intro and water.pptx

ENVIRONMENTAL HEALTH
FOR 2nd YEAR NURSING STUDENTS
Instructor: Lt. Habtamu B.
Course Code: SPH-2012
Credit hours: 2

9/22/2022 ENVIRONMENTAL HEALTH FOR NURSING 2

Introduction to Environmental Health
• Environmental health comprises those aspects of
human health, including quality of life, that are
determined by physical, chemical, biological, and
social and psychological problems in the
environment.
• It also refers to the theory and practice of
assessing, correcting, controlling, and preventing
those factors in the environment that can
potentially affect adversely the health of present
and future generations,
World Health Organization , 1993
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ENVIRONMENTAL HEALTH FOR NURSING

Cont’d
• Environmental health is not new to nursing.
Florence Nightingale was a pioneer in the field of
environmental health and eloquently promoted
the need and value of assessing and controlling
environmental causes of disease. Professional
nursing is just now rediscovering its strong
environmental health roots.
• In 1997, the American Nurses Association House
of Delegates passed a resolution to reduce the
production of toxic pollution within the health
care sector, thereby contributing to the reduction
of the carcinogen load in our environment, as
well as other non-cancer-causing toxins (ANA,
1997).
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Cont’d
• In this resolution, nurses committed to educate
other nurses about medical waste issues, explore
alternatives to polyvinyl chloride (PVC) plastics
(which when incinerated cause carcinogenic air
pollutants), create mercury-free health care delivery
settings, reduce dioxin emissions from hospital waste
incinerators, and develop standards for byproducts
from the use of laser and electro-surgery units.
• Nurses are gradually becoming environmental health
pioneers within the modern health care industry.
When provided with the background knowledge that
to date has not been part of their traditional training,
nurses will be prepared to expand their practice into
the critical area of environmental health.
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Cont’d
• Nursing in the 21st
C. must regain its focus on the control of
environmental causes of disease and begin to build this
body of knowledge. This will make a critical contribution to
prevention strategies that will reduce the chemical load in
our food, water, and air and thereby improve human
health. Nurses need to develop and ultimately share their
expertise in this area of health.
• They must understand the mechanisms and pathways of
exposure to environmental health hazards; basic
prevention and control strategies; the interdisciplinary
nature of effective interventions; and the role of research,
advocacy, and policy. This knowledge must include
pollution prevention, product design, engineering controls,
purchasing choices, and education.
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Definitions
The Environment
• Environment is derived from the French word
environner which means to encircle or surround.
It is believed to have been introduced by biologist
Jacob van Erkul in the early 1900s.
• Not a single organism on this earth is alone. We
all are always surrounded by a lot of things such
as other organisms, plants, water, air, light etc.
Such surroundings—all the living and non living
things-constitute the environment.
• There are many different definitions of the word
environment, in literal and scientific contexts, but
the most acceptable definitions can be as given
here under:
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Definitions…
(i) Environment can be defined as the natural
surroundings of an organism which, directly or
indirectly, influences the growth and development
of that organism.
(ii) Environment is the sum total of all living and
non living elements that compose the surroundings
of any living entity.
(iii) Environment is the sum of all surrounding
external conditions affecting the life and the
development of organisms, people, animals or
plants etc.
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Definitions…
 Comprehensive Definition of Environment
• Summing up all the above expressions, environment can
be defined as:
• The term environment means all the external
surroundings of a living creature which include biotic
and abiotic components affecting its life and growth.
• The biotic (living) component includes plants, animal
predators, other living species with synergistic or
otherwise relationship, bacteria, virus, food etc.
• Abiotic (non living) component typically includes land,
water, air and sunlight. Simply defined the term
environment refers to the sum total of biotic and abiotic
components of the surroundings.
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Definitions…
The Human Environment
• The definition of environment takes a different
dimension while describing environment with
reference to human, as the growth and
development of human is strongly influenced by
social and economic factors also.
• Hence ‘human environment’ comprises of biotic,
abiotic and socio-economic aspects. i.e., bio-geo-
physical and socio-economic aspects. In fact,
human environment has two components,
namely;
(i) Natural environment; and
(ii) Man-made environment.
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Definitions…
(i) The natural environment comprises of 4 spheres:
(a) The Biosphere: space occupied by life.
(b) The Atmosphere: space occupied by air.
(c) The Lithosphere: space occupied by land.
(d) The Hydrosphere: space occupied by water.
(ii) The man-made environment comprises of
(a) Anthropogenic (human related) ecosystems—
interactions among and between humans
(socio-economic), other living beings (biotic) and
non-living (abiotic) things; and
(b) Physical structures:
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Definitions…
Ecological System (Ecosystem)
• “An ecosystem is a dynamic complex of plant,
animal, and microorganism communities and the
nonliving environment interacting as a functional
unit. Humans are an integral part of ecosystems.
Ecosystems vary enormously in size: a temporary
pond in a tree hollow and an ocean basin can both
be ecosystems.”
• The interconnected components of an ecosystem
are in a steady state; disrupting one of the
components can disrupt the entire ecosystem.
FIGURE 1 suggests that the health of the ecosystem
is associated with the health of human beings as
well as that of domestic animals and wildlife.
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FIGURE 1 Ecosystem health
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Definitions…
• Survival of the human population depends upon
ecosystems, which aid in supplying clean air and
water as part of the earth’s life support system.
Ecosystems are being degraded with increasing
rapidity because of human environmental
impacts such as urbanization and deforestation.
• Degradation of ecosystems poses environmental
dangers such as loss of the oxygen-producing
capacity of plants and loss of biodiversity.
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Definitions…
 Environmental Health
• The field of environmental health has a broad
focus and includes a number of sub-
specializations.
• For example, occupational health often is
regarded as a topic that is closely allied with
environmental health and is a subset of broader
environmental health concerns. Consequently, in
view of its broad reach, the term environmental
health does not have a single definition, nor is it
easy to define.
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Definitions…
• According to the World Health Organization:
Environmental health addresses all the physical,
chemical, and biological factors external to a
person, and all the related factors impacting
behaviors.
• It encompasses the assessment and control of
those environmental factors that can potentially
affect health. It is targeted towards preventing
disease and creating health-supportive
environments.
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The Scope of Environmental Health problems
• The World Health Organization (WHO) estimated that in
2012, approximately 12.6 million deaths across the globe
(23% of all deaths) were linked to environmental sources.
• The US Environmental Protection Agency reported that in
2015, industry released 881 million pounds (400 million
kilograms) of toxic chemicals into the air and water (690
million pounds [313 million kilograms] into the air and
191 million pounds [87 million kilograms] into the water).
On the positive side, a declining trend in the release of
these chemicals occurred between 2005 and 2015.
• Elevated blood levels of lead continue to be an important
problem in the United States, with children living in at least
4 million households that expose them to excessive
amounts of lead.
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Scope…
• The number of people with asthma in the United States
increased to 8% of the population in 2009; environmental
factors such as tobacco smoke and air pollution are asthma
triggers.
• “Strong evidence exists that industrial chemicals widely
disseminated in the environment are important
contributors to… the global, silent pandemic of
neurodevelopmental toxicity.”
• “Using air quality standards established by WHO, experts
have estimated that 1.3 billion of the world’s urban
inhabitants breathe air that exceeds these quality
standards.”
• Environmental factors are thought to contribute
significantly to various forms of cancer, including cervical
cancer, prostate cancer, and breast cancer.
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Global aspects and issues
• As the twenty-ﬁrst century begins, population
trends underlie much of the troubled relationship
between humanity and the environment.
• The global population is growing, and much of
this growth is in the poorest parts of the world. In
addition, the world’s population is redistributing
from rural areas to cities. These changes place
enormous pressure on resources and have broad
implications for human health.
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Global…
• According to the United Nations Department of
Economic and Social Affairs, Population Division
(2003), the global population is projected to
continue rising, reaching 7.9 billion by 2025 and 9
billion by 2050 (using the midrange estimates).
• About 99% of this growth will occur in the world’s
poor, developing countries. Not surprisingly, the
highest growth rates are found in the poorest
countries, those the UN categorizes as least
developed. These countries are found
predominately in sub-Saharan Africa, the Middle
East, and South Asia.
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Global…
• Climate change has become widely accepted as a
growing global problem. Solving the problem will
be more difficult than recognizing it. In 1997,
delegates to the UN Framework Convention on
Climate Change conference in Kyoto, Japan,
adopted a global framework for addressing
climate change.
