Introduction to Environmental Health, by Dechasa Adare Mengistu, Haramaya University. 2022/23pdf

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Haramaya University
College of Health and Medical Science
Introduction to Environmental Health
By: Dechasa Adare (MSc.)
2022 Ac. year
dechasaadare@gmail.com
9/8/2023

Learning Objectives
 To understand and discuss the environmental health concepts and
components
 Discuss the association between the human and environment.
 Describe the importance of the environmental health in preventing
the disease and promoting the health
 Identify agents that originate in the environment and can impact
human health
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 Describe specific applications of environmental health concepts
to fields such as water quality control, food safety, occupational
health and safety etc.
 Describe the healthcare waste management and its implication
 Describe the principle, concept and implications of ecology
 Compare and contrast different components of Ecology
 Explain ecological good and services
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Cont…

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Compare and contrast ecosystem based solutions vs manmade
solutions in ecological principles
Discuss ecosystem good and services systematic model
Cont…

Definition terms
 Health
Health is the state of complete physical, mental, and social
wellbeing not merely the absence of the disease infirmity
and the ability to lead a productive life in the society.
 Public Health
Public health is the science and the art of preventing disease,
prolonging life and promoting health and efficiency through
organized community efforts
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Cont…
 Environment
 Environment is the sum of all external influences and
conditions, which affect health and life.
 All the things around us with which we interact
 Living things
 Non-living things
 Social relationships and institutions
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Cont…
• Sanitation: Sanitation is an establishment of environmental conditions
favorable to health.
• It is the principle or art of preventing the diseases by eliminating or
controlling the environmental factors
 Pollution: is the introduction of pollutants or contaminants into a natural
environment that causes instability, disorder, harm or discomfort to the
ecosystem.
 Hygiene : refers to the set of practices associated with the preservation of
health and healthy living. Hair, body, hands, fingers, feet and clothing, etc.
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What is Environmental Health?
 It refers to the theory and practice of assessing, correcting, controlling,
and preventing those factors in the environment that can adversely
affect the health of present and future generations
 It comprises those aspects of human health determined by:
 Physical,
 Biological,
 Social, and
 Psychological factors in the environment.
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Cont…

 Environmental health is broader than hygiene and sanitation
 It encompasses hygiene, sanitation and many other aspects of
the environment.
 It also involves studying the environmental factors that affect
health.
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Cont…

Environmental Health?
The study of how the environment affects your health.
Food
Air
Water
Sunlight
Noise
Soil
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Environmental Health Professional
Work as
scientists in
research labs Work for the
government
writing
regulations and
studying
pollution
Work for
corporations
making sure
workplaces are
safe for workers
People working in the field of
environmental health
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Why is environmental health important?
 The physical, biological, socio-cultural environment, and our habitat are the
most important determinant of human health.
 Lack of access to safe drinking water and sanitation, air pollution and climate
change contribute to:-
 23% of all deaths worldwide
 36% of all deaths among children 0-14 years old
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 An estimated of 1.8 billion people drink from faecally contaminated
water
 2.5 billion people live without basic sanitation facilities that
contributed to diarrhoeal diseases, malnutrition and death
 Unsafe drinking water, poor hygiene, and lack of access to sanitation
contribute to:
 About 88% of deaths from diarrheal diseases,
 Cause 11% of mortality of under 5 children children
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Cont…

 Ambient (outdoor) air pollution was estimated to cause 3.7 million
premature deaths worldwide in 2012
 Urbanization contributes to increased rates of vector-borne diseases
 The health impacts of climate change are numerous and complex.
 Infectious disease:
 Can spread by food, water, air or soil and travel globally
 New diseases are emerging and previous ones reemerging
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Cont…

In Ethiopia: (EDHS, 2011)
 Proportion of population using an improved drinking water
source: 50.8%
 Proportion of population using an improved sanitation
facility: 8.8%
 Thus, protecting the environment and preservation of
ecosystems are the most fundamental steps in preventing the
illness and promoting the health
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Cont…

Therefore, to stop the spread of a communicable
disease, changing the environment can break the chain.
The environmental health also plays an important role
in the control of other non-communicable disease, such
as:
 Chemical poisoning,
 Occupational disease, etc.
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Cont…

Humans and the Environment
 Man can affect the environment: deforestation, fire, air pollution, noise
pollution, waste dumping, radiation pollution, etc.
 Man can be affected by the environment: flooding, draught, famine, disease,
earthquakes, lighting
 Man can maintain environment: afforestation, pollution reduction,
disarmament, international conventions, etc.
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The role of environmental health in public health
 Environmental health play an important role in dealing with the disease
causation :-
 Etiological or a causative agent
 A reservoir or source of infection of the causative agent
 A mode of escape from the reservoir
 A mode of transmission from the reservoir to the potential new host
 A mode of entry into the new host
 A susceptible host
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The disease occur if the following three conditions exist simultaneously
to cause the disease.
1. There must be an a etiologic agent (a germ)
2. There must be the host sensitive or susceptible to the disease
3. There must be a mode of transmission (the pathway of the agent,
i.e. the environment).
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Cont…

Events
Environment
Agent Host
Epidemiological triad or Disease Causation
HOST Characteristics Types of AGENTS ENVIRONMENTAL Factors
Age Biologic – bacteria, virus, molds Housing – crowding, noise
Gender Chemical – poison, alcohol Air – temperature, humidity
Occupation Physical - trauma, fire etc. Water , food etc.
Race
Marital status
Genetic profile
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Cont…

Determinants of Health
Hereditary or biological factors such as
 Diabetes, mental retardation, lack of resistance to disease, etc
Medical care such as
 Technology and interest in medical self-help-
Life style such as
 Lack of sleep and rest, foods, poor exercise, bad behaviors etc..
Environment such as
 The place we live, the water we drink, the food we eat, the air we breathe etc.
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Health intervention models
Health intervention models is classified into two:
1. Clinical intervention model: focuses on the treatment of patients,
2. Public health intervention model: concentrates on the maintenance of
health through education and keeping the environment safe
• The public health intervention can include:
 Having policies, appropriate organizations, sanitation legislation,
technology etc.
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Those to prevent this event we need to focus on the public health
intervention model than the clinical intervention model
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Cont…

Environmental factors that could influence health include
1. Life support: Food, Water, Air etc.
2. Physical factors: Climate, Rain fall
3. Biological factors: Microorganisms, Toxins, Biological waste,
4. Psycho-social and economic: Crowding, Income level, Access to
health care
5. Chemical factors: Industrial wastes, Agricultural wastes, Air
pollution, etc
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In general, environmental sanitation breaks the chain of disease
transmission through three basic strategies:
1. Promotion: targeted to behavioral changes (housing
improvement, basic sanitary provisions.)
2. Prevention of communicable diseases before it happens: safe
water, safe food, latrine provisions, personal hygiene, vector
control etc.
3. Control of communicable diseases through various environmental
interventions.
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Cont…

 Another way to look at the agent-host-environment relationship is from
the ecological point of view.
 Ecology may be defined as the relationship of living thing to their
environment.
 On the basis of the ecologic concept:
 The agents and host are always engaged in a constant struggle, which
one will overpower the other will depend on the environment in which
they interact.
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Cont…

The Scientific Bases for the Practice of Environmental Health
 As a scientific discipline, environmental health begun with:
 Attempts to prevent and control communicable disease caused
by various factors such as:
Poor quality of water
Unhygienic disposal of sewage (excreta).
 Seeks to maintain the ecological balance of nature and the well-
being of man
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Scope or Components of environmental health….
Description Concerns
 Personal hygiene Hygiene of body and clothing.
 Water supply Adequacy, safety (chemical, bacteriological, physical) for domestic,
drinking, and recreational use
 Human waste disposal Proper excreta disposal & liquid waste management
 Solid waste
management
Proper application of storage, collection, disposal: Waste recycling
and generation analysis
 Vector control Control of disease transmitting and harmful arthropods and vectors
 Food hygiene Food safety and wholesomeness in its production, storage,
preparation, distribution, sale, until consumption
 Occupational hygiene Occupational health service, sanitation, safety in working settings
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 Housing sanitation Protection against disease and accidents, psychological, and social
comforts
 Institutional hygiene Communal hygiene in schools, prisons, health facilities, refugee camp,
Detention homes, Settlement areas
 Hygiene and
quarantine service
Hygiene provisions in international ports: air, train, bus
 Disinfection and
sterilization
Control of disease causing organisms in omits, utensils, equipment,
foods, etc.
 Air pollution Nature of atmosphere, pollution sources, global warming, etc.
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Cont…

