chapter 1-public health (environmental pollution and control)
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CHAPTER 1 –PUBLIC HEALTH
INFECTIOUS DISEASE
1. An infectious disease is a clinically evident disease of humans or animals
that damages or injures the host so as to impair host function, and results
from the presence and activity of one or more pathogenic microbial agents,
including viruses, bacteria, fungi, protozoa, multi-cellular parasites, and
aberrant proteins
It is a disease caused by a microorganism that is potentially transferable to
new individuals.
Example: HIV, Malaria
2. A communicable disease is an infectious disease that readily spreads from
person to person, and is easily caught from an infected person.
Example: a cold or chicken pox
3. A non communicable disease an infectious disease (i.e., with a
microorganism etiology) that is not typically spread from person to person.
The distinction, not spread from person to person, is important since it
implies not only that:
i. individuals carrying the disease are not likely to spread the
disease to others
ii. whatever led to the infection in such an individual likely did not
include person to person contact
Example : Cancer, Asthma, Heart Disease
DISEASE CAUSED BY CONTAMINATION
1. Waterborne Disease
Waterborne diseases are caused by pathogenic microorganisms
which are directly transmitted when contaminated fresh water is
consumed.
Waterborne disease can be caused by protozoa, viruses, or bacteria,
many of which are intestinal parasites
Water borne diseases spread by contamination of drinking water
systems with the urine and feces of infected animal or people.
This is likely to occur where public and private drinking water systems
get their water from surface waters (rain, creeks, rivers, lakes
etc.), which can be contaminated by infected animals or people.
Runoff from landfills, septic fields, sewer pipes, residential or industrial
developments can also sometimes contaminate surface water.
Example of Waterborne Disease
1. Diarrhea
is caused by a bacterial, viral, or parasitic infection.
Diarrhea may be accompanied by cramping, abdominal pain, nausea, an
urgent need to use the bathroom, or loss of bowel control. Some infections
that cause diarrhea can also cause a fever and chills or bloody stools.
2. Cholera
Cholera occurs because of the bacteria present in water contaminated
by incorrect sanitation, or in improperly cooked fish, especially
shellfish
Cholera is transmitted through feces contaminated with the bacterium.
The contamination normally appears when sewage water is released
into the waterways, affecting the drinking water, fish and food washed
in the water. In normal conditions it doesn't spread from person to
person, but this is possible in poor sanitary conditions.
Common symptoms include severe diarrhea abdominal cramps, fever
and vomiting.
If not treated immediately, the dehydration can cause death through
circulatory volume shock in just a few hours.
Cholera can be prevented by respecting a number of sanitary rules
3. Typhoid Fever
is caused by the infection with a bacterium called Salmonella typhi. It
is very common, as it is transmitted by water or food contaminated
with feces from infected people.
symptoms including a high fever, slowly rising from 39 to 40 degrees
Celsius (103 to 104 degrees Fahrenheit), chills, bradycardia (low pulse
rate) and weakness
Typhoid fever can be dangerous, and if untreated, it has a mortality
rate between 10 and 30%.
A vaccine is available and it is highly recommended for anyone
traveling to regions where typhoid fever is common.
4. Dysentery
Dysentery is characterized by a severe inflammation of the intestines,
affecting the body in a significant measure. Dysentery used to be a
common disease in the past centuries, but it is becoming less common
today.
Pathogen agent : Shigellosis, caused by Shigella bacteria, an
amoeba called Entamoeba histolytica that transmitted by
contaminated water
The usual sign of epidemic dysentery is blood appearing in the feces,
associated with diarrhea, abdominal cramps, fever and rectal pain.
Sepsis and kidney failure may occur in more severe cases.
Prevention
Clean water is a pre-requisite for reducing the spread of water-borne diseases
It is well recognized that the prevalence of water-borne diseases can
be greatly reduced by provision of clean drinking water and safe
disposal of feces
Water is disinfected to kill any pathogens that may be present in the
water supply and to prevent them from growing again in the
distribution systems
Disinfection is then used to prevent the growth of pathogenic
organisms and to protect public health and the choice of the disinfect
depends upon the individual water quality and water supply system.
Without disinfection, the risk from waterborne disease is increased.
The two most common methods to kill microorganisms in the water
supply are: oxidation with chemicals such as chlorine, chlorine dioxide
or ozone, and irradiation with Ultra-Violet (UV) radiation
2. Food borne Disease
is any illness resulting from the consumption of contaminated food,
pathogenic bacteria, viruses, or parasites that contaminate food,
rather than chemical or natural toxins.