• They agreed that developed countries should
achieve a 5% reduction in emissions of
greenhouse gases by 2008–2012 compared to
their 1990 emission levels. The Kyoto Protocol
was designed to enter into force when at least
fifty-five nations, accounting for at least 55% of
total 1990 carbon dioxide emissions, had ratified
it, a landmark that was reached in February 2005.
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Global
• Ecologists have begun to use the term
environmental distress syndrome to describe the
effects of deteriorating environmental conditions
and growing threats to human health. Paul
Epstein (1997), of Harvard University’s Center for
Health and the Global Environment, lists ﬁve
symptoms of this syndrome:
1. The reemergence of infectious diseases, such as
cholera, typhoid, and pneumonia, and the
emergence of new diseases, such as drug-resistant
tuberculosis and human reproductive disorders
linked to industrial chemicals,
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Global…
2. The loss of biodiversity and the consequent loss
of potential sources of new drugs and crops ,
3. The growing dominance of generalist species,
such as crows and Canada geese,
4. The decline in pollinators, such as bees, birds,
bats, butterflies, and beetles, organisms that are
indispensable for the preservation of flowering
plants,
5. The proliferation of harmful algal blooms along
the world’s coastlines, leading to more deadly
outbreaks of diseases such as ciguatera poisoning
and paralytic shellfish poisoning (see also UNDP,
1998).
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Historical Background
• This section presents a brief review of
environmental health history, categorized as
follows:
ancient history,
occupational health (contributions from about
1500 to the mid-1800s), and
environmental history post 1800.
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Ancient History
• Negative human impacts on the environment are thought
to have begun many thousands of years ago. One of the
initial targets of human activity was forests, which were
cut down for use as timber and burned to clear land for
agriculture and human settlements. Deforestation
subsequently led to soil erosion that caused rivers and
bays to be fouled with silt.
• The observations, insights, and writings of the ancient
Greeks are noteworthy for the history of environmental
health. Around the 5thC. BCE, the ancient Greek
philosophers had developed the concept of the
relationship between environmental factors and human
health; instead of advocating for the workings of
supernatural factors and the belief that magic potions
would have curative powers, their philosophical position
linked the influence of environment to disease.
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Ancient…
• Hippocrates, who lived between 460 and 370
BCE, often is referred to as “the father of
medicine.” Hippocrates emphasized the role of
the environment as an influence on people’s
health and health status in his work titled On Airs,
Waters, and Places.
• The Greek philosopher proposed that
environmental and climatic factors such as the
weather, seasons, and prevailing winds; the
quality of air, water, and food; and one’s
geographic location were influential in causing
changes in human health.
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Ancient…
• For many years, people have known about the
harmful effects of heavy metals. Hippocrates
identified the toxic properties of lead. The toxic
properties of sulfur and zinc were pointed out by
the Roman scholar Pliny the Elder during the 1st
century; Pliny invented a mask constructed from
the bladder of an animal for protection against
dusts and metal fumes.
• During the 2nd century, the renowned Greek
physician Galen outlined the pathological aspects
of lead toxicity and suggested that mists from
acids could endanger the health of copper
miners.
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Ancient…
• The ancient Romans developed the first
infrastructure for maintaining public health.
Among their innovations were systems for the
transport of water and sewage, heating devices
for water and for rooms, and communal baths.
• Beginning about 500 BCE, the Etruscans
constructed a sewer called the Cloaca Maxima in
Rome. As the city grew, a system of aqueducts
that supplied fresh water and a web of sewers
called cloacae were installed.
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Ancient…
• The Romans used lead pipes to supply the homes
of the affluent, who probably suffered from
chronic lead poisoning.
• After the decline of their empire (possibly due, in
part, to chronic lead poisoning), many of the
hygiene- related contributions of the Romans
were forgotten; for several centuries, the
European world endured the abhorrent sanitary
conditions of the medieval era, with its periodic
outbreaks of epidemics of plague, cholera, and
other pestilence.
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Occupational Health (Contributions from
About 1500 to the Mid-1800s)
• The field of occupational health has made numerous
contributions to environmental health history. From about
1500 to the mid-1800s, recognition grew regarding the
contribution of occupationally related exposures to
adverse health conditions.
• There are many examples of explorations of the impacts of
unsafe and hazardous working environments on the health
of workers, especially the effects of exposures to toxic
metals and hazards that occurred among miners.
• Among the historically important figures in occupational
health were Paracelsus (1493–1541), Agricola (1494–
1555), Bernardino Ramazzini (1633– 1714), Percival Pott
(1714–1788), and Alice Hamilton (1869–1970).
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Occupational…
• Although his contributions were not limited
specifically to occupational health, John Graunt
(one of the early compilers of vital statistics data)
published Natural and Political Observations
Made upon the Bills of Mortality in 1662.
• Sometimes Graunt is referred to as the Columbus
of statistics because his book made a
fundamental contribution by attempting to
demonstrate the quantitative characteristics of
birth and death data.
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Environmental History Post-1800
• Just before the commencement of the 1800s,
Jenner (in 1796) devised a method for vaccinating
against smallpox; in 1798, Malthus wrote his well-
known essays on population.
• The history of environmental health since 1800
may be classified into three major eras:
the first wave of environmental concern (19th
century to mid-20th C.),
the second wave of environmental awareness
(mid-20th century to the 1980s), and
the third period of environmental concern (1980s
to the present).
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Environmental…
• The period of approximately 1850 to 1950 was marked by
growing awareness of existing threats to public health from
unsanitary conditions, detrimental social conditions, and
hazardous work environments. For example, a common
employment practice in Europe was the use of child labor.
• This era coincided approximately with the Industrial
Revolution and marked the introduction of public health
reforms to improve environmental conditions.
• In 1800, construction began on sewers that served the city
of London. The British Parliament enacted the Public
Health Act in 1848 to promote clean water and control
infectious diseases. There were major outbreaks of
cholera, including an outbreak in New York City in 1849
that killed 5,000 people.
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Environmental…
• About the same time, John Snow hypothesized
that sewage-contaminated water was associated
with cholera and conducted a “natural
experiment” to demonstrate the cause of an
outbreak in the present Soho district of London.
• John Snow (1813–1858) was an English
anesthesiologist who innovated several of the key
epidemiologic methods that remain valid and in
use today. In Snow’s time, the mechanism for the
causation of infectious diseases was largely
unknown. The Dutchman Anton van
Leeuwenhoek (1632–1723) had used the
microscope to observe microorganisms (bacteria
and yeast).
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Environmental…
• Beginning in 1900, Walter Reed, who was a US
Army medical officer, investigated the causes of
yellow fever, which was a scourge of US troops in
the Caribbean. He showed that yellow fever was
a mosquito-borne affliction.
• Following this discovery, Major William Gorgas
was dispatched to Havana, Cuba, where he
implemented a highly successful mosquito
eradication program. This action led to a drastic
reduction in yellow fever cases in Havana; later
Gorgas conducted a mosquito control program in
the Panama Canal Zone, making possible the
construction of the canal.
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Environmental…
• During the second wave of environmental
concern, defined approximately from the middle
of the 1950s to the 1980s, environmental issues
continued to come to the forefront.
• The period witnessed the occurrence of several
noteworthy air pollution incidents, including the
fatal 1930 incident in the Meuse Valley, Belgium;
an air pollution episode that caused numerous
deaths in Donora, Pennsylvania, in 1948; and the
deadly London fog of 1952.
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Environmental…
• The most recent period in environmental history
(the third wave of environmental concern—1980s
to the present) has been marked by high
population growth rates, industrialization, and
urbanization. Specific concerns have continued
regarding the effects of toxic chemicals in the
environment.
• A new topic has been the emission of greenhouse
gases and their possible contribution to global
warming.
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Brief environmental history time line: ancient
history to the present
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Introduction to safe water supply
• Water is basic necessity of life. It must be pure,
palatable, wholesome and safe for human consumption.
The water should meet the drinking water standards
recommended by World Health Organization or National
agencies with regard to its physical, chemical,
bacteriological, and radiological quality.
• It is the responsibility of water supply engineer to see
that various requisites for a good drinking water supply
are met so that peoples’ health and well being is
ensured. The quality and abundant supply of water is
essential for a suitably designed water supply system.
• The per capita demand of water is mainly governed by
the economic conditions and water use habits of
community and obviously can not be generalized.
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Introduction…
• The availability of a water supply, adequate in
terms of quantity and quality, is essential to
human existence. Historically, humans recognized
the importance of water from quantity viewpoint.
It is an established fact that civilizations have