Water Supply
 Water is a basic necessity of life
 Man, animals and plants can not survive without water
 We can live for sometime without shelter, clothing, and even
without food
 But without water a person soon perishes
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Definition of Terms
 Raw water
 Untreated water from suspicious sources such as rivers, lakes or
from unprotected wells and springs
 Contaminated water
 Water which may contain harmful microorganisms or toxic
chemicals which make it unfit for use.
 It can not be detected by the organs of sight, taste and smell.
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Definition of Terms
 Polluted water
 Water that has come in contact with substances that alter its
physical qualities, so that it changes in color, level of turbidity,
taste or smell.
 Pollution can be detected by the sense organs.
 It can be harmful or not
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Definition of Terms
 Clear water
 Water that has sparkling appearance to the eye
 It can be clean or contaminated
 Clean water
 Water that is free from disease causing organisms
 Palatable Water
 Water which is pleasant to drink and is not necessarily clean
or potable
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Definition of Terms
 Potable water
 This is drinkable water
 Water which is free at all times from any harmful substances
(pathogenic organisms or toxic chemicals).
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Global Total Water and Freshwater Reserves
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Sources of water
• Ground water: wells and springs
• Surface Water: Rivers, streams, lakes, etc
• Rain water: collected over impermeable or non absorbent surfaces.
• Seawater: after removing the salt through desalination by the
process of distinctive
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Importance of Water
• About 70% of the human bodyweight is water
• Water is essential for health and sanitation
• Balancing the environment
• Essential to run industry
• Source of energy
• Useful for recreation,
• fishery and aquatic wealth, etc..
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Basic requirements for safe water
 Safe, adequate and accessible supplies of water, combined with
proper sanitation, are basic needs.
 Minimum acceptable standard (WHO)
 Drinking: 2–3 liters/day
 20–50 liters/capita/day for cooking and basic hygiene
 Water supply is taken as an essential component of primary health
care
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Current Water Issues
 Vulnerability of surface water to:
 Drought (not replenished); i.e.,
lakes, reservoirs
 Diversion of rivers for
agricultural and urban use
 Declining groundwater levels
 Failure to replenish
 Saltwater intrusion
 Surface water pollution from non-
point sources
 Groundwater pollution
 Increasing competition for water
supplies
 World’s available freshwater is
not distributed evenly
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Water Pollution and Pollutants
Water Pollution; The existence of any substances or pollutants than normal
concentration or background concentration.
 Gases: CO2, HS2, CH4, and nitrogenous.
 Dissolved minerals: Ca, Mg, Na, Fe Mn and their carbonates, hydroxides,
chlorides, sulfates, fluorides, nitrates etc.
 Suspended and colloidal materials: bacteria, algae, fungi, protozoa etc.
 Radioactive materials: radioactivity imparted by contact with radioactive
sources such as mining or processing
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Sources of Water Contamination
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Major Causes of Stream and River Pollution
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Water, Health and Disease
 Not all water helps humans to survive
 Water from contaminated sources cause numerous disease and untimely
deaths.
 Several infections, intestinal diseases are transmitted through water
contamination by fecal matter.
 Excreted or fecal matter contain bacteria, viruses, protozoa and parasitic
warms.
 Contaminated water result in different water associated disease or illnesses
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Water associated disease
Water associated disease is classified into 5 groups:
Water-borne disease
Water -washed diseases
Water-based diseases
Water- related diseases
Chemical constituents either excess or shortage
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1. Waterborne- (fecal-oral)-Disease
 Waterborne disease is caused by
pathogens that originate in fecal material
and are transmitted by ingestion.
 Water acts only as a passive vehicle
 May be part of water-washed diseases
 They may transmitted faeco-oral routes
Example:
Cholerae,
Giardiasis,
Salmomellosis,
Poliomyelitis,
Typhoid,
E. Coli
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Infected person
Pathogen in
excreta
Contaminat
ed water
sources
Consumption of
untreated water
Susceptible
person
Cont…
The cycle of
infection
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2. Water-washed diseases disease-
 Water-washed disease is caused by:-
 Pathogens that originate in feces and are transmitted through
contact because of inadequate sanitation or hygiene
 Diseases linked to a lack of water for personal hygiene
Eye diseases: Trachoma & conjunctivitis
Skin diseases: Scabies
Louse-borne typhus and relapsing fever
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3. Water-based disease
 Water-based disease is caused by organisms that originate in water or
spend part of their life cycle in water and come in direct contact with
humans in water.
 As an intermediate host which lives in water
 Infection cannot occur by immediate ingestion, or contact with,
agent.
Schistosomiasis,
Dracunculiasis (helminths) (guinea worm).
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Reading assignments
Read about the life cycle of Schistosomiasis, and
dracunculiasis (guinea worm).
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4. Water-related disease
 Water-related disease is disease caused by insects that live close to water or
breed in the water or aquatic environment.
 Not related to the conception or in contact to the water but proximity to the
water body.
 It spread by mosquitoes, flies and other insects that breed in water or near
it
 Malaria, Yellow fever, Dengue fever, Filariasis, Onchocerciasis, Sleeping
sickness etc.
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How to prevent water associated diseases?
 Briefly explain how to prevent waterborne, water washed, water-based,
and water-related disease??
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5. Chemical constituents
 Some elements or chemicals may be: in excessive/inadequate
amounts
I.e, Fluoride:
Excess: dental flourosis/mottled enamels
 lack : dental cavities (decay)
 Maintaining the optimal level (1mg/l)
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Water impurities
 Impurities of water are found in two forms:
1. Suspended impurities
2. Dissolved impurities
 Suspended impurities: Are very fine particles of insoluble matter, which
float in a liquid are said to be in suspension.
 Microorganisms
 Clay, pesticide.
 Suspended solids generally cause taste, colour or turbidity
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 Algae: that grow in ponds, river banks and in still water, causes
taste, color and turbidity
 Radioactive materials: radioactivity imparted during mining or
processing of ores or by waste from industrial use of radioactivity.
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Cont…

2. Dissolved impurities
 These types of impurities are divided in to two
1. Gasses such as: dissolved oxygen, CO2, H2S
2. Minerals such as salts of calcium and magnesium that causes
hardness and sodium and potassium causes alkalinity.
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Cont…

In general, a source of water supply may require treatment because of
impurities (natural or man made) can be identified by:-
 Naked eye
 Taste or smell
 Laboratory methods
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Cont…

Water Treatment for Municipal water supplies
 Water treatment may be defined as the process of removing all those
substances which are potentially dangerous or undesirable in water supplies
for human and domestic use.
 Biological, chemical or physical
 Surface waters are never pure, therefore, deserve adequate treatment if they
are intended for domestic purposes.
 The type of treatment facilities needed is determined by the type &
concentration of impurities present
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 The impurities vary:-
 From disease causing microorganisms and not cause disease
 From dangerous chemicals to substances which are undesirable
from points of view such as:-
Impurity that cause color, taste, odor, but which are
physiologically harmless.
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Cont…

Main objectives for water treatment:
 To remove pathogenic organisms and prevent waterborne diseases.
 To remove substances which impart color, taste, or odor to the water.
 To remove undesirable chemicals or minerals from the water.
 To regulate essential elements or chemicals (remove excess, limit
amount).
 To remove excess/undesirable dissolved gases.
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Cont…

 Water treatment procedures may involve:
 Simple physical processes like, sedimentation
 Complex physico- chemical and biological processes
 It depending upon the impurities observed in the raw water, that need
removal.
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Cont…

Treatment of Water on a small scale
 For economic reasons, large scale water treatment procedures are not
existing and can not be practical for poor communities.
 Water- borne diseases are prevalent among such community because of
consumption of untreated water.
 Water must be adequately treated before consumption, even in rural
areas.
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 Treatment of house hold water supplies include the following methods.
Boiling: Is one of the most reliable methods of disinfecting water on a
small scale (15-20 minutes.
 All forms of microorganisms including the most resistant spores or
cysts can be destroyed using this method.
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Cont…

Filtration: Using home- made sand filters or candle (ceramic) filters.
Chemical disinfection: Chemical disinfection compounds such as chlorine,
iodine, silver salts and potassium permanganate etc.
Storage and sedimentation
Exposure to sun-light: Exposure to Ultra Violate light radiation (UV-
radiation)
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Cont…

Quality of Water
 Any new or untreated sources of water should be examined for quality
before expensive development is undertaken.
 Good quality water for human use should be:
 Colorless
 Free of harmful bacteria, Sediment, objectionable minerals, tastes,
odor.
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 The tests should be performed to determine the quality of the water before
developing water supply sources
Test for microorganisms
Testing for minerals
Testing for sediments, color, taste, and odor
Testing for Acidity and alkalinity etc.
 These tests should be done at regular intervals to check subsequent
pollution or contamination after development of the water sources
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Cont…

Physical analysis : determining substances which affect the physical property
of the water such as color, taste or odor.
 Suspended solids (like silt, clay particles,
 Floating materials
 Colloidal matter etc.
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Cont…

Chemical analysis: determining the quality and quantity of different types of
chemicals.
• Acidity-alkalinity
• pH
• Hardness
• Dissolved oxygen
• Hydrogen supplied
• Chloride
• Nitrates
• Nitrites, and Ammonia
Chlorine residual
• Fluoride
• Iron
• Manganese
• Toxic substances such as:
• Arsenic, Lead, Mercury, Pesticides etc
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Cont…

Bacteriological analysis:
 This is the most important of all laboratory analysis.
 This enables to determine the degree of contamination of water with
wastes of human or animal origin (coliforms, indicators).
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Cont…

Community Waste Management
 Waste is any discarded material that considered no longer useful in the
economy
 Waste is a by-product of human activities
 The problem of wastes is becoming a global concern.
 Wastes may have effects:
At house-hold levels, community level, national level, cross border
problems,
Becoming concern of the international community.
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 Waste can be classified based on:
 Physical state (solid ,liquid ,gaseous)
 Original use ( packing waste, food waste ,etc.) ;
 Type of material ( glass, paper ,etc.)
 Physical properties (combustible, compostable, recyclable);
 Origin ( domestic ,commercial ,agricultural, industrial etc,)
 Safety level ( hazardous, non-hazardous ) and the like.
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Cont…

Solid wastes
 Materials which are solid in nature which arise from various human
activities and are discarded as useless/unwanted.
 These wastes may be:
 Homogenous masses such as agricultural wastes or
 Heterogeneous wastes from specific factories/industries
 Increase in population and the advances in technology lead to the
increase in amount and complexity of the wastes produced.
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Liquid wastes
 Liquid waste is that part of community water supply after it has been
fouled by filth in a variety of uses.
 Liquid waste may include the following:
 Domestic waste water from residential, institutional and business
areas.
 Industrial waste water.
 Storm/rain run off.
 Combined waste water: combination of the above.
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Definition of terms:
 Pathological wastes: are wastes that include human tissues and dead
animals.
 They are considered as infectious.
 Infectious wastes: Wastes that carry pathogens and includes:
 Patholaogical wastes, body fluids.
 Materials contaminated with blood (needles, gloves, etc.)
 Agricultural wastes: residues from farms (crop residues), animal
manure, etc.
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Objectives of solid waste Management:
 The objectives of SWM is to properly plan, organize and
implementing handling, storage, collection, transport, recovery
and disposal of waste.
 The present concept in SWM is to dispose off small waste as the
possible.
Recovery
Recycling
Re-use
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Public Health Importance of solid wastes
 Problems of improper handling of solid waste include the
following
1. Serve as breeding site for flies, rodents and other animals.
 This leads to disease transmission and property damage.
2. Ecological impacts on water, soil, and air.
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• Leachets from dumps and landfills can contaminate surface and
ground waters.
• Toxic elements may leach) from dumping and land fills (arsenic,
copper, uranium)
• Too much stress of the environment with wastes may create
ecological imbalance in the biosphere
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Cont…

