Ecotoxicology is the science devoted to the study of the adverse effects of chemicals on ecosystems structure, functions, and biodiversity. It is a modern discipline, just developed during the last four decades, directly associated to the need to identify, predict, control, and minimize the negative environmental consequences of the recent human industrial development. Ecotoxicology has always been connected to toxicology, and is in part an extension of human/veterinary toxicology to the investigation of effects on wildlife. In parallel, it also linked ecotoxicology to ecology, from both conceptual and methodological viewpoints.

1. ECOTOXICOLOGY
M.Phil Zoology 2nd Morning

2. Zobia Nasrullah
2020-ag-1715

3. Ecotoxicology
• Introduction to Ecotoxicology
• Types of contaminants
• Sources of contaminants
• Nature ofToxicant
• Nature of man made chemicals
• Common types of environmental hazards
• Types ofToxicants or Pollutants
• Factors influencing toxicity
• Toxicity at organismic level
• Mapping environmental hazards
• Environmental toxicity testing
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•Ecotoxicology is the science devoted to the
study of the adverse effects of chemicals on
ecosystems structure, functions, and
biodiversity. It is a modern discipline, just
developed during the last four decades, directly
associated to the need to identify, predict,
control, and minimize the negative
environmental consequences of the recent
human industrial development.
Introduction to Ecotoxicology

5. Ecotoxicology has
always been connected
to toxicology, and is in
part an extension of
human/veterinary
toxicology to the
investigation of effects
on wildlife. In parallel,
ecotoxicology is also
linked to ecology, from
both conceptual and
methodological
viewpoints.
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6. Types of Contaminants
•Pollutant
•Poison
•Toxicant
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7. Pollutant
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Pollutants are the elements,
molecules and particles
involved in pollution - life can
be harmed when exposed to
these materials, and the
effects of them on humans
and plants are well
known. Pollutants can be
introduced into the
environment in many ways,
both naturally and by humans.

8. Poison
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A poison is any substance that is
harmful to your body. You might
swallow it, inhale it, inject it, or
absorb it through your skin. Any
substance can be poisonous if too
much is taken. Poisons can include.
Prescription or over-the-counter
medicines taken in doses that are
too high.

9. Toxicant
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Toxicants are the man-made harmful
substances such as insecticides and many
other industrial chemicals which are
released to the environment by human
activities. Carcinogens, Mutagens,
Allergens, Neurotoxin and Endocrine
disrupters are the different types of
toxicants. Exposure to toxicants can have
long term health impacts among
organisms.

10. Zunaira Bibi
2020-ag-1735

11. Sources of toxicants and Pollutants
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• Point source
• Non-point source

12. Point Source
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• Point sources release pollutants
from discrete conveyances, such
as a discharge pipe, and are
regulated by federal and state
agencies. The main point source
dischargers are factories and
sewage treatment plants, which
release treated wastewater.
• Location exactly known.

13. Non-point Source
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• Nonpoint source pollution is
a combination of pollutants from a
large area rather than from specific
identifiable sources such as
discharge pipes.
• Runoff is generally associated with
nonpoint source pollution, as water
is emptied into streams or rivers
after accumulating contaminants
from sources like gardens, parking
lots or construction sites.

14. Nature of toxicants
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A toxic agent is anything that can produce an adverse biological
effect. It may be chemical, physical, or biological in form. For
example, toxic agents may be:
• Chemical (such as cyanide)
• Physical (such as radiation)
• Biological (such as snake venom)

15. Sehrish Fatima
2020-ag-1710

16. Natural and Man Made Chemicals
16 4/22/2021 M.Phil Zoology 2nd Semester Morning

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18. Common types of environmental hazards
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• Water: detergents, fertilizer, raw sewage, prescription
medication, pesticides, herbicides, heavy metals, PCBs
• Soil: heavy metals, herbicides, pesticides, PCBs
• Air: particulate matter, carbon monoxide, sulfur dioxide,
nitrogen dioxide, asbestos, ground-level ozone, lead
(from aircraft fuel, mining, and industrial processes)

