KENYATTA UNIVERSITY
SCHOOL OF ENVIRONMENTAL STUDIES
DEPARTMENT OF ENVIRONMENTAL SCIENCE AND EDUCATION
ENS 807: TOXICOLOGY AND ENVIRONMENTAL HEALTH
WRITTEN BY:
DR. ESTHER KITUR
VETTED BY:
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INTRODUCTION
Welcome to this module. Environmental toxicology is a multidisciplinary field of science
concerned with the study of the harmful effects of various chemical, biological and physical agents
on living organisms. Ecotoxicology is a sub discipline of environmental toxicology concerned with
studying the harmful effects of toxicants at the population and ecosystem levels. Organisms can
be exposed to various kinds of toxicants at any life cycle stage, some of which are more sensitive
than others. Toxicity can also vary with the organism's placement within its food web.
Bioaccumulation occurs when an organism stores toxicants in fatty tissues, which may eventually
establish a trophic cascade and the bio magnification of specific toxicants. Harmful effects of such
chemical and biological agents as toxicants from pollutants, insecticides, pesticides, and fertilizers
can affect an organism and its community by reducing its species diversity and abundance. Such
changes in population dynamics affect the ecosystem by reducing its productivity and stability.
Toxicology provides critical information and knowledge that can be used by regulatory agencies,
decision makers, and others to put programs and policies in place to limit our exposures to these
substances, thereby preventing or reducing the likelihood that a disease or other negative health
outcome would occur.
In this module, we shall lay the foundation of environmental toxicology by introducing the basic
terminologies and disciplines related to toxicology. The module takes you through types of toxic
substances and the factors that affect their toxicity. The module further introduces you to the
various methods of testing toxicity and the relationships between toxic substances dose and their
effects. This is followed by the exposure of chemicals to the body and the parts of the body affected
by toxicants as well as the factors that influence this toxicities in the human body. This module
gives us an insight on the effects of chemicals in the environment via bio concentration and bio
magnification. We then look at the types of toxicants in the workplaces and how to control them.
The module enables you to understand the benefits and impacts of heavy metals and pesticides in
the environment. Finally the module looks at ways in which toxic and hazardous substances can
be controlled and their adverse impacts prevented.
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TOXICOLOGY AND ENVIRONMENTAL HEALTH FLOW CHART
WEEK
TOPIC
WEEK 0
INTRODUCTION (YOUR CONTEXT, YOUR GOALS, THOUGHTS
TOXIC SUBSTANCES IN THE ENVIRONMENT)
WEEK 1
CONCEPTS OF TOXICOLOGY AND ENVIRONMENTAL HEALTH
WEEK 2
TOXINS
WEEK 3
DETERMINATION AND MONITORING OF TOXIC LEVELS
WEEK 4
HOW TOXINS WORK AND THEIR EFFECTS ON THE BODY
WEEK 5
BIOLOGICAL CONCENTRATION AND MAGNIFICATION OF TOXIC
SUBSTANCES
WEEK 6
TOXIC SUBSTANCES AND OCCUPATIONAL HAZARDS
WEEK 7
GLOBAL HEAVY METAL POLLUTION
WEEK 8
MYTH OF THE BANNED PESTICIDES
WEEK 9
CONTROL OF TOXIC SUBSTANCES
WEEK 10
CONVENTIONS ON TOXIC AND HAZARDOUS SUBSTANCES
WEEK 11&12
EXAMINATION
OVERVIEW OF THE COURSE
Week 0: Introduction
This lesson is intended to help you acclimatize to blended learning and to create a community of
learners who will motivate each other during the course. You will be required to introduce yourself
to your lecturer and colleagues either physically during a face to face session or even online before
other academic interactions begin. This will be at the discretion of individual universities and
lecturers. It will be important to also state your context and goals as well as what you think about
the effects of toxicants to both human and environmental health.
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Week 1: Concepts of Toxicology and Environmental Health
In this first lesson, we provide an overview of the course by presenting concepts and terminologies
relating to toxicology which is a field of science that helps us understand the harmful effects that
chemicals, substances, or situations, can have on people, animals, and the environment. The
purpose of this lesson is to enable you define the basic terminologies related to toxicology
Week 2: Toxins
This lesson focusses on toxins. A toxin is a harmful substance produced within living cells or
organisms. The purpose of this lesson is to enable you understand various types of toxins and
factors affecting their toxicity.
Week 3: Determination and Monitoring of Toxic Levels
Lesson three looks at how to determine toxic levels of substances. The purpose of toxicity testing
is to generate information about a substance’s toxic properties so that the health and environmental
risks it poses can be adequately evaluated.
Week 4: How Toxins Work and Their Effects on the Body
In this lesson, we focus on toxin exposure to the body and parts of the body affected by toxins. All
living organisms operate through highly integrated sets of biochemical reactions, which are
sensitive to conditions. The purpose of this lesson is to enable you learn about the toxicity of
chemicals in the body and factors that affect their toxicity.
Week 5: Biological Concentration and Magnification of Toxic Substances
This lesson focusses on bioconcentration and biomagnification of toxic substances. Chemicals and
heavy metals flow into the ocean when industrial, agricultural, and human wastes runs off or is
deliberately discharged into rivers that then empty into the sea. In this lesson you will explore bio
concentration and magnification of toxic chemicals using food chains.
Week 6: Toxic Substances and Occupational Hazards
In this lesson we learn about occupational chemical hazards. Chemical hazards and toxic
substances pose a wide range of health hazards such as irritation, sensitization, and carcinogenicity
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and physical hazards such as flammability, corrosion, and explosibility. This lesson provides basic
information about chemical hazards and toxic substances in the workplace.
Week 7: Global Heavy Metal Pollution
Lesson seven focusses on pollution caused by heavy metals. This lesson comprehensively reviews
the different aspects of heavy metals as hazardous materials with special focus on their
environmental persistence, toxicity for living organisms, and bio accumulative potential.
Week 8: Myth of the Banned Pesticides
The eighth lesson looks at myths surrounding the use of pesticides. Pesticides are chemical
compounds that are used to kill pests, including insects, rodents, fungi and unwanted plants. The
purpose of this lesson s to enable you gin knowledge on the merits and demerits of pesticides in the
environment.
Week 9: Control of Toxic Substances
The ninth lesson describes the extent of the hazardous and toxic chemical waste problems
discusses the management, treatment, and disposal methods commonly used. The treatment and
disposal techniques covered are biological, physical-chemical, incineration technologies, and
secure land disposal. The purpose of this lesson is to enable you learn about types of toxic
substance prevention strategies and their benefits.
Week 10: Conventions on Toxic and Hazardous Substances
This final lesson focusses on conventions and treaties developed to curb the effects of toxic and
hazardous substance. The purpose of this lesson is to enable you learn about and appreciate the
conventions and acts that help prevent the dangers posed by toxic substances.
Week 11 & 12: Examination
These two weeks bring together the work you have been doing to an end. This course unit will be
examined and will partially contribute to the award of the degree in the programme that you are
undertaking. We acknowledge that different universities across East Africa may have different
Semester dates. It is however anticipated that most Universities will have a minimum of 13 weeks’
semester. We have therefore placed examinations in the last two weeks but Universities are
allowed to go with their schedules. Your university examinations regulations will apply.
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MODULE LEARNING OUTCOMES
By the end of this module, you will be able to:
1. Explain basic principles of toxicology and their application to public health
2. Identify and understand the different types of toxicants and their effects
3. Understand the toxic effects of various types of metals, pesticides, and other chemicals
4. Predict toxic responses of representatives from major classes of chemicals
5. Apply toxicology to risk assessment of environmental and occupational hazards
6. Critically evaluate different advanced exposure assessment methods
7. Design strategies for study of dose-response relations
COURSE DESCRIPTION
This is a common unit with no prerequisite meant for all students taking master’s degree in
Environmental Sciences and Education. The rationale of offering the course is to equip students
with concepts and science of toxicology and environmental health, and acquire knowledge on toxic
substances and how to control their effects on human health and the environment. The course will
take you 39 instructional hours some of which will be covered face to face and others in online
activities. You will therefore be required to set aside about 5 hours per lesson to complete this
course successfully.
COURSE REQUIREMENTS
This is a blended learning course that will utilize the flex model. This means that learning materials
and instructions will be given online and the lessons will be self-guided with the lecturer being
available briefly for face to face sessions and support and also on-site (online) most of the time.
Your lecturer will be meeting you face to face to introduce a lesson and put it into perspective and
you will actively participate in your search for knowledge by undertaking several online activities.
This means that some of the 39 instructional hours of the course will be delivered face to face
while other lessons will be taught online through various learner and lecturer activities. It is
important for you to note that one instructional hour is equivalent to two online hours. Three
instructional hours will be needed per week. Out of these, one will be used for face to face contact
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with your lecturer (also referred as e-moderator in the online activities) while the other two
instructional hours (translating to four online hours) will be used for online activities otherwise
referred to as e-tivities in the lessons. This will add up to the 5 hours requirement per lesson earlier
mentioned. There are 27 online activities each taking at least two hours and totaling to 54 online
hours. You are advised to follow the topic flow-chart given so that you cover at least a lesson every
week.
You will be required to participate and interact online with your peers and the e-moderator who in
this case is your lecturer. Guidelines for the online activities (which we shall keep referring to as
e-tivities) will be provided whenever there is an e-tivity. Please note that since the online e-tivities
are part of the learning process, they may be graded at the discretion of your e-moderator. Such
grading will however be communicated in the e-tivity guidelines and feedback given as soon as
possible after the e-tivity. The e-tivities will include but will not be limited to online assessment
quizzes, assignments and discussions. There are also assessment questions that you can attempt at
the end of every lesson to test your understanding of the lesson. The answers to all the assessment
questions are at the end of the module after lesson 10. All the resource that have been used in this
module in form of books are available under the resources section after the answers to the
questions.
ASSESSMENT
It is important to note that the module has embedded certain learner formative assessment feedback
tools that will enable you gauge your own learning progress. The tools include online collaborative
discussions forums that focus on team learning and personal mastery and will therefore provide
you with peer feedback, lecturer assessment and self- reflection. You will also be required to do
one major assignment/project that is meant to assess the application of the skills and knowledge
gained during the course. The project score in combination with scores for e-tivities (where graded)
will account for 30% of your final examination score with the remaining 70% coming from a face
to face sit-in final written examination that will be guided by your university examination policy
and procedures.
We wish you the very best of experiences in this course.
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TABLE OF CONTENTS
LESSON ONE: CONCEPTS OF TOXICOLOGY AND ENVIRONMENTAL HEALTH………...10
1.1 Introduction ........................................................................................................................................... 10
1.2 Lesson Learning Outcomes ................................................................................................................... 10
1.3 Assessment Questions ........................................................................................................................... 15
1.4 E – references........................................................................................................................................ 17
LESSON TWO: TOXINS ........................................................................................................................ 18
2.1 Introduction ........................................................................................................................................... 18
2.2 Lesson Learning Outcomes ................................................................................................................... 18
2.3 Assessment Questions ........................................................................................................................... 22
2.4 E – references........................................................................................................................................ 23
LESSON THREE: DETERMINATION AND MONITORING OF TOXIC LEVELS ..................... 25
3.1 Introduction ........................................................................................................................................... 25
3.2 Lesson Learning Outcomes ................................................................................................................... 25
3.3 Assessment Questions ........................................................................................................................... 31
3.4 E – references........................................................................................................................................ 32
LESSON FOUR: HOW TOXINS WORK AND THEIR EFFECTS ON THE BODY ...................... 34
4.1 Introduction ........................................................................................................................................... 34
4.2 Lesson Learning Outcomes ................................................................................................................... 34
4.3 Assessment Questions ........................................................................................................................... 39
4.4 E – references........................................................................................................................................ 40
LESSON FIVE ........... : BIOLOGICAL CONCENTRATION AND MAGNIFICATION OF TOXIC
SUBSTANCES .......................................................................................................................................... 42
5.1 Introduction ........................................................................................................................................... 42
5.2 Lesson Learning Outcomes ................................................................................................................... 42
5.3 Assessment Questions ........................................................................................................................... 48
5.4 E – references........................................................................................................................................ 50
LESSON SIX: TOXIC SUBSTANCES AND OCCUPATIONAL HAZARDS ................................... 51
6.1 Introduction ........................................................................................................................................... 51
6.2 Lesson Learning Outcomes ................................................................................................................... 51
6.3 Assessment Questions ........................................................................................................................... 56
6.4 E – references........................................................................................................................................ 57
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LESSON SEVEN: GLOBAL HEAVY METAL POLLUTION ........................................................... 59
7.1 Introduction ........................................................................................................................................... 59
7.2 Lesson Learning Outcomes ................................................................................................................... 59
7.3 Assessment Questions ........................................................................................................................... 62
7.4 E – references........................................................................................................................................ 64
LESSON EIGHT: MYTH OF THE BANNED PESTICIDES ............................................................. 66
8.1 Introduction ........................................................................................................................................... 66
8.2 Lesson Learning Outcomes ................................................................................................................... 66
8.3 Assessment Questions ........................................................................................................................... 71
8.4 E – references........................................................................................................................................ 72
LESSON NINE: CONTROL OF TOXIC SUBSTANCES.................................................................... 74
9.1 Introduction ........................................................................................................................................... 74
9.2 Lesson Learning Outcomes ................................................................................................................... 74
9.3 Assessment Questions ........................................................................................................................... 80
9.4 E – references........................................................................................................................................ 82
LESSON TEN: CONVENTIONS ON TOXIC AND HAZARDOUS SUBSTANCES ....................... 83
10.1 Introduction ......................................................................................................................................... 83
10.2 Lesson Learning Outcomes ................................................................................................................. 83
10.3 Assessment Questions ......................................................................................................................... 87
10.4 E – references...................................................................................................................................... 88
ANSWERS TO ASSESSMENT QUESTIONS ...................................................................................... 89
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LESSON ONE
CONCEPTS OF TOXICOLOGY AND ENVIRONMENTAL HEALTH
1.1 Introduction
In this first lesson, we provide an overview of the course by presenting concepts and terminologies
relating to toxicology which is a field of science that helps us understand the harmful effects that
chemicals, substances, or situations, can have on people, animals, and the environment.