3. Accident and fire hazards.
4. Adverse effects on land and property value
5. Public nuisance: dust, odor, stray animals, bad sight.
6. Depletion of natural resource.
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Cont…

Solid Waste Management
 Various activities associated with SWM from cradle to grave
(generation to disposal).
 Solid Waste Management may be defined as the process by which
the programs and plans are developed to solve problems of solid
waste.
 There are six functional elements of SWM
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Solid Waste Management
 Various activities associated with SWM from cradle to grave
(generation to disposal).
 Solid Waste Management may be defined as the process by which
the programs and plans are developed to solve problems of solid
waste.
 There are six functional elements of SWM
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Functional elements in SWM
Waste generation
Waste handling, and separation, storage,
and processing at the source
Collection
Transfer and
transport
Separation, processing, and
transformation of Solid
waste
Disposal
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On site handling of waste
• On site handling refers to activities associated with handling of solid waste
until placed in containers for storage before collection.
• This includes handling, storage processing and separation at the source.
• Separation of waste component is an important step in the handling and
storage of solid waste at the source.
• The best place to separate waste material for re-use and recycling is at the
source of generation.
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Cont…

Factors considered in the onsite storage of solid waste
 Type of storage container to be used.
 The location where the container is to be kept.
 Public health and aesthetic considerations:
 Is it infectious, the need for cover, does it smell, etc
 The collection method, time and condition:
 Is there direct hand touch? When is it to be collected? Is it wet or dry,
etc.
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Waste Collection
• Transportation problem associated with collection more complex and
expensive because of:
 It demands experienced/skilled people to manage
 It demands special vehicles
 It demands more manpower and hand tools
 It demands more monetary expenditure for fuel, salary and maintenance
• In most cases collection takes 60-80% of the operational cost in waste
management.
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Disposal of solid waste
 After recovery, reuse or recycling, the leftover solid wastes are collected
and of no further use.
 There are two alternatives for the disposal of solid wastes
1. Disposal on or in the earth’s surface.
2. Disposal under the sea or ocean.
 The most common method in use today is disposal on land.
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Methods of disposal on land:
Open dump
Controlled tipping
Sanitary land fill
Composting
Incineration
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Liquid waste Management
• Liquid waste: Liquid waste is part of a community water after it has
been fouled by a variety of uses.
• The collection and safe disposal of liquid waste and human excreta is
among the most important problem.
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Definition terms
• Sewer: Pipe which is normally closed for carrying sewage.
• Effluent: Liquid waste that flows out.
• Influent: Liquid waste that flows in.
• Sewerage: The organized network of drainage system used to
remove or dispose sewage
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 Excreta: Human faeces and urine
 Gray water: Other wastewater from human activity
 Not directly from human feaces and urine
 Wastewater from washing, bathing, etc.
9/8/2023 92
Cont…

Public health importance of liquid waste
 Untreated liquid waste including human excreta if accumulated and if
not properly disposed of:
 Produces malodorous gases
 May serve as a breeding site for various insects and rodents
 May contain numerous pathogenic organisms and ova of parasites
 Contains nutrients which encourage growth of aquatic plants which
may lead to eutrophication (nutrient rich) of water bodies
9/8/2023 93

• May carry toxic chemicals that have adverse effects on health,
water and soil
• May lead to pollution of water bodies (DO)
• Leads to contamination of ground and surface sources of water
9/8/2023 94
Cont…

0
20
Organics
kg COD/ (Person·year)
12.3
3.6
14.1
Volume
Liter / (Person·year)
500 l 50 l
source:
Otterpohl
0
6
Nutrient content
kg N,P,K / (Person·year)
N
P
K
0.8
5.3
1.0
Composition of Household Waste and Wastewater
Greywater urine faeces
9/8/2023 95

Excreta borne diseases.
• Six factors of the mechanism of disease transmission is vital for the
control and breaking of the chain of transmission of excreta borne
diseases.
• The agent- host- environment dynamic interaction is also vital
• In excreta borne disease transmission, the significance of the 5Fs)
should also be clearly known.
• 5Fs: Feces, fingers, flies, fields /fomites and fluids
9/8/2023 96

Classification of excreta borne diseases:
• Excreta born diseases may be classified in to four groups as follows:
1. Helminthic diseases: This is further divided in to three major
sections
– Round worms e.g Ascaris, trichuriasis, hook worm, etc.
– Flat worms e.g Taneasis-beef, pork, dog, fish tape worm.
2. Protozoan diseases:
• Ameobiasis, giardiasis
9/8/2023 99

3. Bacterial diseases:
– Salmonellosis
– Shigelosis
– Cholera
4. Viral diseases:
• Infectious hepatitis , Poliomyelitis , Viral diarrhea
9/8/2023 100
Cont…

Impacts of excreta borne diseases:
Direct effect: on the health of the individuals and the public
(morbidity and mortality).
Indirect effects:
– Predispose to other diseases
– Retard growth of children
– Economic aspects
– High cost of treatment etc.
9/8/2023 101

Importance of excreta borne diseases to public health in Ethiopia:
 Human excreta borne diseases are the most prevalent and
dominant.
 30-40% of all reported causes of morbidity are excreta borne
annually (MOH).
9/8/2023 102

Factors influencing excreta disposal design and construction in a
community
 Engineering factors of design construction, and installation
 Human factors
 Cost Factors
 Biological and geographical factors
9/8/2023 103

Objective of human waste disposal system
• The cardinal objective of human waste disposal system:
– Is to isolate totally human excreta from man’s food, water
and the immediate environment at large
9/8/2023 104

The seven requirements (criteria) for satisfactory excreta
disposal systems
 Should not contaminate surface soil.
 Should not contaminate surface water.
 Should not contaminate ground water.
 Should not be accessible to flies, cockroaches or other animals.
 Should be free of odor.
 The methods used is simple, inexpensive to construct and operate.
 There should be no handling of fresh excreta
9/8/2023 105

Excreta disposal methods/technologies
 Excreta disposal methods are mainly two types:
 Non-water carriage systems: which normally do not use water for carrying
away excreta.
– Pit latrine, VIP latrine, compost latrine and Ecologic Economic sanitary
latrine (ECOSAN latrine).
 Water carriage systems: Excreta is carried away by water through a sewer
to its final disposal site.
– Water is the primary transporter of excreta in this process.
– Pour- flush latrine, septic tanks, and municipal sewage treatment systems
9/8/2023 106

Human Excreta – Resource or Risk?
• Human excreta as a potential resource
 Contains nutrients (N, P, K, and organic matter)
 Widely used as a fertilizer and soil amendment
• Potential for excreta misuse and environmental pollution
 Nutrients and organic matter (Eutrophication, anoxia, fish kills)
Nitrogen 4.5
Phosphorous 0.6
Potassium 1.2
Organic matter 35
9/8/2023 107

Characteristics of Human Wastes
• Of no major (or less) concern/risk
• Largest portion of wastewater
• Contains almost no (or less) nutrients (simpler treatment)
• Of no major (or less) concern/risk
• Largest portion of wastewater
• Contains almost no (or less) nutrients (simpler treatment)
3. Grey water
3. Grey water
• Less critical (less risk)
• Contains the largest proportion of nutrients available to plants
• May contain hormones or medical residues
• Less critical (less risk)
• Contains the largest proportion of nutrients available to plants
• May contain hormones or medical residues
2. Urine
2. Urine
• Critical (high risk)
• Consists of organics, nutrients and trace elements
• Improves soil quality and increase its water retention capacity
• Critical (high risk)
• Consists of organics, nutrients and trace elements
• Improves soil quality and increase its water retention capacity
1. Feces
1. Feces
characteristic
characteristic
fraction
fraction
9/8/2023 108

Utilisation
Treatment
Substances
Faeces
(Brownwater)
Anaerobic
Digestion,
Drying,
Composting
Biogas,
Soil
Improvement
Constructed
wetlands,
Wastewater ponds, biol.
Treatment, etc.
Greywater
(shower,
Washing, etc.)
Irrigation,
Groundwater-
Recharge or
Direct reuse
Urine
(yellowwater)
Liquid or dry
Fertiliser
Hygienisation by
Storage or
Drying
Options for Excreta and Greywater Utilization
9/8/2023 109

Conventional Sewage Treatment
9/8/2023 110

 Hazardous waste
• The term ''hazardous waste'' means a waste, or combination of solid and
liquid wastes that increase the :-
 Mortality or an increase in serious irreversible (mutagenicity, and
carcinogenicity)
 Potential hazard to human health or the environment
 Loss of life and material damage (disability, death, fire, explosion)
 High concern of trans-boundary movement of toxic waste
9/8/2023 112

 Characteristics of Hazardous Waste
• Ignitability. Ignitable waste can create fires under certain conditions or is
spontaneously combustible
• Corrosivity. Corrosive waste includes acids or bases capable of corroding metal.
• Reactivity. Reactive waste that can cause explosions, toxic when mixed with
water.
• Toxicity. Toxic waste is harmful or fatal when ingested or absorbed.
• Infectivity: a waste with a potential cause for infectious diseases
• Radioactivity : Wastes containing radioactive elements (uranium, cobalt).
9/8/2023 113

 Sources of hazardous wastes
– Healthcare/ clinical wastes
– Other industrial wastes (mining industry, textile industry,
garage, pesticides, pharmaceutical etc..
– Residential areas
– Commercial areas
– Agricultural areas
9/8/2023 114

 Why hazardous waste a concern?
 Couse of mass life and material damage or loss
 Couse environmental pollution
 Couse irreversible health risk
 Increase bioaccumulation
9/8/2023 115

 Hazardous waste control measures
• Sources reduction
– Technology efficiency
– Material substitutes
– Good manufacturing practices
• Waste avoiding
• Waste minimization
• Waste recycling
• Waste treatment
• Disposal
9/8/2023 116