developed around the water bodies that could
support agriculture, transportation and provide
drinking water.
• Of late, the importance of water quality has now
been recognized as a result of the developments
of biological, chemical and medical sciences. Such
advancements have clearly established a link
between water quality and its effects on human
health and well being.
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Introduction…
• Water in itself is a mystery as it exhibits unique
characteristics which makes it a necessity, a
resource and an important factor in water
pollution problems. Such unique characteristics
of water are as under:
(a) Water is a universal solvent: Most of the natural
waters being slightly acidic, they dissolve a great
variety of compounds from simple salts and
minerals (sodium chloride and calcium
carbonate in lime stone) to complex organics like
amino acids.
(b) Compared with most other common liquids
water has high capacity to absorb or store heat.
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Introduction…
(c) Compared with other common liquids water has a high
surface tension—a property that is extremely important in
many physical and biological processes that involve
moving water through or storing in small openings or
small pore spaces.
(d) On freezing the water becomes solid (ice) that is lighter
than its liquid form as it expands by 8%. Water is the only
liquid with such a characteristic. The importance of this
property is that the ice remains at top of the water bodies
and does not sink to the bottom. Had it been heavier than
water, the sinking ice would have killed all the aquatic life.
(e) Water is transparent to sun light allowing photosynthetic
organisms to live below the surface.
(f) Water can exist in all the physical states namely liquid,
solid and gas.
(g) Water is a colorless liquid.
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Introduction…
 The Water Facts:
• Earth’s water: Earth has an abundance of water but
terrestrial ecosystems, humans, agriculture depend on
accessible fresh water which is only 0.77% of the total.
• The total water supply of planet earth is 1,335 million km3
.
It simply means that if we can construct a cubic box of
length, breadth and height of 1 km each we will require
1335 × 106
such boxes to store all water.
• According to one estimate, around 13,000 km3
of water
remains as ‘water vapour’ in the atmosphere at any time.
(This is sufficient to cover the Earth with a water layer of
25 mm thickness).
• Each day, 1150 km3
of water evaporate or transpire to the
atmosphere.
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Introduction…
• About 2.5 to 2.7% of the total water available
on the earth is fresh water of which about
75.2% lies frozen in polar ice caps and glaciers
and another 22.6% is present as ground water.
The rest is available in lakes, rivers,
atmosphere, soil moisture and vegetation.
• This fresh water is continually renewable
resource.
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Terms commonly used in water supply
• Aquifer: an underground zone or layer, which is a
relatively good source of water. It is a rock formation that
bears and yields water when penetrated by wells.
• Confined water: groundwater held between two layers of
impermeable rock.
• Eye of the spring: opening where the water comes out of
the earth.
• Free water: groundwater which can move without
hindrance in response to the force of gravity.
• Impermeable: not allowing passage of, for example, a
liquid.
• Infiltrate: to pass through a permeable substance, usually
slowly, as if through a filter.
• Palatable water: water that is pleasant to drink because
its taste is good but it may not be safe to drink.
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Terms…
• Per capita: literally “by needs” by unit of population by
person.
• Permeable: able to be passed through or penetrated by a
fluid.
• Pollution: the presence of matter whose nature, location,
or quantity produces undefined environmental effects.
• Porosity: the quality of being full of pores and therefore
absorbent and permeable.
• Potable: safe for drinking, free from pathogens which are
introduced to the water through feces, dirty containers,
etc.
• Raw water: water that has not been purified.
• Sedimentation: the action of settling down or depositing
matter in a liquid.
• Turbidity: disturbed, muddy appearance of water.
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SOURCES OF WATER
• Ground water
• Surface water
• Rain water
• Ocean water
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Ground water
Definition:
• Groundwater may be defined as that portion of
the total precipitation which has percolated
downward into the porous space in the soil and
rock where it remains, or from which it finds its
way out to the surface.
• Groundwater is by far the most practical and safe
in nature. It is the most important source of
supply for most rural communities of the world.
Examples of groundwater are wells and springs.
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Advantages of groundwater
A. It is comparatively likely to be free from disease
causing micro-organism
B. it can be used without further treatment if
properly protected and treated immediately
after the completion of construction work on
the well or other source where groundwater is
available.
C. It is not exposed for evaporation and is used as
natural storage in underground.
D. It is most practical and economical to obtain and
distribute.
E. Groundwater can be found near a family or a
community.
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Disadvantages of groundwater
A. It needs pumping unless it comes from a
spring
B. It may contain excess amounts of dissolved
minerals.
C. It is poor in oxygen content.
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Occurrence of groundwater
• ƒGroundwater may be found in the form of perched
water, free water or confined water.
a. Free water: Is groundwater occurring where there is
no interruption or confining formation in the water
– bearing stratum. It is free movement of water
under the water table, in the impervious stratum of
the soil formation.
b. Confined water: Is groundwater located between
the overlying (upper) confined stratum and
underlying (lower) confined stratum.
c. Perched water: may occur where the water-bearing
stratum is blocked by an impervious barrier or bed,
which may itself overlie on another aquifer or
stratum. ƒ
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Occurrence…
• In terms of depths of occurrence of the water –bearing
stratum, groundwater may be tapped by the following
means: Shallow wells, Deep wells, Artesian wells, and
Springs
a. Shallow wells: Are wells that have been dug into the
uppermost permeable stratum. They have a depth of
less than 30 meters. In shallow wells, the water level
always stands with in “sucking” distance of a pump
located at the top of the well.( See Fig below)
b. Deep wells: Are wells that have been sunk through an
impermeable formation until they tap water from a
permeable stratum below it. It is sunk with drilling
machines designed and produced for water. They tap
water from a minimum depth of around 60 meters.
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Occurrence…
• Deep wells frequently penetrate more than one
water bearing stratum; therefore they may
provide a stronger flow. Also, deep sources are
less affected by drought as the water bearing
formations are more likely to be extensive in
area.
• In some areas deposits of salt, sulphur or other
objectionable minerals make it unfit to drill deep
for water. Such conditions can usually be
determined by a survey of existing wells in the
area.
• Deep wells are constructed for water supply in
large communities. The water table in deep wells
does not rapidly fluctuate, and therefore provides
a large and uniform yield.
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Shallow well, deep well, shallow spring, deep
spring in relation to water bearing strata.
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Occurrence…
c. Artesian wells: are wells in which groundwater
gushes out of its own accord above ground level.
In other words, an artesian well can flow
naturally, without any artificial efforts.
An artesian well is formed whenever there is a
favorable hydraulic gradient for groundwater to
be at sufficient hydrostatic pressure to rise above
the zone of saturation. In general these wells are
not common.
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How artesian well are formed
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Occurrence…
d. Springs: Are occurrences of groundwater
naturally issuing at points where the water table
reaches the surface, or where the top confining
layer over the water – bearing strata is broken.
Springs are normally found at the foot of
mountains and hills, in lower slopes of valleys,
and near the banks of major rivers.
The yield (flow rate) of a spring varies with the
position of the water table, which in turn varies
with the rainfall amount at that locality and
season.
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Surface Water
• Surface water is found non-uniformly distributed
over the earth’s surface. As the rain reaches the
surface of the earth, it becomes surface water or
runoff.
• Surface water includes rivers, streams, lakes,
ponds, etc. The quantity and quality of surface
water depend upon the conditions of the surface
or catchment area over which it flows.
• All surface water sources are subject to
continuous or intermittent pollution and must be
treated to make them safe to drink.
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Surface…
• The extent of the treatment required will depend
on the results of a sanitary survey made by an
experienced professional, including physical,
chemical and microbiological analyses.
• Protecting surface water from pollution is difficult
because the activities of upstream users of the
river water will affect the quality of the water for
downstream users and the land use in the
surrounding area will also have an impact.
• Surface waters are, by definition, unprotected
sources.
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Rainwater
• In regions where rainfall is abundant and
frequent, rainwater can be a good source of
water supply for individual families and for small
communities.
• The storage of rainwater is particularly important
in areas with a long dry season. It can be stored in
cisterns or ponds. In some rural sections of
Ethiopia, cistern water is used for all domestic
and farm purpose, including drinking.
• This is particularly true where groundwater is
difficult to obtain or, if obtainable, it is for any
reason unsatisfactory.
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Fig. Rainwater is collected from the roof
(Photo: Pam Furniss)
• The term rainwater harvesting is sometimes used. It
simply means collecting, or harvesting, rainwater as
it runs off from hard surfaces such as rooftops and
storing it in a tank or cistern (Figure below).
9/22/2022 61

