Water, a natural resource, has become a much sought-after good, which is likely to become a major global problem. Increasingly, there is an imbalance between the geographical and seasonal demand for and availability of water. This imbalance leads to over-use and exhaustion of reserves as the total amount of water on the earth is finite, while man’s requirement is accelerating fast with the growth of population, agriculture and industry across the globe. In the course of usage, water is also getting polluted resulting in water becoming a source of death and disease rather than life.

Today, at least one-fifth of all people worldwide lack access to safe drinking water.  In developing countries, most cities discharge 80-90% of the untreated sewage directly into rivers and streams, the water of which are used for drinking, bathing and washing.  This lack of sewage treatment has allowed dangerous microorganisms to spread water borne diseases; particularly diseases transmitted by vectors, which live in the water environment, accounting for about a third of all deaths in the world

The growing pollution of our rivers constitutes the biggest threat to public health.  Polluted waters lead to various gastrointestinal problems, liver infections, cancer, etc.  Children are often the worst affect, dying in large numbers because of diarrhea.  Even in the 1990s more than 1 million children died due to diarrhea and other gastrointestinal disorders.  Since independence, our neglect of water sources has killed more than 50 million children.

Transmission of  water- related diseases:

The water related infections of man are extremely numerous and diverse.  In general the following are the ways in which diseases may be carried by water.

·          Pathogenic organisms are transmitted from one person to another through the domestic water supply system. e.g. cholera, typhoid and hepatitis.

·          Inadequate water supply, lack of personal cleaniness e.g. trachoma and skin infection

·          Infection transmitted by organisms which live in water, like helminths (parasitic flukes) that spend part of their life cycle in water e.g. bilharzia

·          Insect vectors which are related in some way to water, transmit infection e.g yellow fever, malaria etc.

Source of Water Pollutants:

Direct additions

·          Discharge of domestic, industrial or agricultural effluents

·          Direct application of herbicides to control water plants that interfere with man’s use of freshwaters.

·          Direct application of insecticide to fresh waters to destroy larvae of mosquitoes, the vector of malaria.

·          Molluscicides widely used in the tropics to control the snail vectors of schistosomiasis.

Indirect additions

·          Run-off of insecticides and herbicides applied to the land.

·          Carelessly dumped waste pesticide and their empty containers in polls or streams.

·          Land fill sites and toxic waste dumps contaminate ground water

Types of pollutants found in water

·          Organic pollutants

·          Inorganic pollutants

·          Thermal pollutants

·          Radioactive pollutants

Origin

·          Domestic sewage (major source)

·          Urban run-off (from houses, factories and roads)

·          Industrial effluents

Effects

·          Depletion of dissolved oxygen (the recommended DO level for natural water is 4 to 6 ppm)

  Pthogens

Orig in

Faecal contamination of water can introduce a variety of pathogens into waterways,   including

·          Bacteria
·          Virus
·        Protozoans
·          Parasitic worms
·           Vectors

Some water-related diseases and their causative organisms

  Protection against water-borne diseases
It is necessary to be careful about the water you drink and the water you bathe in, since water is a carrier for a number of diseases.

Drinking water

·          Filter water with a cloth or mud pot or candle filter
·          Boil the water for 10 minutes
·   All fruits and vegetables that will not be cooked must be peeled after soaking in treated water
·          Do not eat ice-creams, drinks, etc. sold by street vendors
·          Clean your teeth preferably with treated water

Bathing Water

Bathing can expose the body to several diseases, notably bilharzia, leptospirosis and diarrheic
diseases.
Mud and sand can contain parasite larvae.

Avoid

·          Walking with bare feet
·         Bathing in untreated water

Safe water supply
This is very essential.  In rural areas this can be achieved by chlorination of water and replacement of shallow wells by sanitary wells.

Sanitation barrier
This implies the proper disposal of excreta so that infection does not reach water, soil, milk, food or files.

Health education 
It is essential to educate people for improvement in sanitation and personal hygiene.

Source: Water –The Elixir of Life ,C.P.R. Environmental Education Centre,Chennai.