Hazardous waste management hierarchy
9/8/2023 117

Strategies used to control or prevent hazardous substances?
 Implementation of awareness raising programmes.
 Promotion of waste avoidance and minimization projects.
 Introduction of regulatory provisions
 Identification of existing practices at enterprises
 Development of compliance standard or guidlines.
 Remediation of inadequate facilities for intermediate storage and waste
management at source.
 Closure of inadequate facilities which are not suitable to improve.
9/8/2023 119

 Progressive implementation and enforcement of those standard
 Identification of external factors resulting in poor hazardous
waste management
 Development and implementation of an improved data collection
system
 Promotion of industry uptake of avoidance and minimization
projects by awareness raising
9/8/2023 120
Cont…

 HealthCare Waste/Medical waste
• Medical waste refers to all categories of waste generated
from:-
 Health facilities
 Clinics
 Veterinary hospitals
 Clinical laboratories, and
 Home based treatment of patients
9/8/2023 121

Health-care facility waste can be divided into two main categories:
1. Non-risk waste
Account between 75% and 90% of the waste
Is non-risk and almost comparable to domestic waste.
2. Hazardous / infectious waste
Account 10 - 25% of health-care institution waste
Blood and other fluids
Pathological wastes
Sharps materials
Laboratory wastes
9/8/2023 122
Cont…

Categories of Health care wastes
Health care Waste
Hazardous / Clinical waste
-Sharps
- Pathological
- Hazardhous pharmaceutical
- Chemical
- Radioactive
- Pressurized containers
- Heavy metal content
Non-hazardous / Non-clinical/ General waste
General Wastes
- Office wastes,
- Packing
materials,
- Furniture,
linen plastics
- Outer packages
Food/kitchen wastes
9/8/2023 123
Fig: Categories of medical waste

 Why healthcare facilities ideal for disease transmission?
9/8/2023 124
 Healthcare staff are constantly exposed to potentially
infectious materials
 Patients may have infections that are easily transmitted
 Patients may be more susceptible to infections due to illness
 Services are provided in a limited physical space

 Infectious Medical Waste
Infectious Medical Waste is defined as:-
 Healthcare wastes that are suspected to contain pathogenic
microorganisms (or their toxins) in sufficient concentration or
quantity to cause diseases
 Medical waste capable of producing an infectious disease
9/8/2023 125

Cont..
 Waste is considered infectious when it is:
 Contaminated by an organism that is pathogenic to healthy
humans
 The organism is in significant quantity and virulence to transmit
disease.
9/8/2023 126

 Blood and blood products
 Contaminated sharps,
 Isolation Wastes,
 Laboratory wastes
 Unfixed pathological tissues
 Any materials contaminated
by the BBFs
9/8/2023 127
Cont…

Exposure to blood and body fluids
 Exposures to blood and fluid borne pathogens in the medical
setting typically occur as the result of:-
‣ Puncture from contaminated needles, broken glass, or other
sharps
‣ Contact between non-intact (cut, abraded, acne, or sunburned)
skin and infectious body fluids
‣ Direct contact between mucous membranes and infectious body
fluids
Example: A splash in the eyes, nose, or mouth
9/8/2023 129

Factors increase risk of pathogen transmission
 Infected Source : the disease stage of the source, nature etc.
 Route of Entry: puncture wound, broken skin, or direct
contact with mucus membrane
 Infective Dose: the amount and type of fluid, as well as the
amount of infectious agent in BBFs.
 Susceptible Host: immunocompromised, health status of
the host..
9/8/2023 130

Sources of Disease Transmission
 Main sources for contact transmission of infection to patients
is from:-
 Hands of medical staff
 Contaminated equipment used on patients
 Poorly cleaned surfaces and rooms
 Main source of transmission of infection to medical
staff and waste handlers:
 Needle-stick injuries and other contaminated materials
9/8/2023 131

Routes of Disease Transmission
 If infectious waste is inadequately managed, these
microorganisms/toxins can be transmitted by:
– Direct physical contact
– Transfusion or injection
– Inhalation
– Ingestion
9/8/2023 132

Vulnerable group/host
• Staffs
Mostly exposed to :
 Needle-sticks
 Blood and other fluids
 Pathogenic aerosols
• Patients
Mostly exposed to :
 Improperly discarded sharps
 Exposure to accidental spills
 Spread of hospital infections
9/8/2023 133
• Community
Waste pickers or collectors
Waste scavengers
Residents in illegal recycling sites
Can be exposed to:
• Discarded medical waste washing up on
beaches
• Infectious waste bags found by children
• Reuse of discarded sharps

Collection or Management of health care Waste
 Infectious medical wastes must be:-
 Collected at the point of generation
 Collected in leak-proof and puncture-resistant container
 Collected in the appropriate color coded bags
 Orange bags for autoclaved waste, and red bags for all
other treatment methods
9/8/2023 134

 Biohazard bags must be labeled with the international biohazard
symbol
 Appropriate wording such as:
“Biohazard,” “Biomedical waste,” “infectious medical waste,”
or “regulated medical waste”
Containers should never be completely filled, nor filled above
the full line indicated on box.
9/8/2023 135
Cont…

Different color coding has to be used for effective segregation, as:
 Black : Non-Risk waste.
 Red: Risk waste with Sharps.
 Blue: Risk Waste without sharps.
 Yellow: Radioactive waste
 Green: Chemicals like Mercury & Cadmium
9/8/2023 136
Cont…

• When you mix infectious waste and
regular solid waste together, you are not
permitted to separate them.
• Once combined, the entire contents are
considered infectious waste
9/8/2023 137
Cont…

 Healthcare-associated infection
 Healthcare-associated infection (HCAI) is one of the most
common complications of health care management.
 It is a serious health hazard as it leads to increased:-
 Patients’ morbidity and mortality
 Length of hospital stay and
 The costs associated with hospital stay
9/8/2023 138

Healthcare-associated Infection prevention and control
 Infection control can be defined as measures, practices, protocols and
procedures to prevent and control infection transmission in health care
settings.
 Application of standard Precautions:-
 Standard precautions include the following components:
9/8/2023 139
Hand hygiene
Personal protective equipment
Prevention of needle stick and other
sharps injuries
Respiratory hygiene
Environmental cleaning
Waste disposal
Reprocessing of patient care equipment

Infection control for health care providers
 Pre-placement and safety program
 Health workers immunization
 Personnel health and safety
education
 Periodic infectious disease
screening of healthcare workers
9/8/2023 141
The following measures must be implemented to prevent and control
the infections:-
Risk assessment
Treatment of exposed health worker
Regular follow up and monitoring
Report and recording of the incidents

Example, Flow chart on management of exposures
9/8/2023 142
Cont…

Occupational health & safety
• Occupational health & safety: is defined as the science and art devoted to
the:-
 Anticipation,
 Recognition,
 Evaluation and
 Control of those environmental factors or stressors, arising in or from the
workplace, which may cause:-
Illness, impaired health and well being, or
Significant discomfort and inefficiency among workers or in the
community
9/8/2023 144

In broadest sense, occupational health and safety should aim at the:
Promote and maintain the highest degree of physical, mental & social well-being of
workers of all occupations
Prevent workers from departures due to health caused by their working conditions
Protect workers in their working environment from hazards and risks usually
causing adverse health effects
Place & maintain a worker in an occupational environment adapted to his/her
physiological ability
9/8/2023 145
Cont…

• Recognition is a systematic approach, consisting of gathering
information and workplace survey for identifying:
– what actual and
– potential hazards exist.
• Recognizing a workplace hazard is the first step in overcoming it
Recognition of hazards
9/8/2023 146

Classification of Occupational Health Hazards
1. Chemical hazards
2. Physical hazards
3. Biological hazards
4. Mechanical hazards
5. Ergonomic hazards and
6. Psychosocial hazards
9/8/2023 147

I: Chemical hazards
• All hazardous materials in the workplace must have an up-to-date
MSDS
• Knowledge of health effects may be gained from the material safety
data sheet (MSDS)
9/8/2023 148

• Chemical hazards include
– Asbestos
– Coal dust
– Acids and alkalis
– Gases such as SO2, CO2, CO, nox,
– Heavy metal poisonings
– Long list of toxic substances
9/8/2023 149
Cont…

• For these chemical substances to cause harm, they must first enter the
body
• There are three main routes, these are:
– Inhalation
– Ingestion and
– Absorption/skin
9/8/2023 150

Classification of Toxic Effects
• Local toxicity- occurs at the site of chemical contact
• Systemic toxicity- occurs distant from point of contact, may
involve many organ systems
• Acute toxicity- occurs almost immediately (hours/days) after
an exposure
• Chronic toxicity- represents cumulative damage to specific
organ systems
– Occurs many months or years to have recognizable clinical disease
9/8/2023 151

Occupational Exposure Limits (Standards)
OEL can be defined as the maximum concentration of an
air contaminants and levels of physical agents to which an
employee can be safely exposed for an 8hr period in one workday
without any adverse health effects.
• Exposure limits are numerical values that indicate whether an
exposure may cause harm or not
• At best such values represent bench-marks, or guides for
protection action.
9/8/2023 152

LD 50 - Dose lethal to 50% of test animals
9/8/2023 153
Cont…

Threshold:
•Point at which toxicity first appears
•Occurs at the point where the body's ability to detoxify or
repair toxic injury has been exceeded.
9/8/2023 154
Cont…

Measures of concentration of toxic substances
Threshold Limit Value (TLV)-:
 Average concentration of an airborne substance to which most
workers could be safely exposed over an 8 hr/day or 40 hr/wk
throughout a working lifetime
Maximal Allowable Concentration (MAC)
 Peak or maximum concentration of an airborne to which most
workers could be safely exposed.
9/8/2023 155

A. Routes of Entry
1. The Respiratory System
• Inhalation is the main routs of entry due to the speed
with which toxic substances are absorbed and enter the
blood stream.
Principles of Major Organ Physiology
9/8/2023 156

• Health effects, which may result from exposure to different
types of dust, include:-
1. Pneumoconiosis (accumulation of dust in the lung)
Asbestosis/white lung/
Silicosis
Byssinosis/brown lung/brown lung disease (caused by endotoxin
produced by bacteria)
Black lung (coal miners' pneumoconiosis) caused by coal dusts
Respiratory Effects of Inhaled particles or dusts
9/8/2023 157