Advantages of Rainwater
1. It is a reliable source even if it rains once or twice a year
only.
2. It is cheap and a safe means of water supply that may not
need pipes or pumps and is available at the doorstep. Its
storage needs no fuel, no spare parts, but only very little
skill to construct and maintain.
3. Women and children, who are normally water carriers in
Ethiopia and other African countries, will be relieved of the
burden of walking long distances to fetch inadequate
supply.
4. Since the cistern will be in a closed container, it will not
permit spreading of diseases which are often found in an
unprotected source such as rivers or ponds.
5. It is a system that can be used even in arid and semi-arid
areas.
6. Since rainwater is soft, little soap is needed for laundry
purposes.
9/22/2022 62

Ocean Water
• Ocean water is unfit for human consumption
even though it comprises the largest portion
of water on the earth's surface. It is also too
salty for irrigation and for domestic purposes.
• To make the ocean water fit for these
purposes; it must pass through a process
known as desalination (a process of removal
of salt from water).
• However, it is too expensive to consider.
9/22/2022 63

Public Health Importance of Water
• Water is a basic necessity for life. Unfortunately, not all
water helps human to survive. Water from contaminated
sources causes numerous diseases and untimely deaths.
• The fact that a human needs water and cannot live
without it forces him to use it even for drinking purposes,
from any source, whether pure or contaminated, As a
result, many people suffer or die from waterborne
diseases.
• Hence, every country has to take preventive measures to
avoid pollution and contamination of the available water
resources.
• Therefore, public water supply must be potable, palatable
and wholesome. Water must not have disagreeable
physical change and must be hygienically safe.
9/22/2022 64