Cause by improper handling, preparation, or food storage.
More than 250 different food borne diseases have been described.
Most of these diseases are infections, caused by a variety of bacteria,
viruses, and parasites that can be food borne
Common food borne disease
1. Campylobacter
is a bacterial pathogen that causes fever, diarrhea, and abdominal
cramps.
It is the most commonly identified bacterial cause of diarrheal illness
in the world.
These bacteria live in the intestines of healthy birds, and most raw
poultry meat has Campylobacter on it.
Eating undercooked chicken or other food that has been contaminated
with juices dripping from raw chicken is the most frequent source of
this infection.
2. Salmonella
is also a bacterium that is widespread in the intestines of birds, reptiles
and mammals.
It can spread to humans via a variety of different foods of animal
origin.
The illness it causes, salmonellosis, typically includes fever, diarrhea
and abdominal cramps.
In persons with poor underlying health or weakened immune systems,
it can invade the bloodstream and cause life-threatening infections.
3. E. coli
is a bacterial pathogen that has a reservoir in cattle and other similar
animals.
Human illness typically follows consumption of food or water that has
been contaminated with microscopic amounts of cow feces.
The illness it causes is often a severe and bloody diarrhea and painful
abdominal cramps, without much fever.
In 3% to 5% of cases, a complication called hemolytic uremic
syndrome (HUS) can occur several weeks after the initial symptoms.
This severe complication includes temporary anemia, profuse bleeding,
and kidney failure.
Prevention
1. Keep clean
• Wash your hands before handling food and often during food preparation
• Wash your hands after going to the toilet
• Wash and sanitize all surfaces and equipment used for food preparation
• Protect kitchen areas and food from insects, pests and other animals
2. Separate raw and cooked
• Separate raw meat, poultry and seafood from other foods
• Use separate equipment and utensils such as knives and cutting boards for
handling raw foods
• Store food in containers to avoid contact between raw and prepared foods
3. Cook thoroughly
• Cook food thoroughly, especially meat, poultry, eggs and seafood
• Bring foods like soups and stews to boiling to make sure that they have
reached 70°C. For meat and poultry, make sure thatjuices are clear, not pink.
Ideally, use a thermometer
Reheat cooked food thoroughly
4. Keep food at safe temperatures
• Do not leave cooked food at room temperature for more than 2 hours
• Refrigerate promptly all cooked and perishable food (preferably below 5°C)
• Keep cooked food piping hot (more than 60°C) prior to serving
• Do not store food too long even in the refrigerator
• Do not thaw frozen food at room temperature
5. Use safe water and raw materials
• Use safe water or treat it to make it safe
• Select fresh and wholesome foods
• Choose foods processed for safety, such as pasteurized milk
• Wash fruits and vegetables, especially if eaten raw
• Do not use food beyond its expiry date
3. Vector Disease
Occur in infectious microbes such as viruses, bacteria, parasite, etc
that present in a vector.
Mosquito, birds, rat, insects and all others pests that transfer diseases are
referred to as a vector.
The vector picks up the disease organism from an infected host, an
animal or a human, and transmits it either to an intermediary host or
directly to the human host.
The transfer happens directly by bites, or infestation of tissues, or
indirectly through disease transmission.
Example of Vector Disease
No Vector Disease
1. Aedes Mosquito Chikungunya
Dengue Virus
West Nile Virus
Yellow Fever
2. Anopheles Mosquito Malaria
3. Bird Avian influenza (Bird flu)
4. Rats Leptospirosis
Plague (via Fleas)
Leishmaniasis (via Sand Fly)
Symptom of disease
1.Dengue
Dengue is transmitted by the bite of an Aedes mosquito infected with any
one of the four dengue viruses. It occurs in tropical and sub-tropical areas of
the world. Symptoms appear 3—14 days after the infective bite.
Dengue fever is a febrile illness that affects infants, young children and
adults.
Symptoms range from a mild fever, to incapacitating high fever, with severe
headache, pain behind the eyes, muscle and joint pain, and rash. There are
no specific antiviral medicines for dengue. It is important to maintain
hydration. Use of acetylsalicylic acid (e.g. aspirin) and non steroidal anti-
inflammatory drugs (e.g. Ibuprofen) is not recommended.
Dengue haemorrhagic fever (fever, abdominal pain, vomiting, bleeding) is a
potentially lethal complication, affecting mainly children. Early clinical
diagnosis and careful clinical management by experienced physicians and
nurses increase survival of patients
In January 2009, reported there are 5000 cases of dengue.
