SYMPOSIUM OX SANITATION 5 7 



ance of certain liquid waste producing industries injurious to 

 fish is of so great importance to the general welfare that fish 

 life in certain streams must be sacrificed. 



The maintenance of fish life does not necessarily imply 

 an unpolluted stream. It is merely necessary that the alka- 

 linity of the water be maintained and that the pollution be 

 not so great as to absorb the dissolved oxygen in the water 

 to an extent that will suft'ocate the fish. The fact is : a moder- 

 ate degree of pollution favors fish life in that it favors the 

 growth of microscopic aquatic organisms which constitute 

 valuable fish food. Certain difficulties have been encountered 

 in the contamination of fish by polluted water which causes 

 the fish to decay rapidly and become unfit for human con- 

 sumption. The danger of infection of human beings with 

 specific disease through eating fish taken from polluted 

 streams is almost negligible, for the reason that in this part 

 of the world at any rate fish are not eaten raw. With shell 

 fish, however, the case is quite different, because they are very 

 frequently eaten raw. It has been a common practice along 

 the coast to fli^at oysters in shallow polluted waters which 

 causes them to become bloated and appear fat. Such an 

 oyster perhaps makes a more delectable morsel of food, but 

 in it may be lurking the germs of typhoid fever or some other 

 water borne disease. The problem of protecting the shell fish 

 industry is a very complicated one and all its intricacies have 

 not been worked out. Here again is where the services of 

 experts are needed to study each zone of shell fish pollution 

 in the light of diverse local conditions. As a concrete ex- 

 ample of the efforts that are made to protect shell fish may 

 be mentioned the case of the city of Baltimore, which at the 

 expense of millions of dollars is purifying its sewage so as to 

 convert it into a liquid which is not only clear and inoff'ensive 

 but also practically sterile. 



Discharge of Manufacturing Wastes into Streams 



Many of our important industries, such as paper mills, 

 woolen mills, dye works, starch factories, and tanneries, re- 

 quire large volumes of water to carry on their industrial oper- 

 ations and they also produce large volumes of waste which 

 are capable of undergoing offensive putrefaction. The dis- 

 charge of these wastes into streams often causes unsightly, 

 and malodorous conditions, yet, with the exception of tan- 

 neries, these waters do not menace the public health since 

 they do not contain the specific infections of disease. (Tan- 

 nery wastes may contain anthrax bacilliV In fact some of 

 tlie processes are such that the wastes are quite inimicable to 

 the existence of disease germs. In some cases it is practicable 