Importance of Water
• The following points elaborate the importance of
water:
1. It is impossible to have a clean and sanitary
environment without water. Water is necessary
in promoting personal hygiene and in cleaning
the environment. Without an adequate and
wholesome water supply, health cannot be
maintained.
2. Water is essential for life. Man can live nearly two
months without food, but can live only three or
four days without water. In general 70% of
human body weight is water and a human being
needs two liters of water per day as minimum.
3. Most of the foods that man eats contain water.
9/22/2022 65

Importance…
4. It is essential to run industries. Nearly all modern
industries are thirsty; they need water.
5. It’s important for the balance in ecology (i.e. the
balance in relationship between living things and
the environment in which they live). All animal
life depends directly or indirectly upon vegetation
for food, and vegetation will not grow without
water.
• Vegetable matter, such as leaves and steams, can
be converted to soil by bacterial action. Bacteria
need water in order to thrive. New plants
growing in this soil take up nutrients through
their roots in the form of a solution in water. Any
break in this ecological chain can mean failure of
the whole ecological system.
9/22/2022 66

Importance…
6. Water is important for agriculture, animal
breeding and fishing.
7. Water is a valuable source of energy. It is capable
of generating hydroelectric power.
8. Water facilitates transportation and navigation.
For example, the Baro River is one of the rivers
used for boat transportation in Ethiopia.
9. Water plays an important role in recreation
activities. Lake Langano is an attractive lake for
recreation.
9/22/2022 67

Water and water related diseases
 Water, Health and Disease
• The saying “water is life” is found in many cultures around
the world. It underscores the fact that clean water is an
absolute prerequisite for healthy living. The importance of
water in human welfare cannot be over-emphasized.
• The normal functioning of the human body depends
entirely upon an adequate quantity and quality of water.
But if the water is from contaminated sources, it causes
numerous water-associated diseases.
• In the developed world, water-associated disease are rare,
due essentially to the presence of efficient water supply
and waste water disposal systems. However, in the
developing world, the majority of people are without a
safe water supply and adequate sanitation
9/22/2022 68

Water…
• Water quality is a crucial issue for environmental health,
given that water is essential for life on earth. Residents of
the United States and other developed countries assume
that they will be able to turn on a faucet and draw a
refreshing glass of water that is free from dangerous
contaminants and microbial agents.
• In contrast, a safe water supply is not always available in
the less developed regions of the world, where waterborne
diseases represent a significant public health threat.
• Vulnerable groups such as children, the elderly, and
immunocompromised patients (e.g., those who are
undergoing chemotherapy, taking steroids, or afflicted with
HIV/AIDS) are at special risk of diseases caused by water
contamination.
9/22/2022 69

A WHO survey has highlighted the
following facts
• Each day, 30,000 people die from water-associated
diseases.
• In developing countries, 80% of all illnesses are
water-associated.
Safe, adequate and accessible supplies of water,
combined with proper sanitation, are basic needs.
Therefore, water supply is taken as an essential
component of primary health care (PHC).
Safe, adequate and accessible water supply can help
to reduce many of the disease affecting under-
privileged populations especially those who live in
rural and urban fringe areas.
9/22/2022 70

Water-associated Disease
• Water-associated disease can be defined as a
disease in relation to water supply and
sanitation.
There are four categories:
1. Waterborne disease
2. Water-washed disease
3. Water-based disease
4. Water-related disease
9/22/2022 71

1. Waterborne diseases
• Waterborne diseases are conditions that are “transmitted
through the ingestion of contaminated water and water
acts as the passive carrier of the infectious agent.”
• Waterborne diseases are a source of on-going concern to
the residents of the developing world, where waterborne
diarrheal conditions take a great toll in morbidity and
mortality, and to tourists who travel in these areas. In the
developing world, bacterial waterborne diseases are
associated with the deaths of new-borns and children
from conditions such as dehydration.
• An example of a condition transmitted by water is acute
gastroenteritis, defined as an “inflammation of the
stomach and or intestines or both.” In addition to
gastroenteritis, many serious diseases can be spread
through the water supply. To some extent, these diseases
also affect developed countries including the United
States.
9/22/2022 72

Waterborne…
• Several infections enteric or intestinal diseases of
man are transmitted through water
contamination by fecal matter. Pathogens
excreted in water by an infected person include
all major categories such as bacteria, viruses,
protozoa and parasitic warms. Water acts only as
a passive vehicle for the infectious agent.
• The Table below shows examples of waterborne
diseases.
9/22/2022 73

Waterborne diseases with their etiologies
Types of organism Disease types
Bacteria • ƒ
Typhoid and paratyphoid fever ƒ
• Cholera ƒ
• Diarrheas (caused by salmonella,
yersinia entrocolitica, E.coli) ƒ
• Campylobacter dysentery ƒ
• Bacillary dysentery (caused by
shigella)
Virus • ƒ
Hepatitis A ƒ
• Poliomyelitis ƒ
• Viral gastroenteritis
Protozoa • ƒ
Amoebic dysentery ƒ
• Giardia (lambliasis) ƒ
• Balantidiasis
Helminthes • Helminthiasis caused by Ascaris
and Trichinas
9/22/2022 74

Waterborne…
• To prevent the occurrence of waterborne
diseases, water treatment is very essential.
The cycle of infection due to waterborne
diseases is explained in Fig below:
9/22/2022 75

Waterborne…
• N.B. It should be noted that waterborne
diseases form part of the group of water-
washed diseases as well. They may also be
transmitted by any of the faeco-oral routes:
dirty hands, dirty food, dirty water, etc.
9/22/2022 76

2. Water-washed diseases
• These comprise diseases linked to a lack of water for
personal hygiene. Examples of water -washed diseases
are: ƒ
 Dermatological disease such as scabies ƒ
 Ophthalmic disease such as trachoma and conjunctivitis
 Louse-borne diseases such as louse borne typhus and
relapsing fever. Lack of good personal hygiene and inability
to wash clothes encourages the proliferation of lice and
the problems associated with their presence (itching,
scratching, skin sores).
 To prevent this type of disease, provision of an ample
amount of water and personal hygiene are very essential.
9/22/2022 77

3. Water-based diseases
• These are diseases caused by infectious agents
that are spread by contact with water. The
essential part of the life cycle of the infecting
agent takes place from an aquatic animal.
• A number of diseases depend upon the
pathogenic organisms spending part of their life
cycle in water or in an intermediate host which
lives in water. Thus, infection of humans cannot
occur by immediate ingestion of, or contact with,
the organism excreted by sufferers.
9/22/2022 78