2. Lung Cancer
Exposure to much less asbestos + cigarette smoking.
3. Irritation and inflammatory lung injuries
• Certain dusts have irritant effects up on the upper respiratory tract
and can produce chronic bronchitis or it lead to chronic emphysema.
9/8/2023 158
Cont…

4. Allergic responses
• Some dusts may cause allergic reactions in the respiratory system.
• The two main respiratory diseases of allergic type are:
– Occupational asthma and
– Extrinsic allergic alveiolitis.
9/8/2023 159
Cont…

B. Gastrointestinal Tract
• GIT is another route of entry for toxic substances and is a
major route of excretion.
• In the workplace, ingestion of toxic chemicals is:-
– Usually accidental and
– Most commonly results from handling contaminated:
Food
Food Drink
Drink Cigarettes
Cigarettes
9/8/2023 160
Cont…

C. The Skin
• The skin is not only the largest organ of the body, it is also the organ most
exposed to the external environment.
• Effects of Substances on the skin include:-
– Burns: i.e NaOH, H2SO4, H2O2
– Rashes: i.e Formaldehyde, Xylene and Benzene
– Dermatitis (skin irritation): Formaldehyde, Benzene , Xylene
– Skin cancer
9/8/2023 161
Cont…

D. The Circulatory System
 Once a contaminant has entered the body it is distributed by the circulatory
system.
 Some effects of chemical substances on the Circulatory System
 Insufficient oxygen supply to the heart.
 Anemia and chromosomal damage in white blood cell.
 Enlargement of the heart
i,e: CO, Benzene, Phenol, arsine, etc.
9/8/2023 162
Cont…

II. Physical Hazard
9/8/2023 163

Physical agents in the workplace include:-
1. Noise (unwanted sound)
Noise-induced temporary threshold shift
Noise- induced permanent threshold shift (Noise Induced
Hearing Loss)
Effects on Communication and Performance
Stress, muscle tension, increased blood pressure, increased
breathing rate, etc..
 Recommended amount: 80-90 dB
9/8/2023 165

2.Vibration
• Vibration is the oscillatory motion of a structure or machine
– Vibration can produce noise
There are two types of vibration:
i. Whole Body Vibration(WBV)
• It occurs when the whole body is affected
• Motion sickness as its most familiar effect
• .e.g. Vehicle drivers, riding in vehicles
9/8/2023 166
Cont…

ii. Hand- Arm Vibration
• Hand-Arm Vibration occurs when holding
vibrating tools
• Prolonged or repeated exposure can lead
to a painful and disabling disease known
as vibration white finger
Hand-Arm Vibration
Vibration White Finger
9/8/2023 167
Cont…

3. Heat and Cold Factors
 Humans are warm blooded organism
They can regulate their own body temperature between
certain narrow limits (37 c + 20c).
 Heat generated must be equal to heat lost to maintain equilibrium
Heat Stress: combined effect of high temperatures and the physical
demands of the task
9/8/2023 168
Cont…

B. Cold Stress
• Cold stress could mainly be defined as the effect of the
Very low temperature, i.e. less than 60C
 Reduces blood flow
 It cause frostbite
 Face, ears, fingers, and toes are mostly effected by the Very
low temperature
Frostbite : reddening of skin,
and localized pain.
9/8/2023 169
Cont…

4. Lighting in the Workplace
• The quality of lighting in a workplace can have a significant effect
on productivity.
– Adequate lighting can lead to a 10-50 % increase in
productivity.
– Decrease errors by 30-60%
However, poor Illumination can cause:-
– Visual fatigue
– Delayed eye adaptation
– Accidents
9/8/2023 170

Non-Ionizing Radiation
• It is electromagnetic radiation with varying effects on the
exposed body depending wavelength of the radiation .
• It includes:
– Ultraviolet
– Infrared
– Microwaves
9/8/2023 172
Cont…

Ionizing Radiation
• Any electromagnetic or particulate radiation capable of
producing ions is referred to as ionizing radiation.
• These types of radiations contain a large amount of
energy and are capable of penetrating into living tissue.
• i.e alpha and beta particles, gamma rays, and x-rays
Sources: natural sources or can be technologically produced
Effect: Cancer, precancerous lesions, congenital defects etc.
9/8/2023 173
Cont…

III: Biological Hazards
9/8/2023 174

Biological hazards
9/8/2023
• Biological agents are living things, or substances produced by living
things, that can cause illness or disease in humans
• Bacteria, parasites, viruses, plants, fungi
Viruses Fungi
Bacteria Parasites
175

• Biological agents are living things, or substances produced by
living things, that can cause illness or disease in humans
• Bacteria, parasites, viruses, plants, fungi
Routes of Entry
• Biological agents enter the body via:
– Inhalation, ingestion and absorption (skin)
9/8/2023 176
Cont…

IV: Mechanical Hazards
The mechanical hazards in industries are contributed from
machinery, and moving parts
About 10% of accidents in industry are reported to be mechanical
causes
9/8/2023 177

V: Ergonomic Hazards
9/8/2023
Ergonomics is about 'fit': the fit between people, the things they do, the
objects they use and the environments they work, travel and play
in.
• Back pain,
• Musculoskeletal injuries (MSI)
The
Tool
The
Workstation
The task
(Job content &
context)
The
Organization
The
Environment
178

What is ergonomics?, its gool?
• Goal
– To reduce work-related musculoskeletal disorders (MSDs)
developed by workers
• MSDs are injuries and illnesses that affect muscles, nerves,
tendons, ligaments, joints or spinal discs.
9/8/2023 180

IV: Psychosocial Hazards
 Psychosocial hazards : Those aspects of the design and management of work,
and its social and organizational contexts, which have the potential for causing
psychological or social harm
 Work overload and time pressure
 Lack of influence or control over how day-to-day work is done
 Lack of social support from supervisors or co-workers
 Too little or too much responsibility
 Discrimination or harassment
 Lack of respect for employees and the work they do.
9/8/2023 181

 Assignment
Write the prevention and control strategies of occupational hazards
(10 pts)
Outline
Introduction
Main text
Conclusion
References
9/8/2023 182

• Food hygiene: means all measures necessary for ensuring the
safety, wholesomeness, and soundness of food at all stages
from production/ manufacture to consumption.
9/8/2023 184

9/8/2023 185
Food hygiene and sanitation
 Food: Provide nutritional support
 Assimilated by cells to produce energy,
 maintain life, or
 stimulate growth.

Carbohydrates
Carbohydrates
Fats
Fats
Proteins
Proteins
vitamins
vitamins
minerals
minerals
Contains essential nutrients
9/8/2023 186

• From the nutritional aspect, food stuffs are of two main kinds:
– Organic: Carbohydrates, proteins,
– Inorganic : Water and various mineral elements and
vitamins
9/8/2023 187
Cont…

Food is
essential for:
• For growth and maintenance
• To keep physiological process working
• To keep the body temperature constant
• To provide energy and
• To maintain proper health
9/8/2023 188
Cont…

• Microorganisms also use our food for growth and
multiplication utilizing the nutrient.
• The consequences are:
– Increasing their number
– Changing the food flavor
– Synthesis of new compounds
9/8/2023 189
Cont…

• Food diets should be
– Well balanced
– Palatable
– Attractive
– Culturally and psychologically acceptable
9/8/2023 190
Cont…

• Any kind of arrangements for growing, processing, preserving,
packaging, storing and distribution of foods have many impacts on
the
– Safety
– Nutritional value
– Wholesomeness
– Palatability of food
9/8/2023 191
Cont…

• Consumption of food unsafe for health
– Remain to be a major public health concern globally
– Causes food- borne diseases
• So that food hygiene and safety is crucial for healthful life
9/8/2023 192
Cont…

• An effective program of food sanitation:
Reduce Public health risks
Improve product shelf life
Improve product acceptability
Decrease product salvaging
Etc
9/8/2023 193
Cont…

The basic principles for food sanitation can be summarized in to
three essential activities:
1. Prevention of contamination
2. Elimination / destruction
3. Prevention of the growth/ inhibition of toxin
9/8/2023 194

Food contamination
• Contamination of food can be either from
– Biological agents or
– Chemicals
• Biological agents:
– Bacteria
– Viruses
– Parasites
– Helminthes
– Protozoa
– Etc.
9/8/2023 195

The Need For Food Protection:
• Food protection is needed in order to meet the following food
hygiene objectives:
– To prevent and control of:
– food borne diseases
– food spoilage
– To protect food from adulterants
– To control importation of food-related diseases into the country
and to ensure fair practices in the food trade.
9/8/2023 196

Requirements For Food Handlers
– Ensure that no person while known/suspected to be suffering/carrier of
a disease
– The food handler must be trained and then constantly practice to keep
his or her hands clear.
– Should wear while at work clean, washable, light-colored (white) outer
garments
– Food handlers must be free from food related communicable diseases
9/8/2023 197

Factors Influencing Growth of Microorganisms in Food
• Understanding factors that influence microbial growth essential
to maintaining food quality.
• The factors are:
• Conditions naturally present in food (intrinsic factors)
• Environmental conditions (extrinsic factors)
9/8/2023 198

Food borne diseases
• The term “food borne disease” is defined as a disease usually
either infectious or toxic in nature, caused by agents that enter
the body through the ingestion of food
9/8/2023 199

Factors which lead to food-borne illness outbreaks
 Storage at ambient temperature
 Inadequate cooling
 Inadequate reheating
 Undercooking
 Cross contamination
 Infected food handlers/poor personal hygiene
 Unsanitary dishware, utensils and equipment
9/8/2023 200

Classification and Etiology of Some Food Borne Diseases
• Food borne diseases are classified into two major
categories depending on the causative agent:
I. Food borne infections:
• Are diseases whose etiologic agents are viable pathogenic
organisms ingested with foods and that can establish
infection.
9/8/2023 201

II. Food borne poisonings/intoxications:
• Diseases arising from the ingestion of toxins released by:
• Microorganisms
• Intoxications from:
• Poisonous plants or
• Toxic animal tissues: or
• Due to consumption of food contaminated by chemical
poisons
9/8/2023 202
Cont…