Toxicology uses the power of science to predict what, and how chemicals may cause harm and
then shares that information to protect public health. The purpose of this lesson is to enable you
define the basic terminologies related to toxicology
1.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
1.2.1 Define basic terminologies in toxicology
1.2.2 Discuss in detail toxicology
1.2.3 Evaluate the set toxicity thresholds
1.2.1 Basic definitions and terminology
The following definitions reflect this expanded scope of the science of toxicology:

Toxic—having the characteristic of producing an undesirable or adverse health effect.

Toxicity—any toxic (adverse) effect that a chemical or physical agent might produce within a
living organism.

Toxicology—the science that deals with the study of the adverse effects (toxicities) chemicals
or physical agents may produce in living organisms under specific conditions of exposure. It
is a science that attempts to qualitatively identify all the hazards (i.e., organ toxicities)
associated with a substance, as well as to quantitatively determine the exposure conditions
under which those hazards/toxicities are induced. Toxicology is the science that experimentally
investigates the occurrence, nature, incidence, mechanism, and risk factors for the adverse
effects of toxic substances.
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
Exposure—to cause an adverse effect, a toxicant must first come in contact with an organism.
The means by which an organism comes in contact with the substance is the route of exposure
(e.g., in the air, water, soil, food, medication) for that chemical.

Dose—the total amount of a toxicant administered to an organism at specific time intervals.
The quantity can be further defined in terms of quantity per unit body weight or per body
surface area.

Acute toxicity—an adverse or undesirable effect that is manifested within a relatively short
time interval ranging from almost immediately to within several days following exposure (or
dosing). An example would be chemical asphyxiation from exposure to a high concentration
of carbon monoxide (CO).

Chronic toxicity—a permanent or lasting adverse effect that is manifested after exposure to a
toxicant. An example would be the development of silicosis following a long-term exposure
to silica in workplaces such as foundries.
E – tivity 1.2.1 Basic definitions and terminology
Numbering, pacing and sequencing
1.2.1
Title
Basic definitions and terminology
Purpose
The purpose of this e – tivity is to enable you acquire
knowledge on the basic terminologies of toxicology
Read pages 1-2 of book one, pages 9-18 of book two, pages
Brief summary of overall task
527-529 of book three
Watch the linked video
Define various terms in environmental toxicology
Spark
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Individual task
a) Define seven toxicological terms
b) Define various durations of exposures
Interaction begins
E-moderator interventions
c) Distinguish between risk and hazards
1. Post your work in the discussion forum 1.2.1
2. DRead what your colleagues have posted in the
discussion forum 1.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
Schedule and time
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Toxicology
1.2.2 Toxicology
Toxicology is the study of the adverse effects of chemicals on living organisms. It is the study of
symptoms, mechanisms, treatments and detection of poisoning, especially the poisoning of people.
It is a study of the interaction between chemicals and biological systems in order to quantitatively
determine the potential for chemical(s) to produce injury which results in adverse effects in living
organisms, and to investigate the nature, incidence, mechanism of production, factors influencing
their development, and reversibility of such effects.
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Other fields have come up that include Environmental Toxicology which assesses the effects of
contaminants, usually at low concentrations, released from commercial and domestic sites into the
immediate environment and subsequently widely distributed by and in air, water, and soil.
Environmental Toxicology uses disciplines of study common among all toxicology subspecialties
to assess the effects of contaminants in the environment. Environmental toxicology has an
objective of focusing on increasing higher levels of organization Individual i.e. Population,
Community, and Ecosystem.
E – tivity 1.2.2 Toxicology
Numbering, pacing and sequencing
1.2.2
Title
Toxicology
Purpose
The purpose of this e – tivity is to enable you have an
understanding on the study of toxicology
Read pages 1-20 of book one, pages 9-18 of book two
Brief summary of overall task
Watch the linked videos one and two
Spark
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Individual task
a) In a paragraph, define toxicology
b) Distinguish between toxicology and toxicity
c) Discuss three principles of toxicology
d) Outline five sub-disciplines of toxicology
e) Define four terms related to dose
Interaction begins
E-moderator interventions
1. Post your work in the discussion forum 1.2.2
2. Read what your colleagues have posted in the discussion
forum 1.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
Schedule and time
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Toxicity thresholds
1.2.3 Toxicity thresholds
Toxicity thresholds refer to the exposure level or dose of an agent above which toxicity or adverse
health effects can occur, and below which toxicity or adverse health effects are unlikely. This
situation can be portrayed graphically by means of dose-response curves. The region of the dose
response curve that marks the transition from “no-toxicity” to “toxicity” corresponds to the toxicity
threshold – the dose immediately above which responses caused by the chemical begin to manifest
themselves and below which no effect occurs.
Thresholds for toxicity exist because, up to a certain point, the body can repair damage and
detoxify chemicals to which it is exposed.
If the exposures get too high, however, the
detoxification and repair mechanisms are overwhelmed and toxicity starts to occur. In support of
the threshold hypothesis are many observations that some minimum concentration of a toxic
chemical or its metabolites must encounter a cellular target before any biologically significant
changes take place.
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E – tivity 1.2.3 Toxicity thresholds
Numbering, pacing and sequencing
1.2.3
Title
Toxicity thresholds
Purpose
The purpose of this e – tivity is to enable you explain
toxicology threshold
Read pages 9-18 of the linked book and define toxicity
Brief summary of overall task
threshold
Spark
Individual task
a) Toxicity and toxic effects
b) Using an illustration, briefly explain the threshold of
toxicity
Schedule and time
1. Post your work in the discussion forum 1.2.3
2. Read what your colleagues have posted in the discussion
forum 1.2.3
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Lesson Two – Toxins
Interaction begins
E-moderator interventions
1.3 Assessment Questions
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1. You are worried about contamination of vegetables grown in contaminated soils. What type of
toxicologist would you contact?
a) Regulatory
b) Descriptive
c) Food
d) Environmental
2. A toxic substance produced by biological system is specially referred to as a
a) Toxin
b) Toxicant
c) Poison
d) Xenobiotic
3. What is toxicity equivalence factor?
a) Ratio of the toxicity of a chemical to that of another chemical pollutant chosen as a
reference
b) Ratio of the toxicity of a contaminant to that of another structurally related chemical (or
index compound) chosen as a reference
c) Ratio of the toxicity of a chemical to that of another structurally related chemical (or
index compound) chosen as a reference
d) Ratio of the toxicity of a chemical to that of source
4. What is the main objective of toxicity assessment?
a) To determine chemical concentration
b) To determine source of pathway
c) To analyse chemical exposure
d) To estimate how much of a substance does what kind of harm
5. Eco-toxicology is the study of ________
a) Chemical interactions of organism and environment
b) Thermal interactions of organism and environment
c) Biological interactions of organism and environment
d) Physical interactions of organism and environment
6. Eco-toxicology is based on ______ of chemicals
a) Physical
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b) Chemical
c) Biological
d) Toxicological
7. The term dosage refers to the
a) Length of time the pollutant persists in the environment
b) Concentration of the pollutant in the environment
c) Amount of the pollutant absorbed by an organism per unit of body mass
d) Amount of the pollutant required to cause harm in an organism
8. State the sentence is Correct or Wrong, “Chemical toxicology is the science of study of toxic
chemicals and their mode of action.”
a) Correct
b) Wrong
9. You are concerned about the risks associated with growing vegetables in soil with naturally
high lead and arsenic concentrations. You are speaking of what type of substance?
a) Toxicant
b) Toxin
10. What type of toxicologist takes samples of blood, urine or hair for testing?
a) Analytical
b) Descriptive
c) Forensic
d) Mechanistic
1.4 E – references
1. Gupta, P. K. (2016). Fundamentals of toxicology: Essential concepts and applications.
ProQuest Ebook Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=4661584
2. Khalid, F. (2021, February 13). Toxicology Terminologies. Retrieved from
https://www.youtube.com/watch?v=iPfd-ZCLX0c
3. Levy, B. S., Wegman, D. H., Baron, S. L., & Sokas, R. K. (2011). Occupational and
environmental health: Recognizing and preventing disease and injury. ProQuest Ebook.
Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=631628
4. Maynard, A. (2015, March 10). What is toxicology? Retrieved from
https://www.youtube.com/watch?v=b_y9VTDlmlE
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5. Roberts, S. M., James, R. C., & Williams, P. L. (2015). Principles of toxicology:
Environmental and industrial applications. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=1889220
6. Rose, J. (Ed.). (1998). Environmental toxicology: Current developments. ProQuest Ebook
Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=181512
7. Royal Society of Chemistry. (2019, January 7). Toxicology. Retrieved from
https://www.youtube.com/watch?v=A0NNyjVvnYo
LESSON TWO
TOXINS
2.1 Introduction
This second lesson will focus on toxins. A toxin is a harmful substance produced within living
cells or organisms. Toxins can be small molecules, peptides, or proteins that are capable of causing
disease on contact with or absorption by body tissues interacting with biological macromolecules
such as enzymes or cellular receptors. Toxins vary greatly in their toxicity, ranging from usually
minor such as a bee sting to almost immediately deadly such as botulinum toxin. The purpose of
this lesson is to enable you understand various types of toxins and factors affecting their toxicity.
2.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
2.2.1 Distinguish between various types of toxins
2.2.2 Explain factors affecting activity of toxicants
2.2.3 Cite factors affecting toxicity of chemicals
2.2.1 Types of toxins
There are two groups of toxin types. Endogenous toxins are those produced by the body as a byproduct of biochemical processes, and may tend to accumulate in the joins or various muscle
groups. Exogenous toxins are toxins ingested or absorbed by a person into the body from external
sources, including food, water, air, contact. Technically speaking, there is a third category of
toxins, known as autogenous toxins. These are the toxins that one is born with, in the form of
pathogens or toxic compounds, generally from environmental/dietary exposure over multiple
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generations. These are usually passed down from the maternal line, from the mother to the baby
in the womb. However, these are in a sense just exogenous toxins that happen to be absorbed from
the mother rather than from the environment. Organic chemical compounds include certain
petroleum and petrochemical/synthetic chemical derivatives and plastics, tar from cigarettes and
other smoked herbs, inhaling smoke from joysticks lit by misguided massage practitioners.
Inorganic chemical toxins include: toxic elements, e.g. heavy metals - mercury, arsenic, cadmium;
toxic element salts, e.g. mercuric sulphate, mercuric oxide; ammonia, e.g. cigarette smoke;
preservatives, e.g. nitrites.