Water-based…
• Many of the diseases in this class are caused by
worms, which infest the sufferer and produce
eggs, which are then discharged in feces or urine.
• People can become infected from swimming or
wading in infected water.
• Typical examples are schistosomiasis and
dracunculiasis (guinea worm). See Figs. below for
the cycle of transmission of schistosomiasis and
dracunculiasis .
9/22/2022 79

The cycle of transmission of
schistosomiasis
9/22/2022 80

The cycle of transmission of
Dracunculiasis (guinea worm)
9/22/2022 81

Water-based…
To prevent this group of diseases, the
following methods may be implemented:
• Avoidance of contact with and ingestion of
contaminated water.
• Reduction of intermediate hosts (snail) by
using “endod” or Lemma toxin.
• Storage of water from 24 to 72 hours to kill
the cercaria.
9/22/2022 82

4. Water-related diseases
• These are diseases transmitted by insects that live
close to water. Infections are spread by mosquitoes,
flies and other insects that breed in water or near it.
• There are a number of diseases which are spread by
insects that breed or feed near water so that their
incidence can be related to the proximity of suitable
water sources.
• Infection with these diseases is in no way connected
with human consumption or contact with the water.
• Example: Malaria, sleeping sickness, yellow fever,
onchocerciasis, etc.
To prevent this type of disease, making the water
unsuitable for breeding of insects is essential.
9/22/2022 83

Note that:
• Chemical contamination of water is another
potential cause of health problems. In some
places, water may contain naturally occurring
toxic chemicals such as arsenic and ﬂuoride.
• Other chemicals may get into the water supply
because of pollution. Lead poisoning, for
example, can result from water contaminated
with lead. These diseases are also classiﬁed as
waterborne diseases.
9/22/2022 84

Summary
• All the waterborne and many of the water-based
diseases depend for their dispersion on infecting agents
from human feces getting into drinking water or into
food.
• The chain of disease transmission may be broken
effectively by sanitary disposal of feces and the
provision of safe and adequate water supplies.
• Improvement in the reality of community water supplies
will basically only affect the waterborne disease such as
bacillary dysentery, cholera and typhoid.
• Many of the diarrheal diseases probably are due more
to a lack of safe and adequate quantities of water. Skin
and eye infections are in this group of water-associated
diseases.
9/22/2022 85

Summary...
• When water supplies are developed without
complementary improvements in personal
hygiene, food handling and preparation, and in
general health care, they are unlikely to produce
the expected health benefits.
• Table below discusses, in comparative form, the
four categories of water-associated diseases, and
gives examples of typical diseases in each
category, the causative agents and the preventive
strategies.
9/22/2022 86

The four mechanisms of water-associated
diseases and preventive strategies
9/22/2022 87

Water Treatment
• is defined as the process of removing all those
substances, whether biological, chemical or
physical, which are potentially dangerous or
undesirable in water supply for human and
domestic use.
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Main objective of water treatment
1. To remove pathogenic organisms and consequently to
prevent waterborne disease.
2. To remove substance which impart color, taste or
odor to the water.
3. To remove excess or undesirable chemicals or
minerals from the water.
4. To regulate essential elements or chemicals that may
be in excess or lacking in a certain water supply (e.g.
fluoridation or defluoridation of water, softening of
water, etc.)
5. To remove excess or undesirable dissolved gasses.
9/22/2022 89

Water treatment systems
• Water treatment systems can be categorised
as:
1. small-scale water treatment, which includes
community and household treatment
methods, or
2. large-scale water treatment that might be
found in towns and cities.
9/22/2022 90

Water treatment…
TREATMENT OF WATER ON A SMALL SCALE
• In most rural areas and small communities in
developing countries, adequate water treatment
procedures are almost non-existent, mainly for
economic reasons. Generally, water for human
use is collected from various unprotected water
holes, and is consumed without treatment.
• Naturally, water-borne diseases are prevalent
among communities that consume such
untreated contaminated water, and such
practices must be discouraged. Water must be
adequately treated before consumption, even in
rural areas.
9/22/2022 91

Treatment…
• Therefore, small-scale treatment of water in emergency
situations, temporary settlement areas, at household
level and areas where the municipality is not well
organized is very important to reduce the problem of
waterborne disease through the utilization of different
methods of water treatment.
• Treatment of household water supplies may be effected
by the following methods, used singly or in combination,
depending on the reliability of each method:
 Boiling
 Filtration
 Chemical disinfection
 Household Water Storage
9/22/2022 92

Boiling
• Boiling is one of the most reliable methods of
disinfecting water at household level. Provided
that water is brought to the boiling point, and is
kept boiling for 15 to 20 minutes, all forms of
micro-organisms, including the most resistant
spores or cysts, will be destroyed.
• Furthermore, boiling is effective for all kinds of
raw water, unless the water contains toxic
chemicals which boiling cannot destroy.
9/22/2022 93

Cont’d
• Yet, although boiling is one of the most
practicable methods of treating water, it may not
be used if a community has not developed the
habit of drinking boiled water.
• Boiled water has at least one disadvantage, and
that is its flat taste, due to the loss of dissolved
gases (carbon dioxide and oxygen) and minerals
during the process of boiling.
• This can be remedied, however, by keeping the
boiled water for a few hours in partially filled
containers. The flat taste may not be a hindrance
if a continuous effort is made to develop the
habit of drinking boiled safe water.
9/22/2022 94

Cont’d
• Great care must be taken to avoid
recontamination of the boiled water either during
storage or consumption. It must be stored in a
clean, firmly covered container, preferably the
same container in which it was boiled.
• Health caregivers should take into consideration
the importance of health education to change the
habit of people towards safe water supply
through boiling of water to reduce the problems
of waterborne disease.
9/22/2022 95

Filtration
• Filtration for household water supply is
generally carried out by simple filtration
systems, such as:
Homemade Sand Filters
Home Candle Filters
Stone filters
Cloth filtration to prevent guinea worm
disease
9/22/2022 96

Homemade Sand Filters
• These can be set up in individual homes, in containers
such as steel barrels, drums, etc., that are locally
available. An example is shown in Figure below.
• The components of the filter media and the basic
principles of operation of a homemade sand filter are
the same as those of a slow sand filter. The minimum
depth of filter sand should not be less than 60 cm.
• A properly constructed and carefully maintained
homemade sand filter can remove most of the
substances that cause turbidity, taste and odor, the
cysts and ova of parasites, and other relatively larger
organisms.
9/22/2022 97

Home made sand filter
9/22/2022 98

Some of the limitations of a homemade
sand filter are:
1. It cannot be relied upon to remove all forms
of pathogenic organisms, particularly the viruses
and some of the very small-sized bacteria.
2. It frequently gets clogged, particularly if the
raw water to be filtered is turbid.
9/22/2022 99