19. Muhammad
Ahmed Saqib
2020-ag-1723

20. Types ofToxicants or Pollutants
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Organic
• Toxicants or Pollutants Polychlorinated Biphenyls
(PCBs) are organic that are still present in our
environment today despite being banned in many
countries such as the United States and Canada. Due
to the persistent nature of PCBs in aquatic
ecosystems, many aquatic species contain high levels
of this chemical.
• For example, fish farmed salmon have been shown to
have significantly higher PCB levels.

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Rout of Polychlorinated Biphenyls (PCBs)

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Inorganic
Inorganic pollutants or toxicants comprise mainly of heavy metals,
which are toxic or poisonous even at low concentrations. Example of
heavy metals includes arsenic, mercury, lead, and chromium.They
can enter body system through water, food, and air and cause health
issues.
Some inorganic contaminants are as follow:
• Heavy metal
• pesticides
• Herbicides
• Insecticides

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Heavy Metals
Heavy metals found in food sources, such as fish can also have
harmful effects. These metals can include mercury, lead, aluminum and
cadmium. It has been shown that fish are exposed to higher cadmium levels
and grow at a slower rate than fish exposed to lower levels or none.
Pesticides
Pesticides are a major source of environmental toxicity. These chemically
synthesized agents have been known to persist in the environment long
after their administration. The poor bio-degradability of pesticides can result
in bio-accumulation of chemicals in various organisms along with bio-
magnification within a food web. Pesticides can be categorized according to
the pests they target. Insecticides are used to eliminate agricultural pests
that attack various fruits and crops.

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Herbicides
Herbicides target herbal pests such as weeds and other unwanted
plants that reduce crop production.
Insecticides
Dichlorodiphenyltrichloroethane (DDT) is an organochlorine
insecticide that has been banned due to its adverse effects on both
humans and wildlife. DDT was widely used by farmers in order to kill
agricultural pests. In 1962, the harmful effects of the widespread and
uncontrolled use of DDT were detailed by Rachel Carson in her book
The Silent Spring. Such large quantities of DDT and its metabolite
Dichlorodiphenyldichloroethylene (DDE) that were released into the
environment were toxic to both animals and humans.

25. Factors influencing toxicity
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Toxicity of a substance can be affected by many different
factors, such as the pathway of administration (whether the
toxicant is applied to the skin, ingested, inhaled, injected),
• The time of exposure (a brief encounter or long term),
• The number of exposures (a single dose or multiple doses
over time),
• The physical form of the toxicant (solid, liquid, gas), the
genetic makeup of an individual, an individual's overall
health, and many others.

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Acute exposure
A single exposure to a toxic substance which may
result in severe biological harm or death; acute
exposures are usually characterized as lasting no
longer than a day.
Chronic exposure
Continuous exposure to a toxicant over an extended
period of time, often measured in months or years;
it can cause irreversible side effects.

27. Sjawal Khan
2020-ag-1728

28. Toxicity at organismic level
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• Blood and Cardiovascular/Cardiac Toxicity
• DermalToxicity
• Epigenetic Alterations
• EyeToxicity
• Hepatotoxicity
• Immunotoxicity
• Nephrotoxicity
• Neurotoxicity
• ReproductiveToxicity
• RespiratoryToxicity

29. Blood and Cardiovascular/CardiacToxicity
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Blood and Cardiovascular/CardiacToxicity results from xenobiotics acting
directly on cells in circulating blood, bone marrow, and the heart. Examples of
blood and cardiovascular/cardiac toxicity are:
• Hypoxia due to carbon monoxide binding of hemoglobin preventing
transport of oxygen.
• Decrease in circulating leukocytes due to chloramphenicol damage to bone
marrow cells.
• Leukemia due to benzene damage of bone marrow cells.
• Arteriosclerosis due to cholesterol accumulation in arteries and veins.
• Death of normal cells in and around the heart as a result
of exposure to drugs used to treat cancer.