E – tivity 2.2.1 Types of toxins
Numbering, pacing and sequencing
2.2.1
Title
Types of toxins
Purpose
The purpose of this e – tivity is to enable you distinguish
between various types of toxins
Read chapter 3 of book one and chapter 1 of book two
Brief summary of overall task
Watch the linked videos one, two and three
Giving examples, state four types of toxins
Spark
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Individual task
a) Define toxins
b) Differentiate between toxicants and poisons
c) Outline various ways of classifying toxic chemicals
d) Distinguish endotoxins and exotoxins
e) Outline examples of endotoxins and exotoxins
f) Outline types of toxicants based on various states
Interaction begins
E-moderator interventions
1. Post your work in the discussion forum 2.2.1
2. Read what your colleagues have posted in the discussion
forum 2.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
Schedule and time
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Factors affecting activity of toxicants
2.2.2 Factors affecting activity of toxicants
Toxicant potential is usually determined more by the multitude of related factors than by actual
toxicity of the toxicant. Exposure-related, biologic, or chemical factors regulate absorption,
metabolism, and elimination, and thus, influence observed clinical consequences. Factors related
to exposure include the dose which is the primary concern, however, the exact intake of toxicant
is seldom known. Duration and frequency of exposure are important. The route of exposure affects
absorption, translocation, and perhaps metabolic pathways. Environmental factors, such as
temperature, humidity, and barometric pressure, affect rates of consumption and even the
occurrence of some toxic agents. Biological factors include various species and strains within
species reacting differently to a particular toxicant because of variations in absorption,
metabolism, or elimination. The chemical nature of a toxicant determines solubility, which in turn
influences absorption. Nonpolar or lipid-soluble substances tend to be more readily absorbed than
polar or ionized substances. The vehicle or carrier of the toxic compound also affects its
availability for absorption.
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E – tivity 2.2.2 Factors affecting activity of toxicants
Numbering, pacing and sequencing
2.2.2
Title
Factors affecting activity of toxicants
Purpose
The purpose of this e – tivity is to enable explain factors that
affect the toxicity of toxicants
Read chapter 4 of book one, pages 33-60 of book two and
pages 62-68 of book three
Brief summary of overall task
Watch videos one and two
Discuss mechanisms that affect toxicant toxicity
Spark
Individual task
a) Discuss three factors that affect the toxicity of chemicals
b) Briefly evaluate the biological and chemical factors that
affect toxicity
c) Distinguish between systemic and organ toxicants
d) Lists factors which influence toxicity
Interaction begins
E-moderator interventions
1. Post your work in the discussion forum 2.2.2
2. Read what your colleagues have posted in the discussion
forum 2.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
21
2. Encouraging lurkers (quiet ones) to contribute
Schedule and time
Next
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Lesson Three – Determination and Monitoring of Toxic
Levels
2.3 Assessment Questions
1. Toxic agents can be classified in terms of their physical state, their effects, and their source
a) True
b) False
2. Which of the following is not characteristics of hazardous waste?
a) Toxicity
b) Leakage
c) Ignitibility
d) Corrosivity
3. Belladonna is a toxic weed commonly found in gardens. Although human deaths linked to
Belladonna are generally very few, increased toxicity may occur if leaves from this plant are
ingested along with some medications. This is an example of
a) Chronic toxicity
b) Acute toxicity
c) Bioaccumulation
d) Synergistic action
4. Dioxins consists of two polychlorinated aromatic hydrocarbons associated with which one or
two
a) Organic compounds
b) Inorganic compounds
c) Ether group
d) Halogen group
5. What are the important factors in determining the toxicity of particulate matter (PM)?
a) Size of PM
b) Organic pollutants that are surface-bound to PM
c) Combustion of PM
d) Shape of PM
22
e) All of the above
6. The term toxicant is used when talking about toxic substances that are produced by or are a
by-product of human-made activities.
a) True
b) False
7. Which of the following compounds is not an organic substance?
a) Nicotine
b) Lindane
c) Pyrethrum
d) Rotenone
8. Which of the following is a synthetic compound?
a) Pyrethrum
b) Sabadilla
c) Pyrethroid
d) Ryania
9. Toxins exuded from roots of plants into the soil are called:
a) Phytoallexins
b) Rotenone
c) Pyrethrins
d) Repellents
10. The degree to which a chemical is poisonous to the organism is its
a) Lethal dose
b) Kill value
c) Toxicity
d) Hazard rating
2.4 E – references
1. Anastas, G. (2015, September 23). Toxicology Factors Affecting Toxicity. Retrieved from
https://www.youtube.com/watch?v=ayOIWXTOheQ
2. Gupta, P. K. (2016). Fundamentals of toxicology: Essential concepts and applications.
ProQuest Ebook Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=4661584
23
3. Hayes, A. W., Wang, T., Dixon, D., & Loomis, T. A. (2019). Loomis's essentials of
toxicology. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=5970519
4. Hill, M. K. (2004). Understanding environmental pollution: A primer. ProQuest Ebook
Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=266547
5. Hussain, M. (2017, March 7). Overview of Toxins. Retrieved from
https://www.youtube.com/watch?v=AkXLNn4uYZ8
6. Penningroth, S., & Penningroth, S. S. (2010). Essentials of toxic chemical risk: Science and
society. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=544101
7. Shomu, S. (2016, February 1). Exotoxins and endotoxins. Retrieved from
https://www.youtube.com/watch?v=CuVOy15KVBY
8. Shubham, S. (2020, September 6). Classification of Toxicants and Factors affecting toxicity.
Retrieved from https://www.youtube.com/watch?v=pt41YlbnW-0
24
LESSON THREE
DETERMINATION AND MONITORING OF TOXIC LEVELS
3.1 Introduction
Welcome to the third lesson. The purpose of toxicity testing is to generate information about
substance’s toxic properties so that the health and environmental risks it poses can be adequately
evaluated. Many factors are determinants of health, including socioeconomic status, birth weight,
sex, genetics, diet, pathogens, smoking habits, cultural activities, and the environment. Exposures
to environmental agents contribute to the aggregate effects of the other factors, but the nature and
magnitude of the contribution are often debated. The results of toxicity testing can help to clarify
risks to health posed by environmental exposures and provide support for effective riskmanagement decisions.
3.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
3.2.1 Explain what is considered in a toxicity test
3.2.2 Describe the dose-response relationship and its measurement
3.2.3 Explain various toxicity testing methods
3.2.1 Consideration of toxicity test
The toxicity of a substance depends on three factors: its chemical structure, the extent to which the
substance is absorbed by the body and the body's ability to detoxify the substance and eliminate it
from the body.
The design of any toxicity test takes into consideration the following aspects:
• A test organism, which can range from cellular material and selected strains of bacteria through
higher order plants and animals
• The response or biological endpoint, which can range from subtle changes in
physiology and behaviour to death
• An exposure or test period
• Dose or series of doses
25
E – tivity 3.2.1 Consideration of toxicity test
Numbering, pacing and sequencing
3.2.1
Title
Consideration of toxicity test
Purpose
The purpose of this e – tivity is to enable you understand the
requirements necessary to carry out toxicity test
Read chapter 2 of the linked book and watch the linked video
Brief summary of overall task
and list the requirement of carrying out a good toxicity test
Spark
Individual task
a) Evaluate the environmental pathways of toxic chemicals
b) Outline what is contained in a toxicity test
Interaction begins
E-moderator interventions
Schedule and time
1. Post your work in the discussion forum 3.2.1
2. Read what your colleagues have posted in the discussion
forum 3.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
26
Next
Dose-Response relationship and its measurement
3.2.2 Dose-Response relationship and its measurement
A particular toxicity test exhibits a dose-response relationship when there is a consistent
mathematical relationship between the proportion of individuals responding and a given dose
for a given exposure period. For example, the number of mortalities increases as the dose of
chemical given to a group of organisms increases.
Different species of test organisms differ in how they respond to a specific chemical. In
addition, there are variations in response to a given dose within a group of test organisms of the
same species. Typically, this variations within the same species, follows a normal distribution
when the number of organisms responding is plotted against the degree of response for a given
dose. Several basic relationships can be readily identified from the plots. A dose is often
described as either a lethal dose (LD) in a test where the response is mortality or effective dose
(ED) in a test where the response is some other observable effect.
E – tivity 3.2.2 Dose-Response relationship and its measurement
Numbering, pacing and sequencing
3.2.2
Title
Dose-Response relationship and its measurement
Purpose
The purpose of this e – tivity is to enable you interpret the
relationship between dose and effect
Read pages 9-11 of book one
Brief summary of overall task
Read pages 53-54 of book two
Read pages 17-32 of book three
Read pages 6-15 of book four
Read pages 17-18 of book five
Watch videos one and two
27
Spark
Individual task
a) Define dose response
b) Distinguish between does-response and concentration
response
c) Explain dose-response relationships using an illustration
d) Explain three ways by which dose-response curve can be
used
e) The dose makes the poison. Justify
f) What is the difference between
i.
ii.
iii.
Schedule and time
Median lethal dose and median lethal concentration
Median lethal dose and median effective dose
Lowest Observed Adverse Effects Level and No
Observed Effects Level
1. Post your work in the discussion forum 3.2.2
2. Read what your colleagues have posted in the discussion
forum 3.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Toxicity testing methods
Interaction begins
E-moderator interventions
28
3.2.3 Toxicity testing methods
Many of the current toxicity test methods include the use of laboratory animals (e.g., mice, rats,
rabbits). However the use of animals is expensive, and animal rights groups consider it inhuman
as it inflicts suffering on the animals. Some results from animal tests may not be valid to humans
therefore limiting this. There are alternative test methods are test methods that reduce, refine, or
replace animal use. Reduction, refinement, and replacement are commonly referred to as “the 3Rs
of alternatives” and are further defined as follows:

A reduction alternative decreases the number of animals required for a test method, while
remaining consistent with sound scientific practices necessary to obtain valid results.

A refinement alternative uses procedures that lessen or eliminate pain or distress in animals or
enhances animal well-being.

A replacement alternative uses non-animal systems instead of animals, or uses a
phylogenetically lower species of live animal than the current test.
E – tivity 3.2.3 Toxicity testing methods
Numbering, pacing and sequencing
3.2.3
Title
Toxicity testing methods
Purpose
The purpose of this e – tivity is to enable you acquire
knowledge methods of testing toxicants
Read pages 5-14 of book one, chapter 1 of book two, pages
Brief summary of overall task
55-57 of book three and pages 127-152 of book four
Watch the linked video
Discuss methods of testing toxicity
29
Spark
Individual task
a) Describe methods of acute and chronic toxicity testing
b) Explain three methods of estimating toxicity of
chemicals
c) Briefly explain ways of improving toxicity assessment
d) Outline parameters of basic acute and chronic toxicity
tests
Interaction begins
E-moderator interventions
1. Post your work in the discussion forum 3.2.3
2. Read what your colleagues have posted in the discussion
forum 3.2.3
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
Schedule and time
This task should take you two hours
Next
Lesson Four – How Toxins Work
30
3.3 Assessment Questions
1. You have worked at a chemical facility for 10 years. The facility does not equire protective
equipment, and you have developed a number of serious health affects in the last 7 years. You
are possibly experiencing what type of exposure?
a) Acute
b) Chronic
2. The reference dose (RfD) is generally determined by applying which of the following default
procedures?
a) A risk factor of 10,000 is applied to the NOAEL in subchronic animal studies
b) A risk factor of 1000 is applied to the NOAEL in chronic animal studies
c) An uncertainty factor of 100 is applied to the NOAEL in chronic animal studies
d) An uncertainty factor between 10,000 and 1 million is applied to the NOEL from chronic
animal studies
3. The phrase that best defines "toxicodynamics" is the
a) Linkage between dose and response
b) Dose range between desired biological effects and adverse health effects
c) Linkage between exposure and dose
d) Loss of dynamic hearing range due to a toxic exposure Dynamic nature of toxic effects
among various species
4. Which of the following toxicity can occur due to single exposure?
a) Sub-acute toxicity
b) Acute toxicity
c) Sub-chronic toxicity
d) Chronic toxicity
5. The LD50 is best described as which of the following:
a) The dose at which at least one of the test animals dies
b) The dose at which all of the test animals die
c) The dose at which 50 % of all test animals die
d) The dose at which 50 % of the animals demonstrate a response to the chemical
31
6. Which of the following are common end points:
a) Death
b) Lowest Observable Adverse Effect Level
c) No Observable Adverse Effect Level
d) No Observable Effect Level
e) All of the above
7. ___________ establishes the relationship between the contaminant/s of concern and the
receptor
a) Risk characterization
b) Toxicity assessment
c) Exposure assessment
d) Hazard identification
8. Toxicity test is the experimental study of the adverse effects of exposure of a living organism
to a substance for a defined duration under defined conditions
a) True
b) False
9. Which toxicity test is preferable to determine the acute or chronic toxicity of air, water and
wastewater discharges or total pollutant loads?
