Dr. Nadia Aziz
CABCM
Department of community medicine
Baghdad medical college
Water quality and pollution
Learning Objectives
1- Describe
characteristics
of water according
to source.
2-Descibe
water contamination
3- Describe
characteristics of each contaminant
exposure
introduction
Although 70% of earth is covered by water, only
3% of the earth's water is fresh. Of that 3%,
two thirds is frozen in glaciers and ice caps,
leaving only 1% available for human use.
Sources of water
1-
Rain water
The quality of rain water is generally
reasonable
, but it
may be contaminated by gases and particles that are
washed out of the atmosphere or by accumulation
of dust and debris in catchment systems e.g. the
gaseous
sulfur
and
nitrogen oxides
emitted from
power plants that use fossil fuels react with
atmospheric water forming dilute solution of
sulfuric and nitric acids.
Sources of water
2-
Surface water
Improvement of water quality may result from
storage in a lake providing opportunities for
coagulation and sedimentation of colloidal
and suspended solids that are tributaries for
rivers and stream.
Sources of water
3-
Ground water
Ground water tends to be more
highly mineralized
than surface waters resulting from the solution of
minerals that the ground water comes in contact
with as these waters percolates through the ground
layers.
However these ground waters are generally of
higher
sanitary quality
since;
Ground water
A- They are
not as likely to be subject to microbial
pollution
as surface water sources
B- Passage of water through soil strata often
serves to
improve their bacteriological quality
On the other hand ground water pollution,
particularly from
toxic waste discharge
is a
major problem for this source of water.
Water contamination
1-
Biological agents
A-
microorganisms
:
in developed countries it is rare to have serious dysentery or
enteric fever due to
vibrio cholera
and
salmonella typhi
except in areas where water quality is compromised.
Contaminated bathing waters frequently are associated with
viral upper respiratory
and
gastrointestinal infection
Water contamination
Certain
parasites
form small cysts which pass
through standard filters and are quite
resistant to water disinfectants (like
Cryptosporidium
&
Giardia lamblia
)
Water contamination
B-
Natural toxins
:
Cyanobacteria including Microcystis
aerogenosa produce cyanotoxine some of
which are
hepatotoxic
and
neurotoxic
compounds.
Natural toxins
Cyanobacteria can produce cyanotoxins in such
and even kill
concentrations that they
animals and humans.
Cyanotoxins can also accumulate in other
, and cause
animals such as fish and
.
poisonings such as
Water contamination
2-
Chemical contaminants
:
Thousands of
synthetic organic chemical
are used in
agricultural and industrial process many of these
chemicals as well as antibiotics and other
pharmaceutical pesticides and certain industrial
chemicals frequently are found in waters particularly
downstreams from factories and cities.
Water contamination
A-
Inorganic chemicals
Arsenic
: A ubiquitous metal can be found in the
environment in the
organic
and
inorganic
. Human
activities such as smelting, coal burning, wood
preservation, pesticide distribution and other
industrial process produce at least 3 times more
arsenic than natural processes..
Water contamination
The toxicity of arsenic to humans depends on the
form, with
organic being less toxic than inorganic.
Arsenic is a known human
carcinogen
(
lung
,
bladder
or
skin cancer
)
Arsenic toxicity are different for acute versus
chronic exposures.
Water contamination
Acute high dose exposure to
inorganic arsenic
more
than 3-5 mg /kg affects all major organs including :
GIT
( nausea ,vomiting ,hematemesis ,diarrhea and
abdominal cramping)
heart
(myocardial depression with cardiac conduction
disturbances)
(
hepatic dysfunction
)
brain
,
kidneys
.
Water contamination
inorganic arsenic
bone marrow
( BM suppression, pancytopenia)
skin
( eczematoid eruption ,hyperkeratosis and melanosis,
finger nails may contain
Mees lines
, alopecia may also
occur )
peripheral nervous system
( sensorimotor type typically
involving lower more than upper extremities, clinical
picture mimics
Guillain Barre syndrome
).
Water contamination
Chronic exposure to inorganic arsenic
may
produce generalized fatigue and malaise.
Chromium
: Hexavalent chromium is a
carcinogen.
Water contamination
Lead:
Drinking water represents a potential rout of
exposure to lead. Previously the use of lead piping to
connect water mains to homes was very common.