2. Malaria
Malaria is a major disease in the tropics and subtropics. Each year, it is
estimated that more than 225 million cases of malaria, killing around 781 000
people according to WHO. Historical records suggest that the disease has
infected human since the beginning of mankind.
When a person is infected, he or she will suffer symptoms including fever,
chills, headache, muscle pain, sweating or vomiting. Severe cases will
progress to coma and death. These symptoms normally appear between 10
to 15 days after being bitten by the Anopheles mosquito. The disease can
also be transmitted from a mother to her unborn baby and by blood
transfusions.
3. Bird Flu
Bird flu or avian influenza is a highly contagious disease which can cause
sickness and death especially in domesticated birds like chickens, geese,
ducks and turkeys.
Bird flu is caused by avian influenza (AI) virus which normally only infects
birds, less commonly pigs and rarely horses, seals, whales, humans and other
animals. There are many subtypes of AI virus.
The subtype H5N1 currently circulating among birds worldwide was first
detected in 1997. Since 2003 has spread among many countries in Asia and
Europe causing heavy mortalities in poultry flocks and wild birds. Over 200
million poultry and birds have died or were killed since 1997 due to this virus.
The H5N1 virus is also capable of causing disease in humans under certain
circumstances.
Malaysia has been free from bird flu until August 2004 when cases were
detected for the first time, in Kelantan. The disease was promptly eradicated
and Malaysia’s disease-free status was reinstated on 5 January 2005.
Isolated cases are again reported exactly one year later, in Kuala Lumpur
which is being eradicated.
This disease can spread by migration birds and movement of infected bird
Birds get infected when they come into contact with these, with dead birds
and with contaminated feed and water, equipments, vehicles and other
objects. Virus is shed in feces, saliva and nasal secretions of infected birds.
Avian influenza viruses do not usually infect humans but people can contract
the disease through close contact with infected poultry and the feces. Only
140 human cases reported, mostly in South East Asia (Vietnam, Thailand,
Indonesia, Cambodia and China) with over 70 deaths, despite widespread
outbreaks in poultry and wild birds.
4. Leptospirosis
Leptospirosis is a most common zoonotic disease caused by Leptospira
Interrogans bacterium, which affects both humans and animals. It is
transmitted through contaminated fresh water, food or soil which is
swallowed or comes in contact with broken skin, eyes and mucous
membranes.
This Leptospira spreads through infected animal’s urine and contagious while
it is moist.
Rats, mice and voles known to be primary hosts while dogs, deer, rabbits,
cows, sheeps, and certain marine mammals are possible carrier and known to
be secondary hosts.
This biphasic disease normally begins with flu-like symptoms such as fever,
chills and intense headache. It will then cause meningitis, renal failure and
liver damage that cause jaundice.
Disease Transmission
NON COMMUNICABLE DISEASE
1. Lead
Lead accounts for most of the cases of pediatric heavy metal poisoning
(Roberts 1999).
It is a very soft metal and was used in pipes, drains, and soldering materials
for many years.
Millions of homes built before 1940 still contain lead (e.g., in painted
surfaces), leading to chronic exposure from weathering, flaking, chalking, and
dust.
Every year, industry produces about 2.5 million tons of lead throughout the
world.
Most of this lead is used for batteries. The remainder is used for cable
coverings, plumbing, ammunition, and fuel additives. Other uses are as paint
pigments and in PVC plastics, x-ray shielding, crystal glass production, and
pesticides.
Since lead is chemically very similar to calcium, it is handled by the body as if
it were calcium. Thus the first place to which it is transported is to the plasma
and the membrane sites in soft tissues. It is then distributed to the other sites
where calcium plays an important role, most notably in the teeth of
developing children and in bone at all ages.
Target organs are the bones, brain, blood, kidneys, and thyroid gland
2. Mercury
Mercury is generated naturally in the environment from the degassing of the
earth's crust, from volcanic emissions.
It exists in three forms: elemental mercury and organic and inorganic
mercury.
Mining operations, chloralkali plants, and paper industries are significant
producers of mercury (Goyer 1996).
Atmospheric mercury is dispersed across the globe by winds and returns to
the earth in rainfall, accumulating in aquatic food chains and fish in lakes
(Clarkson 1990).
Mercury compounds were added to paint as a fungicide until 1990. T
These compounds are now banned; however, old paint supplies and surfaces
painted with these old supplies still exist.