a) Direct toxicity test
b) Indirect toxicity test
c) High toxicity test
d) Chemical analysis
10. Acute aquatic toxicity is measured in _______
a) AS
b) CB
c) PS
d) EC
3.4 E – references
1. Amiard-Triquet, C., Amiard, J., & Mouneyrac, C. (Eds.). (2015). Aquatic ecotoxicology
Advancing tools for dealing with emerging risks. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=2068783
32
2. Bites, R. (2013, May 14). What is dose response, and what's a dose response model?
Retrieved from https://www.youtube.com/watch?v=yyvX5hDBPBY
3. Centre of Learning. (2017, October 1). Toxicity Testing studies/ methods. Retrieved from
https://www.youtube.com/watch?v=v4jmPpTcdxQ
4. Duffus, J. H., & Worth, H. G. J. (Eds.). (2006). Fundamental toxicology. ProQuest Ebook
Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=1185552
5. FlinnScientific. (2012, November 30). Basic Principles of Toxicology. Retrieved from
https://www.youtube.com/watch?v=KbOPLBYGKs8
6. Hayes, A. W., Wang, T., Dixon, D., & Loomis, T. A. (2019). Loomis's essentials of
toxicology. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=5970519
7. Metro College of Pharmacy. (2020, April 17). Acute toxicity, subacute toxicity, chronic
toxicity. Retrieved from https://www.youtube.com/watch?v=lKvaOz1bA9Q
8. Penningroth, S., & Penningroth, S. S. (2010). Essentials of toxic chemical risk: Science and
society. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=544101
9. Roberts, S. M., James, R. C., & Williams, P. L. (2015). Principles of toxicology:
Environmental and industrial applications. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=1889220
10. Singh, D. K. (2012). Toxicology: Agriculture and environment. ProQuest Ebook Central.
Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=877019
11. Sparling, D. W., Gaines, K. F., & Linder, G. (2016). Ecotoxicology essentials:
Environmental contaminants and their biological effects on animals and plants. ProQuest
Ebook Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=4509769
12. Svarc-Gajić, J. (Ed.). (2010). General toxicology. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=3020151
13. Trautmann, N. M., & The, E. I. T. (2001). Assessing toxic risk. ProQuest Ebook Central.
Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=355231
33
LESSON FOUR
HOW TOXINS WORK AND THEIR EFFECTS ON THE BODY
4.1 Introduction
In lesson four we focus on toxin exposure to the body and parts of the body affected by toxins. All
living organisms operate through highly integrated sets of biochemical reactions, which are
sensitive to conditions including temperature, pH, and the concentration of other chemicals in the
system. Some chemicals, such as strong acids and bases, are toxic simply because they denature
proteins and dissolve living tissue. Other chemicals, however, exert their toxic effect by binding
with specific receptors in cells, thereby disrupting normal biochemical reactions. The purpose of
this lesson is to enable you learn about the toxicity of chemicals in the body and factors that affect
their toxicity.
4.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
4.2.1 Define chemical toxicity
4.2.2 Describe the parts of the body affected by chemicals
4.2.3 Explain factors that affect the toxicity of chemicals in the human body
4.2.1 Chemical toxicity
The toxicity of a substance is the potential of that substance to cause harm, and is only one factor
in determining whether a hazard exists. The hazard of a chemical is the practical likelihood that
the chemical will cause harm. These effects can strike a single cell, a group of cells, an organ
system, or the entire body. A toxic effect may be visible damage, or a decrease in performance or
function measurable only by a test. All chemicals can cause harm at a certain level. When a small
amount can be harmful, the chemical is considered toxic. When only a very large amount of the
chemical can cause damage, the chemical is considered to be relatively non-toxic. Therefore a
chemical can be considered toxic depending on various factors. These are; chemical structure, the
dose, duration, an individual’s susceptibility, multiple exposures, rate of exposure versus rate of
elimination
34
E – tivity 4.2.1 Chemical toxicity
Numbering, pacing and sequencing
4.2.1
Title
Chemical toxicity
Purpose
The purpose of this e – tivity is to enable you factors that
causes a chemical to be toxic
Watch videos one, two, three and four and explain the causes
Brief summary of overall task
of chemical toxicity
Spark
Individual task
a) In a paragraph, explain what makes a chemical toxic
b) What properties makes a chemical toxic
c) With examples classify hazardous chemicals
Schedule and time
1. Post your work in the discussion forum 4.2.1
2. Read what your colleagues have posted in the discussion
forum 4.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Parts of the body affected by chemicals
Interaction begins
E-moderator interventions
35
4.2.2 Parts of the body affected by chemicals
The foods we eat are the biggest carrier of toxins inside our bodies. In these modern times, every
type of food undergoes processing. The main sources of foods, which are; plants and the animals,
are overwhelmed with varieties of unneeded chemicals and substances to grow. Animals are
known to be injected with hormones, which can harm the normal metabolism of the body and can
break down the system as well. Plants are also exposed to chemicals found in the fertilizers used
to increase or improve growth as well as the pesticides used to destroy or kill plant pests and
prevent diseases. There are various body parts that are affected by toxic chemicals. In order to
have a better understanding of the different body parts affected by chemicals it is important to look
at the different body systems and hence the parts affected within these systems.
E – tivity 4.2.2 Parts of the body affected by chemicals
Numbering, pacing and sequencing
4.2.2
Title
Parts of the body affected by chemicals
Purpose
The purpose of this e – tivity is to enable you explain the parts
of the body affected by toxins and how toxins access the body
Read pages 1-8 of book one, pages 529-535 of book two and
Brief summary of overall task
chapter 2 of book three
Watch videos one, two, three and four
Describe the routes of exposure of toxins in the body
Spark
36
Individual task
a) Explain three ways by which toxins access the body
b) Discuss the effects of toxicants in the body
c) Distinguish between effects of acute and chronic toxicity
d) Explain the routes of chemical exposure to human beings
e) Explain various toxins in the body
f) State ways in which humans are exposed to toxins
g) Explain the effects of human exposure to heavy metals
and pesticides
h) Outline the target organ toxicity and the toxins that affect
this organs
Interaction begins
1. Post your work in the discussion forum 4.2.2
2. Read what your colleagues have posted in the discussion
forum 4.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
E-moderator interventions
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Schedule and time
Next
Factors that affect the toxicity of chemicals in the human
body
4.2.3 Factors that affect the toxicity of chemicals in the human body
The human body is exposed to the outside world through a variety of surfaces. These include the
skin, lungs, nose, mouth and the digestive, urinary, and genital tracts. Hazardous agents such as
chemicals and micro-organisms such as bacteria and viruses can get into the body through any of
these surfaces. In order to cause adverse effects, toxins must come into contact with living tissue.
Toxic substances can enter the body through oral ingestion, inhalation, or skin absorption.
Intravenous injection is another entry route, but it is not normally significant from the point of
view of environmental exposure. After penetrating the initial cellular barrier that is, the intestinal
mucosa, the lining of the respiratory tract, or the skin, the chemical enters the interstitial fluid that
fills the extracellular space of all animals. From this fluid, the substance penetrates the capillaries
37
and enters the bloodstream, which transports it throughout the body. Once the chemical is absorbed
into the body, three other processes are possible: metabolism, storage, and excretion. Many
chemicals are metabolized or transformed via chemical reactions in the body. In some cases,
chemicals are distributed and stored in specific organs. Storage may reduce metabolism and
therefore, increase the persistence of the chemicals in the body. The various excretory mechanisms
(exhaled breath, perspiration, urine, feces, or detoxification) rid the body, over a period of time, of
the chemical. For some chemicals elimination may be a matter of days or months; for others, the
elimination rate is so low that they may persist in the body for a lifetime and cause deleterious
effects.
E – tivity 4.2.3 Factors that affect the toxicity of chemicals in the human body
Numbering, pacing and sequencing
4.2.3
Title
Factors that affect the toxicity of chemicals in the human body
Purpose
The purpose of this e – tivity is to enable understand the
influence of chemical toxicity in the body
Watch video one and video two and discuss factors that
Brief summary of overall task
affect the toxicity of chemicals in the body
Spark
Individual task
a) Discuss methodologies of toxicokinetics
b) Discuss the factors affecting toxicant toxicity in the body
Interaction begins
1. Post your work in the discussion forum 4.2.3
2. Read what your colleagues have posted in the discussion
forum 4.2.3
38
E-moderator interventions
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
Schedule and time
This task should take you two hours
Next
Lesson Five - Biological Concentration And Magnification
4.3 Assessment Questions
1. Which of these groups is usually designated as one of the most sensitive sub-populations for
exposures to toxic substances?
a) Infants
b) Adolescents
c) Adult men
d) Adult women
2. The most common target organ of toxicity is the
a) Lung
b) Heart
c) Skin
d) CNS (brain and spinal cord)
3. The organs least involved in systemic toxicity are --a) Liver and kidney
b) Muscle and bone
c) Brain and peripheral nerves
d) Hematopoietc system and lungs
4. The most rapid exposure to a chemical would occur through which of the following routes
a) Subcutaneous
b) Intramuscular
c) Oral
d) Inhalation
39
5. A chemical that is toxic to the brain but which is detoxified in the liver would be expected to
be
a) More toxic on the skin than intravenously
b) More toxic orally than intramuscularly
c) More toxic via inhalation than orally
d) More toxic rectally than intravenously
6. The different ways a person can come into contact with hazardous chemicals are called
a) Hazard pathways
b) Exposure pathways
c) Chemical pathways
d) Toxic pathways
7. Ingestion can be called secondary exposure pathway after skin contact happens.
a) True
b) False
8. Minamata, Japan hazard outbreak had _____ effect on the population
a) Direct
b) Minimal
c) Chronic
d) Acute
9. Susceptible populations that may be more at risk for illness than others includes the following
EXCEPT:
a) Young children
b) Teenagers
c) Women of Childbearing Age
d) Older adults
4.4 E – references
1. Duffus, J. H., & Worth, H. G. J. (Eds.). (2006). Fundamental toxicology. ProQuest Ebook
Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=1185552
2. Levy, B. S., Wegman, D. H., Baron, S. L., & Sokas, R. K. (2011). Occupational and
environmental health: Recognizing and preventing disease and injury. ProQuest Ebook.
Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=631
40
3. Srivastava, A. K. (2015). Health effects of pesticides. ProQuest Ebook Central. Retrieved
from https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=6318225
4. Wallace, R. (2015, August 31). Examining the effects of human exposure to heavy metals
and pesticides. Retrieved from https://www.youtube.com/watch?v=-bm7RxNwKKU
5. Anastas, G. (2015, September 23). Toxicology Factors Affecting Toxicity. Retrieved from
https://www.youtube.com/watch?v=ayOIWXTOheQ
6. Anastas, G. (2015, September 23). Toxicology. Retrieved from
https://www.youtube.com/watch?v=v6sFdawERRU
7. Gigg, A. (2016, September 1). Toxins in the Body. Retrieved from
https://www.youtube.com/watch?v=BewwzgZxsGE
8. Chembam editor. (2020, April 3). Introduction to toxicology. Retrieved from
https://www.youtube.com/watch?v=FZiIGW6EQog
9. Frely, H. (2020, May 8). Chemical Hazards: A Type of Hazard in the Workplace. Retrieved
from https://www.youtube.com/watch?v=ZVFneD4Rg4I
10. Siddhi, H. (2020, August 10). Hazardous Chemicals. Retrieved from
https://www.youtube.com/watch?v=kS00KcMLF2o
11. ISO Training Institute. (2021, January 7). Chemical Exposure Explained. Retrieved from
https://www.youtube.com/watch?v=IrklQTR3idQ
12. Khade, B. A. (2021, January 12). Factors Influencing Toxicity. Retrieved from
https://www.youtube.com/watch?v=PVXJF8rrXxI
41
LESSON FIVE
BIOLOGICAL CONCENTRATION AND MAGNIFICATION OF TOXIC
SUBSTANCES
5.1 Introduction
Toxic chemicals and heavy metals flow into the ocean when industrial, agricultural, and human
wastes runs off or is deliberately discharged into rivers that then empty into the sea. These
pollutants cause disease, genetic mutations, birth defects, reproductive difficulties, behavioral
changes, and death in many marine organisms. In many cases, animals near the top of the food
chain are most affected because of a process called bio magnification. Many of the most dangerous
toxins settle to the seafloor and then are taken in by organisms that live or feed on bottom
sediments. Because these compounds aren't digested, they accumulate within the animals that
ingest them, and become more and more concentrated as they pass along the food chain as animals
eat and then are eaten in turn. In this lesson you will explore bio concentration and magnification
of toxic chemicals using food chains.
5.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
5.2.1 Discuss bio concentration
5.2.2 Discuss bio magnification
5.2.3 Explain factors affecting bio-accumulation and bio concentration
5.2.1 Bio concentration
Bio concentration is the increase in concentration of a substance that occurs in a food chain as a
consequence of:
• Persistence (can't be broken down by environmental processes)
• Food chain energetics
• Low (or nonexistent) rate of internal degradation/excretion of the substance (often due to waterinsolubility)
Bioaccumulants are substances that increase in concentration in living organisms as they take in
contaminated air, water, or food because the substances are very slowly metabolized or excreted.