Millions of these lead connectors still exist.
Drinking water, particularly that which is
soft
(
low in
calcium or magnesium
) or
below neutral PH
causes
lead to leach out from lead connector pipes.
Water contamination
Clinical effects of lead exposure
on
CNS
are the most common effects including cognitive
impairment measured by IQ test
The peak blood lead level at age 2 years is associated
with lower IQ scores as IQ becomes reliably testable
at age about 4 years. In As blood lead level in 2 year
olds increase by 10 Mg /dl increase, the IQ at age4
years and older declines by 2-3 points..
Water contamination
Based on this currently used
15 Mg /dl
as the
level of concern in an
individual child
, which,
when detected, should prompt a search for
sources of lead exposure and their removal.
Many children above
10 Mg /dl in a community
should prompt a search for community sources
and their removal
Water contamination
Subclinical effects on
hearing
and
balance
may occur at
commonly encountered blood lead levels.
Teeth or bones lead are also used as exposure measures,
Lead interferes with
haem synthesis
beginning at levels of
about 25 Mg/dl.
Environmental exposure to lead may
delay growth
and
pubertal development
.
Water contamination
Lead can cause
abdominal colic
,
peripheral
neuropathy
and
renal disease
in adults with
occupational exposure.
Water contamination
Methyl mercury
: Originates from
natural sources
and from
combustion sources
that release mercury into the air such as
coal fired power plants used for generating electrical energy
and municipal waste incinerators that burn garbage.
Atmospheric mercury ultimately is deposited into lakes and
rivers by dust fall, rain and snow.
Mercury accumulates in
blood
,
CNS
and
renal tissues
and
very slowly eliminated.
Water contamination
B-
Organic chemicals
1-Components of gasoline
: benzene is known
to cause
leukemia
in humans and
aplastic
anemia
at high doses.
Water contamination
2-Nitrates
: Enter the water supply from urban and
agricultural run off of
nitrogen fertilizers
. They also
may be produced by bacterial action on animal waste
run off
Nitrates themselves are non toxic to humans, but can
be converted to more reactive and toxic nitrites by gut
bacteria.
Nitrates may cause
metheamoglobinemia
in infants.
Water contamination
3-
Pesticides
: may not be removed by conventional
drinking water treatment. Some of the older pesticides
were designed to be persistent in the environment for
years and can be found distributed worldwide in water
and soil .Newer pesticides degrade more quickly but still
contaminate water.
4-Trichloroethylene, Tetrachloroethylene, Chlorlform
,
are associated with
childhood leukemia
.
Water contamination
Physical contaminants
Radionuclides
Redon
gas is a product of the radioactive decay of uranium.
It enters the water supply naturally and become
aerosolized during the use of tape water. Radon further
breaks down into radon "daughters or progeny".
Radon in water is important because during showering
radon may be inhaled.
Lung cancer
in adults has been
linked to radon progeny.
Water Purification
1-
Coagulation and flocculation
: Addition of
coagulant like Aluminum sulfate or synthetic
polymers
2-
Sedimentation
: Under action of gravity
3-
Filtration:
Water passes through granular
media; fine particles are removed by adhesion to
the granular media.
Water Purification
4-
Adsorption
:
activated carbon both in granular form as filters
and in powdered form as an additive to water.
It adsorbs unpleasant taste and odors and
organic chemicals.
Water Purification
5-
Disinfection
:
Oxidizing chemicals including halogens (
Chlorine
bromide
which has been the single most important
process for insuring the bacteriological safety of
potable water,
Bromine
,
Iodine
).
Ozone
,
Potassium permanganate
and
Hydrogen
peroxide
. Irradiation by
Ultraviolet light
,
silver ions
,
copper ions.
Biochemical oxygen demand (BOD)
needed by
the amount of
Is
aerobic
biological organisms
in a body of water in
a given water sample at
certain temperature
over
a
specific period of time
.
The term also refers to a chemical procedure for
determining this amount.
Biochemical oxygen demand (BOD)
This is not a precise quantitative test, although it is
widely used as an indication of the organic quality of
water.
The BOD value is most commonly expressed in
milligrams of oxygen consumed per liter of sample
during 5 days of incubation at 20 °C
and is often
used as a surrogate of the degree of
organic
Thank you