Mercury continues to be used in thermometers, thermostats, and dental
amalgam. (Many researchers suspect dental amalgam as being a possible
source of mercury toxicity [Omura et al. 1996; O'Brien 2001].)
Medicines, such as mercurochrome and merthiolate, are still available.
Algaecides and childhood vaccines are also potential sources.
Inhalation is the most frequent cause of exposure to mercury. The organic
form is readily absorbed in the gastrointestinal tract (90-100%); lesser but
still significant amounts of inorganic mercury are absorbed in the
gastrointestinal tract (7-15%).
Target organs are the brain and kidneys.
3. Insecticide
Pesticides are designed to kill "pests", but some pesticides can also cause
health effects in people. The likelihood of developing health effects depends
on the type of pesticide and other chemicals that are in the product you are
using, as well as the amount you are exposed to and how long or often you
are exposed.
Most often, pesticides affect the nervous system (system in your body that
controls your nerves and muscles).
Some health effects from pesticide exposure may occur right away, as you
are being exposed. Some symptoms may occur several hours after exposure.
Other effects may not be noticed for years, for example cancer.
Pesticides can enter your body during mixing, applying, or clean-up
operations. There are generally three ways a chemical or material can enter
the body:
o through the skin (dermal),
o through the lungs (inhalation), or
o by mouth (ingestion).
In general, the risk of illness increases as the concentration (strength) of the
pesticide, and duration (length) of exposure increases. "How much" and "how
long" is necessary to cause illness will depend on the exact type of pesticide
4. Asbestos
Asbestos is the name given to a group of naturally occurring minerals used in
certain products, such as building materials and vehicle brakes, to resist heat
and corrosion. Asbestos includes chrysotile, amosite, crocidolite, tremolite
asbestos, anthophyllite asbestos, actinolite asbestos, and any of these
materials that have been chemically treated and/or altered.
The inhalation of asbestos fibers by workers can cause serious diseases of
the lungs and other organs that may not appear until years after the
exposure has occurred.
For instance, asbestosis can cause a buildup of scar-like tissue in the lungs
and result in loss of lung function that often progresses to disability and
death.
Asbestos fibers associated with these health risks are too small to be seen
with the naked eye, and smokers are at higher risk of developing some
asbestos-related diseases
Employee exposure to asbestos must not exceed 0.1 fiber per cubic
centimeter (f/cc) of air, averaged over an 8-hour work shift. Short-term
exposure must also be limited to not more than 1 f/cc, averaged over
30 minutes. Rotation of employees to achieve compliance with either
permissible exposure limit (PEL) is prohibited.
5. Cadmium
Cadmium is a byproduct of the mining and smelting of lead and zinc
It is used in nickel-cadmium batteries, PVC plastics, and paint pigments.
It can be found in soils because insecticides, fungicides, sludge, and
commercial fertilizers that use cadmium are used in agriculture.
Cadmium may be found in reservoirs containing shellfish.
Cigarettes also contain cadmium. Lesser-known sources of exposure are
dental alloys, electroplating, motor oil, and exhaust.
Inhalation accounts for 15-50% of absorption through the respiratory system;
2-7% of ingested cadmium is absorbed in the gastrointestinal system. Target
organs are the liver, placenta, kidneys, lungs, brain, and bones.
6. Nitrate
Nitrates and nitrites are chemicals that can be found naturally in our
environment. Two of earth’s most common elements, nitrogen and oxygen,
combine to form these nitrogen-containing compounds. Nitrates are essential
(needed) nutrients for plants to grow. Nitrates can be found in the air, soils,
surface waters and ground water
The main exposure route to nitrates is by eating vegetables and preserved
meats (70%). The remainder of the nitrate in a typical diet comes from
drinking nitrate-contaminated water (about 21%)
Exposure to nitrates and nitrites are not usually an immediate (acute) health
threat. When you eat or drink nitrates, they are absorbed from the small
intestine (gut) into the blood. Nitrates then enter the large intestine from the
blood.
If certain, normal conditions exist in the intestine, such as a low pH, the
nitrate is simply processed and removed as waste without any harmful
effects.
However, under other conditions, such as a high pH in the intestine, the
nitrate will be changed into nitrite. This nitrite is then reabsorbed into the
blood where it will react with the blood’s hemoglobin iron to form
methemoglobin.
The hemoglobin in our blood carries (transports) oxygen throughout our
body.
The condition where the nitrite reacts with the iron and hemoglobin is known
as methemoglobinemia (often called “blue baby syndrome”).