Bioconcentration or Bioaccumulation is generally referred to as a process in which the chemical
42
concentration in an organism achieves a level that exceeds that in the respiratory medium (e.g.,
water for a fish or air for a mammal), the diet, or both. The extent to which chemicals
bioaccumulate is expressed by several quantities including the bioconcentration factor (BCF),
bioaccumulation factor (BAF), biomagnification factor (BMF), and trophic or food web
magnification factor (TMF). Whether a substance is considered “bioaccumulative” in the
regulatory context is determined by the regulation. In the text of the Stockholm Convention, there
is no documented definition for a bioaccumulative substance.
E – tivity 5.2.1 Bio concentration
Numbering, pacing and sequencing
5.2.1
Title
Bio concentration
Purpose
The purpose of this e – tivity is to enable you to have an
understanding of how toxins accumulate in an organism
Read pages 198-200 of book one, chapter 6 of book two and
Brief summary of overall task
pages 498-504 of book three
Watch the linked videos one and two
Outline the main causes of Bioaccumulation
Spark
Individual task
a) Explain the main causes bioaccumulation
b) Explain the process of bioaccumulation
c) Explain the advantages and disadvantages of bio
magnification
43
d) Explain the mechanisms of metal accumulation in
aquatic organisms
e) Briefly explain the factors affecting metals
bioaccumulation
Schedule and time
1. Post your work in the discussion forum 5.2.1
2. Read what your colleagues have posted in the discussion
forum 5.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Bio accumulation
Interaction begins
E-moderator interventions
5.2.2 Bio magnification
Bio magnification or biological amplification is a condition in which concentration of certain
chemicals in organisms feeding at high tropic levels in a food chain or web are drastically higher
than concentrations of those chemicals found in organisms feeding at lower tropic levels.
Chemicals that can be biologically amplified include synthetic organic chemicals such as
(pesticides DDT and PCBs), some toxic lead and mercury compounds and some radioactive
materials. The synthetic organic chemicals that can be biologically amplified are insoluble in water
and soluble in fat and are slowly biodegraded by natural processes. This means they become more
concentrated in fatty tissue of organisms at successively higher tropic level in food chains and
webs. Radioactive materials and toxic lead and mercury compounds are biologically amplified
because they are non-degradable or slowly degradable and concentrate in certain parties of bodies
of animals.
44
E – tivity 5.2.2 Bio magnification
Numbering, pacing and sequencing
5.2.2
Title
Bio magnification
Purpose
The purpose of this e – tivity is to enable acclimatize yourself
with the concept of biological magnification
Read pages 196-197 of the linked book
Brief summary of overall task
Watch the linked videos one, two and three
Discuss the process of bio magnification
Using a food web, describe bio magnification of toxins in
organisms
Spark
Individual task
a) Define bio magnification
b) Using a food chain, describe the process of bio
magnification
c) State five substances which are amplified in a food chain
d) Explain why birds which prey on aquatic organisms have
high concentration of heavy metals yet they do not live in
water
e) Explain why small fish amplify less DDT than a larger
fish
Interaction begins
1. Post your work in the discussion forum 5.2.2
2. Read what your colleagues have posted in the discussion
forum 5.2.2
45
Schedule and time
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Factors affecting bio-accumulation and bio concentration
E-moderator interventions
5.2.3 Factors affecting bio-accumulation and bio concentration
Uptake – This is by passive diffusion where chemicals which are lipid soluble move from the
environment where there is high concentration to an organisms body where there is low
concentration.
Storage – Chemicals which are water soluble are less taken up and the ones taken up are easily
excreted hence less stored. Those chemicals that bind with fat are the ones that are stored with
little being excreted.
Elimination – Elimination of a chemical depends on its medium of dissolving. Chemicals that
readily dissolve in fast are not easily eliminated from the body.
Exposure time – Constant exposure to a chemical in the environment leads to an equilibrium point
being reached where the concentration of chemical in the organism =concentration in the
organism.
Long lived. This means that the pollutant should be able to resist being disintegrated or brokendown to enable them long enough time to move from the lowest trophic level to the highest trophic
level.
Mobile. The pollutant should have the ability to move from one place to another and in different
forms. If it’s immobile it doesn’t have the ability to be taken up by other organisms.
46
Soluble in fats. This pollutant should be soluble in fats rather than in water since when in water it
can be easily excreted from the organism’s body. The bio-accumulating pollutants are fat loving
/lipophilic and for this reason they are stored in fatty tissues in the body and not easily excreted.
Biologically active. For a pollutant to raise concern it has to be biologically active otherwise it will
raise concerns as it might not be harmful to human body.
E – tivity 5.2.3 Factors affecting bio-accumulation and bio concentration
Numbering, pacing and sequencing
5.2.3
Title
Factors affecting bio-accumulation and bio concentration
Purpose
The purpose of this e – tivity is to enable you to discuss the
factors that influence bio concentration
Watch the linked video and discuss the factors that influence
Brief summary of overall task
bio concentration
Spark
Individual task
a) Briefly explain factors affecting bio-accumulation and
bio concentration
b) Describe in detail characteristics of pollutants that biomagnify
Interaction begins
1. Post your work in the discussion forum 5.2.3
2. Read what your colleagues have posted in the discussion
forum 5.2.3
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
47
Schedule and time
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Lesson Six - Toxic Substances and Occupational Hazards
E-moderator interventions
5.3 Assessment Questions
1. Hazard estimation in ecotoxicology is done based on _______
a) HWL
b) SARA
c) Accumulation
d) Bio-accumulation
2. The build-up of a harmless chemical in one organism is
a) Biomagnification only
b) Bioaccumulation only
c) Both bioaccumulation and biomagnification
d) Neither bioaccumulation nor biomagnification
3. The build-up of a toxic chemical as it goes up a food chain is:
a) Biomagnification only
b) Bioaccumulation only
c) Both biomagnification and bioaccumulation
d) Neither bioaccumulation nor biomagnification
4. One of the requirements of bioaccumulation is:
a) The toxic chemical dissolves in water
b) The toxic chemical is stable
c) The toxic chemical is stationary
d) The toxic chemical is needed by the organism
48
5. PCBs (polychlorinated biphenyls) are a health risk to humans due to bioaccumulation. Which
one of the following properties contributes most to bioaccumulation?
a) Solubility in fatty tissues
b) Solubility in water
c) High volatility
d) Artificial manufacture by industry
6. Cadmium is toxic to humans as it
a) Is very dense
b) Dissolves readily in water
c) Has low persistence in the environment
d) Bio accumulates in body tissue
7. Examples of non-biodegradeable chemicals:
a) Cellulose, starch and glycogen
b) DDT, PCBs, and dieldrin
c) Amylase, pepsin and protease
8. Which ends up with the most posions/chemicals due to biological magnification?
a) Producers
b) Tertiary consumers
c) Organisms of a low trophic level
d) Organisms of a high trophic level
9. Bioaccumulation is measured by parts per million (ppm)
a) False
b) True
10. Bilogical magnification is caused by poisons/chemicals that can be broken down by
organisms
a) True
b) False
49
5.4 E – references
1. Beyer, W. N., Meador, J. P., Heinz, G. H., & Redmon, A. W. (Eds.). (2011). Environmental
contaminants in biota: Interpreting tissue concentrations, second edition. ProQuest Ebook
Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=729629
2. El, N. A. (2010). Impact, monitoring and management of environmental pollution. ProQuest
Ebook Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=3018184
3. Harmony Square. (2019, October 23). What is Bioaccumulation? Retrieved from
https://www.youtube.com/watch?v=nNjhboUYM2c
4. Koaw, N. (2019, March 28). Bioaccumulation of Methylmercury into Fishes and Humans.
Retrieved from https://www.youtube.com/watch?v=1vwjZseY-9w
5. Thrush, M. (2017, January 18). What's In the Fish? Bioaccumulation and Bio magnification.
Retrieved from https://www.youtube.com/watch?v=DuYDFlGTIWE
6. Unison institute. (2020, June 15). Bio magnification of DDT in aquatic. Retrieved from
https://www.youtube.com/watch?v=TsfwVYxf0WY
7. Wikipedia tts. (2019, June 7). Persistent, bioaccumulative and toxic substances. Retrieved
from https://www.youtube.com/watch?v=PVv8t6fg1hs
50
LESSON SIX
TOXIC SUBSTANCES AND OCCUPATIONAL HAZARDS
6.1 Introduction
Welcome to the sixth lesson on occupational chemical hazards. Chemical hazards and toxic
substances pose a wide range of health hazards such as irritation, sensitization, and carcinogenicity
and physical hazards such as flammability, corrosion, and explosibility. This lesson provides basic
information about chemical hazards and toxic substances in the workplace.
6.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
6.2.1 Define and explain workplace hazards
6.2.2 Describe various types of chemicals found in the work place
6.2.3 Evaluate control strategies for occupational hazards
6.2.1 Workplace hazards
Safety hazards
Working conditions where harm to the workers is of an immediate and violent nature result in
broken bones, cuts, bruises, sprains, loss of limbs, etc. the harm results in some kind of injury to
the worker associated with poorly guarded or dangerous equipment and machinery
Health hazards
Working conditions which result in an illness exposure to dangerous substances or conditions,
such as chemicals, gases, dusts, noise etc. often, latency between exposure and disease.
E – tivity 6.2.1 Workplace hazards
Numbering, pacing and sequencing
6.2.1
Title
Workplace hazards
Purpose
The purpose of this e – tivity is to enable you understand types
of workplace hazards
Read page 5 of the linked book
Brief summary of overall task
Watch the linked videos one and two
Discuss two main types of hazards in the workplace
51
Spark
Individual task
a) Discuss in detail safety and healthy occupational hazards
b) Distinguish between risk and hazard
c) Briefly describe various types of workplace hazards
Schedule and time
1. Post your work in the discussion forum 6.2.1
2. Read what your colleagues have posted in the discussion
forum 6.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Types of chemicals found in the work place
Interaction begins
E-moderator interventions
6.2.2 Types of chemicals found in the work place
Solids – Example: wood that is being cut can turn into wood dust which is then inhaled, welding
rods can decompose into fumes and gases, polyurethane foam is safe in its normal solid form but
gives off deadly gases if it burns.
Dusts – They come from materials that normally exist in dust form (e.g. cement) or from work
processes that create dust (e.g. handling glass fibre can produce toxic dust). The main danger from
harmful dusts is that they can be inhaled into the lungs.
Liquids – Many hazardous substances, such as acids and solvents, are liquids when they are at
normal temperature. Many liquid chemicals give off vapours which can be inhaled and which may
52
be highly toxic, depending on the chemical. Liquid chemicals can be absorbed by the skin. Some
liquid chemicals may cause immediate skin damage (they may or may not be absorbed into the
bloodstream as well). Other liquids pass directly through the skin into the bloodstream, where they
can travel to different parts of the body and cause damaging effects.
Vapours – A Vapours is the gas phase of a material which is normally liquid under standard
conditions. Tiny droplets of liquid which are suspended in the air are called mists. Many liquid
chemicals evaporate at room temperature, i.e. they form a vapour and stay in the air. The vapours
from some chemicals can irritate your eyes and skin. There can be a variety of serious health effects
from inhaling certain toxic chemical vapours.
Gases – Some chemical substances are in the form of a gas when they are at a normal temperature.
However, some chemicals in liquid or solid form become gases when they are heated. Gases can
be inhaled. Some gases produce irritant effects immediately. The health effects of other gases may
be noticeable only after your health has already been seriously damaged. Gases may be flammable
or explosive. Extreme caution should be used when working around flammable or explosive gases.
E – tivity 6.2.2 Types of chemicals found in the work place
Numbering, pacing and sequencing
6.2.2
Title
Types of chemicals found in the work place
Purpose
The purpose of this e – tivity is to enable you outline various
chemicals in the workplace
Read pages 106-113 of the linked book
Brief summary of overall task
Watch the linked videos one and two
Giving examples, describe various groups of chemicals in the
workplace and the hazards they pose
Spark
53
Individual task
a) Explain the health effects of harmful chemicals in the
body
b) Describe four hazardous chemicals in the workplace
c) Explain how you would identify hazards related to
hazardous chemicals in the workplace
d) Discuss the various health effects from chemical
exposure
e) Outline the physical and chemical properties of
substances which cause workplace chemicals to be
hazardous
Schedule and time
1. Post your work in the discussion forum 6.2.2
2. Read what your colleagues have posted in the discussion
forum 6.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Control strategies for occupational hazards
Interaction begins
E-moderator interventions
6.2.3 Control strategies for occupational hazards
1. Substitution and process modification
The use of water-based fountain solutions instead of isopropyl alcohol for printing operations.The
substitution of non-leaded gasoline for leaded gasoline. The development of more efficient
polymerization reactions to reduce (and practically eliminate) the off gassing of vinyl chloride
monomer in the production of polyvinyl chloride plastic. The substitution of cellulose and
bimetallic compounds for former asbestos insulation and brake application. The use of toluene or
xylene instead of benzene in certain solvent applications
2. Worker isolation
If the toxic substance cannot be isolated, then perhaps the worker can be isolated. If it is not feasible
to substitute for the chemical, modify the process, or prevent the release of the air contaminant
into the workers’ environment, then local exhaust or dilution ventilation will be needed.