30. DermalToxicity
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DermalToxicity can occur when a toxicant comes into direct contact
with the skin or is distributed to it internally. Effects range from
mild irritation to severe changes, such as irreversible
damage, hypersensitivity, and skin cancer. Examples of dermal
toxicity include:
• Dermal irritation from skin exposure to gasoline.
• Dermal corrosion from skin exposure to sodium hydroxide (lye).
• Dermal itching, irritation, and sometimes
painful rash from poison ivy, caused by urushiol.
• Skin cancer due to ingestion of arsenic or skin exposure to UV light.

31. Epigenetic Alterations
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Epigenetics is an emerging area in toxicology. In the field of
genetics, epigenetics involves studying how external or
environmental factors can switch genes on and off and change
the programming of cells.
More specifically, epigenetics refers to stable changes in the
programming of gene expression which can alter the phenotype
without changing the DNA sequence (genotype). Epigenetic
modifications include DNA methylation, covalent modifications
of histone tails, and regulation by non-coding RNAs, among
others.
Toxicants are examples of factors that can alter genetic
programming.

32. Eye toxicity
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EyeToxicity results from direct contact with or
internal distribution to the eye. Because the cornea and
conjunctiva are directly exposed to toxicants, conjunctivitis and
corneal erosion may be observed following
occupational exposure to chemicals. Many household items
can cause conjunctivitis. Chemicals in the circulatory system
can distribute to the eye and cause corneal opacity, cataracts,
and retinal and optic nerve damage. For example:
• Acids and strong alkalis may cause severe corneal corrosion.
• Corticosteroids may cause cataracts.
• Methanol (wood alcohol) may damage the optic nerve

33. Hepatotoxicity
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Hepatotoxicity is toxicity to the liver, bile duct, and gall bladder.
Because of its extensive blood supply and significant role in metabolism,
the liver is particularly susceptible to xenobiotics Thus, it is exposed to
high doses of the toxicant or its toxic metabolites. The primary forms
of hepatotoxicity are:
 Steatosis Lipid accumulation in the hepatocytes.
 Chemical hepatitis Inflammation of the liver.
 Hepatic necrosis Death of the hepatocytes.
 Intrahepatic cholestasis Backup of bile salts into the liver cells.
 Cirrhosis Chronic fibrosis, often due to alcohol.
 Hepatic cancer Cancer of the liver.
 Hypersensitivity Immune reaction resulting in hepatic necrosis.

34. Immunotoxicity
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Immunotoxicity is toxicity of the immune system. It can take several forms:
• Hypersensitivity (allergy and autoimmunity)
• Immunodeficiency
• Uncontrolled proliferation (leukemia and lymphoma)
The normal function of the immune system is to recognize and defend against
foreign invaders.This is accomplished by production of cells that engulf and
destroy the invaders or by antibodies that inactivate foreign material.
Examples include:
• Contact dermatitis due to exposure to poison ivy.
• Systemic lupus erythematosus ("lupus") in workers exposed to
hydrazine.
• Immunosuppression by cocaine.
• Leukemia induced by benzene.

35. Nephrotoxicity
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The kidney is highly susceptible to toxicants because a high
volume of blood flows through the organ and it filters large
amounts of toxins which can concentrate in the kidney tubules.
Nephrotoxicity is toxicity to the kidneys. It can result in
systemic toxicity causing:
• Decreased ability to excrete body wastes.
• Inability to maintain body fluid and electrolyte balance.
• Decreased synthesis of essential hormones (for example,
erythropoietin, which increases the rate of
blood cell production).