Prevention and Control of Food-borne Diseases
• Specific modes of intervention vary from area to area depending on:
– environmental,
– economic,
– political,
– technology and
– socio cultural factors.
9/8/2023 203

Personal hygiene of food handlers
• All staff must maintain high standards of personal hygiene.
– Hair, hands, and clothing must be in a clean state
• Staff preparing food must wear of protective clothing (clean apron or
similar)
9/8/2023 204

Methods Of Food Preservation To prevent Spoilage
• We have seen that the causes for food spoilage are from two major
sources. These are:
1. Internal sources: enzymatic activities (undesirable autolytic
activity) which take place in the food itself.
2. External sources: access of microorganisms to food from the
external environment - air, water, soil, insects, animals and
human beings.
9/8/2023 205

Methods implemented in food preservation:
1. Dehydration: This the removing of water or a method of drying
which is one of the oldest methods of food processing and
preservation.
2. Pickling: This is a general term used when immersing certain food
items in concentrated natural acid solution such as vinegar.
9/8/2023 206

3. The use of high temperature:
• Heat is one of the oldest methods of destroying microorganisms in
food processing and preservation.
• Sterilization, disinfection and pasteurization are common methods
which make use of heat in food processing.
4. Canning: is one of the most widely used modern methods. The
principles are:
9/8/2023 207
Cont…

5. Use of low temperature
• Low temperature: normally ranging from 10C to 0C (50F to 32F) or
lower retards or arrests the metabolic process of most microorganisms.
• Low temperatures produce bacteriostasis and do not necessarily kill
microbes in refrigerated foods.
• Freezing: preservation by freezing is achieved by using
temperatures below 0C (32F).
9/8/2023 208
Cont…

6. Use of pH: Most species of pathogenic and spoilage bacteria
normally grow best at natural pH level (pH7), or at slightly alkaline
or slightly acid pH values.
7. Fermentation: is essentially a process of transforming foods into an
acid state, hence based on PH control techniques- e.g. sour milk (lactic
acid production).
9/8/2023 209
Cont…

Definitions
Vector(s): are arthropods or other invertebrates which transmit
infection by biting or depositing of infective materials.
Biological vectors: are vectors that transmit disease pathogens
after the multiplication or development of the pathogen in the
insect gut or muscle. i.e mosquito
9/8/2023 211

Mechanical vectors: are vectors that transmit pathogenic
Microorganisms without undertaking any change either on the
number or form of disease pathogens.
E.g. Housefly for trachoma
Entomology: the study of arthropods
9/8/2023 212
Cont…

• The arthropods involved may be:
• Causal agents themselves
• developmental transfer hosts or
• vectors of pathogens.
• Vector borne diseases are a heavy burden on human populations
– a major cause of work loss and
– a serious impact on economy.
• They require an intermediate living agent for their transmission.
9/8/2023 213
Cont…

Ways of Vector Borne Disease Transmission:
• Generally there are three types of vector borne disease transmission.
1. Mechanical disease transmission
2. Biological disease transmission and
3. Hereditary disease transmission.
9/8/2023 214

1. Mechanical disease transmission: is a type of disease
transmission in which the vector is no more than a carrier
 Without any change in number or form of disease pathogens.
E.g.Trachoma.
2. Biological disease transmission:
• In this type of disease transmission certain developmental pattern
exists either in the vector or host or in both cases.
9/8/2023 215
Cont…

Biological disease transmission is sub-divided in to:
– Propagative: only the number of pathogens increases and the
developmental stage remain constant.
– E.g. plague and typhus
• Cyclo-developmental: only the developmental stage (form) of the
disease pathogen changed while the number of the pathogenic
organism remain constant.
9/8/2023 216
Cont…

• Cyclo-propagative: a combination of both propagative and cyclo-
developmental
• There is a change both in number and developmental form. E.g.
Malaria.
3. Transovarian(Hereditary) disease transmission:
• The causative agent is transmitted to the immature stage ( usually to
egg) from the adult insects and / or other arthropods who carry
disease pathogens. i.e Ticks
9/8/2023 217
Cont…

Advantages and disadvantages of arthropods
A. Health Effects:
• Arthropods affect the health and comfort of man in many different
ways.
– They bite and suck blood.
– They pass infective organisms and may inject toxin to man and animals
(mechanically or biologically).
– Annoy and irritate man and animals etc.s
9/8/2023 218

Health Effects, Vector-borne Disease
• Majority of Vector-borne Disease (VBD) burden borne by developing
countries
• Disproportionate amount in Africa
9/8/2023 219

Vector-borne Disease Dynamics
Susceptible
population
• Migration (forced)
•Vector environment
Vector
•Survival, lifespan
•Reproduction/breeding patterns
•Biting behavior
Pathogen
•Survival
•Transmission
•Replication in host
9/8/2023 220

1. Pollonization of plants.
2. Honey and wax production
3. Improving the soil
4. Source of a commercial varnish
9/8/2023 221
• Predators of other insects
• Parasites of other insects
• Food for human’s and animals.
• Sources for scientific knowledge etc
B. The Beneficial Effects of Arthropods

• Anophelinae
• Culicinae
• Toxorhynictinae: do not feed on blood
• The most important man biting belongs to the genera:
– Anopheles : Malaria, filariasis,
– Culex: filariasis, Encephalitis,
– Aedes: Yellow fever, Dengue fever
– Mansonia:
– Hemagogus and Sabethes.
Blood feeders
Some insects of public health importance
The mosquitoes
9/8/2023 222

Anophelinae; Causative agent
• Single-celled protozoan parasites (genus Plasmodium)
– P. falciparum,
– P. vivax,
– P. ovale, and
– P. malariae
Plasmodium falciparum is the main cause of severe clinical
malaria and death.
9/8/2023 223
Cont…

Mosquito Abatement (Management)
 Mosquito abatement methods may be either:
• long term or
• temporary programs directed against
» larvae or adults.
 Education
 Source Reduction of Larval Habitats
 Personal Protection
 Chemical Control for Adult Mosquitoes
9/8/2023 224
Cont…

Black fly: nuisance, onchocerciasis/river blindness
Sand flies : nuisance, leishmaniasis
Tsetse flies : nuisance, trypanosomiasis/sleeping sickness
House fly: disease transmission (dysentery, typhoid, cholera,
salmonellosis, tuberculosis, trachoma, conjunctivitis
9/8/2023 225
Cont…

Fleas: flea nuisance , plague, Flea-Borne Endemic Typhus etc.
Lice :Louse borne epidemic Typhus , Louse borne epidemic
Relapsing fever
Cockroaches: Mechanical disease transmitter,
9/8/2023 226
Cont…

General Control methods of vectors
 The war (control and eradication) on arthropods by man has
been going on for long period of time.
 Effective vaccines or drugs were not always available for the
prevention or treatments of the diseases associated with vector,
control of transmission of the disease often rely on control of the
vector
9/8/2023 227

• Integrated vector control has been defined as "the utilization of all
appropriate technological and management techniques to bring about an
effective degree of vector suppression in a cost-effective manner".
• It demands an adequate knowledge of:
 The biology, ecology, and behaviour of the vector
 Non target organisms
 The human population
 Ensure effective control
 Human safety and prevention of other unacceptable side effects
9/8/2023 228
Cont…

Methods of controlling arthropods
I. Personal protection
– Physical barriers between a vertebrate and arthropods
– chemical barriers that repel arthropods from actually biting
– arthropod toxicants that are applied directly to or with in a
vertebrate.
II. Environmental manipulation, e.g., flushing streams, changing water
salinity, and removing shade plants;
9/8/2023 229
Cont…

III. Modifying human habitation or behaviour
e.g., locating new settlements away from vector populations, modifying
house design, and changing water supply and waste disposal.
IV. Barrier zones and quarantines:
– An area free from certain vectors, either naturally or as a consequence
of control programs may need protection from invasion.
9/8/2023 230
Cont…

V. Environmental management
– Changing the environment to prevent vector breeding or to
minimize contact between vectors and people can be an effective
control mechanism. It includes:
VI. Environmental modification.
i.e., any permanent or long-lasting change in land, water, or vegetation,
such as filling, draining, or forest clearance
9/8/2023 231
Cont…

VII: Biological control (Bio control):
– Predators (both vertebrate and invertebrate)
– Parasites (generally meaning metazoan arthropods or nematodes)
– Pathogens (viruses, rickettsiae, bacteria, fungi, protozoa etc).
9/8/2023 232
Cont…

VIII: Local control methods: Even though it is difficult to take
control action against arthropods without the fundamental
knowledge of entomology and other related sciences :
– It is obvious that through trail and error, man has established
many local ways of fighting and controlling arthropods.
9/8/2023 233
Cont…

• The following are some of these local control methods practiced in our
country’s (Ethiopian) communities:
 Hot ash to kill or drive away insects like ants.
 Hot water against ants, bedbugs, lice, fleas, etc
 Certain odorous and sticky leaves like white eucalyptus, mimosa, etc
are used as insect repellants.
9/8/2023 234
Cont…

Vector control
(Ivm)
Resource
Person(s)
M.Of science
& technology
Ngos
Ministry of
Agriculture
Academia
Pesticides
Company
Water Resources
Inter- sectoral committee for vector control needs assessment (VCNA)
Un
Agencies
IX. Policy & legislative frameworks)
9/8/2023 235

• Air Pollution and Climate Change
9/8/2023 236

Air Pollution and Climate Change
• Air Pollution can be defined as: the introduction of any
chemical, physical or biological agent into an atmosphere that
has the potential to cause adverse impacts
• Climate change is a change in the average temperature and
cycles of weather over a long period of time.
9/8/2023 237

• Air pollution is one of the most important and most studies
environmental exposures due to:
– Its ubiquitous nature
– The large range of health-related states and events which it
affects
– Impacts on all segments of population
– The huge, but modifiable, health burden it poses (Andersen,
2020)
9/8/2023 238

Sources of pollution
– Natural process
– Traffic (proximity of busy roads, petrol vs. diesel, cars vs. trucks)
– Power plants
– Other industrial plants
– Pollution from constructions
– Waste deposit sites
– Agricultural activity (e.g. spraying pesticides)
– etc.
9/8/2023 239

