socrates
One of the greatest ancient philosophers was
executed by a solution of the hemlock plant
(Conium maculatum) in 399 BC.
 Poison hemlock (Conium maculatum) grows on
rubbish heaps. It contains the alkaloid coniine (most of
the alkaloids are in fruit).
The onset of toxic effects is in 20 – 30 minutes.
The death is most frequently caused by the cessation
of breathing at full consciousness and before cardiac
arrest.

14. SCOPE OF TOXICOLOGY
1. Biomedical:
• Mechanisms of actions
• Effects of exposure
• Understanding biological responses throughmodel
toxiccompounds

15. SCOPE OF TOXICOLOGY
2. Public Health:
• Recognition and identification of hazards
• Occupational exposure
• Development and use of pesticides

16. SCOPE OF TOXICOLOGY
3. Regulatory:
Development of exposure standards
Detection methods
4. Environmental:
Chemical effects on plants, animals & ecosystems
5. Clinical:
Development of antidotes & treatments

17. TOXICITy
• The ability of a poison to cause
adverse effects in living
organisms.
• Toxicity indicates the degree to
which a substance is poisonous

18. • Toxicity is measured as clinical
“endpoints” which include
 Mortality (death)
Teratogenicity (ability to cause birth
defects)
 Carcinogenicity (ability to cause cancer)
 Mutagenicity (ability to cause heritable
change in the DNA)

19. TOXICITY
Factors affecting Toxicity
1. Physical forms
2. Dose
3. Exposure
4. Routes of entry

20. Factors affecting Toxicity
A: Factors related to Poison
1. Dose of Poison:-
Dose is the amount of chemical that comes into contact with the
body or gets inside the body.
The increase of dose will increase the severity of toxicity
2. Form of Poison:-Gaseous state is more toxic than liquid state than the
solid state.
3. Purity:- This depends on the impurity of the poison; if the impurities
are more toxic than the poison, the toxicity will be more and vice
versa.

21. Factors affecting Toxicity
B. Factors related to individual
Age – Health – Sensitivity – Sex
C) Factors related to mode of exposure
Inhalation > IM > ingestion > Skin contact
D) Factors related to environment: –
Temperature, pressure, humidity, radiation can
cause alterations on poisons status.

22. ROUTESOFENTRY
ABSORPTI
ON

23. INGESTION INHALATION
DERMAL
CONTACT
ABSORPTIO
N
Gastrointestinal
tract
FAECES
LUNGS
BILE
LIVER
BLOOD &
LYMPH
KIDNEY LUNGS
BLADDER
URINE EXPIREDAIR
EXTRACELLULAR
FLUIDS
FATS
ORGANS
OF
BODY
SOFT
TISSUES OR
BONES
SECRETI
ON OF
GLANDS
SECRETION
METABOLIS
M
DISTRIBUTI
ON
EXCRETI
ON

24. Toxic dose low (TDLO): The lowest
dose of a substance introduced by any
route, other than inhalation, over any
given period of time, and reported to
produce any toxic effect in humans or
to produce tumorigenic or reproductive
effects in animals.
Toxic concentration low (TCLO):
The lowest concentration of a
Lethal dose low (LDLO): The lowest
dose, other than LD50 of a substance
introduced by any route, other than
inhalation, which has been reported to
have caused death in humans or
animals.
substance in air to which humans or
animals have been exposed for any
given period of time that has produced
any toxic effect in humans or produced
tumorigenic or reproductive effects in
animals.
Lethal dose fifty (LD50): A calculated
dose of a substance which is
expected to cause the death of 50
percent of an entire defined
Lethal concentration low (LCLO):
The lowest concentration of a
substance in air, other than
LC50, which has been reported to
cause death in humans or animals.
experimental animal population. It is
determined from the exposure to the
substance by any route other than
inhalation.
Lethal concentration fifty (LC50): A
calculated concentration of a
substance in air, exposure to which
for a specified length of time is
expected to cause the death of 50
percent of an entire defined
experimental animal population.

25. Support the statement, “ All
substances are a potential poison”.-
Although we call some substances nontoxic, in fact any chemical
can be toxic if we eat, drink, or absorb too much of it. Even
chemicals naturally present in our food and drinks are toxic if
consumed in sufficiently large quantities. For example,
 The caffeine in a normal human diet does not cause illness, but
just 50 times this amount could kill you.
 The oxalic acid found in spinach is harmless in the amounts
anyone would normally eat but could lead to kidney damage or
death if 10 to 20 pounds were consumed at a single sitting.
The dose makes the poison

26. The toxicity of any particular chemical
depends on many factors, including the extent
to which it enters an individual’s body.
Once a chemical gets taken up by an organism,
it may get metabolized, or converted through
biological processes, into other chemical
forms.
The toxicity of each type of chemical also
depends on whether it gets excreted from the
body or stored in the liver, kidneys, fat, or
other tissues.

27. Support the statement, “ All
substances are a potential poison”.-
• Eskimos never eat polar bear liver because it
would be fatal within 24 hours.
• one ordinary sized portion of it contained
1,000 times the human daily requirements of
vitamin A, an acutely fatal dose.

29. Acute toxicity :
• It refers to those adverse effects occurring
following oral or dermal administration of a
single dose of a substance, or multiple doses
given within 24 hours, or an inhalation
exposure of 4 hours

30. • Sub acute Toxicity:
It resembles acute toxicity except that the
exposure duration is greater, from several days
to one month.
• Sub chronic toxicity:
It is the toxic exposures repeated or spread
over an intermediate time range (1 – 3
months)

31. Chronic Toxicity:
• It is the exposures (either repeated or
continuous) over a long (greater than 3
months) period of time.

32. PESTICIDES
• What impact does the pesticides have on
human health and environment. 3
• Write down the symptoms of pesticide
poisoning. 3
• Sign and symptoms of carbamate
insecticides.3

33. • Discuss the common pesticides used in
Nepal and their effects on Public health. 4+6
• Briefly explain the impact of pesticides on
human health and environment. 5

34. Pesticides
• Pesticides can be defined as any substance or
mixture of substances intended for
preventing, destroying, repelling, or mitigating
pests.
• Pests can be insects, rodents, weeds, and a
host of other unwanted organisms.

36.  Pesticides occupy a rather unique position
among the many chemicals that we encounter daily,
in that they are deliberately added to the
environment for the purpose of killing or injuring
some form of life.
Ideally, their injurious action would be highly specific
for undesirable targets; however, most pesticides
are not highly selective, but are generally toxic to
many nontarget species, including humans.
 Thus, the use of pesticides must minimize the
possibility of exposure of nontarget organisms to
injurious quantities of these chemicals

37. Classification of pesticides relies on the target species
they act on.
• The four major classes (and their target pests) are
those of
1. insecticides (insects),
2. herbicides (weeds),
3. fungicides (fungi, molds), and
4. rodenticides (rodents),
But there are also acaricides (mites), molluscides
(snails, other mollusks),larvicides (larvae), and
pediculicides (lice).