OIL AND TAR POLLUTION OF WATERS. 5 
shallow water vegetation which directly or indirectly furnishes fish 
food and shelter; and by impairment of the market value of fish 
through imparting to them an offensive taste. 
DIRECT TOXIC EFFECTS. 
A great variety of tars and tar oils, either from coal or petroleum, 
have been shown to be highly poisonous. Butterfield and writers 
in the (London) Fishing Gazette and the Salmon and Trout Maga- 
zine, and Shelford and Thomas in this country (see bibliography) 
have reported various experiments which show that tar and. tar 
oils are poisonous in great dilutions. Tars or tar ois result from 
distillations of coal, pony suis woods, etc. These distillation 
pepencle are very complex and varying in composition, but all may 
e assumed to contain some of the substances which, in very weak 
dilutions, have been shown to be highly poisonous to various fishes. 
Phenols and cresols (in dilutions of less than 100 parts per million) 
have been found quickly fatal by Butterfield and Shelford. Other 
constituents which are quickly fatal in the dilutions indicated are 
phenanthene and naphthalene (4 to 5 parts per million); xylene, 
toluene, benzenc, and ethylene (22 to 65 parts per million); sulphur 
compounds, as hydrogen sulphide (5 parts per million), sulphur 
dioxide (16 parts per million); carbon bisulphide (100 parts per 
million); thiophene (27 parts per million); ammonia (7 parts per 
million); and ammonium salts and other nitrogenized compounds 
(some hundred atk per million); quinoline and isoquinoline (40 to 
65 parts per million). The strengths given as quickly fatal are those 
which have caused death in one hour, or aes more, to sunfish 
(American) or gudgeon (European), fish which seem more than ordi- 
narily resistant to poisons. It is stated (Seydel) that Russian 
investigators find hexahydrobenzoic acid (C,H,,CO.CH), to be the 
essential poison of Russian petroleum, and that 4 to 16 parts per 
million were quickly fatal to a cyprinid and a percid. 
The experiments of Thomas and others indicate that prolonged 
exposure to very much greater dilutions of these substances are 
fatal. Dilutions of various tars and crude distillates of petroleum, 
which required 66 or more Ree per million for quick fatality, have 
proved fatal in strengths of from 13 to 33 parts pe million in from 
1 to 3 days. A great variety at 13 parts per million proved fatal in 
3 days. One liquid tar waste at 2 parts per million killed sunfish 
(Lepomis humilis) in one day. 
MECHANICAL EFFECTS. 
Certain petroleum products appear to contain no poisonous sub- 
stances soluble in water and to have little direct effect when allowed 
to form a surface film, but when emulsified by agitation prove deadly. 
A high-boiling petroleum distillate and a light fuel oil were found, by 
Thomas to be quite harmless, unless as aeration retarders, or unless 
emulsified, as by continued moderate agitation, when they coated 
the gill membranes of the fish and caused death by suffocation. 
Rushton found that by shaking up | part of benzine with 40,000 parts 
of water, a mixture was formed which killed fish in five minutes, 
apparently entirely from poisonous action. 
68637°—21——-2 