54
3. Administrative controls
Administrative controls describe a family of measures that reduce exposures through planning and
allocation of appropriate resources.
E – tivity 6.2.3 Control strategies for occupational hazards
Numbering, pacing and sequencing
6.2.3
Title
Control strategies for occupational hazards
Purpose
The purpose of this e – tivity is to enable you identify control
measures put in place to minimize occupational hazards
Read pages 105-110 of book one and pages 70-96
Brief summary of overall task
of book two
Watch the linked videos one, two, three and four
Spark
Individual task
a) Define occupational hazard
b) Describe the methods employed in controlling toxic
occupational hazards
c) Explain how you would control chemical spillage in a
workplace
d) Outline the administrative control of hazards in the
workplace
e) Briefly explain the hierarchy of occupational hazard
controls
f) List the steps in hazard control process
55
Interaction begins
E-moderator interventions
1. Post your work in the discussion forum 6.2.3
2. Read what your colleagues have posted in the discussion
forum 6.2.3
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
Schedule and time
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Lesson Seven – Global Heavy Metal Pollution
6.3 Assessment Questions
1. What violations are most commonly cited by OSHA?
a) Fall protection
b) Scaffolding
c) Respiratory protection
d) Hazard communications
2. Under the OSH Act, employers are responsible for providing a __________
a) Land
b) Estimation
c) Insurance
d) Safe workplace
3. OSHA was created to _________
a) Data analysis
b) EIA analysis
c) To reduce hazards
d) Ecological development
4. Hazardous cleaners are those that:
a) Irritate the skin
b) Are harmful if swallowed
c) Cause dizziness if used in an unventilated area
d) All of the above
56
5. Which of the following type(s) of Personal Protective Equipment (PPE) is frequently used?
a) Gloves
b) Safety glasses
c) Face Shields
d) Lab Coats
e) All of the above
6. On the multi-colored chemical label, Blue represents
a) Reactivity Hazard
b) Health Hazard
c) Fire Hazard
d) Personal Protective Equipment
7. Spills of Chemicals should be
a) Prevented by using seal containers
b) Reported immediately
c) Cleaned up by trained employees
d) All of the above
8. If I use chemicals at work I must
a) Never work alone
b) Be very careful
c) Be specifically trained and authorized
d) Wear a respirator
6.4 E – references
1. Alli, B. O. (2008). Fundamental principles of occupational health and safety. ProQuest
Ebook Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=3012417
2. Frely, H. (2020, May 8). Chemical Hazards: A Type of Hazard in the Workplace. Retrieved
from https://www.youtube.com/watch?v=ZVFneD4Rg4I
3. Health and Safety professionals. (2020, February 26).Types of Workplace Hazards.
Retrieved from https://www.youtube.com/watch?v=jP_MKTVT-us
4. Koradecka, D. (Ed.). (2010). Handbook of occupational safety and health. ProQuest Ebook
Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=555706
57
5. Levy, B. S., Wegman, D. H., Baron, S. L., & Sokas, R. K. (2011). Occupational and
environmental health: Recognizing and preventing disease and injury. ProQuest Ebook.
Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=631628
6. Life Gallery Channel. (2020, November 13). Type of Hazards at Workplace. Retrieved from
https://www.youtube.com/watch?v=KykYAvcdM3I
7. Parker, E. (2019, February 21). The Hierarchy of Controls. Retrieved from
https://www.youtube.com/watch?v=XOkPcLD5Soo
8. Phani, K. (2020, April 20). Hazard Control Procedure. Retrieved from
https://www.youtube.com/watch?v=MXk6qBxZTEI
9. Phani, K. (2020, February 23). Spill control procedure. Retrieved from
https://www.youtube.com/watch?v=7GOqgEVbTe0
10. Terry, M. (2020, January 29). Hazardous Chemicals in the Workplace. Retrieved from
https://www.youtube.com/watch?v=ED9as73p3IA
11. Wright, D. A., & Welbourn, P. (2002). Environmental toxicology. ProQuest Ebook Central.
Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=221116
58
LESSON SEVEN
GLOBAL HEAVY METAL POLLUTION
7.1 Introduction
Lesson seven focusses on pollution caused by heavy metals. Heavy metals are well-known
environmental pollutants due to their toxicity, persistence in the environment, and bio
accumulative nature. Their natural sources include weathering of metal-bearing rocks and volcanic
eruptions, while anthropogenic sources include mining and various industrial and agricultural
activities. Contamination of aquatic and terrestrial ecosystems with toxic heavy metals is an
environmental problem of public health concern. Being persistent pollutants, heavy metals
accumulate in the environment and consequently contaminate the food chains. This lesson
comprehensively reviews the different aspects of heavy metals as hazardous materials with special
focus on their environmental persistence, toxicity for living organisms, and bio accumulative
potential.
7.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
7.2.1 Describe the sources of heavy metal pollution
7.2.2 Enumerate the consequences of heavy metal pollution
7.2.1 Sources of heavy metal pollution
Metals occur naturally in the earth's crust, and their contents in the environment can vary between
different regions resulting in spatial variations of background concentrations. The distribution of
metals in the environment is governed by the properties of the metal and influences of
environmental factors. Heavy metals enter the environment by natural and anthropogenic means.
Such sources include: natural weathering of the earth’s crust, mining, soil erosion, industrial
discharge, urban runoff, sewage effluents, pest or disease control agents applied to plants, air
pollution fallout, coal combustion, fertilizers, fossil fuel and a number of others. Mining and
smelting operations are important causes of heavy metal contamination in the environment due to
activities such as mineral excavation, ore transportation, smelting and refining, and disposal of the
tailings and waste waters around mines.
59
E – tivity 7.2.1 Sources of heavy metal pollution
Numbering, pacing and sequencing
7.2.1
Title
Sources of heavy metal pollution
Purpose
The purpose of this e – tivity is to enable you describe the
sources of heavy metal pollution
Read pages 109-113 of book one and pages 177-179
Brief summary of overall task
of book two
Watch videos one and two
Explain three sources of metal pollution
Spark
Individual task
a) Discuss various sources of environmental metals
b) Explain the environmental factors affecting metal
toxicity
c) Briefly describe the properties of metal
d) In a paragraph, explain the pollution of soil by heavy
metal
e) Outline the factors influencing the toxicity of metals
f) State the routes of exposure of various metals in the body
Interaction begins
1. Post your work in the discussion forum 7.2.1
2. Read what your colleagues have posted in the discussion
forum 7.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
60
Schedule and time
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Consequences of heavy metal pollution
E-moderator interventions
7.2.2 Consequences of heavy metal pollution
Among all the pollutants, heavy metals have received a paramount attention to environmental chemists
due to their toxic nature. Heavy metals are usually present in trace amounts in natural waters but many
of them are toxic even at very low concentrations. Metals such as arsenic, lead, cadmium, nickel, mercury,
chromium, cobalt, zinc and selenium are highly toxic even in minor quantity. Increasing quantity of heavy
metals in our resources is currently an area of greater concern, especially since a large number of
industries are discharging their metal containing effluents into fresh water without any adequate
treatment. Heavy metals become toxic when they are not metabolised by the body and accumulate in the
soft tissues. They may enter the human body through food, water, air or absorption through the skin when
they come in contact with humans in agriculture, manufacturing, pharmaceutical, industrial or residential
settings. Industrial exposure accounts for a common route of exposure for adults. Ingestion is the most
common route of exposure in children. Natural and human activities are contaminating the environment
and its resources, they are discharging more than what the environment can handle
E – tivity 7.2.2 Consequences of heavy metal pollution
Numbering, pacing and sequencing
7.2.2
Title
Consequences of heavy metal pollution
Purpose
The purpose of this e – tivity is to enable you discuss the health
and environmental impacts of heavy metal pollution
Read pages 203-214 of book one, pages 121-128 of book two
and pages 43-47 of book three
Brief summary of overall task
Watch the linked videos one, two and three
Explain two impacts each of environmental and health
impacts of metal pollution
61
Spark
Individual task
a) Discuss the effects of three heavy metals on human
health
b) Discuss the effects of heavy metals in soils and plants
c) Distinguish between the health effects of acute and
chronic heavy metal poisoning
Schedule and time
1. Post your work in the discussion forum 7.2.2
2. Read what your colleagues have posted in the discussion
forum 7.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Lesson Eight – Myths of the Banned Pesticides
Interaction begins
E-moderator interventions
7.3 Assessment Questions
1. Environmental disease outbreak in Toyama, Japan was due to ___________
a) Mercury
b) Lead
c) Cadmium
d) Zinc
62
2. Heavy metals like Arsenic, Cadmium and Cyanide effects _________
a) Skin
b) Nervous system
c) Respiratory system
d) Immune system
3. Out of the following elements which is not toxic elements present in water
a) Cadmium
b) Mercury
c) Sodium
d) Arsenic
4. Which metal forms part of the haem group, to which oxygen binds in haemoglobin?
a) Manganese
b) Iron
c) Copper
d) Zinc
5. Which of the following elements are classed as metals? Please select all that apply.
a) Iron
b) Oxygen
c) Lithium
d) Calcium
e) Chlorine
6. Cd causes endocrine disruption in
a) Whales
b) Seals
c) Fish
d) Silver sea breams
7. In sea, dissolved mercury ions are easily absorbed in
a) Animals
b) Plants
c) Fats
d) Sediments
63
8. Heavy metals counted as mercury, lead, cadmium, chromium and
a) Arsenic
b) Carbon
c) Helium
d) Oxygen
9. What are the important factors in determining the toxicity of particulate matter (PM)?
a) Organic pollutants that are surface-bound to PM
b) Size of PM
c) Combustion of PM
d) Shape of PM
e) All of the above
10. Which organs are most affected by the toxic effects of mercury?
a) Lungs
b) Brain
c) Liver
d) Kidneys
e) Heart
f) B & D
7.4 E – references
1. Abou-Donia, M. (2015). Mammalian toxicology. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=1943361
2. Cockerham, L. G., & Shane, B. S. (1993). Basic environmental toxicology. ProQuest Ebook
Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=5628932
3. Gupta, P. K. (2016). Fundamentals of toxicology: Essential concepts and applications.
ProQuest Ebook Central. Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=4661584
4. Hakeem, K., Sabir, M., Ozturk, M., & Mermut, A. R. (Eds.). (2014). Soil remediation and
plants: Prospects and challenges. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=1781032
5. Jannetto, P. (2014, June 10). Heavy Metals: Lead, Arsenic, and Mercury. Retrieved from
https://www.youtube.com/watch?v=j29fF5nl2tM
64
6. Maqbool, T. (2020, July 11). Toxicity of heavy metals. Retrieved from
https://www.youtube.com/watch?v=WUxaQJhnCWU
7. Natalie, D. (2013, May 6). Heavy Metal Poisoning. Retrieved from
https://www.youtube.com/watch?v=_x6AtyEjSjg
8. Torres, E. (2018, May 23). The Pollution of Soil by Heavy Metal. Retrieved by
https://www.youtube.com/watch?v=jL_X1yPUuzk
65
LESSON EIGHT
MYTH OF THE BANNED PESTICIDES
8.1 Introduction
Welcome to lesson eight. Pesticides are chemical compounds that are used to kill pests, including
insects, rodents, fungi and unwanted plants. Pesticides are used in public health to kill vectors of
disease, such as mosquitoes, and in agriculture, to kill pests that damage crops. By their nature,
pesticides are potentially toxic to other organisms, including humans, and need to be used safely
and disposed of properly. Pesticides have numerous beneficial effects. These include crop
protection, preservation of food and materials and prevention of vector-borne diseases. Their mode
of action is by targeting systems or enzymes in the pests which may be identical or very similar to
systems or enzymes in human beings and therefore, they pose risks to human health and the
environment. Pesticides are ubiquitous in the environment and most are synthetic. The purpose of
this lesson s to enable you gin knowledge on the merits and demerits of pesticides in the environment.
8.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
8.2.1 Distinguish between various types of pesticides
8.2.2 Explain the risks associated with pesticides
8.2.3 Discuss various myths of banned pesticides
8.2.1 Types of pesticides
The term pesticide is used to describe all sorts of products which control pests. These range from
synthetic chemicals which are poisonous to weeds, to natural chemicals such as pyrethrums
derived from chrysanthemums used to repel insects or larger animals. Pesticides include herbicides
for destroying weeds and other unwanted vegetation, insecticides for controlling a wide variety of
insects, fungicides used to prevent the growth of molds and mildew, disinfectants for preventing
the spread of bacteria, and compounds used to control mice and rats. Examples include chemical
pesticides, organochlorine insecticides, pyrethroid pesticides and biopesticides.