Unlike hemoglobin that carries oxygen throughout our body, methemoglobin
is unable to transport oxygen.
A person who has methemoglobinemia can lack the proper oxygen levels
needed for the body to function correctly. One of the signs of
methemoglobinemia is cyanosis (turning a blue color).
7. Particular Matter
Particular matter is the sum of all solid and liquid particles suspended in air,
many of which are hazardous. This complex mixture contains for instance
dust, pollen, soot, smoke, and liquid droplets
Particles are either directly emitted into the air by sources such as
combustion processes and windblown dust, or formed in the atmosphere by
transformation of emitted gases such as SO2.
In long-term exposure to current ambient particulate matter concentrations
may affect the lungs of both children and adults and may reduce life
expectancy by a few months, mainly in subjects with pre-existing heart and
lung diseases.
Fine particles are more dangerous than coarse particles. Apart from the size
of the particles, other specific physical, chemical, and biological
characteristics that can influence harmful health effects include the presence
of metals, PAHs, other organic components, or certain toxins.
When particulate matter is combined with other air pollutants, the individual
effects of each pollutant are cumulated. In certain cases, especially for
combinations of particulate matter with ozone or allergens, effects were
shown to be even greater than the sum of the individual effects.
Certain groups of people are more susceptible to suffer health effects due to
ambient particulate matter. These include elderly people, children, people
with a pre-existing heart and lung disease, asthmatics, and socially
disadvantaged and poorly educated populations.
8. Dioxin
Dioxins are a group of chemically-related compounds that are persistent
environmental pollutants.
Dioxins are found throughout the world in the environment and they
accumulate in the food chain, mainly in the fatty tissue of animals.
More than 90% of human exposure is through food, mainly meat and dairy
products, fish and shellfish. Many national authorities have programmes in
place to monitor the food supply.
Dioxins are highly toxic and can cause reproductive and developmental
problems, damage the immune system, interfere with hormones and also
cause cancer.
Short-term exposure of humans to high levels of dioxins may result in skin
lesions, such as chloracne and patchy darkening of the skin, and altered liver
function.
Long-term exposure is linked to impairment of the immune system, the
developing nervous system, the endocrine system and reproductive
functions. Chronic exposure of animals to dioxins has resulted in several
types of cancer.
No Type of Heavy
Metal
Source/Exposure Organ Target/
Disease
1. Lead Used in pipes, drains, and
soldering materials for
many years.
Exposure from
weathering, flaking,
chalking, and dust.
Used for batteries.
The remainder is used for
cable coverings,
plumbing, ammunition,
and fuel additives.
Other uses are as paint
pigments and in PVC
plastics, x-ray shielding,
Transport to
soft tissues
Target organs
are the bones,
brain, blood,
kidneys, and
thyroid gland
crystal glass production,
and pesticides.
2. Mercury generated naturally in the
environment from the
degassing of the earth's
crust, from volcanic
emissions
Mining operations,
chloralkali plants, and
paper industries are
significant producers of
mercury
Used in paint,
thermometer medicine
and medical equipment
Expose by inhalation
Target organ:
brain and
kidney.
3. Insecticide From pesticide
enter body during mixing,
applying, or clean-up
agriculture operations
affect the
nervous system
4. Asbestos used in certain products,
such as building materials
and vehicle brake
cause serious
diseases of the
lungs and other
organs
5. Cadmium byproduct of the mining
and smelting of lead and
zinc
used in nickel-cadmium
batteries, PVC plastics,
and paint pigments.
Effect liver,
placenta,
kidneys, lungs,
brain, and
bones.
Absorb in
can be found in soils
because insecticides,
fungicides, sludge, and
commercial fertilizers that
use cadmium are used in
agriculture.
Cadmium may be found in
reservoirs containing
shellfish
Cigarette
respiratory
system and
gastrointestinal
system
6. Nitrate is by eating vegetables
and preserved meats
from drinking nitrate-
contaminated water
baby blue
syndrome
lack of oxygen
7. Particular Matter From dust, pollen, soot,
smoke, and liquid droplets
emitted into the air by
sources such as
combustion processes
heart and lung
disease
High risk to
elderly people,
children, people
with a pre-
existing heart
and lung
disease,
asthmatics, and
socially
disadvantage
8. Dioxin a group of chemically-
related compounds that
are persistent
environmental pollutants.
cause
reproductive
and
developmental
problems,
exposure is through food,
mainly meat and dairy
products, fish and
shellfish.
damage the
immune system,
interfere with
hormones
also cause
cancer.
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