• TOPICS
KATHMANDU, JANUARY 24
An adult needs to drink at least 1.5 litres of water a day to replace fluid lost in urine, sweat and respired air, and to perform essential biochemical functions. Moreover, almost 90 percent of the body mass is water.
Water, however, can also carry dangerous pathogens and toxic chemicals into the body.
Water also harbours the intermediate stages for many parasites, either as free-living larvae or in some other form, and it is the vehicle for essential stages in the life cycle of many dangerous insect vectors, notably mosquitoes and black flies.
Chemical contamination or pollution of drinking water is another serious problem.
It is important to note that not only drinking water, but also water used for cleaning fruits, vegetables and cooking utensils, and for washing, can convey disease. Indeed, salads that have been washed in polluted water are a frequently overlooked and a rather common source of waterborne diseases, such as cholera or typhoid.
Water sources like springs, rivers and ponds can all be contaminated by faecal matter of human or animal origin. Organic matter of dead animals and decaying vegetation can contaminate drinking water, too.
Water from suspect sources usually can be made safe to drink by boiling. However, boiling is neither practical nor sensible for the treatment of large municipal water supplies.
These must be protected by appropriate treatment measures-filtration and chlorination.
Provision of safe drinking water supplies is among the most effective measures ever taken to advance public's health.
The other essential components in the prevention of waterborne diseases are safe disposal of sewage and the environmental control of toxic chemicals. The combination of sanitary disposal of human sewage and the provision of safe water supplies has virtually eliminated many of the serious waterborne epidemics.
However, sanitary services break down when floods, earthquakes and other disasters occur, and at such times, it is essential to boil water to ensure that pathogens are killed. Other methods, such as the use of iodine, are also helpful.
Even with the best protective measures, however, serious large waterborne epidemics have occurred, not to mention innumerable small ones, often due to contamination of public drinking water supplies by animal waste, which can contain the dangerous E. coli bacteria.
Chemical pollution of water supplies presents problems of a different kind. Chemical contamination can cause acute illnesses, but more often the toxic contaminants are slow poisons, such as carcinogens.
A version of this article appears in the print on January 25, 2022, of The Himalayan Times.