66
E – tivity 8.2.1 Types of pesticides
Numbering, pacing and sequencing
8.2.1
Title
Types of pesticides
Purpose
The purpose of this e – tivity is to enable you state types of
pesticides
Read pages 3-8 of book one and chapter 1 of book two
Brief summary of overall task
Watch videos one and two
Discuss the main groups of pesticides giving example
Spark
Individual task
a) Define pesticides
b) Describe the main types of pesticides
c) Describe the chronology of pesticide development
d) Discuss the evolution, history and changing concepts of
pesticides
Interaction begins
E-moderator interventions
1. Post your work in the discussion forum 8.2.1
2. Read what your colleagues have posted in the discussion
forum 8.2.1
3. Keeping netiquette in mind, comment on at least three of
th-eir answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
67
Schedule and time
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Risks from pesticides
8.2.2 Risks from pesticides
A "banned" pesticide is defined as a pesticide for which all registered uses have been prohibited
by final government action or for which all requests for registration or equivalent action for all
uses have, for health or environmental reasons, not been granted. Because pesticides are selected
for their ability to kill living things, whether plant, insect or animal, they can also harm unintended
targets such as people, wildlife and the environment. They have been associated with claims of
many different health problems such as cancer infertility and eye abnormalities. Due to this, some
countries have banned the use of certain pesticides, especially if there is a risk that they could get
into the food chain, and safety levels have been set for others which are practically avoided.
Organophosphate Pesticides - These pesticides affect the nervous system by disrupting the enzyme
that regulates acetylcholine, a neurotransmitter. Most organophosphates are insecticides. They
were developed during the early 19th century, but their effects on insects, which are similar to their
effects on humans, were discovered in 1932. Some are very poisonous, however, they usually are
not persistent in the environment. Carbamate Pesticides affect the nervous system by disrupting
an enzyme that regulates acetylcholine, a neurotransmitter. The enzyme effects are usually
reversible. There are several subgroups within the carbamates.
E – tivity 8.2.2 Risks from pesticides
Numbering, pacing and sequencing
8.2.2
Title
Risks from pesticides
Purpose
The purpose of this e – tivity is to enable you evaluate the risks
posed by pesticides
Read chapter 5 of book one and pages 29-46 of book two
Brief summary of overall task
Watch the linked videos one and two
Explain the health and environmental impacts of pesticides
68
Spark
Individual task
a) Discuss the acute and chronic toxic effects of pesticides
b) Discuss the pathways of pesticides in the environment
c) Discuss the environmental impacts of pesticides on the
environment
d) Explain ways to reduce the impacts of pesticides
Schedule and time
1. Post your work in the discussion forum 8.2.2
2. Read what your colleagues have posted in the discussion
forum 8.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Types of pesticides
Interaction begins
E-moderator interventions
8.2.3 Myths of banned pesticides
A myth is a story that may be true or not true. A ban is any decree that prohibits something. DDT
(dichlorodiphenyltrichloroethane) is a major banned pesticide. A major myth is that most modern
agricultural chemicals leave few residues. It is believed that they breakdown and do not persist in
our food. It states:"Organophosphorous pesticides, carbamate pesticides are mostly biodegradable,
hence do not concentrate in the food chain. Synthetic pyrethroids are generally biodegradable and
69
therefore tend not to persist in the environment.” This myth states that once a chemical degrades,
it disappears and is harmless. Most agricultural chemicals however leave residues of breakdown
chemicals when they degrade. Most agricultural pesticides such as organophosphates like
Diazinon become even more toxic when they break down. Many of the breakdown chemicals from
agricultural poisons cause health and reproductive problems.
E- tivity 8.2.3 Myths of banned pesticides
Numbering, pacing and sequencing
8.2.3
Title
Myths of banned pesticides
Purpose
The purpose of this e – tivity is to enable you to justify myths
related to the use of pesticides
Watch the linked videos one, two and three and discuss
Brief summary of overall task
positive and negative myths on pesticides
Spark
Individual task
Describe in detail four pesticide myths
Interaction begins
1. Post your work in the discussion forum 8.2.3
2. Read what your colleagues have posted in the discussion
forum 8.2.3
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
E-moderator interventions
70
Schedule and time
This task should take you two hours
Next
Lesson Nine – Control of Toxic Substances
8.3 Assessment Questions
1. If two organophosphate insecticides are absorbed into an organism, the result will be
a) Substraction effect
b) Synergestic effect
c) Additive effect
d) Potentiation
2. Which of the following is not a problem stemming from the use of synthetic organic chemical
pesticides?
a) Adverse environmental and human health effects
b) Increase in diversity of insect pests
c) Development of resistance by pests
d) Resurgences and secondary pest outbreaks
3. Relatively new insecticides that have both low persistence and low toxicity to mammals are
the:
a) Carbamates
b) Triazines
c) Pyrethroids
d) Organophosphates
e) Chlorinated hydrocarbons
4. Exposure to ______ caused environmental hazard in USA in the year 1985
a) Carbamate pesticide
b) Lead
c) Lead in paint
d) Methylisocyanate
5. Pesticides designed to kill birds are called:
a) Birdicides
b) Miticides
c) Herbicides
d) Aviacides
71
6. Which of the following pieces of information is not usually found on a pesticide label?
a) Product name
b) Cost
c) Caution
d) Directions for use
7. Insecticides that act by permeating the entire plant are said to be:
a) Porous insecticides
b) Penetrating pesticides
c) Systemic insecticides
d) Contact poisons
8. Dealing with the LD50 rating, a herbicide with a label warning of "danger-poison" would have
what type of toxicity rating
a) Low
b) Moderate
c) High
d) Slight
9. The potential of a pesticide for causing damage to plants is its:
a) Defoliation ability
b) Chronicity
c) Phytotoxicity
d) Lethal dose
8.4 E – references
1. Chan, K. (2018, February 18). Potential Risks of Pesticides and Trace Organics. Retrieved
from https://www.youtube.com/watch?v=Rdv4B9Zz5mU
2. DeBusk, D. (2019, October 21). Environmental Concerns of Pesticide Use. Retrieved from
https://www.youtube.com/watch?v=LwILnNS0VkU
3. Leu, A. (2014, October 14). The Myths of Safe Pesticides: Pesticides Today. Retrieved from
https://www.youtube.com/watch?v=rcB2kmaw0KQ
4. Leu, A. (2021, March 11). Myth About Pesticides, Farming And Your Health. Retrieved
from https://www.youtube.com/watch?v=qfwjZ9F22xQ
72
5. Misty, J. (2019, May 17). Types of Pesticides. Retrieved from
https://www.youtube.com/watch?v=7tIMaWFyJNs
6. Nohochem, S. (2020, August 8). Pesticides and Its Types. Retrieved from
https://www.youtube.com/watch?v=nD9ONxs5nh4
7. Rathore, H. S., & Nollet, L. M. L. (Eds.). (2012). Pesticides: Evaluation of environmental
pollution. ProQuest Ebook Central. Retrieved from
https://ebookcentral.proquest.com/lib/kenyatta-ebooks/detail.action?docID=1186538
8. Singh, D. K. (2012). Toxicology: Agriculture and environment. ProQuest Ebook Central.
Retrieved from https://ebookcentral.proquest.com/lib/kenyattaebooks/detail.action?docID=877019
9. The Organic Talk. (2020, May 14). The Myths of Safe Pesticides. Retrieved from
https://www.youtube.com/watch?v=c49iTSknye4
73
LESSON NINE
CONTROL OF TOXIC SUBSTANCES
9.1 Introduction
The ninth lesson describes the extent of the hazardous and toxic chemical waste problems
discusses the management, treatment, and disposal methods commonly used. The treatment and
disposal techniques covered are biological, physical-chemical, incineration technologies, and
secure land disposal. The purpose of this lesson is to enable you learn about types of toxic
substance prevention strategies and their benefits.
9.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
9.2.1 Discuss the types of toxic substance prevention
9.2.2 State the benefits of toxin prevention
9.2.3 Discuss the mechanisms for prevention of toxin exposure
9.2.1 Types of toxic substance prevention
A toxic exposure occurs when a susceptible individual or population comes into contact with a
chemical in a particular environment. The individual may be poisoned as a result. Prevention
activities may intervene before, during, or after a “poisoning” event.
Primary prevention
Primary poisons prevention activities intervene before the event, aiming to prevent it happening,
either by controlling the victim’s access to the agent, controlling the action of an agent upon the
victim, or controlling or changing hostile environmental factors. Primary prevention strategies may
be active or passive.
Secondary prevention
Secondary poisons prevention is the action taken after an exposure has occurred, to prevent the
poisoning from progressing to a more serious, irreversible or chronic stage and to restore the victim
74
to his/her former state of health. It includes the initial steps to minimize the effects of the toxic
agent, the diagnosis, decontamination and first aid treatment, and specific anti- dote therapy. This
may include educating both the community and professionals about how to recognize and manage
poisonings and how to give first aid after a toxic exposure by, for example, washing the skin and
eyes immediately after contamination by a pesticide.
Tertiary prevention
Tertiary poisons prevention deals with the diagnosis and treatment of poisoning victims who
cannot be treated to full recovery, to prevent death or permanent disability. It is also concerned
with educating victims and their relatives about how to make the most of the remaining potential
for healthy living, including the avoidance of unnecessary hardships, restrictions and
complications.
E – tivity 9.2.1 Types of toxic substance prevention
Numbering, pacing and sequencing
9.2.1
Title
Types of toxic substance prevention
Purpose
The purpose of this e – tivity is to enable you to come up with
strategies that help prevent toxic substances
Watch the linked videos one and two and discuss various
Brief summary of overall task
types of preventing toxic substances
Spark
Individual task
a) Explain how you would handle hazardous chemicals
b) Explain ways of minimising hazardous substances
75
Schedule and time
1. Post your work in the discussion forum 9.2.1
2. Read what your colleagues have posted in the discussion
forum 9.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Benefits of prevention
Interaction begins
E-moderator interventions
9.2.2 Benefits of prevention
The prevention of poisonings positively improves the quality of health, and thus the quality of life,
of both the individual and the community as a whole. Individual’s benefit from information and
education that gives them an increased awareness of accident risks, a greater control over their
own health and their environments, and more freedom to choose a safe environment and an injuryfree lifestyle. This supports personal and social development. The community benefits from
knowledge, skills and support in articulating their needs. They are enabled to define problems, set
priorities, make decisions, and plan and implement strategies. At the heart of this process is the
empowerment of communities, their ownership and control of their own endeavours and destinies.
There are specific health and economic benefits. Prevention activities save resources and contribute
to the rationalization of medical care in public health systems. Benefits include;
•
Reduced incidence of unintentional, intentional and occupational poisoning occurring in the
home, outdoor and indoor environment, and the workplace
•
Use of appropriate first aid measures at the site of exposure in the home or in the field and a
reduction in adverse effects resulting from use of out- dated, hazardous first aid procedures
•
Reduction in the inappropriate use of emergency departments and emergency medical
transportation systems
•
Improved care for poisoning victims as a result of education for health care professionals in
the management and prevention of poisonings, with a consequent reduction in disabilities and
costly long-term medical care
76
•
Early detection and elimination of unusually hazardous commercial products through
regulatory measures, repackaging or reformulation.
E- tivity 9.2.2 Benefits of prevention
Numbering, pacing and sequencing
9.2.2
Title
Benefits of prevention
Purpose
The purpose of this e – tivity is to enable you to have an
appreciation for
Watch the linked video and discuss the benefits of preventing
Brief summary of overall task
the risks caused by toxicants
Spark
Individual task
In about 500 words discuss the advantages of preventing the
occurring and effects of toxic substances
Interaction begins
1. Post your work in the discussion forum 9.2.2
2. Read what your colleagues have posted in the discussion
forum 9.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
77
4. Read the facilitator’s comments too to get feedback
E-moderator interventions
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
Schedule and time
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Mechanisms for prevention of toxin exposure
9.2.3 Mechanisms for prevention of toxin exposure
a) Risk communication/Alerts about chemical risks
An immediate and widespread alert is needed when large population groups (and the
environment) are at risk of exposure, for example as a result of chemical spills, air, water and
food contamination episodes, pharmaceutical tampering and other such incidents. In such cases,
messages should quickly provide clear instructions about what to do, and information and
education about prevention of poisoning.
b) Labelling
Product labels are an essential part of hazard communication, providing the user with information
about the chemical nature of the hazard, the identity of the substance, advice in case of exposure,
instructions for storage and use, and cautions or warnings. Information may be given in words or
presented in symbols or pictograms.
c) Technology and design
Packaging
Packaging should be suitable for transport, storage and use and be ad- equately labelled.