• There are four types of sources that emit air pollutants
– Stationary Sources
– Mobile Sources
– Area Sources
– Natural Sources
9/8/2023 240

• There are four primary ways in which pollutants can be emitted into
the atmosphere
– Combustion and Thermal Processes
– Evaporation
– Physical (Mechanical) Processes
– Biological (Metabolic) Processes
9/8/2023 241

9/8/2023 242
• All types of air pollution can be divided into two basic types
– Primary Air Pollutants are emitted directly into the atmosphere.
For example, carbon monoxide is emitted by cars and light-duty
trucks.
– Secondary Air Pollutants are formed within the atmosphere by
chemical reactions involving precursors that are emitted into the
atmosphere.
– Ozone a primary component of “smog” is formed by sunlight-
driven reactions involving volatile organic compounds (VOC) and
nitrogen oxide precursors.
Types of Air Pollution

• The U.S. Clean Air Act, separates air pollutants into three categories
– Criteria Pollutants are common pollutants that were known to produce
adverse health effects
• Ozone, particulate matter, sulfur dioxide, carbon monoxide, nitrogen
dioxide, and lead.
– Hazardous Air Pollutants or air toxics are compounds proven, or
expected to be, carcinogenic, mutagenic, teratogenic or capable of
producing other adverse health or environmental effects.
– Greenhouse Gases or Radiatively Important Trace Substances (RITS)
9/8/2023 243

Indoor sources of air pollution
• Dust
• Construction and insulating materials
• Furnishings
• Evaporation of volatile chemicals from new materials
• Paints
• People (exhaled air, smoking?)
• Pets, rodents, insects
• Mould (from moisture)
9/8/2023 244

Health effects of indoor air pollution
Impacts on respiratory system
• Acute effects:
– Mucous membrane irritation (eyes, upper respiratory tracts)
– Coughing (bronchitis symptoms)
– Wheezing, attacks of dyspnoea (heavy breathing) (asthmatic
symptoms)
– Increased responsiveness of the respiratory tracts to allergens
• Increased acute respiratory morbidity (upper- and lower respiratory airway
infections)
9/8/2023 245

Chronic effects:
• Decreased lung function
• Contribution to later pulmonary diseases (COPD)
9/8/2023 246

Impacts on cardiovascular system
• Elevations in arterial blood pressure and heart rate
• Increased levels of stress hormones
Impacts on immune system
• Increased risk of infections (pneumonia)
• Increased levels of biomarkers of oxidative stress and
inflammation
9/8/2023 247

Impacts on central nervous system
• Acute effects:
– Headache, fatigue, dizziness, nausea
– Impaired task performance
• Chronic effects:
– Cognitive and psychomotor development delays, learning
disabilities, etc.
– Prenatal and early childhood exposure can result in
neurodevelopmental diseases
9/8/2023 248

Cancer inducing effect
– Childhood leukaemia, and some central neural system tumours
in children
Endocrine disrupting effects of some chemicals
• Impairments on reproductive system
• Disorders in brain development
• Contribution to later diabetes and obesity
9/8/2023 249

Major air pollutants
• Nitrogen-dioxide (NO2)
– WHO: indoor 1 hour: 200 μg/m3, annual: 40 μg/m3
• Carbon monoxide (CO)
– 15 min: 100 mg/m3
– 1 hour: 35 mg/m3 (INDEX project: 30 mg/m3)
– 8 hours: 10 mg/m3
– 24 hours: 7 mg/m3
9/8/2023 250

• Ozone
– WHO AQG for Europe (2nd ed.) 120 μg/m3 (8
hours),Formaldehyde
• Formaldehyde
– 100 μg/m3 – 30 minutes
• Benzene
– WHO guideline value: 5 μg/m3 – yearly average
• Polycyclic aromatic hydrocarbons (PAHs)
– Excess lifetime cancer risk of 1/100 000 for BaP is 0.12 ng/m3
9/8/2023 251

• Asbestos
– Limit value: No safe concentration
– acceptable risk (10-5 – 10-6): WHO:1000 F/m3 lifetime exp
• Radon
– No safe concentration
– 100 Bq/m3 - minimal risk
• Microbial pollutants
9/8/2023 252

9/8/2023 253
What Is Climate Change?
 What is happening to the
global temperature?
 The planet is becoming
warmer; the climate is
changing.
Climate change is a change in the average temperature and cycles of weather over a
long period of time.
Year
Temperature
Anomaly
(°C)
0
-0.5
0.5
1.0
1.5
1880
1888
1904
1936
1960
2000
2016
1896
1912
1920
1928
1968
1944
1952
2008
1976
1984
1992

9/8/2023 254
Why Is Climate Change a Problem?
• If the climate changes quickly, organisms don’t have enough time
to adapt to new conditions and may no longer be able to survive.
• Climate change disrupts weather patterns and causes extreme
weather events to become more common.
• These include hurricane activity, droughts and floods.
• As the global temperature has increased, so has the number of
reported natural disasters.

9/8/2023 255
• Rising temperatures are causing sea levels to increase.
• The rising water can cover coastal areas, destroying habitats and
displacing whole populations from low-lying areas.
• Rising sea levels are driven by two main processes:
• Ice Melt: When the atmosphere and ocean get warmer, ice sheets
and glaciers melt, resulting in the addition of fresh water to the
ocean.
• Thermal Expansion: As ocean water gets warmer, it expands,
causing sea levels to rise.

9/8/2023 256
• The increase in global temperatures is causing a
reduction in sea ice
• This causes problems for animals that depend on the ice to
hunt, mate and sleep
• When the area of sea ice is reduced, less sunlight is
reflected back into space.
• This causes more ocean warming and reduces the sea ice even further.

9/8/2023 257
What Causes Climate Change?
• Carbon dioxide (CO2),
methane (CH4) and water
vapour (H2O) are greenhouse
gases that are found in the
atmosphere.
• Energy travels from the Sun
to the Earth as short wave
radiation.
• It does not interact strongly
with the greenhouse gas
molecules so it reaches the
Earth’s surface.
CO2
CO2
CH4
H2
O
CH4
CO2
H2
O
CH4
CH4
CO2

9/8/2023 258
• The Earth’s surface emits long wavelength radiation.
This does interact with the greenhouse gas molecules.
• The greenhouse gas molecules absorb some of the energy,
trapping it in the atmosphere.
• This process keeps the Earth warm and is essential for life.

9/8/2023 259
• The higher the proportion
of greenhouse gases in the
atmosphere, the more
radiation is absorbed.
• This causes a rise in the
temperature of the Earth and is
known as the greenhouse
effect.
• This increase in temperature
drives climate change.
CO2
CO2
CH4
H2O
CH4
CO2
H2O
CH4
CH4
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CH4
CH4
CH4

9/8/2023 260
• Climate change can be caused gradually by natural processes or
suddenly by large events, such as a massive meteorite strike or
volcanic activity.
• However, the rapid climate change we are experiencing now is due to
three main human activities:
 Burning fossil fuels for heating and cooking, generating electricity
and powering vehicles releases carbon dioxide into the atmosphere.
 Deforestation (destruction of forests) releases carbon dioxide and
reduces the number of trees able to capture carbon dioxide from
the atmosphere.

9/8/2023 261
 Reduction of biodiversity creates an unstable ecosystem.
Nature loss leads to ecosystems that are less able to capture
carbon from the atmosphere and less resilient to rising
temperatures.

9/8/2023 262
Who Causes Climate Change?
• The 50 least developed countries are thought to have contributed 1% of the
greenhouse gases that have caused global warming.
• The USA, the EU and China alone have contributed around 60%.
Oceania
Africa
South America
North America
Europe
Asia

9/8/2023 263
Who Does Climate Change Affect?
• Everyone will feel the effects of climate change.
• However, some people are currently more affected than others.
• In most cases, the wealth of prosperous countries has come from
activities which contribute to greenhouse gas emissions.
• This wealth allows these countries to protect themselves
from the effects of climate change.

9/8/2023 264
• Poorer countries are less able to adapt to climate change and
therefore suffer the most from its effects.
• The countries who have contributed the least to the climate
crisis are the ones who are affected the most.

9/8/2023 265
Who Can Fix It?
• Governments can make laws and policies that reduce the amount
of greenhouse gas emissions.
• Businesses can change their processes to run more sustainably.
• We can all make choices in our own lives that reduce our carbon footprint
(the impact our actions and purchases have on climate change).
• We can also use our voices to let businesses and governments know that we
want them to act quickly to reduce their impact on climate change.

9/8/2023 266
Opportunities
• The transition to a low-carbon economy in the years ahead brings with
it many opportunities.
• Innovation is the process of turning an idea into a solution that solves a
problem.
• New job sectors will be created and new skills will be valued in the jobs
market.