Maintenance of a homemade sand filter
1. There must be a continuous flow of raw water
over the filter bed.
2. The rate of filtration should normally be
controlled to not more than 1.5 liters per
minute. This rate will be achieved after the filter
has been in operation for a few days.
3. The top-most layer of the sand must be
scraped off, cleaned and replaced at fixed
periods.
9/22/2022 100

Home Candle Filters
• There are commercially made for filtering
individual water supplies. There are various types
and sizes, known by different trade names.
• The core of the filter is a porous cylinder (shaped
like a wax candle, hence the name), made from
high-quality unglazed porcelain (See Figure below).
• The efficiency of filtration depends upon the pore
size of the candle. Different manufacturers
produce candle filters of varying pore sizes, but
generally the pore size varies from a maximum
radius of about 50 microns to a minimum radius of
0.3 micron. (A micron is one-millionth of a meter.)
9/22/2022 101

Candle Filter
9/22/2022 102

Some of the limitations of candle filters
are :
1. The average size of a bacterium is about 1.5
microns. Thus, candle filters with a pore radius of
more than 1.5 microns may not remove all the
pathogenic organisms that may be present in the
water. Viruses, for example, cannot be removed by
a candle filter.
2. The rate of filtration of a candle filter is normally
very low, although the rate can be increased by
having a three-candle or four-candle filter
3. Candle filters are relatively too expensive for
wide use by the general public.
9/22/2022 103

Maintenance during operation
1. The raw water to be filtered must be
reasonably clear, in order to reduce clogging of
the candle pores.
2. The candle needs dismantling once a week,
for washing and sterilizing in boiling water.
9/22/2022 104

Stone filters
• Stone filters are similar to candle filters but are
carved from porous local stone (see Fig. below).
They are generally difficult to clean and heavy to
lift, but have the advantage of being relatively
inexpensive if they can be produced locally.
• If these filters were commonly used in a practical
area, it would be worthwhile to test the water
from a representative sample to determine the
efficiency of removal of fecal contamination.
• This method of filtration could be possible in
Ethiopia using the local “Beha” stone. But it
needs research to introduce this method of
filtration for individual and community use.
9/22/2022 105

Stone filter
9/22/2022 106

Cloth filtration to prevent guinea worm
disease
• Guinea-worm disease (dracunculiasis) is transmitted via
contaminated drinking water (e.g. from stagnate ponds,
cisterns, or step wells).
• The disease occurs in a number of countries in Africa and
Asia and causes severe suffering and disability among the
world's most deprived people. Infected individuals do not
develop immunity.
• There is no known animal reservoir, and people can
disseminate the parasite one year after infection and
during 1-3 weeks after emergence of the worm.
• For these reasons, control of transmission, including
treatment of drinking water, is simple, and global
eradication of this disease is feasible.
9/22/2022 107

Cloth filtration…
• Dramatic reductions in the prevalence of dracunculiasis have
been achieved through improvement of water supplies and by
promoting proper hygiene in areas where the disease is
endemic.
• In such areas, guinea worm (Dracunculus medinensis) can be
effectively eliminated by filtering all drinking water through
fine cloth (see Fig. below). Filtration of drinking water is thus a
primary strategy for the control of guinea-worm disease.
• Filters should be of mesh size less than 130 µm; this should
remove all infected intermediate hosts.
• Monofilament synthetic cloth (nylon) is most suitable because
it clogs less rapidly and is easily cleaned; it has a mesh size of
100-130 µm. Cotton cloth can be used but tends to clog
rapidly.
• Boiling is also effective as a means of controlling the disease.
9/22/2022 108

Cloth filtration
9/22/2022 109

Chemical Disinfection
• Chlorine or its compounds
• Iodine and its compounds
• Silver
9/22/2022 110

Chlorine or its compounds
• Chlorine or its compounds can be applied to
disinfect water on a small scale. Methods such as
siphon-bottle feeders can be used easily for
household water disinfection.
• When dealing in terms of liters, 3 drops of 1%
chlorine stock solution applied to every liter of
water can give satisfactory disinfection; the dose
can be doubled if the water is turbid.
• The tablet forms of chlorine, such as Halazone,
may be effectively used under field conditions
when camping and during travel (dose: 1 tablet
per liter of clear water.)
9/22/2022 111

Method of preparing chlorine solution
using local material
9/22/2022 112

Iodine and its compounds
• Iodine and its compounds have also been
effectively used for individual water disinfection.
In fact, iodine is believed to be a better
disinfectant than chlorine.
• Tablets of iodine, like those of chlorine, are
available under various trade names (Globaline,
Potable Aqua, etc.).
• Tincture of iodine (2%) applied at the rate of 2
drops per liter gives satisfactory results. Iodine,
however, is relatively expensive for ordinary use,
and in addition imparts to the water the familiar
medicinal iodine smell.
9/22/2022 113

Silver
• Colloidal silver was used by the Romans to
protect the quality of water in storage jars
since, at concentrations of about 0.05 mg/l,
silver is toxic to most micro-organisms.
• It is of value for small portable filter units for
field use where silver-impregnated gravel filter
candles remove turbidity and provide
disinfection. The cost becomes excessive for
other than very small supplies.
9/22/2022 114

Household Water Storage
• When household storage is well practiced in the
community, turbidity will be reduced, bacteria
and eggs of parasites will be sedimented, and
schistosomiasis will be prevented because the
chances of cercaria survival after 24 hours of
water storage will be reduced.
• The principal health risk associated with
household water storage is the ease of
recontamination during transport and storage,
particularly if the members of a family or
community do not all follow good hygiene
practices.
9/22/2022 115

Good hygienic measures include the
following:
• Careful storage of household water and regular
cleaning of all household water storage facilities;
• Construction, proper use, and maintenance of
latrines;
• Regular hand-washing, especially after defecation
and before eating or preparing food;
• Careful storage and preparation of food.
Water that is clean from the supply or has been
treated in the household needs to be protected
from recontamination.
9/22/2022 116

The most important elements of water
storage can be summarized as follows:
• Use a clean water source or treat the water,
either at home or in a storage tank.
• Store water in an earthenware or plastic
container with a lid.
• Store the water container at a height that puts
it beyond the reach of children and animals.
• Fit a tap to the container for drawing clean
water in order to prevent contamination by
dirty cups, ladles, or hands.
9/22/2022 117

Storage tanks
• Where a piped water supply to the household
operates intermittently, a storage tank is
commonly used to ensure that there is sufficient
water for the family needs throughout the day.
• The tank should be covered to prevent
contamination of the water and to restrict access
by children and animals.
• It may be located inside or outside the house, but
a secure cover should be fitted to an outdoor
tank.
9/22/2022 118

