environmental health

Dr. Nadia Aziz CABCMDepartment of community medicineBaghdad 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

Water contamination

B- Natural toxins:
Cyanobacteria including Microcystis aerogenosa produce cyanotoxine some of which are hepatotoxic and neurotoxic compounds.


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 )

Water contamination

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)
Is the amount of dissolved oxygen needed by 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 pollution of water.

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