Polluted Water Can Kill You 235 



safety of that water for human consumption. Water may be 

 undesirable because it looks "dirty," but the water is unsafe only 

 when it has been proven to be so by scientific analysis. The 

 chance that water will be non-potable from a purely chemical point 

 of view is rare, and for this reason chemical analyses are not 

 routinely carried out unless the individual is interested in deter- 

 mining what harmful effects the water might have on boilers, pipes, 

 and manufacturing equipment. Certain chemical tests, chiefly 

 those concerned with nitrogen in the combined form, will give 

 useful information to sanitarians who are interested in determining 

 how recently a supply of water has been polluted. As the sewage 

 undergoes decomposition, the bacteria convert the nitrogenous 

 compounds into ammonia, nitrites, and nitrates. The stage of de- 

 composition yields valuable information to a trained interpreter. 



From the standpoint of human health the most important test 

 conducted on water is the bacteriological analysis. While we are 

 interested in knowing the numbers of living organisms present in 

 water to be used for drinking, we are more interested in the source 

 of these bacteria. 



The standard technic calls for the determination of the presence 

 of pollution, and if sewage organisms are found, the water is con- 

 demned. One of the easiest ways to detect sewage is to look for 

 Escherichia coli (the genus is named in honor of Escherich, the 

 discoverer, and the species denotes the origin of the bacteria— the 

 colon). This organism is found in the excreta of man and other 

 warm-blooded animals. Hence, if Escherichia coli is present, there 

 exists the possibility that enteric pathogens might also be expected. 



Patients suffering from enteric diseases, together with healthy 

 carriers of these pathogens, represent potential sources of the pol- 

 lution. Some persons feel that unless water is grossly polluted, 

 the chance of infecting humans is remote. While it may be true 

 that much polluted water could be consumed with no harmful 

 effects, would vou knowingly have a member of your familv drink 

 potentially-harmful water? Statistically, the number of persons 

 who might contract typhoid or some other enteric disease from 

 slightly polluted water may not be significant. But if that number 