Storage…
• If the water running into the tank is clean (i.e.
comes from a protected source or a treatment
plant), the tank should be inspected, cleaned,
and disinfected at least once a year.
• Where the water supplied is not clean, the
tank will require more frequent cleaning, the
frequency depending on the water quality.
• Water of poor quality should be treated by the
most appropriate means.
9/22/2022 119

CONVENTIONAL LARGE SCALE WATER
TREATMENT
Reading assignment
9/22/2022 120

Water pollution and its effects
• A wide range of natural and human influences
affects water quality. The most important of the
natural influence are geological, hydrological and
climatic conditions, since these affect the
quantity and the quality of water available.
• The effect of human activities on water quality
are both widespread and varied in the degree to
which they disrupt the ecosystem and/or restrict
water use.
9/22/2022 121

There are two main types of water
pollution:
1. Chemical pollution of water and diseases
2. Biological pollution of water and diseases
Pollution can be deﬁned as the introduction into
the natural environment (air, water or land) of
substances (pollutants) that are liable to cause
harm to human health or to animals, plants and
the wider environment.
Water pollution occurs when a river, lake or
other body of water is adversely affected due to
the addition of pollutants.
9/22/2022 122

1. Chemical pollution of water and diseases
• Almost every known element existing normally in
the environment can become poisonous when
introduced into the human system in larger than
normal quantities. One major way of introducing
these elements into the environment and later
into the human system is through the discharge
of industrial effluents into water sources such as
rivers.
• These pollutants include detergents, solvents,
nitrogenous substances, dyes, ammonia, etc. This
can affect human health directly or indirectly by
accumulating in aquatic life.
9/22/2022 123

Chemical…
• Some elements or chemicals maybe found in
water in excessive or inadequate amounts. For
instance, excess fluorine in water causes dental
flourosis or mottled enamels while lack of
fluorine in water causes dental cavities
(decay).Therefore, maintaining the optimal level
(1mg/l) is essential.
• It has been observed that surface water is often
low in fluoride content but the concentration is
high in underground water sources.
• A concentration of 10 PPM of nitrate nitrogen is
thought to be harmful. It causes infant
methaemoglobinaemia (blue baby syndrome).
9/22/2022 124

2. Biological pollution of water and
diseases
• Water may contain numerous pathogenic organisms
and thereby become a means of transmission for
many diseases.
• All water-associated disease require an infectious
agent, a transmission route and the exposure of a
susceptible living organisms for their spread. The
relationship can be illustrated in the form of a
triangle as shown in Fig. below.
9/22/2022 125

SOURCES OF WATER POLLUTION
• Water pollutants are categorized as point source or
nonpoint source, the former being identified as all
dry weather pollutants that enter watercourses
through pipes or channels.
• Storm drainage, even though the water may enter
watercourses by way of pipes or channels, is
considered nonpoint source pollution.
• Other nonpoint source pollution comes from
agricultural runoff, construction sites, and other land
disturbances.
• Point source pollution comes mainly from industrial
facilities and municipal wastewater treatment
plants. The range of pollutants is vast, depending
only on what gets “thrown down the drain.”
9/22/2022 126

Sources…
• Point sources are identifiable points or places, such as a pipe
or channel, which discharge directly into a body of water. This
might be from wastewater treatment plants, factories and
industrial plants, latrines, septic tanks or piped discharge from
barnyards and other places where livestock are confined.
• Non-point sources are those where pollution arises over a
wider area and it is often difficult to locate the exact place of
origin. For example, fertiliser or pesticide washed from a field
by rain may seep into a river or stream at many places both
on the surface and through the soil.
• Pollution from non-point sources, also known as diffuse
pollution, contributes most of the contaminants in rivers and
lakes. Other non-point sources are pollution from
construction sites and other land disturbances. The problems
in identifying the exact point of origin make non-point sources
much more difficult to control.
9/22/2022 127

Public health impacts of water pollution
• Waterborne infectious diseases are transmitted
primarily through contamination of the water
sources with excreta of humans and animals who
are either active cases or carriers of disease.
• Carriers do not show any signs of disease
although they have disease-causing agents in
their body that can be transferred to others;
active cases are people who are displaying visible
signs of disease.
• Use of contaminated water for drinking or
cooking, or contact with contaminated water
during washing or bathing, may result in
infection.
9/22/2022 128

Public…
• The dose or amount ingested that is necessary to
cause illness depends on the type of pathogen.
Exposure to a single pathogenic organism does
not always result in infection and disease.
• Sometimes many pathogens, perhaps several
hundred, must be ingested to cause infection.
The minimum infectious dose also varies with the
age, health, nutritional and immunological status
of the exposed individual.
• Infants and young children, people who are
debilitated, people who are living in unsanitary
conditions, people who are sick and the elderly
are at greatest risk of waterborne diseases.
9/22/2022 129

Effects of pollution on water sources
 Streams and rivers
• Streams and rivers are not only potential water sources for
humans, they are also important aquatic habitats for many
plants and animals. Pollution can have a damaging effect on
aquatic ecosystems as well as potentially on human health.
• The effect of pollution on streams and rivers depends on the
type of pollutant. Some substances are acutely toxic to aquatic
plants and animals and will cause dead zones downstream from
the pollutant source in which no living organism is found. Other
pollutants are health concerns to humans, but have little
impact on aquatic communities.
• One of the most common types of freshwater pollutant is
biodegradable organic material. When a high concentration of
organic material such as raw sewage (human excreta) is
discharged into a stream, the levels of dissolved oxygen in the
water may fall so low that the water is completely
deoxygenated.
9/22/2022 130

Effects…
Lakes
• The effect of pollution on lakes differs in several
respects from the effect on rivers. Water
movement in lakes is slower than in rivers so re-
aeration is slower.
• The reduction in ﬂow rate as a stream enters a
lake also causes sediments to settle out of the
water and slowly accumulate on the bottom of
the lake.
• Some pollutants are bound to the solid particles
and will therefore also accumulate in the
sediment.
9/22/2022 131

Effects…
 Groundwater
• Water that moves through the soil will, to some extent,
be puriﬁed naturally. However, this is not always true
because soil cannot remove all pollutants. Many soils
have the ability to remove certain types of pollutants,
including phosphorus, heavy metals, bacteria and
suspended solids.
• However, pollutants that dissolve in water, like nitrate and
ammonia from fertilisers and animal wastes, can pass
through soils into the groundwater. This may cause high
concentrations of pollutants in local drinking water wells.
• Leaking from underground storage tanks, solid waste
landﬁlls, improperly stored hazardous waste, careless
disposal of solvents and hazardous chemicals on ground
surfaces are other potential sources of groundwater
pollution.
9/22/2022 132

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