36. FatimaTuz Zahra
2020-ag-1730

37. Neurotoxicity
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Neurotoxicity represents toxicant damage to cells of
the central nervous system (brain and spinal cord) and
the peripheral nervous system (nerves outside
the CNS).The primary types of neurotoxicity are:
• Neuronopathies (neuron injury)
• Axonopathies (axon injury)
• Demyelination (loss of axon insulation)
• Interference with neurotransmission

38. ReproductiveToxicity
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ReproductiveToxicity involves toxicant damage to either the
male or female reproductive system.Toxic effects may cause:
• Decreased libido and impotence.
• Infertility.
• Interrupted pregnancy (abortion, fetal death, or premature
delivery).
• Infant death or childhood morbidity.
• Altered sex ratio and multiple births.
• Chromosome abnormalities and birth defects.
• Childhood cancer.

39. RespiratoryToxicity
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Respiratory Toxicity relates to effects on the upper respiratory system (nose,
pharynx, larynx, and trachea) and the lower respiratory
system (bronchi, bronchioles, and lung alveoli).The primary types of respiratory
toxicity are:
• Pulmonary irritation
• Asthma/bronchitis
• Reactive airway disease
• Emphysema
• Allergic alveolitis
• Fibrotic lung disease
• Pneumoconiosis
• Lung cancer

40. Ahmad Raza
2020-ag-1720

41. Mapping environmental hazards
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There are many environmental health mapping tools.
• TOXMAP is a Geographic Information System (GIS) from the
Division of Specialized Information Services of the United States
National Library of Medicine (NLM) that uses maps of the United
States to help users visually explore data from the United States
Environmental Protection Agency's (EPA)Toxics Release
Inventory and Superfund programs.
• TOXMAP is a resource funded by the US Federal Government.
TOXMAP's chemical and environmental health information is
taken from:
• NLM'sToxicology Data Network (TOXNET)
• PubMed

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Bio-monitoring is undertaken sometimes as
the “prelude to remediation.” Remediation
aims to remove potential toxic substances from
a contaminated site, thus restoring ecosystem
function as far as is reasonably possible
following the removal of the ecotoxicity by
biological, physical, or chemical means.
Bio-monitoring

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Molecular toxicology is the branch of toxicology (the study of the effects of
manifestly poisonous substances on individuals) that adopts
the biochemical approach to the understanding of the detrimental threats
to life, often recognized by a range of morbid conditions in a variety of
fauna and flora. Such pathology can be understood at a molecular level in
terms of biomolecular damage undergone by such macromolecules as DNA
(deoxyribonucleic acid: the genetic determinant mainly residing in the
nucleus of the living cell), RNA (ribo-nucleic acid: responsible for transfer of
the genetic message inherent in DNA structure sequence to the cytoplasm
of the cell), and diverse proteins constructed from a choice of sequence of
residues of 20 amino acids (obtained mainly from dietary protein hydrolysis
during digestion).
Molecular toxicology

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Environmental toxicity testing typically focuses on
organism-level endpoints such as:
• Mortality
• Growth
• Reproduction
risk assessment guidelines specify protection goals at
the level of the population and above.
Environmental toxicity

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One method of linking these different levels of biological
organization is the development of models that
extrapolate toxicant impacts at the individual level to
adverse outcomes at the population level. However,
annual population growth projections in highly fecund
species such as fathead minnow are subject to extreme
uncertainty.

46. End Points forVariousToxicity Studies
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Study End Points
Developmental toxicity
Fetus: mortality, growth retardation, skeletal variations,
gross external malformations, soft tissue/internal organ
defects
Female parent: general toxicity
ReproductiveToxicity
Male parent: general toxicity, effects on fertility,
reproductive organ changes
Offspring: effects on viability, sex ratio, growth, behavior
Carcinogenicity Tumor development and general toxicity
Neurotoxicity
Behavior, function, and motor activity deficits; microscopic
nervous tissue changes
Mutagenicity Heritable lesions leading to altered phenotypes

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