Ask A Scientist© Environmental Science Archive

Author:     Marge
Text:       Are all the water supplies in the world polluted?

Response #: 1 of 1
Author:     Don Libby
Text:       Not all water on earth is polluted, or more correctly, not all 
water IN earth is polluted. Many people rely on wells drilled into the ground 
for their water, and this water has generally remained untainted by human 
activity (except possibly in the pipes during transportation). In some 
agricultural areas, there is concern that pesticides may leach through sandy 
soils and contaminate some of this underground water. In other places, there 
is concern that too much water has been drawn out for irrigation, and that the 
wells will go dry. The good news is that water can be unpolluted by filtering, 
boiling, or by chemical treatment, so drinking water supplies are safe most of 
the time. Recently, the city of Milwaukee (in my home state of Wisconsin) 
experienced a breakdown in their water purification system and many people got 
sick from a bacteria that was not filtered out. People in poor countries also 
get sick from drinking contaminated water quite often, because they have not 
been able to afford to build water treatment systems. So, while much of the 
surface water on earth may be polluted (either by natural bacteria or by 
agricultural or industrial waste), there is some hope that almost everyone can 
get water clean enough to drink.