Introduction to Toxicology
9/8/2023 267

Definition
Toxicology is the study of how toxicants cause adverse effects
on living organisms.
Toxicant (Poison):
• A chemical capable of producing a harmful reaction in a living
organism.
• All substances are poisons; there is none that is not a poison.
• The right dose differentiates a poison and a remedy.
9/8/2023 268

Some health effects of Toxicants
• Mercury in fish
 brain damage
• Lead in paint
 brain damage
• Dioxin poisoning
 Facial scarring (chloracne)
9/8/2023 269

What amount causes harm?
Some chemicals are good in small amounts, but toxic in large
amounts
9/8/2023 270
Dose
• Dose refers to the amount of a toxicant entering the body
• Dose is measured as milligrams of toxicant per kilogram of body
weight = mg/kg

• The concentration of the toxicant
• The chemical properties of the toxicant
• The number of times of exposure (frequency)
• The length of time of exposure (duration)
• How it gets into the body (exposure pathway)
What factors determine the dose of a toxicant that
causes harm?
9/8/2023 271

Response: an abnormal change in an organism
Depending on the toxicant, dose, and route of exposure, the response
can be:
• Local (effects part of the organism) or systemic (effects the
whole organism)
• Reversible or irreversible
• Immediate or delayed
9/8/2023 272

Dose-Response Relationship:
As the dose increases, the percent of individuals who respond increases
Dose (mg/kg body weight)
0
25
50
75
100
0 10 20 30 40 50 60 70 80 90 100
%
of
Individuals
Responding
9/8/2023 273

• Age - young or old
• Gender - male or female
• Genetic differences – different genes
• Nutrition
• Health – previous or current diseases
• Exposure to other toxicants – previous or current
Factors can cause a difference in response
9/8/2023 274

Frequency of Exposure
Number of times of exposure Time in between exposure
or
or
9/8/2023 275

Duration of Exposure: How long the exposure lasted
 Acute: < 24hr 1 high dose
 Subacute: 1 month repeated exposures
 Subchronic: 1-3months repeated low dose
 Chronic: > 3months repeated low dose
The amount of toxicant can build up in body over time and:
• Can move to different organs (example - lead)
• Can overwhelm the bodies’ ability to repair damage and remove
the toxicant (example - radiation)
9/8/2023 276

Routes of Exposure
Skin (dermal)
Lung (inhalation)
Oral (gut)
Injection
9/8/2023 277

Distribution: Where the toxicant accumulates in the body
• Bone
• Muscle
They can be:-
• Fat soluble
• Water soluble
9/8/2023 278

Not all organs are affected equally by a toxicant
Target organs: higher concentration of toxicant
→ more adverse effects
• Liver
• Kidney
• Lung
• Neurons
• Heart muscle
• Bone marrow
• Intestines
9/8/2023 279

Target Organs: Mechanisms of Action
• Adverse effects can occur at the level of the:
 Molecule
 Cell
 Organ
 Organism
• Toxicant can interact with:
 Proteins
 Lipids
 DNA
9/8/2023 280

Metabolism of Toxicants
• How the body breaks down a toxicant
 Using enzymes in the body
• What the toxicant turns into
 Water-soluble toxicants are easier to excrete
• How fast does this occur
 Can take hours, days, weeks or years
9/8/2023 281

Risk Assessment
Risk: The probability or likelihood that exposure to a particular
toxicant at a specific concentration or dose may cause an
adverse effect.
Risk Assessment: The process used to estimate the likelihood that
humans will be adversely affected by a chemical or physical
agent under a specific set of conditions.
9/8/2023 282

Risk Assessment
Toxicity
Assessment
Exposure
Assessment
An estimate of the likelihood that exposure to a toxicant
may cause harm
9/8/2023 283

Toxicity Assessment
• Toxicity testing
 Determines the hazard which a substance may present to
humans
 Exposure limits are established
• If exposure to the substance is kept below the exposure limit, the
risk from the substance is considered to be acceptable.
9/8/2023 284

Exposure Assessment
Must evaluate potential for exposure to a substance
 Where do you encounter it?
 How often will you encounter it?
 How might it enter the body?
 How long does it remain in the body?
9/8/2023 285

Risk Assessment
• Must take into account the possible harmful effects of the
toxicant on many individual people
9/8/2023 286

Precautionary Principle
• If the consequences of an action are unknown, but judged to
have some potential for negative consequences, then it is better
to avoid that action.
“Better safe than sorry.”
9/8/2023 287

• Environmental Impact Assessment (EIA)
9/8/2023 288

Environmental Impact Assessment: “the process of identifying,
predicting, evaluating and mitigating the biophysical, social, and
other relevant effects of development proposals prior to major
decisions being taken and commitments made.”
9/8/2023 289

9/8/2023 290
Key environmental impact assessment concepts
• Defining “impact” • Defining
“activity”
• Characterizing the
baseline situation
Time
Water
table

9/8/2023 291
What are impacts?
The impact of an activity is the change from the baseline situation
caused by the activity.
• The baseline situation is the existing environmental
situation or condition in the absence of the activity.
• The baseline situation is a key concept in
environmental impact assessment.
!
To measure an impact, you
must know what the baseline
situation is.
In EIA, the term “impacts” is used
instead of “effects of activities.”
What is an impact?

9/8/2023 292
Baseline situation
• The baseline situation is not just a snapshot in time.
• This chart of groundwater levels shows both variability
and a trend over time.
• Both are part of the groundwater baseline situation.

9/8/2023 293
In characterizing the baseline
situation, many environmental
components MAY be of
interest
Water Quantity, quality, reliability,
accessibility
Water Quantity, quality, reliability,
accessibility
Soils Erosion, crop productivity,
fallow periods, salinity,
nutrient concentrations
Soils Erosion, crop productivity,
fallow periods, salinity,
nutrient concentrations
Flora Composition and density of
natural vegetation,
productivity, key species
Flora Composition and density of
natural vegetation,
productivity, key species
Fauna Populations, habitat
Fauna Populations, habitat
Special Key species
ecosystems
Special Key species
ecosystems
Env Health Disease vectors, pathogens
Env Health Disease vectors, pathogens
The components of interest
are those that are likely to
be affected by your
activity—or upon which
your activity depends for its
success
The components of interest
are those that are likely to
be affected by your
activity—or upon which
your activity depends for its
success

Environmental impacts
 Type and nature
 Magnitude
 Extent
 Timing
9/8/2023 294
Duration
Uncertainty
Reversibility
Significance
It depend up on:-

Aims and objectives of EIA
9/8/2023 295
EIA can used to:-
• Modify and improve design
• Ensure efficient resource use
• Enhance social aspects
• Identify key impacts and measures for mitigating them
• Inform decision-making and condition-setting
• Avoid serious and irreversible damage to the environment
• Protect human health and safety

• Ensure environmental considerations are explicitly addressed and
incorporated into the decision-making process
• Anticipate and avoid, minimise and offset the adverse significant
biophysical, social and other relevant effects of development
proposals
• Protect the productivity and capacity of natural systems and the
ecological processes which maintain their functions
• Promote development that is sustainable and optimises resource
use and management opportunities.
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9/8/2023 297
Key aspects around EIA
• Widely established world-wide Applicable to projects with potential
significant adverse impacts on the environment
• Decision-informing in development consent
• Traditionally impact-centered
• Often also addresses socio-economic impacts (ESIA)

9/8/2023 298
EIA principles
• Early
• Transparent
• Participatory
• Independent
• Rigorous
• Objective
• Clear

9/8/2023 299
 Biophysical and resource use
 Social and cultural
 Health and safety
 Economic and fiscal
 Landscape and visual
 Indigenous peoples’ rights and traditional areas
The EIA process addresses the following environmental effects:

EIA—Three core values
 Integrity - the EIA process will conform to agreed standards
 Utility - the EIA process will provide balanced, credible
information for decision-making
 Sustainability - the EIA process will result in environmental
safeguards
9/8/2023 300

EIA — guiding principles
• The EIA process should be:
– Purposive – meeting its aims and objectives
– Focused – concentrating on the effects that matter
– Adaptive – responding to issues and realities
– Participative – fully involving the public
– Transparent – clear and easily understood
9/8/2023 301

 Rigorous – employing ‘best practicable’ methodology
 Practical – establishing mitigation measures that work
 Credible – carried out with objectivity and professionalism
 Efficient – imposing least cost burden on proponents
9/8/2023 302

Key operating principles of good EIA practice
• EIA should:
 Be applied to all proposals with significant impacts
 Begin early in the project cycle
 Address relevant environmental, social and health impacts
 Identify and take account of public views
 Result in a statement of impacts and mitigation measures
 Facilitate informed decision making and condition setting
9/8/2023 303

9/8/2023 305
• Scope
• Evaluate baseline situation
• Identify & choose alternatives
• Identify and characterize potential
impacts of proposed activity and each
alternative
• Develop mitigation and monitoring
• Communicate and document
Phase I:
Initial inquiries
Phase II:
Full EIA study
(if needed)
Our focus!
•Understand proposed
activities
•Screen
•Conduct preliminary
assessment (if needed)
The EIA process

The EIA process
The EIA process comprises
• Screening - to decide if and at what level EIA should be applied
• Scoping - to identify the important issues and prepare terms of
reference
• Impact analysis - to predict the effects of a proposal and evaluate
their significance
• Mitigation - to establish measures to prevent, reduce or
compensate for impacts
9/8/2023 306

• Reporting - to prepare the information necessary for decision-
making
• Review - to check the quality of the EIA report.
• Decision-making - to approve (or reject) the proposal and set
conditions
• Follow up – to monitor, manage and audit the impacts of
project implementation
• Public involvement - to inform and consult with stakeholders
9/8/2023 307

9/8/2023 308
Implementation / follow-up of EMP
Implementation / follow-up of EMP
Monitoring Control and verification
Decision
Decision
Go No-go Conditional
Public enquiry
Public enquiry
Formal, additional to other opportunities
Prepare Environmental Management Plan
Prepare Environmental Management Plan
Define ‘mitigation measures’ – Mitigation Hierarchy
Define ‘mitigation measures’ – Mitigation Hierarchy
Avoid, minimise impact Calculate residual impact
Maximise positive
impacts
Assessment
Assessment
Different
techniques
Mainly
quantitative
Beyond
compliance
Inter-disciplinary
Scoping
Scoping
Participatory Key aspects, methodologies, approach
Screening
Screening
Positive lists Screening criteria
Public
Participation

Benefits of EIA include:
• Environmentally sound and sustainable design
• Better compliance with standards
• Savings in capital and operating costs
• Reduced time and costs for approvals
• Increased project acceptance
• Better protection of the environment and human health
9/8/2023 309

Delays are caused during EIA when:
– The EIA is commenced too late in the project cycle
– The terms of reference are poorly drafted
– The EIA is not managed to a schedule
– The EIA report is inadequate and needs to be upgraded
– There is a lack of technical data
9/8/2023 310

9/8/2023 311
Common shortcomings in EIA systems
• ‘Catch-all’ approaches
• Limited participation
• Manipulation of data
• Unclear/un-precise
• Little or no follow-up

Ensuring fairness in the EIA process
• Register consultants’ names and terms of reference
• Name consultants and their expertise in the EIA report
• Publish the terms of reference in the EIA report
• Make EIA reports available to the public
• Publish lists of screening and final decisions along with
conditions for approval
9/8/2023 312

Introduction to Environmental Health, by Dechasa Adare Mengistu, Haramaya University. 2022/23pdf

Introduction to Environmental Health, by Dechasa Adare Mengistu, Haramaya University. 2022/23pdf

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