Formulation
Taste deterrents have been added to dangerous liquids, such as ethylene glycol or methylated
spirits, to prevent ingestion of toxic amounts by small children, but their effectiveness has not been
proved.
Operational control
Engineering controls are a method for preventing poisoning in an occupational setting. Several
measures are available to control, minimize or eliminate exposure.
78
Legislation and chemical safety
Regulation and enforcement are important government actions for the pro- motion of safety and
health in the manufacture, transport, storage, use and disposal of chemicals and chemical products.
Monitoring people and the environment
Health surveillance consists of the regular assessment of health status, including medical
surveillance and biological monitoring. Public and occupational health surveillance programmes:

assess exposure to chemicals in the environment or workplace

indicate the need for preventive actions to protect health

evaluate how well people are complying with advice for reducing exposure

assess the adequacy of protective measures
E – tivity 9.2.3 Mechanisms for prevention of toxin exposure
Numbering, pacing and sequencing
9.2.3
Title
Mechanisms for prevention of toxin exposure
Purpose
The purpose of this e – tivity is to enable you acclimatize
yourself with strategies of toxin prevention
Watch the linked videos one and two
Brief summary of overall task
Spark
79
Individual task
a) Discuss ways of preventing chemical exposures
b) Explain how you would conduct a hazardous chemical
risk assessment
Interaction begins
E-moderator interventions
Schedule and time
Next
1. Post your work in the discussion forum 9.2.3
2. Read what your colleagues have posted in the discussion
forum 9.2.3
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Lesson Ten – Conventions on Toxic and Hazardous
Substances
9.3 Assessment Questions
1. Regulatory toxicology aims at guarding the public from dangerous chemical exposures, and
depends primarily on which form of study:
a) Controlled human studies
b) Controlled laboratory animal studies
c) Environmental studies
d) Observational human studies
2. What are the steps involved in evaluation of toxicity?
a) Hazard identification and dose-response evaluation
b) Evaluation of long term impact
c) Pathway analysis
d) Chemical analysis
3. _________ is an interpretation tool which enables toxicity of unknown mixtures of chemicals
be converted into the concentration of an equivalently toxic reference substance
a) Toxicity index
b) Toxicity equivalencing
c) Toxicity interpretation
80
d) Toxicity proportion
4. What is the third step of risk assessment?
a) Toxicity assessment
b) Hazard identification
c) Corrosivity assessment
d) Exposure assessment
5. Dealing with label information, what would be some good information
to put on the label?
a) Company name and address
b) Directions for use
c) Storage and limitations of product
d) All of the above
6. _________ species is used as screening of chemicals
a) Eisinia foetida
b) Zebrafish
c) Folsomia candida
d) Enchytraeus albidus
7. Which agency deals with the health effects that may occur from environmental exposure to
toxic chemicals?
a) The Centers for Disease Control and Prevention
b) The Environmental Protection Agency
c) The Centers for Disease Control and Prevention
d) The Nuclear Regulatory Commission
e) The Agency for Toxic Substances and Disease Registry
8. Which of the following is NOT a step in the Risk Assessment Process?
a) Hazard evaluation or dose-response assessment
b) Exposure dose
c) Risk characterization
d) Hazard identification
81
9. What activities should be conducted during the hazard identification step of the risk
assessment?
a) Describing the physical/chemical properties of the toxic substances
b) Identifying the substance name
c) Identifying the exposure pathway
d) Identifying the sources of toxicity information
e) All of the above
10. The exposure assessment step in the risk assessment process identifies all EXCEPT which of
the following?
a) Type of chemical exposure
b) Frequency of exposure
c) Calculation of the amount of exposure
d) Route of exposure
e) Length of time of exposure
9.4 E – references
1. Elliots, K. (2010, February 12). Hazardous Substances Safety. Retrieved from
https://www.youtube.com/watch?v=rpf2xeCgX1Q
2. FlinnScientific. (2012, November 30). Reducing Exposure to Laboratory Chemicals.
Retrieved from https://www.youtube.com/watch?v=0X4iuPVF1qY
3. GreenFacts. (2014, November 24). Hazard, Risk & Safety. Retrieved from
https://www.youtube.com/watch?v=PZmNZi8bon8
4. Gregory, R. (2019, July 11). Conducting Hazardous Chemicals Risk Assessment. Retrieved
from https://www.youtube.com/watch?v=L4QZOPulI1U
5. Ravi, M. (2018, December 28). Handling of hazardous chemicals or substances or Chemical
safety. Retrieved from https://www.youtube.com/watch?v=e2KV1ateKUQ
82
LESSON TEN
CONVENTIONS ON TOXIC AND HAZARDOUS SUBSTANCES
10.1 Introduction
This final lesson focusses on conventions and treaties developed to curb the effects of toxic and
hazardous substances. These multilateral environmental agreements together cover the
management of hazardous chemicals with toxic, persistent, and bio accumulative characteristics.
The purpose of this lesson is to enable you learn about and appreciate the conventions and acts
that help prevent the dangers posed by toxic substances.
10.2 Lesson Learning Outcomes
By the end of this lesson, you will be able to;
10.2.1 Discuss the United Nations Conventions on toxic and hazardous substances
10.2.2 State the acts on regulations of toxic and hazardous substances
10.2.1 United Nations Conventions on toxic and hazardous substances
There are three conventions developed by the United Nations under the auspices of the United
Nations Environment Program. These conventions together provide an international framework
for governing the environmentally sound management of hazardous chemicals through their
lifecycle.
The Basel Convention on the Control of Trans-boundary Movements of Hazardous Wastes and
their Disposal. This convention was adopted in 1989 in response to concerns about toxic waste
83
from developed countries being dumped in developing countries and countries with economies in
transition
The Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous
Chemicals and The Rotterdam Convention is a multilateral treaty to promote shared
responsibilities in relation to importation of hazardous chemicals. So many substances are covered
under the treaty which include; DDT, Dieldrin and Mercury.
The Stockholm Convention on Persistent Organic Pollutants (POPs) was adopted in 2001. This
convention was response to the urgent need for global action to protect human health and the
environment from “POPs”. These substances are persistent, bio-accumulative and toxic. (UNEP,
2003). Pesticides in International Trade was adopted in 1998.
E – tivity 10.2.1 United Nations Conventions on toxic and hazardous substances
Numbering, pacing and sequencing
10.2.1
Title
United Nations Conventions on toxic and hazardous
substances
The purpose of this e – tivity is to enable you appreciate
conventions that help in the control of toxicants
Watch the linked videos one, two, three, four and five and
Purpose
Brief summary of overall task
discuss three conventions concerned with controlling
hazardous substances
Spark
Individual task
a) State the aims of Stockholm Convention on Persistent
Organic Pollutants
b) Discuss the pros and cons of Stockholm convention
84
c) In a paragraph, explain the importance of Basel
Convention
d) Explain an incidence which led to the creation of Basel
Convention
e) What is the Rotterdam Convention?
f) What are the objectives and mechanisms of Rotterdam
Convention?
Interaction begins
E-moderator interventions
1. Post your work in the discussion forum 10.2.1
2. Read what your colleagues have posted in the discussion
forum 10.2.1
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
Schedule and time
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Acts on regulations of toxic and hazardous substances
10.2.2 Acts on regulations of toxic and hazardous substances
Industries can get chemicals as raw materials, process them into finished products, emit to air or
discharge to water or dispose with waste. There is no uniform and comprehensive legal regulation
to control toxic and hazardous substances. However, different legal requirements exist and should
be applied for any of these specific areas.
E – tivity 10.2.2 Acts on regulations of toxic and hazardous substances
Numbering, pacing and sequencing
10.2.2
Title
Acts on regulations of toxic and hazardous substances
Purpose
The purpose of this e – tivity is to enable you to understand
acts that are put in place to regulate toxic substances
Watch videos one, two, three and four and state various acts
Brief summary of overall task
on toxic and hazardous substances
85
Spark
Individual task
a) Discuss the toxic, hazardous and nuclear substances act
of 1990
b) Why was the toxic substances control act created?
c) What is contained in the toxic substance control act?
d) Outline the penalties meted for those who break the toxic
substance control act
Schedule and time
1. Post your work in the discussion forum 10.2.2
2. Read what your colleagues have posted in the discussion
forum 10.2.2
3. Keeping netiquette in mind, comment on at least three of
their answers
4. Read the facilitator’s comments too to get feedback
1. Stimulate further learning and generation of new ideas
through discussions.
2. Encouraging lurkers (quiet ones) to contribute
3. Provide feedback on the learning progress.
4. Close discussion
This task should take you two hours
Next
Examination
Interaction begins
E-moderator interventions
86
10.3 Assessment Questions
1. When was the Rotterdam convention adopted?
a) February 2005
b) February 2004
c) February 2006
d) January 2004
2. When was the first Rotterdam conference held?
a) September 2004
b) February 2004
c) August 2004
d) March 2004
3. What is the main objective of Rotterdam convention?
a) To protect human health and environment from toxic pesticides and hazardous chemicals
b) Chemical analysis of hazardous substance
c) Pathway analysis of chemical substance
d) To protect human health and environment from chemicals
4. The PIC helps participating countries to learn about ____________
a) Characteristics of toxins
b) Characteristics of chemicals
c) Characteristics of hazardous chemicals
d) Characteristics of pesticides
5. This Rotterdam Convention does not apply to banned or severely restricted chemicals
a) True
b) False
6. How many pesticides did the Rotterdam convention initially covered?
a) 24
b) 22
c) 23
d) 21
7. How many chemicals does the current convention covers?
a) 38
b) 39
c) 40
d) 42
87
8. What chemicals are covered under the Rotterdam convention?
a) Insecticide
b) Herbicide
c) Pesticide
d) Rodenticide
10.4 E – references
1. Jones, B. (2017, March 7). TSCA. Retrieved from
https://www.youtube.com/watch?v=SvK3WiXoZn4
2. Knowledge TV. (2021, February 21). Toxic Substances, Hazardous and Nuclear Waste
Control Act of 1990. Retrieved from https://www.youtube.com/watch?v=psnxoCk200k
3. Pontiveros, D. (2019, November 2). Toxic Substances and Hazardous and Nuclear Wastes
Control Act of 1990. Retrieved from https://www.youtube.com/watch?v=xSggwGp5l_Q
4. RedVectorOnline. (2018, October 3). Toxic Substance Control Act (TSCA) Compliance.
Retrieved from https://www.youtube.com/watch?v=c_oovVuG7fw
5. SafePlanet. (2013, July 11). The Rotterdam Convention Prior Informed Consent Procedure.
Retrieved from https://www.youtube.com/watch?v=5UFMB2FdvRs
6. Thinkers IAS. (2015, July 9). Stockholm Convention on Persistent Organic Pollutants.
Retrieved from https://www.youtube.com/watch?v=Eb9_eH6jss0
7. Thinkers IAS. (2015, July 9). The Basel convention on the control of Tran boundary
movement of Hazardous wastes. Retrieved from
https://www.youtube.com/watch?v=I9GYb2EqXFk
8. Thinkers IAS. (2015, July 9). Rotterdam Convention on the Prior Informed Consent
Procedure. Retrieved from https://www.youtube.com/watch?v=SBGiGMXEM6Y
9. Yagya, V. (2020, October 19). Basel Convention. Retrieved from
https://www.youtube.com/watch?v=K7JLanpxbHk
88
ANSWERS TO ASSESSMENT QUESTIONS
1.3
1. D
2. A
3. C
4. D
5. A
6. D
7. C
8. A
9. B
10. A
2.3
1. A
2. B
3. D
4. C
5. E
6. A
7. B
8. A
9. B
10. C
3.3
1. B
2. C
3. A
4. B
5. C
6. E
7. B
8. A
9. A
10. D
89
4.3
1. A
2. D
3. B
4. D
5. C
6. B
7. A
8. C
9. B
5.3
1. D
2. B
3. A
4. B
5. A
6. D
7. B
8. B
9. B
10. B
6.3
1. A
2. D
3. C
4. D
5. E
6. B
7. D
8. C
7.3
1. C
2. B
3. C
4. B
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5. A, C, D
6. D
7. D
8. A
9. E
10. F
8.3
1. C
2. B
3. D
4. A
5. D
6. B
7. C
8. C
9. D
9.3
1. B
2. A
3. B
4. A
5. D
6. B
7. E
8. B
9. E
10. A
10.3
1. B
2. A
3. A
4. C
5. B
6. C
7. B
8. C
91